I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why? I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits. ~Seth
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
Because we are stupid.
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
That makes you smarter than the average guy. But, if we were really smart, we'd run at least 277, or maybe 347. Countless amounts of money would be saved on losses (transformation), copper (smaller wire), and many other areas. Most of the stuff we all run is already insulated for these voltage levels. Even better would be all two pole 2 pole 480's or 2 pole 600's, then we wouldn't need neutrals.
From: Alex Rubenstein <alex@corp.nac.net> Date: Tue, 26 May 2009 15:43:20 -0400
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
Because we are stupid.
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
That makes you smarter than the average guy.
But, if we were really smart, we'd run at least 277, or maybe 347. Countless amounts of money would be saved on losses (transformation), copper (smaller wire), and many other areas. Most of the stuff we all run is already insulated for these voltage levels.
Even better would be all two pole 2 pole 480's or 2 pole 600's, then we wouldn't need neutrals.
Oh, yeah! Nothing sounds like more fun than working in a room full of 480 or 600 delta. I LIKE neutrals. (Sort of like I like continuing to have a functioning heart.) -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751
Even better would be all two pole 2 pole 480's or 2 pole 600's, then we wouldn't need neutrals.
Oh, yeah! Nothing sounds like more fun than working in a room full of 480 or 600 delta. I LIKE neutrals. (Sort of like I like continuing to have a functioning heart.)
Nobody said delta.
Oh, yeah! Nothing sounds like more fun than working in a room full of 480 or 600 delta. I LIKE neutrals. (Sort of like I like continuing to have a functioning heart.) Nobody said delta.
If you just run 7200vac into your 1u chinese made peecee servers, then you can eliminate the space use of the step-down transformer in the mechanical room.
Why stop there? Grab a 20,000 volt feeder and create a Tesla datacenter. Think of all the copper you will save... -----Original Message----- From: telmnstr@757.org [mailto:telmnstr@757.org] Sent: Tuesday, May 26, 2009 3:16 PM Cc: nanog@nanog.org Subject: RE: Why choose 120 volts?
Oh, yeah! Nothing sounds like more fun than working in a room full of 480 or 600 delta. I LIKE neutrals. (Sort of like I like continuing to have a functioning heart.) Nobody said delta.
If you just run 7200vac into your 1u chinese made peecee servers, then you can eliminate the space use of the step-down transformer in the mechanical room.
On May 26, 2009, at 3:29 PM, Barney Wolff wrote:
On Tue, May 26, 2009 at 03:23:46PM -0500, Kurt Anderson wrote:
Why stop there? Grab a 20,000 volt feeder and create a Tesla datacenter. Think of all the copper you will save...
Oh, c'mon people! We need to all think green here too. All you need is to locate it in the right spot on the planet and set up a big lightning rod. The first sustainable energy datacenter with no emissions! -Andy
So when one server fails, all the rest fail too? Sorting out holiday lighting is bad enough.... could you imagine having to go through rack after rack finding the one "burned out" server? On Tue, 2009-05-26 at 16:29 -0400, Barney Wolff wrote:
Doesn't even need non-standard servers - just wire them all in series.
On Tue, May 26, 2009 at 03:23:46PM -0500, Kurt Anderson wrote:
Why stop there? Grab a 20,000 volt feeder and create a Tesla datacenter. Think of all the copper you will save...
-- "Prediction is very difficult, especially about the future." Niels Bohr -- Ray Sanders Linux Administrator Village Voice Media Office: 602-744-6547 Cell: 602-300-4344
On May 26, 2009, at 1:34 PM, Ray Sanders wrote:
So when one server fails, all the rest fail too?
Sorting out holiday lighting is bad enough....
could you imagine having to go through rack after rack finding the one "burned out" server?
Who has to imagine? Some of us remember thinnet (10base2). Owen
Ugh, please don't remind me of the hell that was coax. On Tue, 2009-05-26 at 13:45 -0700, Owen DeLong wrote:
On May 26, 2009, at 1:34 PM, Ray Sanders wrote:
So when one server fails, all the rest fail too?
Sorting out holiday lighting is bad enough....
could you imagine having to go through rack after rack finding the one "burned out" server?
Who has to imagine? Some of us remember thinnet (10base2).
Owen
-- "Prediction is very difficult, especially about the future." Niels Bohr -- Ray Sanders Linux Administrator Village Voice Media Office: 602-744-6547 Cell: 602-300-4344
I still have a couple of Ethernet cards for 10Base2, and cables. ^.^ Yes, if someone unplug or it is loosen in the middle/end, it will be fun. I guess it's going to be another bagel/coffee time except network support people. Alex Ray Sanders wrote:
Ugh, please don't remind me of the hell that was coax.
On Tue, 2009-05-26 at 13:45 -0700, Owen DeLong wrote:
On May 26, 2009, at 1:34 PM, Ray Sanders wrote:
So when one server fails, all the rest fail too?
Sorting out holiday lighting is bad enough....
could you imagine having to go through rack after rack finding the one "burned out" server?
Who has to imagine? Some of us remember thinnet (10base2).
Owen
Yes - think of all the nasty partial failure cases that can be eliminated - each entire datacenter is either up or down. Much simpler! Getting back to reality, I've watched more than one electrician do a two-finger liveness test on a 120v circuit, and done it myself. 240v HURTS, and I've not seen a pro finger it deliberately. But I haven't actually asked. On Tue, May 26, 2009 at 01:34:41PM -0700, Ray Sanders wrote:
So when one server fails, all the rest fail too?
On Tue, 2009-05-26 at 16:29 -0400, Barney Wolff wrote:
Doesn't even need non-standard servers - just wire them all in series.
On Tue, May 26, 2009 at 03:23:46PM -0500, Kurt Anderson wrote:
Why stop there? Grab a 20,000 volt feeder and create a Tesla datacenter.
-- Barney Wolff I never met a computer I didn't like.
Barney Wolff wrote:
Getting back to reality, I've watched more than one electrician do a two-finger liveness test on a 120v circuit, and done it myself. 240v HURTS, and I've not seen a pro finger it deliberately. But I haven't actually asked.
During my residential electrical apprenticeship, one of the tricks of the trade I learnt was a quick two finger test on 120, but never anything higher than that. That was years ago. I would never do anything of the sort intentionally ever again, even on low voltage systems (my girlfriend is an Occupational Health and Safety Officer, and she frowns on that sort of thing ;) It really depends on your conductivity to ground ie what you are standing on and the shoes you are wearing whether you will remain safe by 'testing' for hotness on a circuit by touching it. @120V, 1.2 mA is enough to tell you that the line is live. 15mA is the let-go threshold, and 100mA can kill within a second. 200mA will pretty much kill instantly. Even at 120V on non-conductive ground, if you ever accidentally touched the grounded box while touching the live wire, you will likely be dead before the breaker trips. Steve
It will be like at Christmas time, trying to find the bad bulb. -----Original Message----- From: Barney Wolff [mailto:barney@databus.com] Sent: Tuesday, May 26, 2009 4:29 PM To: nanog@nanog.org Subject: Re: Why choose 120 volts? Doesn't even need non-standard servers - just wire them all in series. On Tue, May 26, 2009 at 03:23:46PM -0500, Kurt Anderson wrote:
Why stop there? Grab a 20,000 volt feeder and create a Tesla datacenter. Think of all the copper you will save...
It will be like at Christmas time, trying to find the bad bulb.
This sounds like an opportunity for you guys to find "that special tool" everyone needs, and sell it to all of us. ;-) (Dave's with Stayonline, and if you haven't been to his company's web site, they're full of wonderful odds and ends ... at a bit of a mark- up.) ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.
