From: Wayne Bogan [mailto:wbogan@infoave.net]
For those AC only powered units, you can also purchase an invertor for DC to AC conversion. You would then have the advantages of DC for your AC equipment. This does, however, add the potential of another point of failure such as fuses or breakers in the invertor.
Not to mention additional cost of wasted electricity (which does add up significantly when it is anything but a spot solution) and pitfalls of inverters (like their imperfect sine waves). And if you're putting spot solution UPS units out into the bottom of a particular rack, be ware their canny ability to catch fire when the price is right. Inverters or rectifiers should be point solutions in a plant layout. If you have a lot of AC & DC, get two protected plants. Only way to live. Sometimes that's not just nice to have, but simply required. If you're primarily a systems shop and have environmentally conditioned space, get AC. If you're in a nasty colo spot, with poor environmental (read: not guaranteed meat locker climate 24x7), get DC & NEBS hardware or hardware which meets NEBS almost entirely but doesn't carry the sticker for some silly reason such as "easily flammable plastic used for front grill". Depending on what your colo requires. There are many different flavors of colo. Speaking of flavors, consider the impact of a turf vendor based on whatever decision you chose when going into colo space. May or may not be an issue. See what equipment offers what, do the math on cost of plant and gear, pros & cons. And make a business decision based on engineering data. (uh, right) But, as Stephen already eluded to... Compared with an AC plant design, to me, one of the biggest drawbacks of a DC plant is safety (I have had to kick a fellow worker away from the rack before). One of the biggest advantages is simplicity of design when it comes to battery plant. There is no universal answer, it all depends. And one ends up shuffling off and having to do a bunch of homework. Of course, this is all IMHO and I've been wrong before. Thanks, Christian -----Original Message----- From: Wayne Bogan [mailto:wbogan@infoave.net] Sent: Sunday, December 29, 2002 1:06 PM To: nanog@merit.edu Subject: Re: DC power versus AC power ----- Original Message ----- From: "Stephen Sprunk" <ssprunk@cisco.com> To: <ipdude@cattle-today.com>; <nanog@merit.edu> Sent: Sunday, December 29, 2002 1:58 AM Subject: Re: DC power versus AC power
Thus spake ip dude <ipdude@cattle-today.com>:
Hello NANOG group. I am trying to make a case for using DC power supplies versus AC power supplies for typical IP networking equipment. Is there any published whitepapers detailing this subject? Do you have any suggestions to aide my argument?
Most of the argument depends on the facility you're in. Assuming you're asking as an end-customer:
DC requires clue from your staff when installing/removing equipment, and this means safety training at a minimum. Power choice also affects your equipment purchasing: DC versions of gear are often priced higher, and
gear
not intended for telcos/ISPs may not have a DC option available at all.
OTOH, many colos -- especially ones run by telcos -- don't provide AC UPS. If you want AC UPS in these environments, you'll have to provide your own, which is expensive, bulky, and a maintainance burden.
If you're building your own datacenter, please specify that and I'm sure you'll get a whole different discussion :)
S
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| Not to mention additional cost of wasted electricity (which does add up | significantly when it is anything but a spot solution) and pitfalls of | inverters (like their imperfect sine waves). And if you're putting spot | solution UPS units out into the bottom of a particular rack, be ware their | canny ability to catch fire when the price is right. Switched power supplies really don't care about the quality of the sine waves that feeds them, as long as they have energy to put into the "tank". On the other hand, video monitors like sine waves, and they may not get along with DC inverters/rectifiers (or even portable AC no-breaks, which usually generates AC from DC). Rubens Kuhl Jr.
----- Original Message ----- From: "Kuhtz, Christian" <christian.kuhtz@BellSouth.com> To: "Wayne Bogan" <wbogan@infoave.net>; <nanog@merit.edu> Sent: Sunday, December 29, 2002 9:37 AM Subject: RE: DC power versus AC power
But, as Stephen already eluded to... Compared with an AC plant design, to me, one of the biggest drawbacks of a DC plant is safety (I have had to kick a fellow worker away from the rack before). <<
What was the worker doing? Is this 48 VDC? Thanks, --Michael
Unnamed Administration sources reported that Michael Painter said:
But, as Stephen already eluded to... Compared with an AC plant design, to me, one of the biggest drawbacks of a DC plant is safety (I have had to kick a fellow worker away from the rack before). <<
What was the worker doing? Is this 48 VDC?
