Reminder: Never connect a generator to home wiring without transfer switch
Currently a problem in the north-east USA, but applicable after every storm. People in the south have more experience with hurricanes, and are used to this advice. But apparently, some folks up north aren't in practice. Never connect an electric generator to home electrical wiring without installing a transfer switch to disconnect power from the electric grid. Back feeding electric power into the utility lines is dangerous for the repair crews working on utility lines. Also, never run a generator indoors or in the garage. Only outdoors 20-feet away from doors and windows. FCC has activated DIRS reporting for tropical storm Henri. So we should see some communication system disaster reporting this afternoon.
On 8/23/21 19:53, Sean Donelan wrote:
Currently a problem in the north-east USA, but applicable after every storm.
People in the south have more experience with hurricanes, and are used to this advice. But apparently, some folks up north aren't in practice.
Never connect an electric generator to home electrical wiring without installing a transfer switch to disconnect power from the electric grid. Back feeding electric power into the utility lines is dangerous for the repair crews working on utility lines.
Standard advice when you do any kind of distributed or embedded generation outside of the grid. Mistakes like these are more likely to come from DIY'ers who put in 2hrs of Youtube and think they are suddenly qualified electricians. Same advice applies to solar or stationery storage inverters. Typically, these are automated enough to disconnect from the grid after an outage, if you don't have a local battery; or the battery inverter will isolate away from the grid in case of grid failure, but still form its own micro-grid for the building. So back-feeding into the grid is not a concern. But for combustion generators, yeah, have a qualified electrician do the install. Just saves time, money and lives. Mark.
Back feeding electric power into the utility lines is dangerous for the repair crews working on utility lines. Same advice applies to solar or stationery storage inverters. Typically, these are automated enough to disconnect from the grid after an outage, if you don't have a local battery; or the battery inverter will isolate away
How would this not load the generator or inverter into oblivion? (Just curious, I know people who use a suicide cord usually turn off the main breaker.) - Ethan
On 8/25/21 15:59, Ethan O'Toole wrote:
How would this not load the generator or inverter into oblivion?
Not sure I understand your question. Say again, please.
(Just curious, I know people who use a suicide cord usually turn off the main breaker.)
At the home, you typically have someone that is responsible for knowing what to do in case of an outage, and switching over to self-generation. If that person is not there, or has passed out from too many bottles of wine that evening, someone else might think it's just a matter of starting the generator, unwinding a suicide cord and plugging it into the wall - totally forgetting about the main breaker. You need to make these things fool-proof. We haven't traveled in over a year but the day we do, it's a recipe for disaster if the person that deals with this stuff is on the road when the power goes out back at home. Mark.
How would this not load the generator or inverter into oblivion? Not sure I understand your question. Say again, please.
If you hook 100KW of neighbors up to your 5KW/20% THD garden generator it would probably trip the breaker, or stall. I suppose it could be an issue if it was a single house on a branch where the break being serviced was just that branch (rural customers.) Was just curious why it wouldn't overload the generator trying to power all the neighbors houses if connected to the grid. - Ethan
On 8/25/21 16:24, Ethan O'Toole wrote:
If you hook 100KW of neighbors up to your 5KW/20% THD garden generator it would probably trip the breaker, or stall.
Assuming that you don't want to deliberately simulate a utility grid on the same transformer as your neighbors, the bad news is that line workers could be injured by your back-feeding. Not so likely for your neighbors because they wouldn't be touching the lines, but yeah, not great for line workers actually working on them. At any rate, you will trip any generator once you overload it. Worst case, you'll burn out its electrical components.
I suppose it could be an issue if it was a single house on a branch where the break being serviced was just that branch (rural customers.)
Typical assumption, regardless of it's urban or rural, as each house would have its own main breaker anyway - both at the customer panel, as well as at the utility source point (last one may vary by country).
Was just curious why it wouldn't overload the generator trying to power all the neighbors houses if connected to the grid.
If you did not isolate your self-generation equipment from the grid, then you may very well become a provider for your neighbors all hooked on to the same distribution wiring, or even on the same transformer. It would likely never work in any meaningful way, and you increase your chances of starting a fire or breaking things irreparably. AC-coupled grid-tied solar inverters automatically stop making PV power once the grid disappears, to avoid this very problem, if you do not have a local battery to substitute. This is defined under UL 1741 that all major PV inverter OEM's follow. There have been some changes defined under "California Rule 21 Tariff" that ease UL 1741 somewhat, to avoid PV inverters from disconnecting from the grid during an outage in order maintain grid stability, i.e., when a grid provider is accepting significant amounts of feed-in from private or commercial self-generation customers, a sudden disconnect of all that capacity during a main grid outage could make for a very unstable grid due to massive and sudden variations in voltage and frequency. I'm not yet sure of any other places besides California that implemented this requirement against PV inverter OEM's. I haven't tracked it since 2017. I know that here in South Africa, UL 1741 is still the main and only requirement. A grid-tied battery inverter will automatically disconnect from the grid when it disappears, so it has no chance of transferring PV or battery energy on to the grid network. Generators are not usually that intelligent. Some manual switching required to avoid grid back-feed, which was Sean's initial point. If done well, the generator would have an ATS (automatic transfer switch, either integrated or an add-on) to take care of all of this. In the absence of that (due to cost management or a lack of a thorough job), a manual changeover is highly recommended. Mark.
Ok, I'll be the curmudgeon... Is this really a problem in practice? Most people I've known who worked around electrical mains etc assumed the worst at all times and it isn't all that difficult to protect against as one works. I realize one can infinitely invoke "better safe than sorry!", "an ounce of prevention...!" <OBLIGATORY FUNNY STORY> Except maybe that one guy at Harvard who came to replace what turned out to be a 100+ year old, home made, "breaker" which fed our machine room which was hidden in a narrow dark hallway winding around our machine room behind an unmarked metal, locked doorway. I had no idea it existed but we had no power so I called for help. It was just a single copper bar about the size of a small candy bar tensioned into hot clips. Probably 400A but who remembers. He removed the old one confidently enough, grabbed the new one with rubber-handled pliers and gloves and... Him: Have you ever played football? Me: Actually, yes, I have, why? Him: If something doesn't look right when I put this thing in just tackle me clear of it as hard and as fast as you can. Me: Um, ok. It all worked out fine and I wrote a memo that maybe Harvard could spring for a proper $500 breaker box? </OBLIGATORY FUNNY STORY> -- -Barry Shein Software Tool & Die | bzs@TheWorld.com | http://www.TheWorld.com Purveyors to the Trade | Voice: +1 617-STD-WRLD | 800-THE-WRLD The World: Since 1989 | A Public Information Utility | *oo*
Barry, It’s really a problem. Several lineman are maimed or killed every year because of DIY ignorance. I’ve already provided one incident. You can easily find more. It’s virtually impossible for lineman to protect against this risk while working. These guys aren’t idiots, they are highly trained professionals. They make sure power lines are de-energized from the grid before they touch them, but there comes a point where they have to put hands on in order to affect repairs. It’s while they are doing this hands-on work that some thoughtles homeowner decides to fire up his DIY wrongheaded generator, feeding 120 V backwards through a cascade of transformers to produce 12,000 or more volts. It takes only a few milliamps through the heart to kill someone. But often these accidents result in horrific third-degree burns. We all know people, and we might even be people, who have home generators. I suspect many of these use direct attach rather than transfer switches. You could help teach them the right thing to do. -mel
On Aug 25, 2021, at 11:33 AM, bzs@theworld.com wrote:
Ok, I'll be the curmudgeon...
Is this really a problem in practice?
Most people I've known who worked around electrical mains etc assumed the worst at all times and it isn't all that difficult to protect against as one works.
I realize one can infinitely invoke "better safe than sorry!", "an ounce of prevention...!"
<OBLIGATORY FUNNY STORY>
Except maybe that one guy at Harvard who came to replace what turned out to be a 100+ year old, home made, "breaker" which fed our machine room which was hidden in a narrow dark hallway winding around our machine room behind an unmarked metal, locked doorway. I had no idea it existed but we had no power so I called for help.
It was just a single copper bar about the size of a small candy bar tensioned into hot clips. Probably 400A but who remembers.
He removed the old one confidently enough, grabbed the new one with rubber-handled pliers and gloves and...
Him: Have you ever played football?
Me: Actually, yes, I have, why?
Him: If something doesn't look right when I put this thing in just tackle me clear of it as hard and as fast as you can.
Me: Um, ok.
It all worked out fine and I wrote a memo that maybe Harvard could spring for a proper $500 breaker box?
</OBLIGATORY FUNNY STORY>
-- -Barry Shein
Software Tool & Die | bzs@TheWorld.com | http://www.TheWorld.com Purveyors to the Trade | Voice: +1 617-STD-WRLD | 800-THE-WRLD The World: Since 1989 | A Public Information Utility | *oo*
On Wed, Aug 25, 2021 at 2:34 PM <bzs@theworld.com> wrote:
Ok, I'll be the curmudgeon...
Is this really a problem in practice?
Most people I've known who worked around electrical mains etc assumed the worst at all times and it isn't all that difficult to protect against as one works.
I realize one can infinitely invoke "better safe than sorry!", "an ounce of prevention...!"
<OBLIGATORY FUNNY STORY>
Except maybe that one guy at Harvard who came to replace what turned out to be a 100+ year old, home made, "breaker" which fed our machine room which was hidden in a narrow dark hallway winding around our machine room behind an unmarked metal, locked doorway. I had no idea it existed but we had no power so I called for help.
It was just a single copper bar about the size of a small candy bar tensioned into hot clips. Probably 400A but who remembers.
He removed the old one confidently enough, grabbed the new one with rubber-handled pliers and gloves and...
Him: Have you ever played football?
Me: Actually, yes, I have, why?
Him: If something doesn't look right when I put this thing in just tackle me clear of it as hard and as fast as you can.
Me: Um, ok.
It all worked out fine and I wrote a memo that maybe Harvard could spring for a proper $500 breaker box?
</OBLIGATORY FUNNY STORY>
... and my "funny" story. We used to live in San Jose. There was a large heat-wave, and much of SJC lost power because of A/C load, etc. Anyway, my wife and I go and camp in one of the office conference rooms for a few days because the office still has power and A/C. Eventually PG&E claims that power is back on our street, so we drive back to San Jose and... no power. I flag down a passing PG&E truck and ask if they know when it will *really* be back. Lineman says that it is. I say it isn't. He says it is. I say it isn't. He gets annoyed, opens up the pedestal box and sticks a meter in it, and agrees that I have no power. He then sticks the meter across the 800A fuse, and discovers that the fuse blew. "Ah. I can fix that fer you..." he says, and goes to the back of the truck... "Doh. I'm out of 800A fuses. Um.... er.... well, here is a 6,000A fuse, that'll do..." I briefly question the logic of this (presumably the lines in the ground are sized somewhere around 800-1,200A), but he says that this'll do, and he'll come back in the next few days to replace it. I lived there for another 8 or so months, and it was never replaced, but, well,... not my wires, so, um ¯\_(ツ)_/¯ I guess... W
-- -Barry Shein
Software Tool & Die | bzs@TheWorld.com | http://www.TheWorld.com Purveyors to the Trade | Voice: +1 617-STD-WRLD | 800-THE-WRLD The World: Since 1989 | A Public Information Utility | *oo*
-- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra
On 8/25/21 21:09, Warren Kumari wrote:
... and my "funny" story.