On May 26, 2009, at 4:23 PM, Kurt Anderson wrote:
Why stop there? Grab a 20,000 volt feeder and create a Tesla datacenter. Think of all the copper you will save...
http://video.google.com/videoplay?docid=4468957986746104671 - Jared
I stop at licking the 9v batteries, intentionally, but I have been burned by 50KV before. Just imagine the copper you could save by just sending the energy thru the air, but then I guess the DC would sound and look more like the death star. -----Original Message----- From: Jared Mauch [mailto:jared@puck.nether.net] Sent: Tuesday, May 26, 2009 6:56 PM To: Kurt Anderson Cc: nanog@nanog.org Subject: Re: Why choose 120 volts? On May 26, 2009, at 4:23 PM, Kurt Anderson wrote:
Why stop there? Grab a 20,000 volt feeder and create a Tesla datacenter. Think of all the copper you will save...
http://video.google.com/videoplay?docid=4468957986746104671 - Jared
1) Equipment used to not be dual voltage 2) For smaller scale, 120V UPS and distribution equipment is usually cheaper 3) 120V embedded itself into operations as a result. 4) We're all lazy and hate change. On Tue, May 26, 2009 at 12:39:10PM -0700, Seth Mattinen wrote:
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
~Seth
--- Wayne Bouchard web@typo.org Network Dude http://www.typo.org/~web/
Also, adding followings. 5) availability from local power provider(s) 6) local regulation such as fire department safety rules... 7) for your own safety... (120V may not kill people, but 240V can do...) If you want better, why not just have everything to DC power ? Something like 48V... Alex Wayne E. Bouchard wrote:
1) Equipment used to not be dual voltage
2) For smaller scale, 120V UPS and distribution equipment is usually cheaper
3) 120V embedded itself into operations as a result.
4) We're all lazy and hate change.
On Tue, May 26, 2009 at 12:39:10PM -0700, Seth Mattinen wrote:
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
~Seth
--- Wayne Bouchard web@typo.org Network Dude http://www.typo.org/~web/
On May 26, 2009, at 1:48 PM, Alex H. Ryu wrote:
Also, adding followings.
5) availability from local power provider(s)
I don't know of anywhere in the US/Canada where power comes into the building as strictly 110-120V. That is almost always delivered either as 1 leg of a 3-phase 208 service (most commercial/industrial deliveries) or as two hots (240V across the two hots) and a neutral (120V from either hot to neutral). Most datacenters are taking much higher voltage feeds from their utilities and most of the readily available step-down transformers and UPSs will produce 208 three-phase or 240V as described above. I am not an expert on power outside of the US, but, to the best of my knowledge, Japan's 100V/50Hz is one of the few other countries using less than 208V as their standard.
6) local regulation such as fire department safety rules...
I seriously question this one. Can you point to any examples?
7) for your own safety... (120V may not kill people, but 240V can do...)
It's relatively easy to kill someone with 12V, so, I don't see how 10x that is significantly less dangerous than 20x. Sticking your fingers in a light socket is going to hurt regardless of the voltage. Yes, 240V can hurt more and faster, but, at the end of the day, it's not significantly more likely to kill you than 110. Fortunately, most servers don't have light sockets in the high voltage portion of the server.
If you want better, why not just have everything to DC power ? Something like 48V...
There's a whole host of reasons, but, the biggest one boils down to cost... Cost of the larger wires, cost of the increased line losses, etc. Owen
Alex
Wayne E. Bouchard wrote:
1) Equipment used to not be dual voltage
2) For smaller scale, 120V UPS and distribution equipment is usually cheaper
3) 120V embedded itself into operations as a result.
4) We're all lazy and hate change.
On Tue, May 26, 2009 at 12:39:10PM -0700, Seth Mattinen wrote:
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
~Seth
--- Wayne Bouchard web@typo.org Network Dude http://www.typo.org/~web/
As a Holder of two different FCC licenses I can tell you voltage is not what kills, it is amps and location that kill. Actually in certain cases as long at you have good electrical isolation, high enough dielectric breakdown voltage, and good grounding higher voltages can be safer and more efficient. Also, Thomas Edison was the one that discovered that trying to deliver DC more than a few feet was not a good idea. -- ----------------- Brian Raaen Network Engineer email: /braaen@zcorum.com/ <mailto:braaen@zcorum.com> FCC GROL (General Radiotelephone Operators License) FCC Amateur Extra Class KG4CXN (Also certified volunteer examiner with CAVAC and ARRL) Alex H. Ryu wrote:
Also, adding followings.
5) availability from local power provider(s)
6) local regulation such as fire department safety rules...
7) for your own safety... (120V may not kill people, but 240V can do...)
If you want better, why not just have everything to DC power ? Something like 48V...
Alex
Wayne E. Bouchard wrote:
1) Equipment used to not be dual voltage
2) For smaller scale, 120V UPS and distribution equipment is usually cheaper
3) 120V embedded itself into operations as a result.
4) We're all lazy and hate change.
On Tue, May 26, 2009 at 12:39:10PM -0700, Seth Mattinen wrote:
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
~Seth
--- Wayne Bouchard web@typo.org Network Dude http://www.typo.org/~web/
The early problems with distance transmission of DC really didn't have anything to do with the inherent properties of DC current, but with the fact that, at the time, there was no good way to convert DC voltages up and down in a similar fashion to the function performed by transformers with AC. The inability to step DC up to high voltage for distant transmission was the real killer for early use of DC. Lately, very high voltage DC is actually a better performer than AC for some long distance transmission situations. In particular, DC can be used to move power between unsynchronized grids without the usual problems, and to transmit power through undersea cables, where AC capacitance losses would add up. See: http://en.wikipedia.org/wiki/High-voltage_direct_current#Advantages_of_HVDC_... The main thing that has changed since the early days is that much better semiconductors are available to make the voltage conversion feasible... -Dorn 2009/5/27 Brian Raaen <braaen@zcorum.com>:
As a Holder of two different FCC licenses I can tell you voltage is not what kills, it is amps and location that kill. Actually in certain cases as long at you have good electrical isolation, high enough dielectric breakdown voltage, and good grounding higher voltages can be safer and more efficient. Also, Thomas Edison was the one that discovered that trying to deliver DC more than a few feet was not a good idea.
-- ----------------- Brian Raaen Network Engineer email: /braaen@zcorum.com/ <mailto:braaen@zcorum.com> FCC GROL (General Radiotelephone Operators License) FCC Amateur Extra Class KG4CXN (Also certified volunteer examiner with CAVAC and ARRL)
Alex H. Ryu wrote:
Also, adding followings.
5) availability from local power provider(s)
6) local regulation such as fire department safety rules...
7) for your own safety... (120V may not kill people, but 240V can do...)
If you want better, why not just have everything to DC power ? Something like 48V...
Alex
Wayne E. Bouchard wrote:
1) Equipment used to not be dual voltage
2) For smaller scale, 120V UPS and distribution equipment is usually cheaper
3) 120V embedded itself into operations as a result.
4) We're all lazy and hate change.
On Tue, May 26, 2009 at 12:39:10PM -0700, Seth Mattinen wrote:
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
~Seth
--- Wayne Bouchard web@typo.org Network Dude http://www.typo.org/~web/
Brian Raaen wrote:
As a Holder of two different FCC licenses I can tell you voltage is not what kills, it is amps and location that kill. Actually in certain cases as long at you have good electrical isolation, high enough dielectric breakdown voltage, and good grounding higher voltages can be safer and more efficient. Also, Thomas Edison was the one that discovered that trying to deliver DC more than a few feet was not a good idea.
Hi Brian, as a Radio Amateur you should know AC radiates, DC not. We did have really big trouble when when an ocean liner had to pass under a cable bridge and for the passage, that cable bridge had to be grounded. Eddies running through the grid brought half of the grid down. The other half killed my computer with overvoltage. Hydro Que'bec is running DC from the northpole down to South Florida. http://www.abb.com/cawp/gad02181/c1256d71001e0037c12568340029b5c4.aspx?&opendatabase&v=17ea&e=us&m=100a& Apropos, I remember a frenchman who fed his personal computer 288 Volts DC. Theory says no matter whether the setting of the powersupply is 120 AC ord 240 AC it should work. Try at your own risk. I haven't :) Kind regards Peter DL2FBA -- Peter and Karin Dambier Cesidian Root - Radice Cesidiana Rimbacher Strasse 16 D-69509 Moerlenbach-Bonsweiher +49(6209)795-816 (Telekom) +49(6252)750-308 (VoIP: sipgate.de) mail: peter@peter-dambier.de http://www.peter-dambier.de/ http://iason.site.voila.fr/ https://sourceforge.net/projects/iason/ ULA= fd80:4ce1:c66a::/48
On Wed, 27 May 2009, Peter Dambier wrote:
Theory says no matter whether the setting of the powersupply is 120 AC ord 240 AC it should work. Try at your own risk. I haven't :)
I have. Was in the Netherlands last week, and plugged my laptop power supply into the 240v (or so) feed, without incident (after referring to the label). I haven't seen a PC power supply which is incapable of both 120v/60hz and 240v/50hz in a very long time. I think even my 486 from 1994 had a switch for 120/240 -- nowadays it auto-senses, no switch required. --------------------------------------------------------------------------- Peter Beckman Internet Guy beckman@angryox.com http://www.angryox.com/ ---------------------------------------------------------------------------
On 27 mei 2009, at 18:03, Peter Beckman wrote:
I haven't seen a PC power supply which is incapable of both 120v/ 60hz and 240v/50hz in a very long time.