Bet so. And note, it's not just ISP's, of course. I heard that Sprint PCS ha[s,d] a Dallas tech in critical condition and a dead switch after a dropped wrench & resulting fire. In the words of Phil Esterhaus: Let's be careful out there.... -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
Is 48V DC at the amps present normallyin switch rooms etc enough to cause electricucian? I have seen bad things with wrenches dropped across batteries even 12 volt car batteries although in this case it was a large battery bank in a submarine but I was curious about the 48V sources in switch rooms. ----- Original Message ----- From: "David Lesher" <wb8foz@nrk.com> To: "nanog list" <nanog@merit.edu> Sent: Sunday, December 29, 2002 4:43 PM Subject: Re: DC power versus AC power
Unnamed Administration sources reported that Michael Painter said:
But, as Stephen already eluded to... Compared with an AC plant
design, to
me, one of the biggest drawbacks of a DC plant is safety (I have had to kick a fellow worker away from the rack before). <<
What was the worker doing? Is this 48 VDC?
Bet so.
And note, it's not just ISP's, of course. I heard that Sprint PCS ha[s,d] a Dallas tech in critical condition and a dead switch after a dropped wrench & resulting fire.
In the words of Phil Esterhaus:
Let's be careful out there....
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
Unnamed Administration sources reported that Scott Granados said:
Is 48V DC at the amps present normallyin switch rooms etc enough to cause electricucian? I have seen bad things with wrenches dropped across batteries even 12 volt car batteries although in this case it was a large battery bank in a submarine but I was curious about the 48V sources in switch rooms.
Electrocution is but one way to die from too many columbs. Internal burning is a big one. Most people die, not from immediate cardiac arrest, but rather from kidney/spleen/liver failure as they try to remove the cooked you parts from your bloodstream, and clog up. (First responder treatment is multiple saline inputs to flush you out, and keep flushing you. This via a friend who was "lit" and lived.) The instantaneous short circuit current available from a CO-grade battery string is nothing short of frightening. It will easily turn a 18" crescent wrench bright orange and start spitting the molten metal around within few seconds. I'm surprised you're still around after a sub battery accident. They're a grade up from most CO's in available current, I'd bet. -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
On Sun, Dec 29, 2002 at 08:11:46PM -0500, David Lesher wrote:
I'm surprised you're still around after a sub battery accident. They're a grade up from most CO's in available current, I'd bet.
I'd bet the other way. CO battery has to supply ring current, dial tone and voice current, not just run the switch itself, at least in the Copper Age. I don't think -48VDC is an electrocution risk unless you're sweaty, but a vaporized wrench sure can burn you, and I don't think GFIs existed for DC. Anyway, nukes don't need the battery capacity of the old diesels. -- Barney Wolff http://www.databus.com/bwresume.pdf I'm available by contract or FT, in the NYC metro area or via the 'Net.
Unnamed Administration sources reported that Barney Wolff said:
I'm surprised you're still around after a sub battery accident. They're a grade up from most CO's in available current, I'd bet.
I'd bet the other way. CO battery has to supply ring current, dial tone and voice current, not just run the switch itself, at least in the Copper Age. I don't think -48VDC is an electrocution risk unless you're sweaty, but a vaporized wrench sure can burn you, and I don't think GFIs existed for DC.
Anyway, nukes don't need the battery capacity of the old diesels.