We used to live in San Jose. There was a large heat-wave, and much of SJC lost power because of A/C load, etc. Anyway, my wife and I go and camp in one of the office conference rooms for a few days because the office still has power and A/C. Eventually PG&E claims that power is back on our street, so we drive back to San Jose and... no power. I flag down a passing PG&E truck and ask if they know when it will *really* be back. Lineman says that it is. I say it isn't. He says it is. I say it isn't. He gets annoyed, opens up the pedestal box and sticks a meter in it, and agrees that I have no power. He then sticks the meter across the 800A fuse, and discovers that the fuse blew. "Ah. I can fix that fer you..." he says, and goes to the back of the truck... "Doh. I'm out of 800A fuses. Um.... er.... well, here is a 6,000A fuse, that'll do..."
I briefly question the logic of this (presumably the lines in the ground are sized somewhere around 800-1,200A), but he says that this'll do, and he'll come back in the next few days to replace it. I lived there for another 8 or so months, and it was never replaced, but, well,... not my wires, so, um ¯\_(ツ)_/¯ I guess...
You annoyed him enough to give you a larger fuse, and be done with you :-). Obviously, a safety hazard all on its own. Mark.
On Aug 25, 2021, at 1:30 PM, bzs@theworld.com wrote:
<OBLIGATORY FUNNY STORY>
Except maybe that one guy at Harvard who came to replace what turned out to be a 100+ year old, home made, "breaker" which fed our machine room which was hidden in a narrow dark hallway winding around our machine room behind an unmarked metal, locked doorway. I had no idea it existed but we had no power so I called for help.
It was just a single copper bar about the size of a small candy bar tensioned into hot clips. Probably 400A but who remembers.
He removed the old one confidently enough, grabbed the new one with rubber-handled pliers and gloves and...
Him: Have you ever played football?
Me: Actually, yes, I have, why?
Him: If something doesn't look right when I put this thing in just tackle me clear of it as hard and as fast as you can.
Me: Um, ok.
It all worked out fine and I wrote a memo that maybe Harvard could spring for a proper $500 breaker box?
</OBLIGATORY FUNNY STORY>
When I was working at the MCI training facility in 1994, I went into the power facility classroom where they had battery strings, rectifiers, transfer switches, etc for students to learn on. I noticed that every 8-10 feet there was an 8 foot long 3/4 inch PVC pipe with about 16 feet of rope threaded through it. When I asked what those were for, the instructor said “We will use those to pull people off the electricity in case anyone gets shocked.” I never heard that they were used, so that’s good. —Chris
On 8/25/21 20:30, bzs@theworld.com wrote:
Ok, I'll be the curmudgeon...
Is this really a problem in practice?
The issue is that "it can be". Solar inverter OEM's have long argued that UL 1741 is too stringent because the assumption is that linesmen always check for voltage on the line before working on it. Multiple layers of protection are the way to go here. Just as in our industry, just a route-map may not be enough. A route-map + prefix list is a better plan. Mark.
So the issue here is even a small 120vac current becomes a very fatal event at 7.2 or 11 or 14.4kV. It’s a safety issue for linepersons doing emergency restoration work. Ms. Lady Benjamin PD Cannon of Glencoe, ASCE 6x7 Networks & 6x7 Telecom, LLC CEO lb@6by7.net "The only fully end-to-end encrypted global telecommunications company in the world.” FCC License KJ6FJJ Sent from my iPhone via RFC1149.
On Aug 25, 2021, at 7:24 AM, Ethan O'Toole <telmnstr@757.org> wrote:
How would this not load the generator or inverter into oblivion? Not sure I understand your question. Say again, please.
If you hook 100KW of neighbors up to your 5KW/20% THD garden generator it would probably trip the breaker, or stall.
I suppose it could be an issue if it was a single house on a branch where the break being serviced was just that branch (rural customers.)
Was just curious why it wouldn't overload the generator trying to power all the neighbors houses if connected to the grid.
- Ethan
It's the specific combination of current and voltage that is hazardous. Too much current, through/across the heart, is the main, potentially fatal, hazard. This is why 120v GFCIs trip near 5 milliamps (mA). (20-30 mA in the wrong place is too much.) A voltage pushes a current through a resistance, be that insulation or skin or soil. A 12 volt car battery can produce several hundred amps current, enough to weld, if the terminals are shorted together, but a 12 volt battery doesn't have a high enough voltage to push that current through dry skin. It isn't dangerous to touch a single battery with dry hands. Static electricity can be thousands of volts, but at extremely low current. We feel it as the voltage is high enough, but it isn't actually dangerous (to people; electronic equipment is another matter). Holding the current constant at the danger threshold (20 mA), we can also look at the power levels for various voltages. 20mA at 120v = 2.4 watts. On the other side of the transformer, 20 mA at 7200v = 144 watts. Conclusion: a single small 150 watt inverter is powerful enough to be create a hazard for linemen working on an islanded section of 7200v powerline. There are several categories of electrical hazards, as delineated by voltage. Under 50v is generally considered to not be a shock hazard. More details on voltage categories: https://eecoonline.com/determining-safe-distances-from-electrical-hazards/ More details on GFCIs: https://en.wikipedia.org/wiki/Residual-current_device On Wed, Aug 25, 2021, 13:16 Lady Benjamin Cannon of Glencoe, ASCE < lb@6by7.net> wrote:
So the issue here is even a small 120vac current becomes a very fatal event at 7.2 or 11 or 14.4kV. It’s a safety issue for linepersons doing emergency restoration work.
Ms. Lady Benjamin PD Cannon of Glencoe, ASCE 6x7 Networks & 6x7 Telecom, LLC CEO lb@6by7.net "The only fully end-to-end encrypted global telecommunications company in the world.”
FCC License KJ6FJJ
Sent from my iPhone via RFC1149.
On Aug 25, 2021, at 7:24 AM, Ethan O'Toole <telmnstr@757.org> wrote:
How would this not load the generator or inverter into oblivion? Not sure I understand your question. Say again, please.
If you hook 100KW of neighbors up to your 5KW/20% THD garden generator it would probably trip the breaker, or stall.
I suppose it could be an issue if it was a single house on a branch where the break being serviced was just that branch (rural customers.)
Was just curious why it wouldn't overload the generator trying to power all the neighbors houses if connected to the grid.
- Ethan
On 8/25/21 20:15, Lady Benjamin Cannon of Glencoe, ASCE wrote:
So the issue here is even a small 120vac current becomes a very fatal event at 7.2 or 11 or 14.4kV. It’s a safety issue for linepersons doing emergency restoration work.
Yep, because the home generator will be boosted up by the neighborhood transformer, in the back-feed direction. Mark.
On Aug 25, 2021, at 10:04 AM, Mark Tinka <mark@tinka.africa> wrote:
You need to make these things fool-proof. We haven't traveled in over a year but the day we do, it's a recipe for disaster if the person that deals with this stuff is on the road when the power goes out back at home.
This is why I personally spent the $$ on a proper standby generator with multiple ATS for the multiple panels. - Jared
On 8/25/21 16:59, Jared Mauch wrote:
This is why I personally spent the $$ on a proper standby generator with multiple ATS for the multiple panels.
Same here. Massively painful, which led to some boring moments testing, testing and more testing. But after 5 months with electricians, electrical certifiers, battery vendors and inverter vendors (and a little voltage/amp sensor to capture slow voltage grid brownouts that kept tripping my battery), it's been solid for nearly a year. And looking good. I can now travel and not worry about the Mrs. waking me up from my sleep, on the far side of the world :-). Mark.
Back feed is a significant problem but bringing a generator that is not synchronized to the grid can have dramatic results, typically only once Dave
On Aug 25, 2021, at 11:11 AM, Mark Tinka <mark@tinka.africa> wrote:
On 8/25/21 16:59, Jared Mauch wrote:
This is why I personally spent the $$ on a proper standby generator with multiple ATS for the multiple panels.
Same here.
Massively painful, which led to some boring moments testing, testing and more testing. But after 5 months with electricians, electrical certifiers, battery vendors and inverter vendors (and a little voltage/amp sensor to capture slow voltage grid brownouts that kept tripping my battery), it's been solid for nearly a year. And looking good.
I can now travel and not worry about the Mrs. waking me up from my sleep, on the far side of the world :-).
Mark.
On 8/25/21 11:26 AM, Dave wrote:
Back feed is a significant problem but bringing a generator that is not synchronized to the grid can have dramatic results, typically only once
This, IMO, is a great thread, lots of good reading here. My $dayjob is at a site where the previous occupants did indeed operate, under PE supervision and special permit from the electric cooperative, grid-synchronized generators. Most of the required switchgear is still here, including the dual-incandescent-bulb sync indicators. Since we don't have the required 24x7 PE (that's licensed Professional Engineer, by the way) supervision, we don't do this, but over a period of several years had normal ATS setups with isolated generation installed, with a more distributed setup with only critical loads on UPS. But grid-sync generation is a form of UPS. The process of going from grid being offline, then adjusting the generator governors to sync-in and closing the main breakers (three of them, 2,500A each) at the very instant of sync, was apparently quite the sight to behold, with the sync indicators blinking and pulsing, until they locked in.... At the 2,500A level it is definitely not a pretty sight to reclose out of sync. Synchronous generators were more reliable and less expensive in those days than battery backups, especially in the megawatt class, and if you only required intermittent uninterruptable power. The largest battery backup on site was 500KVA and was a Piller motor-generator with a huge battery on the DC bus. The total site drew a bit over 2MW on a normal day, and so loads were prioritized and during critical operations only the required generator capacity was brought online in synchronous mode. The main breakers were set up with power-loss instant trip; when we went ATS and regular generator operations (much much less load for us) we disabled the power-loss trip functions on the three 2,500A mains. I have some friends who work for the local electric cooperative, and all of them have backfeed stories. Around here, which is very rural, it's not at all uncommon to have a single house isolated on a distribution spur; nor is it at all uncommon for some people to have the 'suicide dryer cord' 'ATS' in use. One story I heard was that one individual had been a repeat offender, and several line workers had gotten bit (none were injured, thankfully) by his 4KVA generator; so after the repair of one outage, a line worker taught the individual a lesson by hitting the recloser without letting the individual know ahead of time (they had been letting the individual know that power was coming back on) and watching the individual's generator, out in his yard, explode from the out-of-sync condition.
On 8/30/21 22:13, Lamar Owen wrote:
I have some friends who work for the local electric cooperative, and all of them have backfeed stories. Around here, which is very rural, it's not at all uncommon to have a single house isolated on a distribution spur; nor is it at all uncommon for some people to have the 'suicide dryer cord' 'ATS' in use. One story I heard was that one individual had been a repeat offender, and several line workers had gotten bit (none were injured, thankfully) by his 4KVA generator; so after the repair of one outage, a line worker taught the individual a lesson by hitting the recloser without letting the individual know ahead of time (they had been letting the individual know that power was coming back on) and watching the individual's generator, out in his yard, explode from the out-of-sync condition.
As General Taylor in "Delta Force 2" used to lament, "Sh**! Always the hard way :-)". https://youtu.be/pJIGy4zHo6E?t=124 Mark.