After this nice voltage discussion, what about hertz? Would it be more efficient for us Europeans to run our stuff at 60 Hz rather than 50? I hear that a 50 Hz grid loses 15% more due to inefficiencies than a 60 Hz grid. Not sure if that also applies over short distances, though. And apparently you can run your Apple laptop's power supply on 80V DC... The switching power supply doesn't care as long as the voltage is low enough to not fry the half of the rectifier diodes in continuous use. (Try at your own risk, of course.)
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
208 isn't all that great. On one hand, a 20A 208V circuit is vaguely more convenient than a 30A 120V circuit because it is delivering a bit more power to the rack (3328 vs 2880), and it's likely to work with a lot of modern equipment containing autoranging power supplies. On the flip side, with 120, you don't have to have "odd cords," and it is somewhat easier to "right-size" power for a rack (20A, 30A, 2x20A), so for an average rack that isn't crammed with high power webhosting 1U's (etc), a customer might actually find that the ability to right- size the power feed is more flexible with 120V. And I don't like not having anywhere to plug in my power screwdriver's recharger... I suppose I should see if I can find someplace that has a transformer of an appropriate size, or does anyone already have the part number for something that can provide a few hunderd milliamps of 120V from 208? :-) ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.
Joe Greco wrote:
208 isn't all that great. On one hand, a 20A 208V circuit is vaguely more convenient than a 30A 120V circuit because it is delivering a bit more power to the rack (3328 vs 2880), and it's likely to work with a lot of modern equipment containing autoranging power supplies.
On the flip side, with 120, you don't have to have "odd cords," and it is somewhat easier to "right-size" power for a rack (20A, 30A, 2x20A), so for an average rack that isn't crammed with high power webhosting 1U's (etc), a customer might actually find that the ability to right- size the power feed is more flexible with 120V.
I don't find it makes much difference, really. People are used to working with 120 only because that's how we roll in the USA; scary high voltage is for the oven and dryer. I like odd cords; it makes the protected power stuff blazingly obvious and slightly harder to plug dumb things into a UPS branch circuit because hey, a plug is a plug, right?
And I don't like not having anywhere to plug in my power screwdriver's recharger... I suppose I should see if I can find someplace that has a transformer of an appropriate size, or does anyone already have the part number for something that can provide a few hunderd milliamps of 120V from 208? :-)
True, you do lose the convenience outlet factor. I made up for it by placing standard 120V outlets (utility/generator only) along the walls. It works out because I hate those stupid "wall warts" with a passion. I go out of my way to buy products that come with a corded transformer, especially if it has a C14 connector on it. If you're adept at electrical stuff you can always get a small transformer, put it in a box, stick a C14 on the high side and a 5-15 on the low side. Nothing fancy required. ~Seth
On Tue, May 26, 2009 at 03:39:30PM -0500, Joe Greco wrote:
And I don't like not having anywhere to plug in my power screwdriver's recharger... I suppose I should see if I can find someplace that has a transformer of an appropriate size, or does anyone already have the part number for something that can provide a few hunderd milliamps of 120V from 208? :-)
We always seem to have an odd device or three that needs 120V, like a wallwart for an external modem or LCD KVM console, or some legacy specialized gear (CBORD comes to mind). For those we have been providing a single circuit/PDU in the room that runs at 120V and running extension cords as necessary. Everything else is 208V.
Once upon a time, Joe Greco <jgreco@ns.sol.net> said:
And I don't like not having anywhere to plug in my power screwdriver's recharger... I suppose I should see if I can find someplace that has a transformer of an appropriate size, or does anyone already have the part number for something that can provide a few hunderd milliamps of 120V from 208? :-)
Isn't 208V usually provided as a connection across two phases of a 3 phase circuit? In that case, you get 120V by going between one phase and neutral (no transformer required). You need a NEMA 14 (4 wire) connector to get two phases, neutral, and ground (provides 1 208V circuit and/or 2 120V circuits) or a NEMA L21 (5 wire) connector to get all three phases, neutral, and ground (provides 3 208V circuits and/or 3 120V circuits). -- Chris Adams <cmadams@hiwaay.net> Systems and Network Administrator - HiWAAY Internet Services I don't speak for anybody but myself - that's enough trouble.
Yes, you are correct Chris. The loss from getting 240 from two legs is due to the fact that it is at 120 instead of 180 deg's. -----Original Message----- From: Chris Adams [mailto:cmadams@hiwaay.net] Sent: Tuesday, May 26, 2009 7:52 PM To: Joe Greco Cc: nanog@nanog.org Subject: Re: Why choose 120 volts? Once upon a time, Joe Greco <jgreco@ns.sol.net> said:
And I don't like not having anywhere to plug in my power screwdriver's recharger... I suppose I should see if I can find someplace that has a transformer of an appropriate size, or does anyone already have the part number for something that can provide a few hunderd milliamps of 120V from 208? :-)
Isn't 208V usually provided as a connection across two phases of a 3 phase circuit? In that case, you get 120V by going between one phase and neutral (no transformer required). You need a NEMA 14 (4 wire) connector to get two phases, neutral, and ground (provides 1 208V circuit and/or 2 120V circuits) or a NEMA L21 (5 wire) connector to get all three phases, neutral, and ground (provides 3 208V circuits and/or 3 120V circuits). -- Chris Adams <cmadams@hiwaay.net> Systems and Network Administrator - HiWAAY Internet Services I don't speak for anybody but myself - that's enough trouble.
Once upon a time, Joe Greco <jgreco@ns.sol.net> said:
And I don't like not having anywhere to plug in my power screwdriver's recharger... I suppose I should see if I can find someplace that has a transformer of an appropriate size, or does anyone already have the part number for something that can provide a few hunderd milliamps of 120V from 208? :-)
Isn't 208V usually provided as a connection across two phases of a 3 phase circuit? In that case, you get 120V by going between one phase and neutral (no transformer required).
Yes, but this doesn't imply that you have access to those other phases. It is easy enough to be delivered 208V single phase service in a data center environment. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.
Once upon a time, Joe Greco <jgreco@ns.sol.net> said:
And I don't like not having anywhere to plug in my power screwdriver's recharger... I suppose I should see if I can find someplace that has a transformer of an appropriate size, or does anyone already have
See: http://www.3phasepower.org/3phasewiring.htm -----Original Message----- From: Joe Greco [mailto:jgreco@ns.sol.net] Sent: Tuesday, May 26, 2009 8:20 PM To: Chris Adams Cc: nanog@nanog.org Subject: Re: Why choose 120 volts? the
part number for something that can provide a few hunderd milliamps of 120V from 208? :-)
Isn't 208V usually provided as a connection across two phases of a 3 phase circuit? In that case, you get 120V by going between one phase and neutral (no transformer required).
Yes, but this doesn't imply that you have access to those other phases. It is easy enough to be delivered 208V single phase service in a data center environment. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.
Joe Greco wrote:
And I don't like not having anywhere to plug in my power screwdriver's recharger... I suppose I should see if I can find someplace that has a transformer of an appropriate size, or does anyone already have the part number for something that can provide a few hunderd milliamps of 120V from 208? :-) Isn't 208V usually provided as a connection across two phases of a 3
Once upon a time, Joe Greco <jgreco@ns.sol.net> said: phase circuit? In that case, you get 120V by going between one phase and neutral (no transformer required).
Yes, but this doesn't imply that you have access to those other phases. It is easy enough to be delivered 208V single phase service in a data center environment.
... JG
Correct. I have a Smart-UPS RT connected across two legs of 3 phase for 208. The unit does not have a neutral, only ground, so it's 3 wires in and 3 out. The output is only 208 L-L with odd voltages on L-G. Since there's no neutral, it can only be used to drive 208 loads or a transformer for 120. ~Seth
On Tue, 26 May 2009, Joe Greco wrote:
Once upon a time, Joe Greco <jgreco@ns.sol.net> said:
And I don't like not having anywhere to plug in my power screwdriver's recharger... I suppose I should see if I can find someplace that has
Yes, but this doesn't imply that you have access to those other phases. It is easy enough to be delivered 208V single phase service in a data center environment.