<http://www.relocationspecialists.org/bat/cell.html> and <www.jjma.com/Documents/Features/batteryd.pdf> -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
While I would normally think some of this exaggeration. When I was at Netrail, I did a road trip to upgrade a facility in DC. It's kinda amazing what passed for colo in those days. The little UPS actually had a string of Pet boys car batteries. Nathan Estes dropped a wrench into the battery bay and there was a nice explosion according to him. The wrench literally vaporized. Now I said that wasnt possible. He will stick to his story to this day. The only thing I could figure was that it literally moltified into super small droplets and just sprayed. Regardless of whether it's completely accurate, he was out searching for another wrench... it took a lot of chocolate mile to relax him after that. At 20:11 -0500 12/29/02, David Lesher wrote:
Unnamed Administration sources reported that Scott Granados said:
Is 48V DC at the amps present normallyin switch rooms etc enough to cause electricucian? I have seen bad things with wrenches dropped across batteries even 12 volt car batteries although in this case it was a large battery bank in a submarine but I was curious about the 48V sources in switch rooms.
Electrocution is but one way to die from too many columbs. Internal burning is a big one. Most people die, not from immediate cardiac arrest, but rather from kidney/spleen/liver failure as they try to remove the cooked you parts from your bloodstream, and clog up. (First responder treatment is multiple saline inputs to flush you out, and keep flushing you. This via a friend who was "lit" and lived.)
The instantaneous short circuit current available from a CO-grade battery string is nothing short of frightening. It will easily turn a 18" crescent wrench bright orange and start spitting the molten metal around within few seconds.
I'm surprised you're still around after a sub battery accident. They're a grade up from most CO's in available current, I'd bet.
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
-- David Diaz dave@smoton.net [Email] pagedave@smoton.net [Pager] www.smoton.net [Peering Site under development] Smotons (Smart Photons) trump dumb photons
Yes it will the wrench will become litterally liquid and spray. So no it doesn't explode in the litteral sense but it appears to and also sounds like it:). A safe experiment to do which many people probably did as Kids is to take a piece of tin foil and place it across the terminals of say a trainset transformer or perhaps a 6 V drycell battery that you set up with a proper switch so you can switch on the flow when you are standing back. The foil will sizzle and pop used to be the way you could demonstrate how fuses worked. Imagine that but this time the wrench handle goes pop. ----- Original Message ----- From: "David Diaz" <techlist@smoton.net> To: <wb8foz@nrk.com>; "nanog list" <nanog@merit.edu> Sent: Sunday, December 29, 2002 5:45 PM Subject: Re: DC power versus AC power
While I would normally think some of this exaggeration. When I was at Netrail, I did a road trip to upgrade a facility in DC. It's kinda amazing what passed for colo in those days. The little UPS actually had a string of Pet boys car batteries. Nathan Estes dropped a wrench into the battery bay and there was a nice explosion according to him. The wrench literally vaporized. Now I said that wasnt possible. He will stick to his story to this day.
The only thing I could figure was that it literally moltified into super small droplets and just sprayed. Regardless of whether it's completely accurate, he was out searching for another wrench... it took a lot of chocolate mile to relax him after that.
At 20:11 -0500 12/29/02, David Lesher wrote:
Unnamed Administration sources reported that Scott Granados said:
Is 48V DC at the amps present normallyin switch rooms etc enough to
cause
electricucian? I have seen bad things with wrenches dropped across batteries even 12 volt car batteries although in this case it was a large battery bank in a submarine but I was curious about the 48V sources in switch rooms.
Electrocution is but one way to die from too many columbs. Internal burning is a big one. Most people die, not from immediate cardiac arrest, but rather from kidney/spleen/liver failure as they try to remove the cooked you parts from your bloodstream, and clog up. (First responder treatment is multiple saline inputs to flush you out, and keep flushing you. This via a friend who was "lit" and lived.)
The instantaneous short circuit current available from a CO-grade battery string is nothing short of frightening. It will easily turn a 18" crescent wrench bright orange and start spitting the molten metal around within few seconds.
I'm surprised you're still around after a sub battery accident. They're a grade up from most CO's in available current, I'd bet.
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
--
David Diaz dave@smoton.net [Email] pagedave@smoton.net [Pager] www.smoton.net [Peering Site under development] Smotons (Smart Photons) trump dumb photons
Unnamed Administration sources reported that Scott Granados said:
Is 48V DC at the amps present normallyin switch rooms etc enough to
cause
electricucian? I have seen bad things with wrenches dropped across batteries even 12 volt car batteries although in this case it was a large battery bank in a submarine but I was curious about the 48V sources in switch rooms.
