I'm trying to get some new wiring installed into my garage so I can add some high power servers (mining rigs). Anyway I bought some Evga 1000w G3 power supplies which are 240v capable, but my electrician wants me to find out if they are neutral or phase to phase. Why do I need to find this out, isn't there a single standard in the US? But if I need to does anyone know? The manufacturer site does not have this info and their chat tech help does not know either.

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    The product is certified for use in North America by TUV Rheinland which is an accredited testing laboratory, so it shouldn't matter if it's phase-to-neutral or phase-to-phase - the safety marks should be good enough for the electrician in my estimation. – Adam Lawrence Dec 7 '17 at 23:05
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    Perhaps the electician is asking if it should be connected to a normal 120 volt circuit, or to a 240 volt circuit (that would be phase-to-phase). A 240 Volt outlet would be "unusual" in North America - usually only required for high-powered tools - he wouldn't expect a computer to need 240 volts.. – Peter Bennett Dec 7 '17 at 23:19
  • The nameplate rating is 100-240VAC so I don't see what the issue is. – Adam Lawrence Dec 7 '17 at 23:48
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    I believe he is asking if it is a straight 240 with ground and no neutral, or is it leg to leg with a ground and a neutral, it would make a difference on the wire he pulls. – Ed Beal Dec 8 '17 at 0:16
  • What he really needs to know is what NEMA pin configuration that you need for your equipment, answer that question for him and all other questions are answered. – Tyson Dec 8 '17 at 4:08

Current flows in loops, so the power supply has two conductors coming into it. (In Codeland we don't count safety ground as a conductor).

A world-voltage server power supply could contend with five styles of power. I'm mentioning voltage compared to ground, and neutral is near ground by design.

  • Euro 240V polarized: one 220-240V hot, and one neutral. (Illustration, upper left)
  • Euro 240V non-polarized: either conductor could be 220-240V, the other neutral. (Upper right) To deal with this, the unit must be insulated for 240V on either conductor.
  • North American 120V: one 120V hot, and one neutral, polarized. (Both lower left)
  • North American 240V: two 120V hots, out of phase so they stack to 240V, often no neutral. (Both lower right)
  • NYC or commercial 208V: two of 3 phases, both 120V from ground. (Not shown)

In 3 of 5 instances, the world-power device must be insulated for both conductors to be potentially hot, as high as 240V. So the item would need to be tested/listed for hot on both of its conductors. The electrician is asking if that is so.. It's a routine question.

He should be using /2 cable and fitting NEMA 6-15 receptacles. If the breaker is 20A he can fit 6-15 or 6-20 receptacles.

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Or if you are coming out to a PDU, he can fit something larger like 30A or 50A. But if you do that, have him run neutral and use NEMA 14-30 or 14-50 receptacles. This will give you much more versatility: the PDU could support 120V switches or fans... the receptacle could support welders, EV chargers, you name it... Or the cable could support a future subpanel.

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US 240V has both supply conductors at 120V relative to ground. European 230V normally has one supply conductor (the "line") at 230V relative to ground and the other supply conductor (the "neutral") at roughly ground potential.

Some countries in Europe have polarised plugs, others don't. Modern portable equipment intended for sale in Europe is designed to harmonised European standards meaning it is safe to use with Live and Neutral reversed. As a side affect of this it will also be safe and functional on a US style 240V system.

A couple of notes

  1. You may need to be more careful about vintage equipment or equipment designed for fixed installation.
  2. I strongly recommend you come up with a scheme for identifying which power cords have 240V on them so that you don't accidentally plug them into a 120V-only device.
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This is very simple - The answer is: it does not matter. The PS is designed to connect safely to 120 VAC or 240 VAC supply. For 120 VAC, one line will be HOT (Phase) and one will be NEUTRAL. For 208 VAC or 240 VAC both lines will hot (phase to hhase). Any qualified electrician will install proper replaceable and cord cap for appropriate voltage and current. (I am a master electrician as well as power supply designer)

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