I told my wife that she is my critical load as such I like to treat our place like a datacenter. House wide UPS for all lights and all bedroom and office outlets, large generator system, ATS and lots of fuel. Last time I was at a nanog and the power went out she chuckled when I told her it was out, she had just come home from work and driven right into the garage with all the lights on thinking the utility was still working. I did all my commissioning and calculations myself, even coordinated breakers for both sources into the sub panels, but I'm far from a home DIY when it comes to electrical. My home 277/480v service is pretty cute compared to the stuff I normally play with and design. I've cabled my other portables into panels at people's houses before but I refuse to talk them through how to do it, if you don't know how to properly pull the utility breakers etc you have no business temping anything up, and making cables that make it easy is irresponsible safety wise. Power is serious business and mistakes can be very dangerous. The last few days has me feeling for all the folks keeping the hospitals and critical facilities running in Louisiana, seems like most made it through pretty well, huge testament to planning and the reliability of backup systems. -----Original Message----- From: NANOG <nanog-bounces+john=vanoppen.com@nanog.org> On Behalf Of Mark Tinka Sent: Wednesday, August 25, 2021 8:12 AM To: Jared Mauch <jared@puck.nether.net> Cc: nanog@nanog.org Subject: Re: Reminder: Never connect a generator to home wiring without transfer switch On 8/25/21 16:59, Jared Mauch wrote:
This is why I personally spent the $$ on a proper standby generator with multiple ATS for the multiple panels.
Same here. Massively painful, which led to some boring moments testing, testing and more testing. But after 5 months with electricians, electrical certifiers, battery vendors and inverter vendors (and a little voltage/amp sensor to capture slow voltage grid brownouts that kept tripping my battery), it's been solid for nearly a year. And looking good. I can now travel and not worry about the Mrs. waking me up from my sleep, on the far side of the world :-). Mark.
On 8/31/21 07:37, John van Oppen wrote:
I told my wife that she is my critical load as such I like to treat our place like a datacenter. House wide UPS for all lights and all bedroom and office outlets, large generator system, ATS and lots of fuel. Last time I was at a nanog and the power went out she chuckled when I told her it was out, she had just come home from work and driven right into the garage with all the lights on thinking the utility was still working.
Me too :-). She wasn't amused when all the contractors are faffing about for 8 months installing the system. But she is pleased when the power goes out and we just keep going.
I did all my commissioning and calculations myself, even coordinated breakers for both sources into the sub panels, but I'm far from a home DIY when it comes to electrical. My home 277/480v service is pretty cute compared to the stuff I normally play with and design.
I've cabled my other portables into panels at people's houses before but I refuse to talk them through how to do it, if you don't know how to properly pull the utility breakers etc you have no business temping anything up, and making cables that make it easy is irresponsible safety wise.
Power is serious business and mistakes can be very dangerous.
I did all my design and planning too, but used qualified contractors to install and certify the setup. I am not an electrician. I won't even replace a breaker panel cover label sticker myself. I don't play those games :-). Mark.
I just wish the electrical code would permit or require certain low cost things which make temporary generator connections more likely to be safe. For example, code requires most furnaces to be hardwired. But a furnace is one of the first things you want on a generator in an extended winter power outage. If instead of hardwired, the code required plug and socket connections at each 120v furnace then Joe homeowner would be more likely to run an extension cord from his generator to his furnace instead of trying to rig up his generator with a suicide cord. On Mon, Aug 30, 2021, 11:38 PM John van Oppen <john@vanoppen.com> wrote:
I told my wife that she is my critical load as such I like to treat our place like a datacenter. House wide UPS for all lights and all bedroom and office outlets, large generator system, ATS and lots of fuel. Last time I was at a nanog and the power went out she chuckled when I told her it was out, she had just come home from work and driven right into the garage with all the lights on thinking the utility was still working.
I did all my commissioning and calculations myself, even coordinated breakers for both sources into the sub panels, but I'm far from a home DIY when it comes to electrical. My home 277/480v service is pretty cute compared to the stuff I normally play with and design.
I've cabled my other portables into panels at people's houses before but I refuse to talk them through how to do it, if you don't know how to properly pull the utility breakers etc you have no business temping anything up, and making cables that make it easy is irresponsible safety wise.
Power is serious business and mistakes can be very dangerous.
The last few days has me feeling for all the folks keeping the hospitals and critical facilities running in Louisiana, seems like most made it through pretty well, huge testament to planning and the reliability of backup systems.
-----Original Message----- From: NANOG <nanog-bounces+john=vanoppen.com@nanog.org> On Behalf Of Mark Tinka Sent: Wednesday, August 25, 2021 8:12 AM To: Jared Mauch <jared@puck.nether.net> Cc: nanog@nanog.org Subject: Re: Reminder: Never connect a generator to home wiring without transfer switch
On 8/25/21 16:59, Jared Mauch wrote:
This is why I personally spent the $$ on a proper standby generator with multiple ATS for the multiple panels.
Same here.
Massively painful, which led to some boring moments testing, testing and more testing. But after 5 months with electricians, electrical certifiers, battery vendors and inverter vendors (and a little voltage/amp sensor to capture slow voltage grid brownouts that kept tripping my battery), it's been solid for nearly a year. And looking good.
I can now travel and not worry about the Mrs. waking me up from my sleep, on the far side of the world :-).
Mark.
On 8/31/21 11:11, Forrest Christian (List Account) wrote:
I just wish the electrical code would permit or require certain low cost things which make temporary generator connections more likely to be safe.
For example, code requires most furnaces to be hardwired. But a furnace is one of the first things you want on a generator in an extended winter power outage. If instead of hardwired, the code required plug and socket connections at each 120v furnace then Joe homeowner would be more likely to run an extension cord from his generator to his furnace instead of trying to rig up his generator with a suicide cord.
Are you referring to a forced-air central electric furnace? Mark.
Yes. Or any other furnace where the electricity is only used for circulation of the heat. Gas fired Hot water furnaces would be another example where there is minimal electricity used to run the furnace controls and circulate the hot water. All of these run on 120V and usually well under 15A. It's silly that you are prohibited by code from installing a dedicated plug and socket for these. On Tue, Aug 31, 2021, 3:19 AM Mark Tinka <mark@tinka.africa> wrote:
On 8/31/21 11:11, Forrest Christian (List Account) wrote:
I just wish the electrical code would permit or require certain low cost things which make temporary generator connections more likely to be safe.
For example, code requires most furnaces to be hardwired. But a furnace is one of the first things you want on a generator in an extended winter power outage. If instead of hardwired, the code required plug and socket connections at each 120v furnace then Joe homeowner would be more likely to run an extension cord from his generator to his furnace instead of trying to rig up his generator with a suicide cord.
Are you referring to a forced-air central electric furnace?
Mark.
On 8/31/21 12:26, Forrest Christian (List Account) wrote:
Yes. Or any other furnace where the electricity is only used for circulation of the heat. Gas fired Hot water furnaces would be another example where there is minimal electricity used to run the furnace controls and circulate the hot water.
Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light. But fully-electric heating has a much higher impact on energy sources (heat pumps being the least). I believe typical electric central furnaces are anywhere between 10kW - 15kW systems. Would a standard 4kVA - 8kVA generator for average Jane cut it? Not sure. Then again, I live in a more forgiving climate, so I have a very limited need to understand this better. But I can understand why the code has not caught up to this yet, and insists on hard-wiring the devices... because the majority of home and buildings will still be using all-electric equipment that require plenty of energy, where things can go wrong if you allow Jane to just run her suicide cord any way she may like. Yes, there may be more folk moving over to other energy sources that eliminate or reduce the need for electricity, but the code has to cater for the wider demographic. Mark.
Mark, I think you’re forgetting about the all-important blower fan in a gas-fired furnace. That said, the reason the code requires furnaces to be hardwired is to ensure that the blower interlock system can’t be bypassed. An electrical interlock ties a heat recover ventilator to circulation air blower operation of a forced-air furnace system. This ensure that the blower circulates supply and return air within the structure. A plug-in power source leads to the possibility that this interlock could be accidentally defeated, resulting in an overheat within the flame box. -mel
On Aug 31, 2021, at 3:38 AM, Mark Tinka <mark@tinka.africa> wrote:
On 8/31/21 12:26, Forrest Christian (List Account) wrote:
Yes. Or any other furnace where the electricity is only used for circulation of the heat. Gas fired Hot water furnaces would be another example where there is minimal electricity used to run the furnace controls and circulate the hot water.
Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light.
But fully-electric heating has a much higher impact on energy sources (heat pumps being the least).
I believe typical electric central furnaces are anywhere between 10kW - 15kW systems. Would a standard 4kVA - 8kVA generator for average Jane cut it? Not sure.
Then again, I live in a more forgiving climate, so I have a very limited need to understand this better.
But I can understand why the code has not caught up to this yet, and insists on hard-wiring the devices... because the majority of home and buildings will still be using all-electric equipment that require plenty of energy, where things can go wrong if you allow Jane to just run her suicide cord any way she may like. Yes, there may be more folk moving over to other energy sources that eliminate or reduce the need for electricity, but the code has to cater for the wider demographic.
Mark.
On 8/31/21 16:06, Mel Beckman wrote:
I think you’re forgetting about the all-important blower fan in a gas-fired furnace.
Well, I was referring to a pure electric furnace, not one that uses a blower over a gas-fired one :-). In that case, the blower is not a major draw on power. But again, we don't have those things here, so :-).
That said, the reason the code requires furnaces to be hardwired is to ensure that the blower interlock system can’t be bypassed. An electrical interlock ties a heat recover ventilator to circulation air blower operation of a forced-air furnace system. This ensure that the blower circulates supply and return air within the structure. A plug-in power source leads to the possibility that this interlock could be accidentally defeated, resulting in an overheat within the flame box.
Makes sense. Does this, then, mean that if the blower itself were to fail, the gas burner would not light? Mark.
Mark, But you said “Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light.” There is no gas-fired furnace I know of that doesn’t require a blower fan. How else does the heat get out of the furnace? To answer your question, you need to understand that this safety system has two components. The first component, the furnace interlock relay, is designed to interlock the blower with the forced-air system, which also includes an outside air supply valve. When the blower is energized, a circuit inside the furnace gets power. The blower and furnace operate continuously when this circuit is energized, and the supply valve opens and closes as needed to ensure the air doesn’t get stale. The safety second component is the limit switch, which primarily turns the blower fan on and off, but also has a safety role. When the temperature in the air supply plenum gets too hot, the limit switch turns off the furnace burner (or boiler, in a water-based system) to prevent damage, and possibly a fire, from overheating. The actual state mechanics are thus not as simple as “if the blower fails the furnace won’t light”. And it’s because of these complex state mechanics that furnace electricity is hard wired. Without AC power, no furnace can operate in a power outage. So that’s certainly not “no impact” from a utility failure. But the many thousands of deaths that occurred in homes and offices before these safety systems were put into the code is why you need a generator transfer switch if you want heat (or A/C) in your home during an outage. -mel
On Aug 31, 2021, at 7:15 AM, Mark Tinka <mark@tinka.africa> wrote:
On 8/31/21 16:06, Mel Beckman wrote:
I think you’re forgetting about the all-important blower fan in a gas-fired furnace.
Well, I was referring to a pure electric furnace, not one that uses a blower over a gas-fired one :-).
In that case, the blower is not a major draw on power.
But again, we don't have those things here, so :-).
That said, the reason the code requires furnaces to be hardwired is to ensure that the blower interlock system can’t be bypassed. An electrical interlock ties a heat recover ventilator to circulation air blower operation of a forced-air furnace system. This ensure that the blower circulates supply and return air within the structure. A plug-in power source leads to the possibility that this interlock could be accidentally defeated, resulting in an overheat within the flame box.
Makes sense.
Does this, then, mean that if the blower itself were to fail, the gas burner would not light?
Mark.