Electrocution is but one way to die from too many columbs. Internal burning is a big one. Most people die, not from immediate cardiac arrest, but rather from kidney/spleen/liver failure as they try to remove the cooked you parts from your bloodstream, and clog up. (First responder treatment is multiple saline inputs to flush you out, and keep flushing you. This via a friend who was "lit" and lived.)
The only way I've seen anyone die from being shocked is heart failure. This was a very very large AC hit though not DC.
The instantaneous short circuit current available from a CO-grade battery string is nothing short of frightening. It will easily turn a 18" crescent wrench bright orange and start spitting the molten metal around within few seconds.
I'm surprised you're still around after a sub battery accident. They're a grade up from most CO's in available current, I'd bet.
Yes, they are I don't recall the amps off hand but it was amazing. It does take a lot of juice though to spin motors that large and run all that equipment considering your primary power source is nuclear also. In my case I wasn't the one who was hit I was a fair distance off and someone working, an electrician, touched a wrench across the terminals on one cell only. For get a few seconds pretty instantly the wrench was gone as well as a better part of his hand and wrist. However, touching both terminals on the cell did not yield a shock which was what made me think and ask the question i the first place. I can't imagine the damage possible though if someone in that setting touched one of the main bus's.
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
On Sun, 29 Dec 2002, Scott Granados wrote:
but I was curious about the 48V sources in switch rooms.
Don't forget there's a quiet yet resourceful list over at datacenter@shorty.com. They love talking about this kind of stuff. Additionally I wonder why non-conductive tools wouldn't be the norm in an environment where there's an "open" power grid? :) Charles
----- Original Message ----- From: "David Lesher" <wb8foz@nrk.com> To: "nanog list" <nanog@merit.edu> Sent: Sunday, December 29, 2002 4:43 PM Subject: Re: DC power versus AC power
Unnamed Administration sources reported that Michael Painter said:
But, as Stephen already eluded to... Compared with an AC plant
design, to
me, one of the biggest drawbacks of a DC plant is safety (I have had to kick a fellow worker away from the rack before). <<
What was the worker doing? Is this 48 VDC?
Bet so.
And note, it's not just ISP's, of course. I heard that Sprint PCS ha[s,d] a Dallas tech in critical condition and a dead switch after a dropped wrench & resulting fire.
In the words of Phil Esterhaus:
Let's be careful out there....
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
----- Original Message ----- From: "Scott Granados" <scott@wworks.net> To: <wb8foz@nrk.com>; "nanog list" <nanog@merit.edu> Sent: Sunday, December 29, 2002 3:40 PM Subject: Re: DC power versus AC power
Is 48V DC at the amps present normallyin switch rooms etc enough to cause electricucian? I have seen bad things with wrenches dropped across batteries even 12 volt car batteries although in this case it was a large battery bank in a submarine but I was curious about the 48V sources in switch rooms.
I've laid across the buss-bars before...definitely an uneasy feeling, but never felt it unless I was sweaty. <g> Capability of thousands of Amps, but it's the old "power transfer" deal...internal resistance of the source vs. internal resistance of the load (your body). --Michael
----- Original Message ----- From: "David Lesher" <wb8foz@nrk.com> To: "nanog list" <nanog@merit.edu> Sent: Sunday, December 29, 2002 4:43 PM Subject: Re: DC power versus AC power
Unnamed Administration sources reported that Michael Painter said:
But, as Stephen already eluded to... Compared with an AC plant
design, to
me, one of the biggest drawbacks of a DC plant is safety (I have had to kick a fellow worker away from the rack before). <<
What was the worker doing? Is this 48 VDC?
Bet so.
And note, it's not just ISP's, of course. I heard that Sprint PCS ha[s,d] a Dallas tech in critical condition and a dead switch after a dropped wrench & resulting fire.
In the words of Phil Esterhaus:
Let's be careful out there....