Uh. 208v single phase is functionally the same as 240v single phase. You grab 1 hot, neutral off the ground, and you have a common 110v circuit. Even if you're 3 phase to your PDU, it's still single phase to the servers. (specialty gear excluded, but those generally plug direct to the circuit, not to a PDU). This makes it very very easy to solve this problem, and I keep a few of these floating around at all of my datacenters, with big labels saying who they belong too. (ignoring the fact that for drill charging at least there's usually house power available, but crash carts need these...) C14 (M) to 5-15 (F) adaptor cable: http://www.cdw.com/shop/products/default.aspx?edc=1036852 I also use them to run wall warts, etc, as needed. --- david raistrick http://www.netmeister.org/news/learn2quote.html drais@icantclick.org http://www.expita.com/nomime.html
On Tue, 26 May 2009, Joe Greco wrote:
Once upon a time, Joe Greco <jgreco@ns.sol.net> said:
And I don't like not having anywhere to plug in my power screwdriver's recharger... I suppose I should see if I can find someplace that has
Yes, but this doesn't imply that you have access to those other phases. It is easy enough to be delivered 208V single phase service in a data center environment.
Uh. 208v single phase is functionally the same as 240v single phase.
Yes, functionally, it is.
You grab 1 hot, neutral off the ground, and you have a common 110v circuit. Even if you're 3 phase to your PDU, it's still single phase to the servers. (specialty gear excluded, but those generally plug direct to the circuit, not to a PDU).
Go tell your electrical inspector that you're using the ground as a neutral. I'll make the popcorn ... put simply, that's not allowed, for Very Good Reasons.
This makes it very very easy to solve this problem,
No it doesn't, and the following doesn't even seem to relate:
and I keep a few of these floating around at all of my datacenters, with big labels saying who they belong too. (ignoring the fact that for drill charging at least there's usually house power available, but crash carts need these...)
C14 (M) to 5-15 (F) adaptor cable:
http://www.cdw.com/shop/products/default.aspx?edc=1036852
I also use them to run wall warts, etc, as needed.
Great, you're the latest person to invent a way to present a 5-15R that offers something besides 120VAC. This is neither new nor novel, but it *is* dangerous and risky, and in no way "solves the problem." Plugging a device that is designed to run on 120V into 208V will probably result in (at least!) one of: 1) smoke 2) fire 3) burning components 4) dead device 5) burning batteries (in the case of the aforementioned charger) 6) general excitement and panic in the data center in the event that none of the above happen immediately, but rather some time after you leave. 7) etc. The basic problem here is that there are still many devices out there that do not have autoranging power supplies. As for "for drill charging at least there's usually house power available", well, that sucks. We're at Equinix. There are periods where no one uses the drill, or the power screwdriver, for months at a time. With 120V in the cage, I left the chargers hooked up and trickle charging. Neither the drill nor the power screwdriver have autoranging power supplies. So now with 208V, someone has to bring along batteries, because we can't leave them on-site, or they'll go stale. Bleh. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.
On Tue, 26 May 2009, Joe Greco wrote:
Great, you're the latest person to invent a way to present a 5-15R that offers something besides 120VAC. This is neither new nor novel, but it *is* dangerous and risky, and in no way "solves the problem."
No, this does NOT present 208v at a 5-15R. Don't believe me, buy one and put a voltmeter across it. I'll leave the FUD to others. --- david raistrick http://www.netmeister.org/news/learn2quote.html drais@icantclick.org http://www.expita.com/nomime.html
Seems like if the c14 was connected to a 240v PDU the 5-15 would deliver 240v to the equipment, arc/pop tripping the breaker on the PDU as soon as it is connected killing power to everything on that PDU. Or am I missing something, Also hard to believe it is UL since the c14 is rated 125/250v and well captain obvious says the 5-15 125v max. -----Original Message----- From: david raistrick [mailto:drais@icantclick.org] Sent: Wednesday, May 27, 2009 5:37 PM To: Joe Greco Cc: nanog@nanog.org Subject: Re: Why choose 120 volts? On Tue, 26 May 2009, Joe Greco wrote:
Great, you're the latest person to invent a way to present a 5-15R that offers something besides 120VAC. This is neither new nor novel, but it *is* dangerous and risky, and in no way "solves the problem."
No, this does NOT present 208v at a 5-15R. Don't believe me, buy one and put a voltmeter across it. I'll leave the FUD to others. --- david raistrick http://www.netmeister.org/news/learn2quote.html drais@icantclick.org http://www.expita.com/nomime.html
Seems like if the c14 was connected to a 240v PDU the 5-15 would deliver 240v to the equipment, arc/pop tripping the breaker on the PDU as soon as it is connected killing power to everything on that PDU.
Well, the latter half of that is making all sorts of assumptions. Your typical 208V 20A circuit is capable of delivering watts roughly equivalent to a 120V 30A circuit; if whatever is being destroyed is beefy enough to momentarily short out that much power, yes, the breaker should trip, but in many cases, a power supply might only be designed to handle a hundred watts or so, and who knows what component leads, PCB traces, components, etc., might burn out quickly before the PDU breaker really "notices."
Or am I missing something, Also hard to believe it is UL since the c14 is rated 125/250v and well captain obvious says the 5-15 125v max.
It is UL when used in the intended manner. Note that it is marketed as a monitor feedthrough power adapter (or something like that) - not a 208V-to-120V converter dongle. There are many examples of things you *can* do that are hazardous with UL listed devices. UL listing mainly means that something isn't all that dangerous (from an insurance perspective, at that). Consider, for example, that you can plug a household extension cord (UL listed, 14ga, ~13A @ 120V) into a 20 amp circuit, and then plug in 16 amps worth of stuff, and watch the cord heat. It isn't UL rated for such use. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.
Dave Larter wrote:
Seems like if the c14 was connected to a 240v PDU the 5-15 would deliver 240v to the equipment, arc/pop tripping the breaker on the PDU as soon as it is connected killing power to everything on that PDU. Or am I missing something?
If you plug a PDU into a service that's higher voltage than expected, why would the PDU circuit breaker trip? That breaker is measuring current, AFAICT, though in the end it might be measuring power. Regardless, it isn't measuring voltage, because that isn't constant (it's AC, after all) and is likely to drop under a short circuit, not skyrocket like the current will. pt
I was referring to, when a 120v device is attached to the 5-15 end of the cord. On the inside of these grounded devices I often find that the neutral is tied to ground. So in the case of the c14 being connected to a 240v PDU when I 120v device is connected it will ground one of the load lines. And yes, voltage will drop while current spikes, thus tripping the breaker. -----Original Message----- From: Pete Templin [mailto:petelists@templin.org] Sent: Thursday, May 28, 2009 10:39 AM To: Dave Larter Cc: nanog@nanog.org Subject: Re: Why choose 120 volts? Dave Larter wrote:
Seems like if the c14 was connected to a 240v PDU the 5-15 would deliver 240v to the equipment, arc/pop tripping the breaker on the PDU as soon as it is connected killing power to everything on that PDU. Or am I missing something?
If you plug a PDU into a service that's higher voltage than expected, why would the PDU circuit breaker trip? That breaker is measuring current, AFAICT, though in the end it might be measuring power. Regardless, it isn't measuring voltage, because that isn't constant (it's AC, after all) and is likely to drop under a short circuit, not skyrocket like the current will. pt
Dave Larter wrote:
I was referring to, when a 120v device is attached to the 5-15 end of the cord. On the inside of these grounded devices I often find that the neutral is tied to ground.
Often??? Name one device designed that way. And please tell us how well that device works when you plug it in to a GFCI-protected outlet in your kitchen. I believe that you are very mistaken. -- Jay Hennigan - CCIE #7880 - Network Engineering - jay@impulse.net Impulse Internet Service - http://www.impulse.net/ Your local telephone and internet company - 805 884-6323 - WB6RDV
david raistrick wrote:
On Tue, 26 May 2009, Joe Greco wrote:
Great, you're the latest person to invent a way to present a 5-15R that offers something besides 120VAC. This is neither new nor novel, but it *is* dangerous and risky, and in no way "solves the problem."
No, this does NOT present 208v at a 5-15R. Don't believe me, buy one and put a voltmeter across it.