Is this conversation really taking place on NANOG? Don't backfeed power. Got it. Stupid people are going to be stupid, we won't solve it here. Josh Luthman 24/7 Help Desk: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Tue, Aug 31, 2021 at 10:41 AM Mel Beckman <mel@beckman.org> wrote:
Mark,
But you said “Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light.” There is no gas-fired furnace I know of that doesn’t require a blower fan. How else does the heat get out of the furnace?
To answer your question, you need to understand that this safety system has two components. The first component, the furnace interlock relay, is designed to interlock the blower with the forced-air system, which also includes an outside air supply valve. When the blower is energized, a circuit inside the furnace gets power. The blower and furnace operate continuously when this circuit is energized, and the supply valve opens and closes as needed to ensure the air doesn’t get stale.
The safety second component is the limit switch, which primarily turns the blower fan on and off, but also has a safety role. When the temperature in the air supply plenum gets too hot, the limit switch turns off the furnace burner (or boiler, in a water-based system) to prevent damage, and possibly a fire, from overheating.
The actual state mechanics are thus not as simple as “if the blower fails the furnace won’t light”. And it’s because of these complex state mechanics that furnace electricity is hard wired.
Without AC power, no furnace can operate in a power outage. So that’s certainly not “no impact” from a utility failure. But the many thousands of deaths that occurred in homes and offices before these safety systems were put into the code is why you need a generator transfer switch if you want heat (or A/C) in your home during an outage.
-mel
On Aug 31, 2021, at 7:15 AM, Mark Tinka <mark@tinka.africa> wrote:
On 8/31/21 16:06, Mel Beckman wrote:
I think you’re forgetting about the all-important blower fan in a gas-fired furnace.
Well, I was referring to a pure electric furnace, not one that uses a blower over a gas-fired one :-).
In that case, the blower is not a major draw on power.
But again, we don't have those things here, so :-).
That said, the reason the code requires furnaces to be hardwired is to ensure that the blower interlock system can’t be bypassed. An electrical interlock ties a heat recover ventilator to circulation air blower operation of a forced-air furnace system. This ensure that the blower circulates supply and return air within the structure. A plug-in power source leads to the possibility that this interlock could be accidentally defeated, resulting in an overheat within the flame box.
Makes sense.
Does this, then, mean that if the blower itself were to fail, the gas burner would not light?
Mark.
It’s germane to NANOG. Just last week I visited a “data center” that uses a roll up generator and a cheater cord to power the racks. “Oh, this is safe”, they told me. “We have a policy that you must throw the main breaker before plugging in the generator. Since you have to open the garage door to wheel in the generator (!), you walk right by the switchgear and a sign that reminds you to throw the breaker.” Code enforcement is on the way. :) -mel On Aug 31, 2021, at 7:50 AM, Josh Luthman <josh@imaginenetworksllc.com> wrote: Is this conversation really taking place on NANOG? Don't backfeed power. Got it. Stupid people are going to be stupid, we won't solve it here. Josh Luthman 24/7 Help Desk: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Tue, Aug 31, 2021 at 10:41 AM Mel Beckman <mel@beckman.org<mailto:mel@beckman.org>> wrote: Mark, But you said “Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light.” There is no gas-fired furnace I know of that doesn’t require a blower fan. How else does the heat get out of the furnace? To answer your question, you need to understand that this safety system has two components. The first component, the furnace interlock relay, is designed to interlock the blower with the forced-air system, which also includes an outside air supply valve. When the blower is energized, a circuit inside the furnace gets power. The blower and furnace operate continuously when this circuit is energized, and the supply valve opens and closes as needed to ensure the air doesn’t get stale. The safety second component is the limit switch, which primarily turns the blower fan on and off, but also has a safety role. When the temperature in the air supply plenum gets too hot, the limit switch turns off the furnace burner (or boiler, in a water-based system) to prevent damage, and possibly a fire, from overheating. The actual state mechanics are thus not as simple as “if the blower fails the furnace won’t light”. And it’s because of these complex state mechanics that furnace electricity is hard wired. Without AC power, no furnace can operate in a power outage. So that’s certainly not “no impact” from a utility failure. But the many thousands of deaths that occurred in homes and offices before these safety systems were put into the code is why you need a generator transfer switch if you want heat (or A/C) in your home during an outage. -mel
On Aug 31, 2021, at 7:15 AM, Mark Tinka <mark@tinka.africa> wrote:
On 8/31/21 16:06, Mel Beckman wrote:
I think you’re forgetting about the all-important blower fan in a gas-fired furnace.
Well, I was referring to a pure electric furnace, not one that uses a blower over a gas-fired one :-).
In that case, the blower is not a major draw on power.
But again, we don't have those things here, so :-).
That said, the reason the code requires furnaces to be hardwired is to ensure that the blower interlock system can’t be bypassed. An electrical interlock ties a heat recover ventilator to circulation air blower operation of a forced-air furnace system. This ensure that the blower circulates supply and return air within the structure. A plug-in power source leads to the possibility that this interlock could be accidentally defeated, resulting in an overheat within the flame box.
Makes sense.
Does this, then, mean that if the blower itself were to fail, the gas burner would not light?
Mark.
On Tue, Aug 31, 2021 at 12:17 PM Mel Beckman <mel@beckman.org> wrote:
It’s germane to NANOG. Just last week I visited a “data center” that uses a roll up generator and a cheater cord to power the racks. “Oh, this is safe”, they told me. “We have a policy that you must throw the main breaker before plugging in the generator. Since you have to open the garage door to wheel in the generator (!), you walk right by the switchgear and a sign that reminds you to throw the breaker.”
Many many (> 20 ) years ago I worked for a small ISP in New York. The official disaster recovery plan included: "Drive over to Warren's house {Address]. Under the deck, you will find a key hanging on a nail. Use this to open the closet and take out the generator [SAFETY WARNING: it is heavy]. Put it in your car, and drive back to the office. Please in the big cable <picture>, *then* start the generator and let it idle for a few minutes. Then flip the big switch marked TRANSFER." Anyway, hurricane Floyd comes along and knocks out one feed to the office/datacenter, and we initiate the DR plan. One of the employees has a station wagon, so he's the one designate to go fetch the generator -- but, first we have to unload the nine 30lb bags of dry cat food which he inexplicably has in the back of the car. I still have no idea why, but... Anyway... The "datacenter" is 8 relay racks in the front of the office, powered by around 25 consumer/soho style UPSs. Of course, the rear of the racks are ~4 feet from the wall, and the UPSs are buried under many feet of cable, etc... oh, and the room lights have no battery backup. We immediately start stumbling around behind the racks with flashlights, trying to shuffle things around, powering off unneeded devices (PM4s and TNT MAX draw much power), etc. We then start cycling out UPSs with low battery levels for more charged ones (move the second PSU to a charged UPS, unplug the first one, move that to new UPS, etc) and using some UPSs to recharge other UPSs connected to devices that don't have redundant power supplies, etc. This is all a huge mess of wires, we only have flashlights, there isn't much space, etc -- and somehow someone manages to hook the output of UPS A -> UPS B -> UPS C -> UPS D. This all worked OK... right up until someone managed to hook the output of UPS D back to the input of UPS A. UPSs might claim to have "Pure Sine(TM)" output, but, well, they don't... and so they all start clicking like a swarm of angry wasps, and then they all simultaneously let out the magic smoke, as well as much fire and noise... I'm still convinced that I managed to jump right over the racks when this occurred. W
Code enforcement is on the way. :)
-mel
On Aug 31, 2021, at 7:50 AM, Josh Luthman <josh@imaginenetworksllc.com> wrote:
Is this conversation really taking place on NANOG?
Don't backfeed power. Got it. Stupid people are going to be stupid, we won't solve it here.
Josh Luthman 24/7 Help Desk: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373
On Tue, Aug 31, 2021 at 10:41 AM Mel Beckman <mel@beckman.org> wrote:
Mark,
But you said “Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light.” There is no gas-fired furnace I know of that doesn’t require a blower fan. How else does the heat get out of the furnace?
To answer your question, you need to understand that this safety system has two components. The first component, the furnace interlock relay, is designed to interlock the blower with the forced-air system, which also includes an outside air supply valve. When the blower is energized, a circuit inside the furnace gets power. The blower and furnace operate continuously when this circuit is energized, and the supply valve opens and closes as needed to ensure the air doesn’t get stale.
The safety second component is the limit switch, which primarily turns the blower fan on and off, but also has a safety role. When the temperature in the air supply plenum gets too hot, the limit switch turns off the furnace burner (or boiler, in a water-based system) to prevent damage, and possibly a fire, from overheating.
The actual state mechanics are thus not as simple as “if the blower fails the furnace won’t light”. And it’s because of these complex state mechanics that furnace electricity is hard wired.
Without AC power, no furnace can operate in a power outage. So that’s certainly not “no impact” from a utility failure. But the many thousands of deaths that occurred in homes and offices before these safety systems were put into the code is why you need a generator transfer switch if you want heat (or A/C) in your home during an outage.
-mel
On Aug 31, 2021, at 7:15 AM, Mark Tinka <mark@tinka.africa> wrote:
On 8/31/21 16:06, Mel Beckman wrote:
I think you’re forgetting about the all-important blower fan in a gas-fired furnace.
Well, I was referring to a pure electric furnace, not one that uses a blower over a gas-fired one :-).
In that case, the blower is not a major draw on power.
But again, we don't have those things here, so :-).
That said, the reason the code requires furnaces to be hardwired is to ensure that the blower interlock system can’t be bypassed. An electrical interlock ties a heat recover ventilator to circulation air blower operation of a forced-air furnace system. This ensure that the blower circulates supply and return air within the structure. A plug-in power source leads to the possibility that this interlock could be accidentally defeated, resulting in an overheat within the flame box.
Makes sense.
Does this, then, mean that if the blower itself were to fail, the gas burner would not light?
Mark.
-- “If you have an important point to make, don’t try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time-a tremendous whack.” -- Winston Churchill -- Perhaps they really do strive for incomprehensibility in their specs. After all, when the liturgy was in Latin, the laity knew their place. -- Michael Padlipsky
On 8/31/21 16:41, Mel Beckman wrote:
But you said “Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light.” There is no gas-fired furnace I know of that doesn’t require a blower fan. How else does the heat get out of the furnace?
I was conceptualizing it the same way we have on-demand or tank-based gas water heaters here, where the heat is not distributed by a blower. Like I said before, we don't generally use furnaces in this part of the world to heat homes. So I don't have experience with that :-).
To answer your question, you need to understand that this safety system has two components. The first component, the furnace interlock relay, is designed to interlock the blower with the forced-air system, which also includes an outside air supply valve. When the blower is energized, a circuit inside the furnace gets power. The blower and furnace operate continuously when this circuit is energized, and the supply valve opens and closes as needed to ensure the air doesn’t get stale.
The safety second component is the limit switch, which primarily turns the blower fan on and off, but also has a safety role. When the temperature in the air supply plenum gets too hot, the limit switch turns off the furnace burner (or boiler, in a water-based system) to prevent damage, and possibly a fire, from overheating.
The actual state mechanics are thus not as simple as “if the blower fails the furnace won’t light”. And it’s because of these complex state mechanics that furnace electricity is hard wired.
You learn something new everyday. Thanks, Mel.
Without AC power, no furnace can operate in a power outage. So that’s certainly not “no impact” from a utility failure. But the many thousands of deaths that occurred in homes and offices before these safety systems were put into the code is why you need a generator transfer switch if you want heat (or A/C) in your home during an outage.
Makes sense. My solar PV-based water heating system requires an AC reference to make solar power to energize the water tank element. If there is a loss of AC, it shuts off (not unlike a regular UL 1741-compliant PV inverter). To workaround that, I asked the vendor to add a UPS input, where I can attach a UPS that the system can use as a reference, to keep making solar power in the event of loss of grid mains. Of course, that was before I had whole-home backup, but it did the job during the gap. Mark.