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
Unnamed Administration sources reported that Michael Painter said:
I've laid across the buss-bars before...definitely an uneasy feeling, but never felt it unless I was sweaty. <g> Capability of thousands of Amps, but it's the old "power transfer" deal...internal resistance of the source vs. internal resistance of the load (your body).
True. It's all Ohms law. But for those of you who (unlike me) speak C and mean a language, not 3E8m/s..... let's look at 13.8v car battery and a 120v line cases. Ohms are what resist the flow of [I'll say so even though I'll wince] electrons. I = E/R. I = current, E voltage, R resistance. People are not good conductors; let's just say you have oh 100Kohm from one DRY thumb to another. Most of that is skin. Get inside the ?epidermous [sp]? and it goes down fast. Get even slightly sweaty, and same deal. So I = 13.8/100k is not much current. Not enough to hurt. I = 120v/100K is 1.2ma. That's not enough to cook you, but may be enough to screw up your heart. That's why the "one hand rule" exists. Loop one hand through belt at your ass, work with other. Iffen you get bit finger to finger on the same hand, it won't pass though your trunk. (Assuming rubber shoes...) Now, consider that dropped screwdriver. Say the total resistance of it across the contacts is 0.05 ohms. (It's dirty...) I = 13.8/0.05 = 276 A. Sparks fly. Tool melts, you hope. I = 120v/0.05 = 2400 A. Here, the 20A breaker should clear as fast as it can, and it's likely only going to be oh 1000A until it does. Still shit flies and if your eyes are in the way... Now, milliseconds later [if the fuse/breaker has not cleared] that initial current gets enough things hot, melts/cleans parts, LOWERING THE RESISTANCE as it ..improves.. the connection... Worst case, you get a plasma arc that LOVES to conduct. In that case, the resistance goes to near zero. The current is only limited by other resistances in the battery string, and you have good tight connections and large cables, right? If you are lucky, the screwdriver is consumed and the short stops. If not, well soon you get badly burnt. Wrenches are a lot more massive; and will do more damage. Some major burn cases live. I'm not sure they are the lucky ones. Short summary: 120vac line may "electrocute" you easily; a high current lower voltage system can cook you just as dead. Neither is "safe" to futz with casually. -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
Ouch... nas-corp.com is rejecting me for "profanity".... Was it the 'sweaty' or the posterior term? Jeeze.... -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
Thus spake "Scott Granados" <scott@wworks.net>
Is 48V DC at the amps present normallyin switch rooms etc enough to cause electricucian? I have seen bad things with wrenches dropped across batteries even 12 volt car batteries although in this case it was a large battery bank in a submarine but I was curious about the 48V sources in switch rooms.
2500-class devices only need 2A, but a GSR needs 60A -- and 60A DC is significantly more dangerous than 60A AC due to the duty cycle. If you _remember_ to defuse/disable the leads from the A _and_ B fuse panels to the device you're working on, you'll be okay. The real danger is when people are working on the "upstream" side of the power panel, which is often difficult/impossible to defuse and carries significantly higher amperages. S
Absolutely. Often, there are more than a few hundred amps available. Remember, many of those switch rooms were built to specs to drive a very large number of solenoids, relays, etc. All relatively high-current devices compared to today's solid state stuff. Alot of the specs were never reduced, the rooms just got bigger, and the number of customers. There's a reason the backbone is multiple copper plates and not just wire. Owen --On Sunday, December 29, 2002 5:40 PM -0800 Scott Granados <scott@wworks.net> wrote:
Is 48V DC at the amps present normallyin switch rooms etc enough to cause electricucian? I have seen bad things with wrenches dropped across batteries even 12 volt car batteries although in this case it was a large battery bank in a submarine but I was curious about the 48V sources in switch rooms.
----- Original Message ----- From: "David Lesher" <wb8foz@nrk.com> To: "nanog list" <nanog@merit.edu> Sent: Sunday, December 29, 2002 4:43 PM Subject: Re: DC power versus AC power
Unnamed Administration sources reported that Michael Painter said:
But, as Stephen already eluded to... Compared with an AC plant
design, to
me, one of the biggest drawbacks of a DC plant is safety (I have had to kick a fellow worker away from the rack before). <<
What was the worker doing? Is this 48 VDC?