It indeed can and does present 208V (or 240v in some cases) to a 5-15R. I use one of them for that purpose to power my laptop charger from the IEC power strips present in racks fed from 208v. That cord is just an adapter with three copper wires. Putting a voltmeter on its output will just measure what is present on its input. That cord mated to an IEC cord in Europe will put 240v 50 Hz on the receptacle. Mated to an IEC PDU on a 208v-wired rack, it will measure 208v. This is not necessarily dangerous, *IF* you are aware of it and don't leave it plugged in for someone unaware of the voltage present to use. Radio Shack sells an adapter from the Schucko round pin 240v receptacles to a 5-15R. It works just fine for my laptop because the laptop power supply is *designed* to operate on any voltage from 100 to 240 volts. It would NOT work just fine if someone plugged in a 120v-only appliance. If you leave that cord plugged in to a 208V-fed rack and walk away from it, there is a likelihood that someone else looking for a convenience outlet will discover it and plug something in. If that "something" isn't happy with the 208v it gets, the magic smoke that is contained in the device will escape. As we all know, once the smoke gets out, the device will stop functioning. -- Jay Hennigan - CCIE #7880 - Network Engineering - jay@impulse.net Impulse Internet Service - http://www.impulse.net/ Your local telephone and internet company - 805 884-6323 - WB6RDV
david raistrick wrote:
On Tue, 26 May 2009, Joe Greco wrote:
Great, you're the latest person to invent a way to present a 5-15R that offers something besides 120VAC. This is neither new nor novel, but it *is* dangerous and risky, and in no way "solves the problem."
No, this does NOT present 208v at a 5-15R. Don't believe me, buy one and put a voltmeter across it.
I'll leave the FUD to others.
Here's the L-G voltage off the 208v taps from an isolation transformer in a system with no neutral: http://ninjamonkey.us/not_120_volts.jpg In other words, in a system with no neutral, it's not designed to do 120v loads. The L-L voltage on that same PDU is 211. Also, the device you linked will present high voltage because again, no neutral. ~Seth
On Wed, 27 May 2009, Seth Mattinen wrote:
Here's the L-G voltage off the 208v taps from an isolation transformer in a system with no neutral: http://ninjamonkey.us/not_120_volts.jpg
Not 120, but 90 give or take. 90 is at the low end of the acceptable range for common household 110/120v service. Depending on how the phases are balanced in your facility, you may see that fluctuate up or down, of course. If you measure hot to hot on the same PDU, do you get anywhere close to 208? I'm going to suspect either your fairly out of balance, or you've got a good bit of voltage drop by the time it arrives.... But since the concensus from those who haven't used this is that the device will present 208/240 at the 5-15 plug, I withdraw my suggestion and leave you to your own methods. (for the rest, test it yourself) I also won't argue using ground for neutral, that's like arguing bonded vs unbonded panels. --- david raistrick http://www.netmeister.org/news/learn2quote.html drais@icantclick.org http://www.expita.com/nomime.html
The ground is not supposed to carry any current where as the neutral is. If you tried to carry current on the ground of a CGFI protected circuit it would trip. -----Original Message----- From: david raistrick [mailto:drais@icantclick.org] Sent: Wednesday, May 27, 2009 6:30 PM To: Seth Mattinen Cc: nanog@nanog.org Subject: Re: Why choose 120 volts? On Wed, 27 May 2009, Seth Mattinen wrote:
Here's the L-G voltage off the 208v taps from an isolation transformer in a system with no neutral: http://ninjamonkey.us/not_120_volts.jpg
Not 120, but 90 give or take. 90 is at the low end of the acceptable range for common household 110/120v service. Depending on how the phases are balanced in your facility, you may see that fluctuate up or down, of course. If you measure hot to hot on the same PDU, do you get anywhere close to 208? I'm going to suspect either your fairly out of balance, or you've got a good bit of voltage drop by the time it arrives.... But since the concensus from those who haven't used this is that the device will present 208/240 at the 5-15 plug, I withdraw my suggestion and leave you to your own methods. (for the rest, test it yourself) I also won't argue using ground for neutral, that's like arguing bonded vs unbonded panels. --- david raistrick http://www.netmeister.org/news/learn2quote.html drais@icantclick.org http://www.expita.com/nomime.html
On Wed, 27 May 2009, Seth Mattinen wrote:
Here's the L-G voltage off the 208v taps from an isolation transformer in a system with no neutral: http://ninjamonkey.us/not_120_volts.jpg
Not 120, but 90 give or take. 90 is at the low end of the acceptable range for common household 110/120v service.
Yeah, but that's L-G voltage (geez, did you even look at the picture?) And Seth just finished telling us that it was 211 L-L: Seth > "The L-L voltage on that same PDU is 211." What's going to be presented at the neutral and hot of the 5-15R of the monitor power adapter are the L and L. Think about it. Or get out a meter and test.
Depending on how the phases are balanced in your facility, you may see that fluctuate up or down, of course. If you measure hot to hot on the same PDU, do you get anywhere close to 208?
Yes, Seth just finished telling us that in the portion of his message you conveniently snipped.
I'm going to suspect either your fairly out of balance, or you've got a good bit of voltage drop by the time it arrives....
But since the concensus from those who haven't used this is that the device will present 208/240 at the 5-15 plug, I withdraw my suggestion and leave you to your own methods. (for the rest, test it yourself)
For those of us who *have* used this, we're telling you that it'll present 208/240 at the 5-15R.
I also won't argue using ground for neutral, that's like arguing bonded vs unbonded panels.
No it's not. Only idiots argue for using ground for neutral. In doubt? Ask your electrical inspector. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.
On Tue, 26 May 2009, Joe Greco wrote:
Great, you're the latest person to invent a way to present a 5-15R that offers something besides 120VAC. This is neither new nor novel, but it *is* dangerous and risky, and in no way "solves the problem."
No, this does NOT present 208v at a 5-15R. Don't believe me, buy one and put a voltmeter across it.
I _don't_ believe you, because we've put a voltmeter across it. I know a number of cages where someone has extended a 208 or 240V service using a monitor power adapter, a 5-15 extension cord, and an ordinary 5-15 outlet strip; the smart people put a BIG WARNING STICKER on it because they know that the voltage present isn't 120. The dumb ones are unaware of what they've done and figure "my laptop works so all is good".
I'll leave the FUD to others.
... and move right on to outright misstatements? ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.
On Wed, 27 May 2009, Joe Greco wrote:
... and move right on to outright misstatements?
No, statements based on personal experience. I -fully- expected to get 208v out of them, but in testing didn't. Perhaps the ten I ordered were unique. Or perhaps I don't know how to operate a VOM, or perhaps I'm full of sh!t. I didn't expect this to generate such an uproar...but I forgot this is nanog. ;-) .d --- david raistrick http://www.netmeister.org/news/learn2quote.html drais@icantclick.org http://www.expita.com/nomime.html
On Wed, May 27, 2009 at 07:25:50PM -0400, david raistrick wrote:
On Wed, 27 May 2009, Joe Greco wrote:
... and move right on to outright misstatements?
No, statements based on personal experience. I -fully- expected to get 208v out of them, but in testing didn't.
Note that it is also perfectly possible and reasonable to use IEC 320 C13 PDUs for 120V service. You may have unknowingly used the monitor adapter on a 120V feed, having assumed that C13 == 208/240, when it doesn't necessarily mean that.
On Tue, 26 May 2009 19:51:42 -0400, Chris Adams <cmadams@hiwaay.net> wrote:
Isn't 208V usually provided as a connection across two phases of a 3 phase circuit? In that case, you get 120V by going between one phase and neutral (no transformer required).
Indeed it is. If you want to see it yourself, measure the voltage between "hots" on different circuits. I see 208-212V depending on the legs (they aren't evenly loaded.) This is easier to do in a data center, but with a long extention cord it can be done with the office. :-) (of course, having the building wiring diagram(s) makes for a short hunt.) --Ricky
Our power is handed to us at 480v. We then deliver it to the customer at whatever they need. The nice thing about 120v is that everything uses it. No odd cords (as mentioned before) or expensive PDUs. I've had a lot of people suggest that running our servers at 240v would save us money because we'd use less amps. Last time I looked at my bill I was being billed by the kWh, not amp and 240v at half the amps is still the same wattage. I've been told this so many times though that I'm starting to doubt myself. If anyone can present a reason for me to switch to 240v I'd like to hear it. Aaron -----Original Message----- From: Seth Mattinen [mailto:sethm@rollernet.us] Sent: Tuesday, May 26, 2009 2:39 PM To: nanog@nanog.org Subject: Why choose 120 volts? I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why? I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits. ~Seth
Aaron Wendel wrote:
Our power is handed to us at 480v. We then deliver it to the customer at whatever they need. The nice thing about 120v is that everything uses it. No odd cords (as mentioned before) or expensive PDUs.
