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 Post subject: Just curious, anyone running folding PCs at 240Volts AC?
PostPosted: Fri Jan 04, 2013 10:34 am 
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I ask this question because most PS's seem to have slightly better efficiency at the higher voltage. I've never actually seen an IEC cord designed for 240VAC.

Oh, and Happy New Year.

OT - At some point I will reconsider folding, because my electric rate is 12 cents an hour. I had not noticed for a long time that a large part of my bill is a flat monthly charge. In fact in the summer months the flat charge equals or surpasses my electric usage.

Aris

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 Post subject: Re: Just curious, anyone running folding PCs at 240Volts AC?
PostPosted: Fri Jan 04, 2013 11:40 am 
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Location: UK
aristide1 wrote:
I've never actually seen an IEC cord designed for 240VAC.

The UK runs 240V (well Great Britain at least, Northern Ireland only runs 220V). IEC C13 power cables here are normally rated at 250V. Maybe you can not find them in the US because of the limitations of the NEMA type connector on the other end, not the C13? What would you normally use as a plug design for 240V in the US?

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Last edited by edh on Fri Jan 04, 2013 1:17 pm, edited 1 time in total.

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 Post subject: Re: Just curious, anyone running folding PCs at 240Volts AC?
PostPosted: Fri Jan 04, 2013 12:55 pm 
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The common NEMA 1 and 5 (ungrounded, grounded) connectors are rated for only 125V max. There are several NEMA versions that are rated for 250V. Most common in NA households are probably the NEMA 14 variants used for electric stoves and clothes dryers.

Most "240V" household service in NA is actually split-phase 120V. That is two 120V circuits that are 180 degrees out of phase with each other. It gives 240V total across them, but it's not the same as single phase 240V found in many other countries. I don't know if a power supply would be happy with 240 split-phase and what effect it would have on efficiently.

I've worked in several data centres and any equipment that expected 240V was wired with single phase 240V, not the split-phase found in households. To get 240V single-phase in a household would require a step-up transformer or special connection from the power company. Using a transformer would likely negate any efficiency gains.


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 Post subject: Re: Just curious, anyone running folding PCs at 240Volts AC?
PostPosted: Fri Jan 04, 2013 1:31 pm 
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washu wrote:
I don't know if a power supply would be happy with 240 split-phase and what effect it would have on efficiently.

I think MikeC may do this for PSU tests at 240V. You may want to check the SPCR PSU test methodology and perhaps MikeC may have some comment also.

A 120V neutral is not so much of a concern for making the PSU work in the first place. In some medical IPS installations with a floating earth, neutral and live both sit at 120V, 180 degrees out of phase and this reliably works for powering computers. A concern I would raise from operational experience is to make sure that there is good earthing and all equipment is powered from this same supply. Different equipment sets up a ground connection quite differently and if you are not careful you might find an AC voltage flowing over the Ground wire of a video cable between your monitor and computer, each having a different floated ground voltage. You shouldn't be able to fry anything, but signal quality is at risk.

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