Bet so.
And note, it's not just ISP's, of course. I heard that Sprint PCS ha[s,d] a Dallas tech in critical condition and a dead switch after a dropped wrench & resulting fire.
In the words of Phil Esterhaus:
Let's be careful out there....
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
It only takes 30ma to put your heart into atrial fibrillation. In the usa, gfi's are set to trip at 5ma. Normally 48VDC wouldn't be considered a 'lethal' voltage (I've talked to telephone technicians who said they used to play a game in the CO by wiring a handle to 90V ring voltage and seeing who could grab it for the longest time), but you've got to consider the extreme cases where the working environment may be wet or a worker could get exposed through open wounds, puncture wounds or mucus membranes. Under the right circumstances, nearly any voltage can be lethal. Joe On 12/29/02 5:40 PM, "Scott Granados" <scott@wworks.net> wrote:
Is 48V DC at the amps present normallyin switch rooms etc enough to cause electricucian? I have seen bad things with wrenches dropped across batteries even 12 volt car batteries although in this case it was a large battery bank in a submarine but I was curious about the 48V sources in switch rooms.
----- Original Message ----- From: "David Lesher" <wb8foz@nrk.com> To: "nanog list" <nanog@merit.edu> Sent: Sunday, December 29, 2002 4:43 PM Subject: Re: DC power versus AC power
Unnamed Administration sources reported that Michael Painter said:
But, as Stephen already eluded to... Compared with an AC plant
design, to
me, one of the biggest drawbacks of a DC plant is safety (I have had to kick a fellow worker away from the rack before). <<
What was the worker doing? Is this 48 VDC?
Bet so.
And note, it's not just ISP's, of course. I heard that Sprint PCS ha[s,d] a Dallas tech in critical condition and a dead switch after a dropped wrench & resulting fire.
In the words of Phil Esterhaus:
Let's be careful out there....
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
Thus spake joe mcguckin <joe@via.net>:
It only takes 30ma to put your heart into atrial fibrillation. In the usa, gfi's are set to trip at 5ma.
Did you mean 5A, or am I misunderstanding GFIs?
Normally 48VDC wouldn't be considered a 'lethal' voltage (I've talked to telephone technicians who said they used to play a game in the CO by wiring a handle to 90V ring voltage and seeing who could grab it for the longest time),
That explains so many things... S
Unnamed Administration sources reported that Stephen Sprunk said:
It only takes 30ma to put your heart into atrial fibrillation. In the usa, gfi's are set to trip at 5ma.
Did you mean 5A, or am I misunderstanding GFIs?
5ma is correct. It takes very little current to cause fibrillation. GFI's compare the current going out the hot lead of a receptacle with that coming back the neutral. If there is more out than back, it makes the assumption the rest is going through Jill Winecooler/ Joe Sixpack to ground, and trips. -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
"Stephen Sprunk" <ssprunk@cisco.com> writes:
Thus spake joe mcguckin <joe@via.net>:
It only takes 30ma to put your heart into atrial fibrillation. In the usa, gfi's are set to trip at 5ma.
Did you mean 5A, or am I misunderstanding GFIs?
it's 5ma. http://www.national.com/ds/LM/LM1851.pdf ---rob
Thus spake Robert E. Seastrom <rs@seastrom.com>:
"Stephen Sprunk" <ssprunk@cisco.com> writes:
Thus spake joe mcguckin <joe@via.net>:
It only takes 30ma to put your heart into atrial fibrillation. In the usa, gfi's are set to trip at 5ma.
Did you mean 5A, or am I misunderstanding GFIs?
it's 5ma. http://www.national.com/ds/LM/LM1851.pdf
Perfect, thanks. I learn so many interesting things on NANOG, it almost makes up for the noise :) S
participants (12)
-
Barney Wolff -
Charles Sprickman -
David Diaz -
David Lesher -
joe mcguckin -
Kuhtz, Christian -
Michael Painter -
Owen DeLong -
rs＠seastrom.com -
Rubens Kuhl Jr. -
Scott Granados -
Stephen Sprunk