I've had a lot of people suggest that running our servers at 240v would save us money because we'd use less amps. Last time I looked at my bill I was being billed by the kWh, not amp and 240v at half the amps is still the same wattage. I've been told this so many times though that I'm starting to doubt myself. If anyone can present a reason for me to switch to 240v I'd like to hear it.
Some servers (HP/Compaq comes to mind) and Cisco switches have limitations in terms of performance and/or capacity on 120v circuits. Yes, it all gets crunched down to 5VDC and similar low voltages in the power supply. The limitation is likely due to the gauge of wire used and copper losses in the input circuitry. Higher current connectors and switches, larger copper conductors, etc. are costly. If you have an application that needs that kind of power, higher voltages make sense. This is just as true if the application is a server as it is if it's an electric stove or clothes dryer. Most of the rest of the world has 240v as conventional domestic power, and most server rooms or datacenters supporting >2KVA single devices have 208 or 240v available, so it makes sense for manufacturers of high-power gear to save the money on copper and connectors and insist on higher input voltages for full spec output. Yes, it would be nice to be able to plug in your laptop charger, etc. And the voltage on that charger is likely compatible with anything from 100 to 240V. Wiring a NEMA 5-15 with 208V is just wrong, though. I have an IEC male to NEMA 5-15 female pigtail (old-school "monitor cord") with a big sticker saying "208V - Be very careful what you plug in here" for just that purpose. -- Jay Hennigan - CCIE #7880 - Network Engineering - jay@impulse.net Impulse Internet Service - http://www.impulse.net/ Your local telephone and internet company - 805 884-6323 - WB6RDV
Jay Hennigan wrote:
Most of the rest of the world has 240v as conventional domestic power, and most server rooms or datacenters supporting >2KVA single devices have 208 or 240v available, so it makes sense for manufacturers of high-power gear to save the money on copper and connectors and insist on higher input voltages for full spec output.
We're all 230vac here in Oz (it's a compromise between our old 240v standard and the Euro 220v one). In Oz we basically have a single style of outlet for AC for low amps and a couple of ones for higher amps. The higher powered PSUs are much easier to deal with on that - everytime we get ready to commission a new router etc for the US or Japan we look in amazement at the endless list of NEMA plugs and voltage options and different kinds of APC power gear we need to do everything. It kind of freaks me out - locking, not locking etc. Admittedly I find the standard 2 pin US style power connector somewhat wobbly and scary - ours seems to lock in much better. Since we get the same gear as North America mostly almost all of it copes with 90v to 240v AC 50/60hz. It's rare these days to find things without switching PSUs. It's worth noting that despite higher voltages here there aren't more deaths or injuries - but maybe it's because people take it more seriously. Admittedly no one I know is nuts enough to use body parts for "liveness testing". MMC
Yes, it would be nice to be able to plug in your laptop charger, etc. And the voltage on that charger is likely compatible with anything from 100 to 240V. Wiring a NEMA 5-15 with 208V is just wrong, though. I have an IEC male to NEMA 5-15 female pigtail (old-school "monitor cord") with a big sticker saying "208V - Be very careful what you plug in here" for just that purpose.
-- Jay Hennigan - CCIE #7880 - Network Engineering - jay@impulse.net Impulse Internet Service - http://www.impulse.net/ Your local telephone and internet company - 805 884-6323 - WB6RDV
It's worth noting that despite higher voltages here there aren't more deaths or injuries - but maybe it's because people take it more seriously. Admittedly no one I know is nuts enough to use body parts for "liveness testing".
(sorry for being kinda late in this discussion) I've never felt the urge to do so either, maybe I'm just a wimp. ;-) But here is a something I've heared from people who do/have or know people who do have. And usually they are people with a degree in the field of electronics: use the back of the hand don't grap wires, when current passes through your body, muscles contract and you don't want to hold on to it when those muscles make a fist or more that arm towards your body. You just want to touch it lightly. Just to make things clear, I am NOT going to suggest you should do so, just telling you what I think I heared.
AC Grabs, DC Pushes. And for the record, I am confident this is the longest thread in the history of this list lol. Note to self, consult nanog on facility power when building next datacenter. *laugh* //warren Warren Bailey GCI Communication Corp. RF Network Engineering 907.868.5911 office 907.903.5410 mobile -----Original Message----- From: Leen Besselink [mailto:leen@consolejunkie.net] Sent: Thursday, May 28, 2009 12:05 AM Cc: nanog@nanog.org Subject: Re: Why choose 120 volts?
It's worth noting that despite higher voltages here there aren't more deaths or injuries - but maybe it's because people take it more seriously. Admittedly no one I know is nuts enough to use body parts for "liveness testing".
(sorry for being kinda late in this discussion) I've never felt the urge to do so either, maybe I'm just a wimp. ;-) But here is a something I've heared from people who do/have or know people who do have. And usually they are people with a degree in the field of electronics: use the back of the hand don't grap wires, when current passes through your body, muscles contract and you don't want to hold on to it when those muscles make a fist or more that arm towards your body. You just want to touch it lightly. Just to make things clear, I am NOT going to suggest you should do so, just telling you what I think I heared.
Warren Bailey wrote:
AC Grabs, DC Pushes.
And for the record, I am confident this is the longest thread in the history of this list lol. Note to self, consult nanog on facility power when building next datacenter. *laugh*
Yeah, my fault for starting it. ;) I was really just curious how many people in the US use high voltages or stick with low voltage (in the form of 120 AC or even lower DC). The feeling I'm getting is that some are comfortable with it and use high voltages, but there's enough confusion because unlike other countries, over 120 is relatively uncommon. ~Seth
In a message written on Tue, May 26, 2009 at 12:39:10PM -0700, Seth Mattinen wrote:
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
If folks are making their own choices, mainly for historical and convenience reasons. If folks are building data centers for others, it's that customers demand 120V power in many instances, for some good, and many bad reasons. However, for all the talk of power loss that's not the real issue. The loss due to wire or amperage is a very small part of the equation. While this paper is very much vendor produced, it's a good high level summary none the less: http://www.apcmedia.com/salestools/NRAN-6CN8PK_R0_EN.pdf Note that in a 600Kw installation power loss is reduced from 8,894 W to 845 W, a savings of 1.3%. Note that they have included the savings from additional cooling in that figure. Even at 1.3%, if you looked at the cost of rewiring an existing data center based on that figure you'd be nutty; return on investment would be forever. But what you'll find in the paper is that the change allows you to re-architect the power plant in a way that saves you money on PDU's, transformers, and other stuff. Thus this makes the most sense to consider in a green field deployment. Thus, to reframe your question, in your existing, already built out data center is it worth replacing 120V circuits with 208V/230V ones to save power? No. Savings is likely well under 1% in that situation, and time you add in the capital cost to do the work it makes no sense. In your green field, new data center, does it make sense to look at power from an entirely new point of view? Quite possibly. -- Leo Bicknell - bicknell@ufp.org - CCIE 3440 PGP keys at http://www.ufp.org/~bicknell/
Leo Bicknell <bicknell@ufp.org> writes:
... http://www.apcmedia.com/salestools/NRAN-6CN8PK_R0_EN.pdf ... But what you'll find in the paper is that the change allows you to re-architect the power plant in a way that saves you money on PDU's, transformers, and other stuff. Thus this makes the most sense to consider in a green field deployment.
noting also that "architect" is a noun, i find that on large plants the cost of copper wire and circuit breakers add up, where sizes (and prices) are based on ampherage not wattage. in the old days when a rack needed 6kW, that was 208V 30A (10 gauge wire) or it was two of 120V 30A (also 10 gauge wire). somewhere near the first hundred or so racks, the price of the wire and breakers starts to seem high, and very much worth halving. once in a while some crashcart CRT monitor won't run on anything but 120V but for $50 NRC it can be replaced with an LCD. everything else that's still worth plugging in (that is, having a power/heat cost per performance better than that of a blow dryer) doesn't care what voltage it lives on. -- Paul Vixie KI6YSY
On Tue, 26 May 2009 20:32:54 -0400, Paul Vixie <vixie@isc.org> wrote:
once in a while some crashcart CRT monitor won't run on anything but 120V but for $50 NRC it can be replaced with an LCD. everything else that's still worth plugging in (that is, having a power/heat cost per performance better than that of a blow dryer) doesn't care what voltage it lives on.