On Tue, Aug 31, 2021 at 10:44 AM Mel Beckman <mel@beckman.org> wrote:
Mark,
But you said “Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light.” There is no gas-fired furnace I know of that doesn’t require a blower fan. How else does the heat get out of the furnace?
To answer your question, you need to understand that this safety system has two components. The first component, the furnace interlock relay, is designed to interlock the blower with the forced-air system, which also includes an outside air supply valve. When the blower is energized, a circuit inside the furnace gets power. The blower and furnace operate continuously when this circuit is energized, and the supply valve opens and closes as needed to ensure the air doesn’t get stale.
The safety second component is the limit switch, which primarily turns the blower fan on and off, but also has a safety role. When the temperature in the air supply plenum gets too hot, the limit switch turns off the furnace burner (or boiler, in a water-based system) to prevent damage, and possibly a fire, from overheating.
The actual state mechanics are thus not as simple as “if the blower fails the furnace won’t light”. And it’s because of these complex state mechanics that furnace electricity is hard wired.
Without AC power, no furnace can operate in a power outage.
Depending on what you mean by furnace -- in some places, the term is used to cover basically any permanent (usually non-wood) heater. We have something like this in a holiday/weekend property: https://www.vermontcastings.com/products/radiance-direct-vent-gas-stove?page... It has an (optional) blower motor on the back to help with circulating the heat, and also plugs in to allow easier starting, but if mains power isn't available it can still be started with 4 "D" cells, or, if you are willing to scrummage around underneath (where all the spiders live!), you can hold down an override switch and start it by clicking a piezo button (or, if you really don't like the hair on your arm, with a match). Even without the blower motor operating, it makes a surprising amount of heat, and also looks purdy... W P.S: Yes, we've clearly gotten away from the "Don't plug a generator in without a transfer switch, don't run a generator indoors, remember to test your smoke alarms every N, brush yer teeth, eat an apple, regularly exercise, drink plenty of water, etc., but sometimes it's nice to just have a chat - I miss NANOG...)
So that’s certainly not “no impact” from a utility failure. But the many thousands of deaths that occurred in homes and offices before these safety systems were put into the code is why you need a generator transfer switch if you want heat (or A/C) in your home during an outage.
-mel
On Aug 31, 2021, at 7:15 AM, Mark Tinka <mark@tinka.africa> wrote:
On 8/31/21 16:06, Mel Beckman wrote:
I think you’re forgetting about the all-important blower fan in a gas-fired furnace.
Well, I was referring to a pure electric furnace, not one that uses a blower over a gas-fired one :-).
In that case, the blower is not a major draw on power.
But again, we don't have those things here, so :-).
That said, the reason the code requires furnaces to be hardwired is to ensure that the blower interlock system can’t be bypassed. An electrical interlock ties a heat recover ventilator to circulation air blower operation of a forced-air furnace system. This ensure that the blower circulates supply and return air within the structure. A plug-in power source leads to the possibility that this interlock could be accidentally defeated, resulting in an overheat within the flame box.
Makes sense.
Does this, then, mean that if the blower itself were to fail, the gas burner would not light?
Mark.
-- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra
On 8/31/21 17:07, Warren Kumari wrote:
Depending on what you mean by furnace -- in some places, the term is used to cover basically any permanent (usually non-wood) heater. We have something like this in a holiday/weekend property: https://www.vermontcastings.com/products/radiance-direct-vent-gas-stove?page... <https://www.vermontcastings.com/products/radiance-direct-vent-gas-stove?page=Options>
Pretty much all the furnaces I've seen in southern Africa are wood-fired, with a vent that trails up into the ceiling, or comes out of the house as a chimney. The heat is radiated either via the vent or directly from the front access, or both. Mark.
Here’s an example of the type I was describing in my previous post: https://diy.stackexchange.com/questions/23330/how-can-i-retrofit-this-existi... (Primarily for the image, not the subject matter of the page)
On Aug 31, 2021, at 07:41 , Mel Beckman <mel@beckman.org> wrote:
Mark,
But you said “Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light.” There is no gas-fired furnace I know of that doesn’t require a blower fan. How else does the heat get out of the furnace?
For central heating, you’re absolutely correct. However, there used to be (don’t know if they are still sold in the US) wall-mounted single and/or double-sided gas radiant heaters that distributed hot air out of the top via convection and radiated heat from a vertical heat exchanger as well.
To answer your question, you need to understand that this safety system has two components. The first component, the furnace interlock relay, is designed to interlock the blower with the forced-air system, which also includes an outside air supply valve. When the blower is energized, a circuit inside the furnace gets power. The blower and furnace operate continuously when this circuit is energized, and the supply valve opens and closes as needed to ensure the air doesn’t get stale.
I have no such valve (external air) in my house. I suspect this is applicable primarily in industrial/commercial HVAC. The blower interlock is also slightly different in how it operates on my system. When the thermostat calls for heat, the electronic ignition starts up. When it reaches ignition temperature, the gas solenoid is activated and the burner lights off. If ignition is not detected within a set period of time, the safeties will shut the system down to error mode. Assuming ignition is detected, the blower is engaged. If the blower fails to start or the temperature in the flame box exceeds a certain value, then the safeties will shut the system down to error mode.
The safety second component is the limit switch, which primarily turns the blower fan on and off, but also has a safety role. When the temperature in the air supply plenum gets too hot, the limit switch turns off the furnace burner (or boiler, in a water-based system) to prevent damage, and possibly a fire, from overheating.
The actual state mechanics are thus not as simple as “if the blower fails the furnace won’t light”. And it’s because of these complex state mechanics that furnace electricity is hard wired.
Without AC power, no furnace can operate in a power outage. So that’s certainly not “no impact” from a utility failure. But the many thousands of deaths that occurred in homes and offices before these safety systems were put into the code is why you need a generator transfer switch if you want heat (or A/C) in your home during an outage.
Yep… Unless you have an old-fashioned fireplace, in which case, you can have heat without electricity. Owen
I guess I sort of started this part of the thread because I was thinking: Gosh, I sure hope people who own home generators read NANOG regularly (or linepersons have some other plan). -- -Barry Shein Software Tool & Die | bzs@TheWorld.com | http://www.TheWorld.com Purveyors to the Trade | Voice: +1 617-STD-WRLD | 800-THE-WRLD The World: Since 1989 | A Public Information Utility | *oo*
On Aug 31, 2021, at 07:15 , Mark Tinka <mark@tinka.africa> wrote:
On 8/31/21 16:06, Mel Beckman wrote:
I think you’re forgetting about the all-important blower fan in a gas-fired furnace.
Well, I was referring to a pure electric furnace, not one that uses a blower over a gas-fired one :-).
In that case, the blower is not a major draw on power.
But again, we don't have those things here, so :-).
That said, the reason the code requires furnaces to be hardwired is to ensure that the blower interlock system can’t be bypassed. An electrical interlock ties a heat recover ventilator to circulation air blower operation of a forced-air furnace system. This ensure that the blower circulates supply and return air within the structure. A plug-in power source leads to the possibility that this interlock could be accidentally defeated, resulting in an overheat within the flame box.
Makes sense.
Does this, then, mean that if the blower itself were to fail, the gas burner would not light?
Yes… Sort of. In most cases, the burner lights off ever so slightly before the blower starts up (if you’ve ever tried to light a campfire in high wind, you’ll understand why). However, if the blower fails to start producing wind on demand, the gas to the burner will be shutoff and the system will go into an error mode requiring a reboot or service intervention. Of course a reboot without correcting the blower issue probably results in a repeat of the process. Owen
On 8/31/21 07:06, Mel Beckman wrote:
Mark,
I think you’re forgetting about the all-important blower fan in a gas-fired furnace.
We're *really* getting in the weeds here. A single note to the list about not backfeeding has really blown up.
That said, the reason the code requires furnaces to be hardwired is to ensure that the blower interlock system can’t be bypassed. An electrical interlock ties a heat recover ventilator to circulation air blower operation of a forced-air furnace system. This ensure that the blower circulates supply and return air within the structure. A plug-in power source leads to the possibility that this interlock could be accidentally defeated, resulting in an overheat within the flame box.
This doesn't compute. In a conventional forced air furnace the 24V transformer operating the thermostat, logic, and gas valve is powered by the same electrical source as the blower. In the event of someone unplugging the furnace, or for that matter a power failure, the gas valve will close when the power disappears. Yes, there are old-school pilot light thermocouple-powered gas valves in wall and floor heaters that require no electricity at all. They rely on convection to distribute the heat, not a blower. -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
In this old (really not all that old comparatively, mid-late 19th c) Boston neighborhood there are apparently still appliances w/o thermocouple gas shut-offs. I know because a local gas guy I was talking to told me it was a nightmare if they had to shut off the gas in the street. They had a list of those homes and had to send people to them one by one when the gas came back on. Go ahead, tell me that's not code...hahaha, that's not code, but this is Boston. -- -Barry Shein Software Tool & Die | bzs@TheWorld.com | http://www.TheWorld.com Purveyors to the Trade | Voice: +1 617-STD-WRLD | 800-THE-WRLD The World: Since 1989 | A Public Information Utility | *oo*
On Aug 31, 2021, at 03:36 , Mark Tinka <mark@tinka.africa> wrote:
On 8/31/21 12:26, Forrest Christian (List Account) wrote:
Yes. Or any other furnace where the electricity is only used for circulation of the heat. Gas fired Hot water furnaces would be another example where there is minimal electricity used to run the furnace controls and circulate the hot water.
Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light.
Depends… Forced air gas-fired furnaces (as in most central heating systems) also need something to run the squirrel-cage blower. Most gas furnaces that are not forced air these days do require some electricity to run the thermostat, but that’s usually generated from the pilot light (very low current 24VAC for the “C” wire). Don’t get me started on the whole mess that is the C-Wire and the various hacks to accommodate legacy systems that don’t have one.
But fully-electric heating has a much higher impact on energy sources (heat pumps being the least).
Yep.
I believe typical electric central furnaces are anywhere between 10kW - 15kW systems. Would a standard 4kVA - 8kVA generator for average Jane cut it? Not sure.
15kW is 1.5kVA in a simple radiant electric heat application. (it’s a simple resistive load with no power factor weirdness). Whether you could do this with 4-8kVA depends on what else you’re trying to run. If you’ve got 3 teenagers all trying to run blow-driers at the same time and you also want to run your electric clothes dryer, you’re probably SOL. If you’re trying to charge a cellphone, a laptop, and run a mostly closed refrigerator/freezer, you’re probably OK.
Then again, I live in a more forgiving climate, so I have a very limited need to understand this better.
Louisiana actually mostly doesn’t get all that cold. In fact, AC is a more likely issue in Louisiana than heating. In the winter, Tennessee gets down to ~9.4C on average (49F), which is still well within human tolerance with blankets/coats/sleeping bags. This time of year, it still tends to be fairly warm there, similar to Louisiana (in fact, today’s temperatures in both states are nearly identical).
But I can understand why the code has not caught up to this yet, and insists on hard-wiring the devices... because the majority of home and buildings will still be using all-electric equipment that require plenty of energy, where things can go wrong if you allow Jane to just run her suicide cord any way she may like. Yes, there may be more folk moving over to other energy sources that eliminate or reduce the need for electricity, but the code has to cater for the wider demographic.
