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David Cummings
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Should I switch my servers from 110v to 220v?

We have a rack in a datacenter with about 12 rack mounted servers.  Right  now, all the servers are running on 110v, though they all have 110v-220v switches on their power supplies.  The data center is offering us new power at a cheaper rate, but it is 208v  (not sure why 208 instead of 220) and I am considering making the switch.


Question: is there a risk in  turning off each server, unplugging the old power, switching the power supplies to 220v, plugging in the new power, turning on the server using the new "208v" circuit?  


Could the power supply fail?  Could it fail to switch back to 110v?  Could the procedure actually damage the mother board?


I've left out all the details as to why the data center wants to make the change because they aren't important to the question I'm asking here which is:  is it dangerous to switch from 110v to 220v (208v) using the power switch on the power supply and plugging in to the new power source?


Thank you in advance for any opinions anyone might have on this subject.

Server Hardware

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serialband

8/22/2022 - Mon
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David Favor

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David Cummings

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Thanks.  I'm going to wait for other comments but I really appreciate yours.
David Cummings

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David Cummings

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It is 208v, not 220v.  That's what the datacenter is saying.  I just didn't understand the difference myself, so forgive my initial confusion on that.

And of course, plugging in 208v to 110-only power supply won't work.  I understand that.

And yes, I am aware of the need for new cables, with the PDU's themselves being supplied by the data center.

My original question was: will servers that have been running for months/years on 110v be adversely affected or risked in some way by the correct-method-switch from 110v to 208v.  Seems like the answer to that is no.  And I am satisfied on that question.

But it's interesting that all three of you say there's not much benefit, which I find confusing.

By P=EI, don't I use less current if I switch to higher voltage?  Doesn't that mean I can run significantly more servers on 208v than on 110v?

I would like to hear what you think about that but you have all answered my original question and I'm going to be closing this out tomorrow.

Thank you very, very much for your guidance on this.

This is the best money I have ever spent. I cannot not tell you how many times these folks have saved my bacon. I learn so much from the contributors.
rwheeler23
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kevinhsieh

The advantage is that you can draw more power using the same amperage. Power supplies are also more efficient when running from 208 or 220 vs 110V. This means less heat as a byproduct. There probably isn't much advantage to you, more for the data center because there is less waste heat to remove.

The power supply shouldn't fail when you switch between the two. If your server have dual power, you can possibly switch the inputs of the first power supply and then the second, without powering down the server.

Everything in my data centers that accepts higher voltage inputs are on them.
andyalder

Ditto Kevinhisieh

There's a slight power saving using the higher voltage, there's a graph in this white paper https://media.zones.com/images/pdf/White_paper_APC_Efficiency_and_Other_Benefits.pdf

I borrowed a 240-120V transformer once and proved the switchover can be done live if a server has dual PSUs, it ran quite happily with one auto-ranging PSU fed by 120v and the other fed by 240v. (Was a DL380 G7). I doubt it would tolerate a sudden change from 120 to 240v but since cabled had to be swapped the change wasn't sudden.
serialband

At 208 V, the power supply runs more efficiently, but your server still uses the same total power in its circuits.  The power savings is mainly at the power supply unit not wasting power as heat when it runs more efficiently.  If that saves me money, I'd switch.

If your servers have been running 24/7 for years, the only possible other side effect is leaving them shut off too long.  If you have spinning disk drives, they could possibly die on you during when you power them back up after they've been off too long.  If you power them back on relatively quickly, you should generally have no issues.  Don't leave them off for weeks, a day or so should be mostly fine.  The shorter the downtime, the better.  It all depends on how heavily used the disks are.

If you have dual power supplies and ever switch from multi-phase 208V to single phase 110V, you need to make sure both power supply units get on the same phase or some devices will burn out.  Someone messed up the wiring at one place and some of their devices died when their dual power supplies were plugged into different phase 110V power.  It was bad equipment design, and possibly some mis-wiring, but still something to watch out for.  Going to higher voltage shouldn't have that problem.

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