Or go to Radio Shack and get one of those "international traveler" power converter packs. I have a number of systems (ok, yes, they're old) that a) do not have autosensing power supplies (someone has to get a paperclip and flip a switch), and b) will not work on 208v -- 120 or 240, but not 208. --Ricky
On Tue, May 26, 2009 at 12:39:10PM -0700, Seth Mattinen wrote:
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
~Seth
I love 208V but I have to fight almost everytime with our datacenter provider. They got 50 or so "Colo's" which are all cookie cutter. Then there is our datacenter, the only facility where they can deliver 3-phase and monitor actual power usage. Everytime when we ask for 3-phase it is a fight now. Our latest circuits (50-amp although we won't use more than 16A under normal use (A+B load)), took me 9 months to get out of them. :-( -- Regards, Ulf. --------------------------------------------------------------------- Ulf Zimmermann, 1525 Pacific Ave., Alameda, CA-94501, #: 510-865-0204 You can find my resume at: http://www.Alameda.net/~ulf/resume.html
Seth Mattinen <sethm@rollernet.us> writes:
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
I've spent the last several days going back and forth with salespeople, trying to find a rack with 208v power in the south bay, or a cheap 100M connection from market post tower to heraklesdata in Sacramento. (where I have cheap 208v power) From what I see, most places in the bay area just can't handle the kind of heat density that a 30a 208v circuit per rack would bring. (they won't sell me more than 2 20A 120v circuits, either, and many will only sell me a single 15a circuit per rack. I assume that's an effort to keep the heat output within cooling system capabilities.) But that still doesn't explain why they don't hand out 10a 208v circuits. I've also seen employers pick 208v over 120v even after I pointed out the cost per watt advantages of 208v, even without counting efficiency gains. In one case they provisioned one rack with 208v, because the vendor of some particularly expensive bit of equipment recommended it, then they left all the commodity servers on 120v. Why didn't they put everything on 208v? I pointed out that the cost per watt was lower. Maybe I blew my credibility by wanting to research 48v power supplies for our kit before that? (it was a telco facility, after all, and I was young.) 30a 208v is about perfect for a rack, if you ask me. (I imagine the guys who have to deal with cooling feel differently, but at my scale, that's all priced into the power.) -- Luke S. Crawford http://prgmr.com/xen/ - Hosting for the technically adept We don't assume you are stupid.
Seth Mattinen wrote: I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why? I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits And you have been doing something that is a right step in the right direction, but may well not be the best ultimate solution. Lets half ignore codes. Not to be illegal, but they CAN be changed and you can often get specific exceptions if you are not just in the back room of an office but are in a clearly professionally managed facility with well trained staff plugging in equipment. Every time I look at a nameplate and I see 100-250VAC I get very frustrated. If only that had been perhaps 100-300VAC, I could then run it on 277VAC and that is especailly nice for many reasons. Most large USA buildings already have 277 and probably all their flourescent lighting is run off it (277VAC ballasts are readily available and what look like rats-ass wall switches but are higher rated ones are readily available - both even at home despot if you look hard enough), so nothing terribly new has to be learned by electricians, etc. 277 is the phase leg to NEUTRAL voltage of a 277/480 WYE system that most everything except small human plugged appliances use in any but the very largest USA office building. It is what typically comes in from the power company. 120/208 is the output of typically a delta/wye transformer that steps that down for the dumb humans to safely use and you are paying the penalty of the WHOLE LOAD having to go through a second less than 100% efficient transformer. The beauty of 277 is that on a single breaker pole (unlike 208 where you are most likely to have 2 HOT legs and need a 2 pole simultaneous trip breaker) on reasonable size branch circuits that you are still allowed to plug MULTIPLE loads into without individual fuses or breakers (that is "allowed to" - you may chose to protect each outlet in the rack, but that is not compulsory) you get 277/120=2.31 times as much power available. Sadly routers, servers, switches, etc. typically are rated to 250VAC, so using raw 277 won't work. But let us see how close HP/IBM/ACP and many many others are getting still using ONE breaker pole per much more efficient branch circuit. NB that as you go to larger branch circuits in AMPS, you MUST be supplying just ONE load or MUST have additioanl breakers or fuses as you split it up. We all know 120/208 and 277/480. What about another NEW pair of voltages in WYE connection! Lets use 240/415. It is exactly twice 120/208 (well it is not stated as 240/416 I'd guess since 240 x 1.73259 = 415.82 they just truncate rather than round - though 2400/4160 is a standard designation...) and is inside the 250V max rating of the switching power supplies. It still uses a single breaker pole. Your get EXACTLY twice as much power out of a 240/415 WYE branch circuit as you would out of a 120/208 at the same AMPs. But you may save a transformer and its continuous power waste or at least part of it in between. How do you get to 240/415 is the next issue. If you have 2400/4160 or 7,960/13,800 primary into your building, and you do all your own transformers, getting 240/415(6) can be a single transformer step for you, and you will probably have many transformers so can also create seperate 277/480 for modest size AC inits and lighting, While LARGE chillers can be ordered at the higher voltages, and for the relatively small amount of 120/208 you probably should come off 277/480 into standard 120/208 delta wye transformers because normal electricians can do that rather then the 13K gods($$$$). But if you are a smaller building the only voltage that makes sense that the utility is supporting is 277/480. Rather than take all your rack power through another transformer step with the losses and the extra heat to eject from the building, consider instead using buck (as in the classic BOOST/BUCK transformers) to knock that 277/480 down to 240/415. It can be packaged as a 3 phase unit for less than three singles, and will be smaller and less costly to have wired up, but the three singles may be available from stock. It is the same sort of device you must have in front of a load that needs 240 or 250 and can't handle 208, but in that case is wired BOOSTING rather than BUCKING. FWIW an electric range burner or a hot water heater element rated for 240 produces EXACTLY 75% of the heat if run on 208 (go do the math...), but you should NOT use boost bucks for such a simple situation because optional heating elements can be ordered originally OR bought as replacements for less than $10 each and easily replaced in the field to give the original 240 rated wattage on 208 supply. In any case the 3 phase buck transformer VA rating will just need to be 3 x (277-240) x per-phase-AMPs on the load side. Or look at it this way: 37/240 = 15.4% to just buck rather than the KVA of a transformer dropping the whole load. Remember the buck transformer's secondary in this case simply is 37 volts and is wired in series but 180 degrees out of phase so drops the 277 to 240VAC But maybe that isn't wizest in the big picture but may work for you. If you are into really big systems you really need folks that know what they are doing. Those that simply tell you to buy K rated transformers may be missing a slick opportunity to knock out power factor problems caused by triplen harmonics related to the multigrounded neutral system. So you may not want to BUCK, but instead use an exceptional transformer SYSTEM. Look at these folks (this is just one PDF, they have plenty more, and a few dollars more spent with them can bring a rapid ROI just on power factor savings alone on the utility bill let alone the dramatically lower transformer losses) : http://mirusinternational.com/downloads/CAT-EC01-08-F10a_w.pdf NB that one of their tricks is to have the load split to separate outputs with different phase shifts within these special transformers so the troublesome harmonics are canceled and not reflected back into the primary. Even though newer power supplies will be more efficient and better power factor corrected that years ago, this is still an issue to be very aware of. Anyway, GOOGLE for 415 volts or 240/415 and these days you will find many hits from big names you already know. Maybe any "issues" with local codes can be solved or already have been. Some folks have been bucking down from 277 to more like 250 for years (to neutral, so single breaker) with the local inspector staying totally clueless at to what was "accidentally" happening. He was probably aware of plugged in PDUs with integral 277/480 to 120/208 DeltaWye transformers in use so probably assumed a lot of the higher voltage breaker panels were feeding more of that. A 30 amp 3 phase feed at 240/415 to a big power strip with 15 or 20 amp breakers for smaller groups of single phase IEC outlets is a STANDARD product from multiple sources and at the 80% allowed loading provides 240 x 30 x 3 x .8 = 17,280 VA and just two of these feeds gets you to almost 35 KVA per cabinet that drives folks to liquid CO2 cooling systems that