There are a multitude of reasons that a suicide cord is a bad idea beyond just the load planning issues and the lack of understanding of load planning by the average consumer. The average consumer probably doesn’t understand that it’s a bad idea to feed 100A of current through a “heavy duty” 20A extension cord into a 15A outlet to back-feed 200A panel through a 15A breaker. Owen
On Aug 31, 2021, at 2:33 PM, Owen DeLong via NANOG <nanog@nanog.org> wrote:
...
15kW is 1.5kVA in a simple radiant electric heat application. (it’s a simple resistive load with no power factor weirdness). Whether you could do this with 4-8kVA depends on what else you’re trying to run.
Owen
15kW is 15kVA (not 1.5 kVA) at a power factor of 1.0, if the heat is all resistive. Eric
I have a gas-fired hot water system, the electricity is also used to run the gas blower. I believe most of the electricity it uses is for circulating the hot water which you mention but it won't do anything w/o electricity. Actually I can bypass the circulator and it will do its best to circulate the hot water by convection or whatever it is, I've had to do that on occasion, failed circulator. It works "ok" like that, a lot better than nothing on a New England winter day. It's kind of quaint, an old converted coal furnace about chest high and oh maybe 8'x6' footprint with spyglass doors, probably original 1890-ish, very steampunk. But the gas blower is pretty much the usual standard little thing, looks like a big hair dryer. I do have wrkng frpls. On August 31, 2021 at 12:36 mark@tinka.africa (Mark Tinka) wrote:
On 8/31/21 12:26, Forrest Christian (List Account) wrote:
Yes. Or any other furnace where the electricity is only used for circulation of the heat. Gas fired Hot water furnaces would be another example where there is minimal electricity used to run the furnace controls and circulate the hot water.
Gas-fired furnaces or heaters should not have an impact because the only electrical requirement is to fire up the pilot light.
But fully-electric heating has a much higher impact on energy sources (heat pumps being the least).
I believe typical electric central furnaces are anywhere between 10kW - 15kW systems. Would a standard 4kVA - 8kVA generator for average Jane cut it? Not sure.
Then again, I live in a more forgiving climate, so I have a very limited need to understand this better.
But I can understand why the code has not caught up to this yet, and insists on hard-wiring the devices... because the majority of home and buildings will still be using all-electric equipment that require plenty of energy, where things can go wrong if you allow Jane to just run her suicide cord any way she may like. Yes, there may be more folk moving over to other energy sources that eliminate or reduce the need for electricity, but the code has to cater for the wider demographic.
Mark.
-- -Barry Shein Software Tool & Die | bzs@TheWorld.com | http://www.TheWorld.com Purveyors to the Trade | Voice: +1 617-STD-WRLD | 800-THE-WRLD The World: Since 1989 | A Public Information Utility | *oo*
On 8/31/21 02:19, Mark Tinka wrote:
On 8/31/21 11:11, Forrest Christian (List Account) wrote:
For example, code requires most furnaces to be hardwired. But a furnace is one of the first things you want on a generator in an extended winter power outage. If instead of hardwired, the code required plug and socket connections at each 120v furnace then Joe homeowner would be more likely to run an extension cord from his generator to his furnace instead of trying to rig up his generator with a suicide cord.
Are you referring to a forced-air central electric furnace?
More likely a forced-air gas furnace with an electric blower. An electric furnace would be a heavy lift for a portable generator. -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
----- On Aug 31, 2021, at 2:11 AM, Forrest Christian (List Account) lists@packetflux.com wrote: Hi,
I just wish the electrical code would permit or require certain low cost things which make temporary generator connections more likely to be safe.
For example, code requires most furnaces to be hardwired. But a furnace is one of the first things you want on a generator in an extended winter power outage. If instead of hardwired, the code required plug and socket connections at each 120v furnace then Joe homeowner would be more likely to run an extension cord from his generator to his furnace instead of trying to rig up his generator with a suicide cord.
Now I'm wondering which jurisdiction you're talking about. I live in California in a home which was finalized in 2019. As I'm the first owner, I was there when the inspector went up into the attic and checked my HVAC. My HVAC has a plug in power cord running into a regular household socket (all in the attic). The inspector didn't say a word about it and issued the occupancy permit. My electrically powered oven is hardwired, but I guess that's because it requires two 50amp breakers? Thanks, Sabri
On Aug 31, 2021, at 09:23 , Sabri Berisha <sabri@cluecentral.net> wrote:
----- On Aug 31, 2021, at 2:11 AM, Forrest Christian (List Account) lists@packetflux.com wrote:
Hi,
I just wish the electrical code would permit or require certain low cost things which make temporary generator connections more likely to be safe.
For example, code requires most furnaces to be hardwired. But a furnace is one of the first things you want on a generator in an extended winter power outage. If instead of hardwired, the code required plug and socket connections at each 120v furnace then Joe homeowner would be more likely to run an extension cord from his generator to his furnace instead of trying to rig up his generator with a suicide cord.
Now I'm wondering which jurisdiction you're talking about. I live in California in a home which was finalized in 2019. As I'm the first owner, I was there when the inspector went up into the attic and checked my HVAC. My HVAC has a plug in power cord running into a regular household socket (all in the attic). The inspector didn't say a word about it and issued the occupancy permit.
My electrically powered oven is hardwired, but I guess that's because it requires two 50amp breakers?
It only sort of looks like two 50amp breakers… In reality, it’s a “ganged” breaker that is 50A on both sides of a 220V circuit so that if either side of the circuit exceeds 50A, it will trip both breakers and shut down both sides. A 220V circuit in the US (or 215/230/240, varies widely from utility to utility and for other reasons) is both hot sides. The three wires coming into your house from the utility are the two hots from opposite ends of the secondary winding in the utility stepdown transformer along with a center-tapped “neutral”. The neutral is (or at least should be) tied to earth ground at exactly one place in your home (usually inside the main breaker panel). The two “hot” sides each provide a 110V(approximately) AC source relative to the reference (0V Neutral and Ground), but they provide that at a phase difference of 180º. This means that the potential between the two hot lines is (nominally) 220VAC. Owen
On Tue, 31 Aug 2021, Forrest Christian (List Account) wrote:
I just wish the electrical code would permit or require certain low cost things which make temporary generator connections more likely to be safe.
For example, code requires most furnaces to be hardwired. But a furnace is one of the first things you want on a generator in an extended winter power outage. If instead of hardwired, the code required plug and socket connections at each 120v furnace then Joe homeowner would be more likely to run an extension cord from his generator to his furnace instead of trying to rig up his generator with a suicide cord.
Is $40-60 low cost enough for you for safe, temporary generator connections? - Generator Interlock Kit: $20-25 (Safety) - Breaker: $5 (30amp 120v) to $20 (60amp 240v) (Dedicated Power connection) - Generator Power Inlet Input: $15 (indoor 120v) to $50 (outdoor 240v) A Generator Interlock Kit is a few pieces of metal that, once installed on your existing electrical panel, allows one to run a properly-sized circuit and breaker to an outlet that you can plug your 120v or 240v generator inverter RV output into. Add a Generator Power Inlet Input (indoor or outdoor) rated at 30Amp 240v NEMA L6-30P, for example, then plug your generator into that. The Generator Interlock Kit physically prevents the mains from being on when the generator Breaker is on. This is the safety component. This seems affordable ($60 plus some wire and a few minutes inside your electrical panel) and safe. Add a few bucks to have your locality inspect and certify the work. If this is too much, why? What would be easier while also being equally as safe? This is work that, with a few minutes on YouTube, could do safely, as long as the power is disconnected at the meter outside the home during installation. PS - I suppose you could also move all of your emergency 120v stuff to one side of your panel and also provide only 120V to one side of your panel. This would also reduce costs a bit. Why believe me? In 2019 I read the NEC code and learned how to install a 60amp circuit for an electric charger. I did the work myself. I had it inspected and certified by the county. I did so for about $100 total for all parts and wire. Beckman --------------------------------------------------------------------------- Peter Beckman Internet Guy beckman@angryox.com http://www.angryox.com/ ---------------------------------------------------------------------------
On 9/1/21 21:13, Peter Beckman wrote:
On Tue, 31 Aug 2021, Forrest Christian (List Account) wrote:
Is $40-60 low cost enough for you for safe, temporary generator connections?
[snip]
Add a Generator Power Inlet Input (indoor or outdoor) rated at 30Amp 240v NEMA L6-30P, for example, then plug your generator into that.
You'll want a neutral. L14-30P. -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
Let me clarify since this thread has resurrected itself. In the northern climates where I live, almost 100% of the heat during winter is either natural gas or propane. It's either fan forced or hot water. In each case, the amount of electricity consumed by a typical furnace is well under 15 amps. Like a few hundred watts for all but the biggest furnaces. When the power fails during the coldest part of the year the most critical thing to keep running is the furnace. You can have frozen pipes and other cold related damage in a relatively short time. The amount of time is irrelevant but think multiple hours not days. We all have flashlights, the fridge isn't a big issue (natural freezer outdoors, and usually free ice) and so on. But the furnace having power is critical. The quickest fastest way to get that furnace back on is to fire up a generator or some other suitable power source and then hook the generator up to it. The problem is that people rarely think ahead, so they're trying to come up with a quick solution, and most of them don't really understand wiring. Because, by code, the furnace may not be connected with a plug and socket the homeowner has no option but to open up an electrical box and try to figure out how to hook his generator up. With the not uncommon enough result of the generator trying to power the neighborhood. The solution is dirt cheap. Instead of requiring a hardwired connection, move to a standard 120V 15A plug and socket connection. Based on other requirements in the code such as for a disconnecting means near the furnace which this would replace as well, the cost is likely to be zero. Its not uncommon to see this done even though it is against code. Whether it will pass inspection depends on the attitude of the inspector. On Wed, Sep 1, 2021, 10:13 PM Peter Beckman <beckman@angryox.com> wrote:
On Tue, 31 Aug 2021, Forrest Christian (List Account) wrote:
I just wish the electrical code would permit or require certain low cost things which make temporary generator connections more likely to be safe.
For example, code requires most furnaces to be hardwired. But a furnace is one of the first things you want on a generator in an extended winter power outage. If instead of hardwired, the code required plug and socket connections at each 120v furnace then Joe homeowner would be more likely to run an extension cord from his generator to his furnace instead of trying to rig up his generator with a suicide cord.
Is $40-60 low cost enough for you for safe, temporary generator connections?
- Generator Interlock Kit: $20-25 (Safety) - Breaker: $5 (30amp 120v) to $20 (60amp 240v) (Dedicated Power connection) - Generator Power Inlet Input: $15 (indoor 120v) to $50 (outdoor 240v)
A Generator Interlock Kit is a few pieces of metal that, once installed on your existing electrical panel, allows one to run a properly-sized circuit and breaker to an outlet that you can plug your 120v or 240v generator inverter RV output into.
Add a Generator Power Inlet Input (indoor or outdoor) rated at 30Amp 240v NEMA L6-30P, for example, then plug your generator into that.
The Generator Interlock Kit physically prevents the mains from being on when the generator Breaker is on. This is the safety component.
This seems affordable ($60 plus some wire and a few minutes inside your electrical panel) and safe.
Add a few bucks to have your locality inspect and certify the work.
If this is too much, why? What would be easier while also being equally as safe? This is work that, with a few minutes on YouTube, could do safely, as long as the power is disconnected at the meter outside the home during installation.
PS - I suppose you could also move all of your emergency 120v stuff to one side of your panel and also provide only 120V to one side of your panel. This would also reduce costs a bit.
