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I've decided to move most of my servers out of our closet at work and into a datacenter. All of our servers are 110v, however we're starting to purchase some new ones, and the datacenter tech recommended we opt for the 208v since it was cheaper for the cage we are getting.

I've looked up on most of our servers that we traditionally use 110v for, however they SEEM to all support 208v as well (HP DL360 g4, Dell 2850's, and Dell 2650's).

Is there anything wrong with putting all of these servers on 208v??

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5 Answers

up vote 6 down vote accepted

DL360's should handle 208v with no problems. They have auto-switching power supplies which'll handle the switch for you. Also, running at 208v is slightly more efficient than running at 120v. A few percentage points gained, which can add up for a server that routinely burns 300+ watts.

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Yup, I'm currently running two brand new DL360 G7s on 208, along with a gaggle of other server/storage equipment. For the most part, all modern computing equipment (including monitors, laptop power supplies, cell phone chargers, etc.) all have switching power supplies and as such, should be able to handle either voltage. –  EEAA Nov 24 '10 at 4:39
    
@sysadmin1138: Happen to have any references for 208 being a little bit more efficient wattage wise than 120? –  Kyle Brandt Oct 19 '12 at 13:12
    
@KyleBrandt You can see it in most of the Anandtech power-supply reviews, but a good example is here. The 115VAC test shows 87.4% efficiency at 50% load, and the 230VAC test 88.12% efficiency at 50% load. As I said, it's small but measurable. That trend has been there for several years in their reviews. –  sysadmin1138 Oct 19 '12 at 17:37
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If the servers support 208v (and most do these days) then you'll be fine. The datacenter tech is correct, this will save you money as most data centers charge per amp for power and running your servers at 208v will reduce the number of amps you'll need to power the servers.

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I don't think datacenters really charge just by the amp, do they? They must charge by the watt, which conveniently reduces to amps if the voltage is constant (that is, all 110v or all 208v). It certainly doesn't cost them half as much to use the higher voltage for the same amount of work. As sysadmin1138 says, the power supplies are slightly more efficient running at higher voltages, so there's the savigns. –  mattdm Nov 24 '10 at 4:40
    
Every DC I've seen charges per kWh (just like the power company), or power is rolled into the monthly cost. At 208v the server will probably run a bit more efficiently, so they're still ahead on the power bill. –  Chris S Nov 24 '10 at 13:16
    
All the datacenters I've ever talked to charge for power per amp. I get billed a flat monthly rate for a 30amp circuit, regardless of the actual power consumed during that month. With a 208v circuit I would only need a 20amp circuit instead of a 30amp circuit and thereby reduce my monthly cost. –  joeqwerty Nov 24 '10 at 13:37
    
If they're charging that way, they are either eating the costs on 208V, or else overcharging you on 110V, because they're sure not getting billed that way by the power company. –  mattdm Nov 24 '10 at 14:29
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I'm wondering why exactly 208 volt - from where came this digit 208 ?

In most of the Europe the voltage is 220 volt and this is a standart. As a standart it allows you to have a little deviation for example as a low minimum 200 volt and as a maximum 240 volt, but now one speaks about 208 volt as a standart voltage for equipment.

Why do you think that power supplies at higher voltage are more effective ? If we speak only for the voltages (ignoring ampers) I think that more effective will be conversion from 110 to 3, 5, 12 volt compared to 220 to 3,5,12 volt. When the gap between two voltages is low you will have low losses caused by conversion.

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(total guess). As a kid i was told voltage is basically how big the jolts of electricity are, and amps are how fast you shove them through a wire ("volts jolt, mils kill"), consequently high ampage makes a lot of heat - which is why overhead lines run at huge voltages rather than huge ampages. Soooo armed with that comically dodgy knowledge, I'm guessing maybe they run cooler at a slightly higher voltage rather than a high throughput ? –  Sirex Nov 24 '10 at 11:10
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208v is a standard voltage because when you have 3Φ240v and use any two legs of it, you get 208v. It's called 3Φ240v in the first place because the maximum swing in voltage away from ground is -120v to +120v. –  Chris S Nov 24 '10 at 13:25
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@Sirex, it's easier to think of as water in a pipe. Volts = Pressure and Amps = cross section (area). Using a higher voltage allows you to get more electricity through a smaller wire and with less resistance, thus it's more efficient. –  Chris S Nov 24 '10 at 13:29
    
Here in the US, the standards that one is most likely to see in a datacenter are 120v, 208v, and 240v. Pretty easy to tell 120 apart since the plug is different (actually, there's 2 similar plug designs for 120v depending on if it's 15a or 20a) from 2xxv. Have to be careful with 208/240 as the plug is the same and some equipment will handle one, but not the other! –  Brian Knoblauch Nov 24 '10 at 14:23
    
In these posts/comments few people talk about 110V other 120V - why is this discrepancy ? –  ntk Nov 24 '10 at 14:52
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208v vs 220 v is a factor of how the voltage is derived from the transmission line; whether or not it's delivered as single-phase or three-phase.

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While 208v is definitely OK for most recent Dell hardware, and probably most Cisco, etc., double check everything you're planning to add to the cabinet. We've had two ugly surprises with 110v-only equipment on a 208v circuit.

One, an off-brand chassis hosting our voicemail system, simply couldn't take 110v. Nice smoky smell, and a weekend without voicemail.

The other was an older Dell workstation-used-as-a-server which had a physical switch that nobody noticed, which was still set at 110v. The guy who hooked that up connected the power cord to the strip first, then connected the cord to the machine. Bright flash and cracking sound right in his face. He was unharmed but seriously shaken.

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