can easily function in a datacenter without a raised floor, and do it without CRAC created hurricanes or huge air ducts trying to cool the room and failing. NB that such a power strip using IEC outlets uses EXACTLY the same cords as you would use for 120VAC - nothing weird other than NOONE is using the "WEIRD" North American plugs and outlets Well, almost. The power strip could be built for BOTH 120/208 AND 240/415 and would require NO outlet changes. Breakers, shoild be picked for the higher voltage. IEC outlets in these voltages are THE SAME - they just change between 15 and 20 amps and there are specials for high temperature usage. The one thing that should be done is to be sure be to use S cord rather than SJ cord (600V class vs 300V class - well even better use the "O"il option too, simply because it lasts a lot longer - SO cord) - or use a plastic equivalent for any cords carring more than one HOT from 240/415. The old code allowed 42 poles per breaker panel. That would be 7 cabinets worth of just these handy size 30 amp 3 phase feeds for 241920 VA total - almost 1/4 of a megawatt. Bigger branch circuit amps can give you a lot more, obviously, but short of going to Square-D I Line panels, you probably don't want much more load than this in a typical breaker panel. It would be "nice" to have the two 30 amp 240/415 WYE feeds to any cabinet be fed from the SAME breaker numbers in two totally separate breaker panels, and each server's power supplies split between the two branch circuits. Just be VERY VERY certain you check each device as there are still some 120 volt ONLY devices some idiot will want to plug in. Three phase isn't all that weird.. Keeping it simple, if you have three separate coils on a generator that each produce AC 120 degrees out of phase with each other, and connect one end of each coil to a single grounded point called "neutral" , you WON'T have twice the single coil voltage between any two of the other ends of the coils (the HOT wires), but have the square root of 3 times it instead because they are not a full 180 degrees out of phase the way single phase house power is, or two flash cells that when you ground the center connection between the cells and call it neutral, you will find 3 volts between the ends of the two cell battery and 1.5 from that middle to either end BUT with opposite polarity.from the center. The sign waves coming out of that 3 phase generator peak in succession at each hot leg in turn, and a three phase motor will reverse direction if you swap any two of the three wires. Just as on a single phase neutral where you can reduce the neutral current to ZERO if you have two identical resistive loads (ie non reactive) from each hot leg to neutral, so can you if you have three identical resistive loads each on one of the three phase hot legs to neutral. If you put one of those resistive loads on just one phase leg, obviously the NEUTRAL has the same current as the one in use phase leg. The trick question is how much is on neutral if you had just two of the three resistors connected. Think of it this way. If all three are on, neutral has ZERO amps. cut ONE off, and you just CHANGED what is on neutrasl by one resistor's worth of current. When we remove that resistor from the common neutral wire that was reading ZERO amps, we will get a one amp reading on neutral. If we were to turn that resistor back on and shut OFF the other two, we would also get 1 amp on neutral, BUT there would be an exact 180 degree phase shift if we were watching the two currents on a scope. Together they cancel. But but but why 180 when 3 phases are all 120 degrees apart? Those two other legs ARE 120 degrees apart and each 120 apart from the third leg, but those two 120 degrees apart currents sum to being 180 degrees from the third leg (still assuming each resistor is indentical). Anything other than resistors and current may lead or lag voltage and harmonics may add in ugly ways so neutral current can easily exceed that on any phase leg and thus we have all the power factor issues and charges from utilities and mandates for better power factor corrected supplies and codes dictating over sized neutrals where switching power supplies abound. I was cheerily suggesting hot leg to neutral WYE (aka STAR) connections ( and I still do!). But actually those using two hot pole branch circuits ( or two hots of a three phase branch ciruuit broken into many smaller two wire 208 ones ) are NOT using the neutral at all in each of those SINGLE PHASE connections and avoid the triplen harmonic currents summing in the neutral, and can also still use the neutral for small random 120V loads but need not oversize the neutral. Actually any load including three phase DELTA stuck across there that avoids the neutral avoids the harmonics issues. I was just using the 208 single phase loads because they seemed to have been used more than I had suspected. Using a three phase branch circuit (say 30 amps as that would be a handys size, but DOES NOT MATTER here) at 120/208 - whether you are using it as 3 120 volt circuits or 3 208 volt circuits ( as EACH of those connection options gets EXACTLY the same max power out of the circuit!!!) gives you EXACTLY 1/2 the power you could get from the same ampere circuit running 240/415 (which would normally ONLY be running phase to neutral loads at 240V, but were 415 volt capable devices available you still get the same total out - EXACTLY twice what the 120/208 can deliver). NOTE that I carefully was refering to 4 wire 3 phase legs and a neutral for these example branch circuits. IF you are comparing two wire single phase circuits from the breaker panel to the cabinet (how silly! unless it is from a PDU in an adjacent cabinet), 208 volts gets you about 13% less power on your two wires than you could get at the same amperage on a 2 wire circuit at 240 volts. Whether those wires are both hots or a hot and a neutral makes no matter as it is simply the voltage between those two wires times max allowed amps (80% of branch ckt rating) that determines what you can get out. A switching supply simply sucks more amps at lower input voltage so gets the power it needs in either case, but you can inflict a larger load at the higher voltage. Thus 240/415 (240/416...) DELIVERS twice what 120/208 does amp for amp with full three phase wiring, and that is why it is so great.
On Tue, 2009-05-26 at 12:39 -0700, Seth Mattinen wrote:
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
We are using 120V in our colocation spaces.
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
The reason why we are using 120V is because we have pre-existing equipment (such as PDUs) that only support 120V operation. I believe our newer PDUs support 120/208/240, but do not have the time to investigate that, and we still have a couple of older APC units still in service. Our servers don't really care which voltage we provide, most of the PSUs can determine 120 vs 240 automatically, even. Also, at least at Equinix Chicago, 120V service was cheaper when we colocated there. I do not know if this is the same case at Steadfast in Chicago, and as far as I know, HE does not offer 208/240 service in their Fremont-2 facility. I could be misinformed on that, though. -- William Pitcock SystemInPlace - Simple Hosting Solutions 1-866-519-6149
I have some similar input. At my company, we use both 120 and 208 volt depending on what servers we are putting in the racks. We can fill up every single rack to full capacity 100% of the time by using energy efficient servers. The fact that it is 120 volt or 208 volt hardly matters on most machines except Xeon/Opeteron class systems. We use a lot of Core 2 duo, Atom and Xeon Low Voltage processors. This allows us higher density on the same power and makes 208 volt mostly irrelevant. On Thu, May 28, 2009 at 11:18 AM, William Pitcock <nenolod@systeminplace.net> wrote:
On Tue, 2009-05-26 at 12:39 -0700, Seth Mattinen wrote:
I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why?
We are using 120V in our colocation spaces.
I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits.
The reason why we are using 120V is because we have pre-existing equipment (such as PDUs) that only support 120V operation. I believe our newer PDUs support 120/208/240, but do not have the time to investigate that, and we still have a couple of older APC units still in service. Our servers don't really care which voltage we provide, most of the PSUs can determine 120 vs 240 automatically, even.
Also, at least at Equinix Chicago, 120V service was cheaper when we colocated there. I do not know if this is the same case at Steadfast in Chicago, and as far as I know, HE does not offer 208/240 service in their Fremont-2 facility. I could be misinformed on that, though. -- William Pitcock SystemInPlace - Simple Hosting Solutions 1-866-519-6149
participants (40)
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Aaron Wendel -
Alex H. Ryu -
Alex Rubenstein -
Andy Ringsmuth -
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Barton F Bruce -
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Colin Alston -
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david raistrick -
Dorn Hetzel -
Iljitsch van Beijnum -
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Jay Hennigan -
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Kevin Oberman -
Kurt Anderson -
Leen Besselink -
Leo Bicknell -
Luke S Crawford -
Matthew Moyle-Croft -
Michael Thomas -
Owen DeLong -
Paul Vixie -
Pete Templin -
Peter Beckman -
Peter Dambier -
Ray Sanders -
Ricky Beam -
Ronald Cotoni -
Seth Mattinen -
Steve Bertrand -
telmnstr＠757.org -
Ulf Zimmermann -
Warren Bailey -
Wayne E. Bouchard -
William Pitcock