Why believe me? In 2019 I read the NEC code and learned how to install a 60amp circuit for an electric charger. I did the work myself. I had it inspected and certified by the county. I did so for about $100 total for all parts and wire.
Beckman --------------------------------------------------------------------------- Peter Beckman Internet Guy beckman@angryox.com http://www.angryox.com/ ---------------------------------------------------------------------------
Here’s a nice article on the code issue, which is nationwide in the US (it’s part of the NEC). It speaks specifically about the generator requirements: https://temperaturemaster.com/furnaces-hardwired-what-you-need-to-know/ TLDR: The NEC is against plugged-in furnaces for a good reason: they consume so much electricity that they need a dedicated circuit. When you have a plug-in furnace, you’re likely to plug it into a shared outlet with other appliances. As a result, the circuit gets overloaded, damaging the furnace and the other plugged-in electrical devices or even resulting in a fire. So, converting a hardwired furnace into a plugged-in constitutes an NEC code violation. The article then proceeds to show how to safely violate the NEC with a plug and socket, and how to follow the letter of the law with a transfer switch or interlock kit. I think these are the same devices my brother Peter might be talking about. :) -mel On Sep 1, 2021, at 11:20 PM, Forrest Christian (List Account) <lists@packetflux.com<mailto:lists@packetflux.com>> wrote: Let me clarify since this thread has resurrected itself. In the northern climates where I live, almost 100% of the heat during winter is either natural gas or propane. It's either fan forced or hot water. In each case, the amount of electricity consumed by a typical furnace is well under 15 amps. Like a few hundred watts for all but the biggest furnaces. When the power fails during the coldest part of the year the most critical thing to keep running is the furnace. You can have frozen pipes and other cold related damage in a relatively short time. The amount of time is irrelevant but think multiple hours not days. We all have flashlights, the fridge isn't a big issue (natural freezer outdoors, and usually free ice) and so on. But the furnace having power is critical. The quickest fastest way to get that furnace back on is to fire up a generator or some other suitable power source and then hook the generator up to it. The problem is that people rarely think ahead, so they're trying to come up with a quick solution, and most of them don't really understand wiring. Because, by code, the furnace may not be connected with a plug and socket the homeowner has no option but to open up an electrical box and try to figure out how to hook his generator up. With the not uncommon enough result of the generator trying to power the neighborhood. The solution is dirt cheap. Instead of requiring a hardwired connection, move to a standard 120V 15A plug and socket connection. Based on other requirements in the code such as for a disconnecting means near the furnace which this would replace as well, the cost is likely to be zero. Its not uncommon to see this done even though it is against code. Whether it will pass inspection depends on the attitude of the inspector. On Wed, Sep 1, 2021, 10:13 PM Peter Beckman <beckman@angryox.com<mailto:beckman@angryox.com>> wrote: On Tue, 31 Aug 2021, Forrest Christian (List Account) wrote:
I just wish the electrical code would permit or require certain low cost things which make temporary generator connections more likely to be safe.
For example, code requires most furnaces to be hardwired. But a furnace is one of the first things you want on a generator in an extended winter power outage. If instead of hardwired, the code required plug and socket connections at each 120v furnace then Joe homeowner would be more likely to run an extension cord from his generator to his furnace instead of trying to rig up his generator with a suicide cord.
Is $40-60 low cost enough for you for safe, temporary generator connections? - Generator Interlock Kit: $20-25 (Safety) - Breaker: $5 (30amp 120v) to $20 (60amp 240v) (Dedicated Power connection) - Generator Power Inlet Input: $15 (indoor 120v) to $50 (outdoor 240v) A Generator Interlock Kit is a few pieces of metal that, once installed on your existing electrical panel, allows one to run a properly-sized circuit and breaker to an outlet that you can plug your 120v or 240v generator inverter RV output into. Add a Generator Power Inlet Input (indoor or outdoor) rated at 30Amp 240v NEMA L6-30P, for example, then plug your generator into that. The Generator Interlock Kit physically prevents the mains from being on when the generator Breaker is on. This is the safety component. This seems affordable ($60 plus some wire and a few minutes inside your electrical panel) and safe. Add a few bucks to have your locality inspect and certify the work. If this is too much, why? What would be easier while also being equally as safe? This is work that, with a few minutes on YouTube, could do safely, as long as the power is disconnected at the meter outside the home during installation. PS - I suppose you could also move all of your emergency 120v stuff to one side of your panel and also provide only 120V to one side of your panel. This would also reduce costs a bit. Why believe me? In 2019 I read the NEC code and learned how to install a 60amp circuit for an electric charger. I did the work myself. I had it inspected and certified by the county. I did so for about $100 total for all parts and wire. Beckman --------------------------------------------------------------------------- Peter Beckman Internet Guy beckman@angryox.com<mailto:beckman@angryox.com> http://www.angryox.com/ ---------------------------------------------------------------------------
On 9/2/21 09:33, Mel Beckman wrote:
Here’s a nice article on the code issue, which is nationwide in the US (it’s part of the NEC). It speaks specifically about the generator requirements:
https://temperaturemaster.com/furnaces-hardwired-what-you-need-to-know/ <https://temperaturemaster.com/furnaces-hardwired-what-you-need-to-know/>
TLDR: The NEC is against plugged-in furnaces for a good reason: they consume so much electricity that they need a dedicated circuit. When you have a plug-in furnace, you’re likely to plug it into a shared outlet with other appliances. As a result, the circuit gets overloaded, damaging the furnace and the other plugged-in electrical devices or even resulting in a fire.
So, converting a hardwired furnace into a plugged-in constitutes an NEC code violation.
The article then proceeds to show how to safely violate the NEC with a plug and socket, and how to follow the letter of the law with a transfer switch or interlock kit.
I think these are the same devices my brother Peter might be talking about. :)
We have two kettles in our kitchen, and one of them seems to be slowly breaking down. So my Mrs. ran both at the same time last week, and was wondering why one of the breakers in our panel kept tripping. The two separate sockets that serve each kettle are wired to the same 20A breaker into the panel. That was an easy one to explain... run one at a time. Just easier to not encourage folk to breakout high-current devices such as these into regular wall sockets. Most people do not understand the effects of cascading loads on a single circuit, especially when they don't get that different loads generate different current, even if the voltage is the same. And nor should they, if we always implement and certify code compliance. But alas, the real world... Mark.
On Wed, Aug 25, 2021 at 11:06 AM Jared Mauch <jared@puck.nether.net> wrote:
On Aug 25, 2021, at 10:04 AM, Mark Tinka <mark@tinka.africa> wrote:
You need to make these things fool-proof. We haven't traveled in over a year but the day we do, it's a recipe for disaster if the person that deals with this stuff is on the road when the power goes out back at home.
This is why I personally spent the $$ on a proper standby generator with multiple ATS for the multiple panels.
Yah. I suspect that a fair bit of this depends on where you live. I have a fairly rural house, and the power comes across the (Shenandoah) river, and then down an overhead feed which branches off to 6 or 8 neighbors, before running up the hill to a transformer on a pole near my house. We would lose power around once every 2 or 3 months (trees, wind, snow, etc). We installed a whole house generator (with transfer switch), and ... well, actually, just after we did this the local power company did a bunch of maintenance and now the supply is more stable, but still.... This all reminds me that I need to go and do an oil change/maintenance on the generator -- it sent me an alert the week before last that it has reached its maintenance interval, but it's been a bit too hot to do this yet... W - Jared -- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra
On 8/25/21 07:04, Mark Tinka wrote:
On 8/25/21 15:59, Ethan O'Toole wrote:
How would this not load the generator or inverter into oblivion?
Not sure I understand your question. Say again, please.
If you fail to isolate your generator from the incoming utility feed so that you're back-feeding the utility and the power is out for your neighborhood or the whole city, would not the load of trying to light up the whole town completely overwhelm your little generator to the point that it fails, stalls, or trips its own output breaker? -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
Jay, No, because transformers work in both directions :) Plus, to the previous commenter that talked about “suicide cords”: they’’re more correctly termed “homicide cords”: “ The lineman killed yesterday was working for Pike Electric and picked up a line that was connected to someones house that hooked up a generator and did not disconnect from the distribution system. The linemans name was Ronnie Adams, age unknown. He had two children and a wife. As far as I know he was from Louisiana. They are trying to set up a fund for his family, but nothing I have heard of yet. I will let yall know more as I hear of it. I wish they would really teach folks the proper connection of generators, this was a really tragic and preventable accident. Stay Safe and think about it before you do it.” https://powerlineman.com/lforum/showthread.php?711-Storm-Death -mel On Aug 25, 2021, at 10:12 AM, Jay Hennigan <jay@west.net> wrote: On 8/25/21 07:04, Mark Tinka wrote: On 8/25/21 15:59, Ethan O'Toole wrote: How would this not load the generator or inverter into oblivion? Not sure I understand your question. Say again, please. If you fail to isolate your generator from the incoming utility feed so that you're back-feeding the utility and the power is out for your neighborhood or the whole city, would not the load of trying to light up the whole town completely overwhelm your little generator to the point that it fails, stalls, or trips its own output breaker? -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
In theory, Jay is correct, but assuming that theory will always work in practice is, in this case, how linemen end up dead. We're all well aware of never assuming theory = practice, but admittedly the stakes tend to be a little lower in our world. Ensuring that a generator physically cannot backfeed is just one layer of protection against the already very high risk of the job of a lineman. Then there is, of course, checking for the presence of voltage before starting work, but it's possible for a generator to start AFTER this check. Another layer of protection is grounding all conductors prior to beginning work, so that if power does come back (via the grid or a backfeed) A: The lineman and bucket is not the best path to ground and B: The source is tripped. Reading through that forum post, it sounds like that particular contractor had a reputation for lacking proper safety precautions, so one or more safety layers may have been removed, making the risk/impact of any single mistake much greater than it should be. -Matt On Wed, Aug 25, 2021 at 11:25 AM Mel Beckman <mel@beckman.org> wrote:
Jay,
No, because transformers work in both directions :)
Plus, to the previous commenter that talked about “suicide cords”: they’’re more correctly termed “homicide cords”:
“ The lineman killed yesterday was working for Pike Electric and picked up a line that was connected to someones house that hooked up a generator and did not disconnect from the distribution system. The linemans name was Ronnie Adams, age unknown. He had two children and a wife. As far as I know he was from Louisiana. They are trying to set up a fund for his family, but nothing I have heard of yet. I will let yall know more as I hear of it. I wish they would really teach folks the proper connection of generators, this was a really tragic and preventable accident. Stay Safe and think about it before you do it.”
https://powerlineman.com/lforum/showthread.php?711-Storm-Death
-mel
On Aug 25, 2021, at 10:12 AM, Jay Hennigan <jay@west.net> wrote:
On 8/25/21 07:04, Mark Tinka wrote:
On 8/25/21 15:59, Ethan O'Toole wrote:
How would this not load the generator or inverter into oblivion?
Not sure I understand your question. Say again, please.
If you fail to isolate your generator from the incoming utility feed so that you're back-feeding the utility and the power is out for your neighborhood or the whole city, would not the load of trying to light up the whole town completely overwhelm your little generator to the point that it fails, stalls, or trips its own output breaker?
-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
-- Matt Erculiani ERCUL-ARIN
In theory, Jay is correct, but assuming that theory will always work in practice is, in this case, how linemen end up dead. We're all well aware of never assuming theory = practice, but admittedly the stakes tend to be a little lower in our world.
right. my grandpa was a high-voltage/wattage engineer. He always said, `an engineer can make an error, but only once'. Luckily, we can make many errors :) -- Amir Herzberg Comcast professor of Security Innovations, Computer Science and Engineering, University of Connecticut Homepage: https://sites.google.com/site/amirherzberg/home `Applied Introduction to Cryptography' textbook and lectures: https://sites.google.com/site/amirherzberg/applied-crypto-textbook <https://sites.google.com/site/amirherzberg/applied-crypto-textbook> On Wed, Aug 25, 2021 at 1:55 PM Matt Erculiani <merculiani@gmail.com> wrote:
In theory, Jay is correct, but assuming that theory will always work in practice is, in this case, how linemen end up dead. We're all well aware of never assuming theory = practice, but admittedly the stakes tend to be a little lower in our world.
Ensuring that a generator physically cannot backfeed is just one layer of protection against the already very high risk of the job of a lineman. Then there is, of course, checking for the presence of voltage before starting work, but it's possible for a generator to start AFTER this check.
Another layer of protection is grounding all conductors prior to beginning work, so that if power does come back (via the grid or a backfeed) A: The lineman and bucket is not the best path to ground and B: The source is tripped.
Reading through that forum post, it sounds like that particular contractor had a reputation for lacking proper safety precautions, so one or more safety layers may have been removed, making the risk/impact of any single mistake much greater than it should be.
-Matt
On Wed, Aug 25, 2021 at 11:25 AM Mel Beckman <mel@beckman.org> wrote:
Jay,
No, because transformers work in both directions :)
Plus, to the previous commenter that talked about “suicide cords”: they’’re more correctly termed “homicide cords”:
“ The lineman killed yesterday was working for Pike Electric and picked up a line that was connected to someones house that hooked up a generator and did not disconnect from the distribution system. The linemans name was Ronnie Adams, age unknown. He had two children and a wife. As far as I know he was from Louisiana. They are trying to set up a fund for his family, but nothing I have heard of yet. I will let yall know more as I hear of it. I wish they would really teach folks the proper connection of generators, this was a really tragic and preventable accident. Stay Safe and think about it before you do it.”
https://powerlineman.com/lforum/showthread.php?711-Storm-Death
-mel
On Aug 25, 2021, at 10:12 AM, Jay Hennigan <jay@west.net> wrote:
On 8/25/21 07:04, Mark Tinka wrote:
On 8/25/21 15:59, Ethan O'Toole wrote:
How would this not load the generator or inverter into oblivion?
Not sure I understand your question. Say again, please.
If you fail to isolate your generator from the incoming utility feed so that you're back-feeding the utility and the power is out for your neighborhood or the whole city, would not the load of trying to light up the whole town completely overwhelm your little generator to the point that it fails, stalls, or trips its own output breaker?
-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
-- Matt Erculiani ERCUL-ARIN
Matt, The practice you describe, called “parallel grounding”, was flawed and discontinued in the 1970s. It was replaced by equipotential grounding, which protects against accidental grid-delivered voltages, but still can’t protect against customer-delivered voltages. https://www.leafelectricalsafety.com/blog/electrical-safety/equipotential-gr... -mel beckman On Aug 25, 2021, at 5:31 PM, Amir Herzberg <amir.lists@gmail.com> wrote: In theory, Jay is correct, but assuming that theory will always work in practice is, in this case, how linemen end up dead. We're all well aware of never assuming theory = practice, but admittedly the stakes tend to be a little lower in our world. right. my grandpa was a high-voltage/wattage engineer. He always said, `an engineer can make an error, but only once'. Luckily, we can make many errors :) -- Amir Herzberg Comcast professor of Security Innovations, Computer Science and Engineering, University of Connecticut Homepage: https://sites.google.com/site/amirherzberg/home `Applied Introduction to Cryptography' textbook and lectures: https://sites.google.com/site/amirherzberg/applied-crypto-textbook<https://sites.google.com/site/amirherzberg/applied-crypto-textbook> On Wed, Aug 25, 2021 at 1:55 PM Matt Erculiani <merculiani@gmail.com<mailto:merculiani@gmail.com>> wrote: In theory, Jay is correct, but assuming that theory will always work in practice is, in this case, how linemen end up dead. We're all well aware of never assuming theory = practice, but admittedly the stakes tend to be a little lower in our world. Ensuring that a generator physically cannot backfeed is just one layer of protection against the already very high risk of the job of a lineman. Then there is, of course, checking for the presence of voltage before starting work, but it's possible for a generator to start AFTER this check. Another layer of protection is grounding all conductors prior to beginning work, so that if power does come back (via the grid or a backfeed) A: The lineman and bucket is not the best path to ground and B: The source is tripped. Reading through that forum post, it sounds like that particular contractor had a reputation for lacking proper safety precautions, so one or more safety layers may have been removed, making the risk/impact of any single mistake much greater than it should be. -Matt On Wed, Aug 25, 2021 at 11:25 AM Mel Beckman <mel@beckman.org<mailto:mel@beckman.org>> wrote: Jay, No, because transformers work in both directions :) Plus, to the previous commenter that talked about “suicide cords”: they’’re more correctly termed “homicide cords”: “ The lineman killed yesterday was working for Pike Electric and picked up a line that was connected to someones house that hooked up a generator and did not disconnect from the distribution system. The linemans name was Ronnie Adams, age unknown. He had two children and a wife. As far as I know he was from Louisiana. They are trying to set up a fund for his family, but nothing I have heard of yet. I will let yall know more as I hear of it. I wish they would really teach folks the proper connection of generators, this was a really tragic and preventable accident. Stay Safe and think about it before you do it.” https://powerlineman.com/lforum/showthread.php?711-Storm-Death -mel On Aug 25, 2021, at 10:12 AM, Jay Hennigan <jay@west.net<mailto:jay@west.net>> wrote: On 8/25/21 07:04, Mark Tinka wrote: On 8/25/21 15:59, Ethan O'Toole wrote: How would this not load the generator or inverter into oblivion? Not sure I understand your question. Say again, please. If you fail to isolate your generator from the incoming utility feed so that you're back-feeding the utility and the power is out for your neighborhood or the whole city, would not the load of trying to light up the whole town completely overwhelm your little generator to the point that it fails, stalls, or trips its own output breaker? -- Jay Hennigan - jay@west.net<mailto:jay@west.net> Network Engineering - CCIE #7880 503 897-8550 - WB6RDV -- Matt Erculiani ERCUL-ARIN
On 8/25/21 10:25, Mel Beckman wrote:
Jay,
No, because transformers work in both directions :)
I think you mean, "Yes, because transformers work in both directions." First of all, I absolutely agree that no one should attempt to energize their home wiring with a standby generator unless there is a proper transfer switch in place. I very much understand the safety concerns. The question that Ethan raised makes sense, however. If power to several blocks is out and I connect my little 2KW Honda to my house wiring without a transfer switch, because transformers work in both directions my generator will see the load of the whole neighborhood. This will immediately and severely overload the generator and at best cause it to stall out or trip its output breaker, at worst to fail catastrophically. In the very rare case that the outage is at the fuse on the pole pig feeding just my house or that of me and one or two neighbors, then indeed the generator may continue to run and that transformer will have distribution voltage of 4KV or so on the utility side, a very dangerous condition. That's a pretty unusual situation, however. Typical power outages are substantially more widespread. My little generator would be looking at the load of the entire outage area reflected through the (bidirectional as you note) transformers. The load of half the town will, as Ethan speculated, completely overwhelm any practical residential standby generator to the point that it stops producing power either by failure or by tripping its breaker. Even if the generator were massive and survived, its branch circuit breaker or the house main would trip long before sufficient power to feed a large area was able to flow back into the utility's wiring. Yes, connecting a generator without a transfer switch is a horrible idea and likely to get someone killed, agreed.* However, as the vast majority of power failures involve more than a single residence, the generator will fail to produce power immediately anyway due to looking at essentially a dead short. * Every time I've seen utility workers working on lines that are assumed to be dead, the first thing they do is clamp them to ground to be certain. When the lines are assumed to be live, massive insulation sleeves, heavy gloves, insulated booms and the like are used. -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
On 8/25/21 11:11 AM, Jay Hennigan wrote:
The question that Ethan raised makes sense, however. If power to several blocks is out and I connect my little 2KW Honda to my house wiring without a transfer switch, because transformers work in both directions my generator will see the load of the whole neighborhood. This will immediately and severely overload the generator and at best cause it to stall out or trip its output breaker, at worst to fail catastrophically.
I know that a nearby house burned down and was blamed on back feeding the grid. I assume that it failed catastrophically. Bad idea all around. Mike
On 8/25/21 19:25, Mel Beckman wrote:
Jay,
No, because transformers work in both directions :)
Plus, to the previous commenter that talked about “suicide cords”: they’’re more correctly termed “homicide cords”:
“ The lineman killed yesterday was working for Pike Electric and picked up a line that was connected to someones house that hooked up a generator and did not disconnect from the distribution system. The linemans name was Ronnie Adams, age unknown. He had two children and a wife. As far as I know he was from Louisiana. They are trying to set up a fund for his family, but nothing I have heard of yet. I will let yall know more as I hear of it. I wish they would really teach folks the proper connection of generators, this was a really tragic and preventable accident. Stay Safe and think about it before you do it.”
https://powerlineman.com/lforum/showthread.php?711-Storm-Death <https://powerlineman.com/lforum/showthread.php?711-Storm-Death>
Oh dear. This is sad. There are some people that say UL 1741 is draconian because, in general, linesmen ALWAYS check wires before they start working on them. Even if they did before and there was no voltage, it could easily happen after the fact :-(... Mark.
On 8/25/21 19:10, Jay Hennigan wrote:
If you fail to isolate your generator from the incoming utility feed so that you're back-feeding the utility and the power is out for your neighborhood or the whole city, would not the load of trying to light up the whole town completely overwhelm your little generator to the point that it fails, stalls, or trips its own output breaker?
Long answered. Mark.
----- On Aug 25, 2021, at 7:04 AM, Mark Tinka mark@tinka.africa wrote: Hello Mark,
At the home, you typically have someone that is responsible for knowing what to do in case of an outage, and switching over to self-generation. If that person is not there, or has passed out from too many bottles of wine that evening, someone else might think it's just a matter of starting the generator, unwinding a suicide cord and plugging it into the wall - totally forgetting about the main breaker.
At my home, I use this: https://www.amazon.com/gp/product/B00CONE4MG The interlock kit is installed in such a way that either the main or the generator circuit breaker is closed. If the main is on, you can't switch to generator power, and vice versa (see the pictures on the listing, mine is installed the exact same way). Thanks, Sabri
On 8/25/21 19:21, Sabri Berisha wrote:
At my home, I use this: https://www.amazon.com/gp/product/B00CONE4MG
The interlock kit is installed in such a way that either the main or the generator circuit breaker is closed. If the main is on, you can't switch to generator power, and vice versa (see the pictures on the listing, mine is installed the exact same way).
Yes, I've seen these on some Youtube videos. Work great. Mark.
participants (23)
-
Amir Herzberg -
bzs＠theworld.com -
Chris Boyd -
Dave -
Eric Germann -
Ethan O'Toole -
Forrest Christian (List Account) -
Haudy Kazemi -
Jared Mauch -
Jay Hennigan -
John van Oppen -
Josh Luthman -
Lady Benjamin Cannon of Glencoe, ASCE -
Lamar Owen -
Mark Tinka -
Matt Erculiani -
Mel Beckman -
Michael Thomas -
Owen DeLong -
Peter Beckman -
Sabri Berisha -
Sean Donelan -
Warren Kumari