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I am planning on adding a server to one of the closets in my house. In order to do that I need to run electrical to the location of the server. For severs they recommend having 2 independent lines of power, for redundancy, that way if one breaker trips the server won't go down. The server has 2 power supplies with independent cords. I am wondering if I can do a single 240v run from my breaker box to the location of the server and then separate the 240 to 120 and into 2 outlets, also can I run it into 2 outlet with 2 plugs, and would there be any code violations?

This is what I'm thinking, except this is all a 4-wire cable instead of 4 separate wires.

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    This is known as a multiwire-branch circuit, there are a few other questions on this site about exactly that and their requirements. – ratchet freak Sep 3 at 9:21
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    Guys read the question the op wants to run 2 neutrals! This IS NOT a mwbc. There is nothing stopping his plan in code if he uses a 20 amp breaker a 20 amp receptacle must be used and both jumpers broken. If he uses 15 amp receptacles 15 amp breakers can be used again both jumpers broken. The Handel ties in this case prevent the computers built in second power supply from taking over when a fault trips the first one and the MFG usually requires this setup. I know Hewlett-Packard required this for there dual powered servers. – Ed Beal Sep 3 at 13:52
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    If you look close the neutrals overlap but the text states 2 separate cables. I have probably wired close to a thousand of these all were in server rooms with blade servers only a few in residential ant the inspector was quick to jump on no handle tie I told him the computer MFG required this and included the 2 separate circuits labeling this way each server was not only double fed but we rotated legs to keep the 3 phase 208 balanced and an additional level of protection on a separate leg (I don’t actually remember that saving anything). Maybe I read it wrong but if separate neutrals It’s ok. – Ed Beal Sep 3 at 14:06
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    2 seperate cables are ok as each receptacle is a separate circuit. You would need a 12-4 with ground, 12-2-2 with ground would be more commercially available I believe. Or 2 separate cables. – Ed Beal Sep 3 at 17:12
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    @Austinthemighty, as long as we're learning, "Romex" is a company which makes a great many products. Just "cable" works, or NM (non-metallic) cable if you want to be specific. Folks outside the industry or the US may not know what romex is. – isherwood Sep 3 at 17:33
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Cannot do it. Nosirree.

Cannot use a MWBC

As you have stated it in your question, you are describing a multi-wire branch circuit (MWBC).

Singular.

That is not 2 independent circuits. It is a multi-wire branch circuit.

Further, it has a serious defect in that it is taking power from unrelated points on the panel. Code absolutely requires that MWBCs be both opposite-phased, and handle-tied for common shutoff (which in the real world means common trip most of the time). This defeats your purpose.

Even worse, if you simply put the breakers "wherever" on the panel, then over the years as you rearrange circuits in the panel, you may accidentally wind up with both MWBC legs on the same phase. That means instead of carrying only differential current, neutral would carry the sum of currents causing an overload of the neutral. Neutrals don't have breakers. On almost every panel type, handle-ties force the breakers onto opposite poles, so use of handle ties averts this danger. (Usually; looking at you GE).

So your MWBC absolutely requires either a 2-pole or handle-tied breakers. 2-poles definitely have common trip, and handle-tied breakers usually have common trip (not guaranteed but very likely from handle motion).

For the circuits to be independent, they need to each have their own neutral wires. But wait.

Cannot put 2 independent circuits on the same yoke

That receptacle there, with 2 sockets, is on what's called a "Yoke". That means a single device of any kind - switch, pilot light, GFCI, whatever, that mounts through the usual mounting screws.

So, suppose you run a second neutral. Now you're splitting the receptacle and having 2 circuits each with its own neutral, one powering each socket. You can't do that either. Or to be more precise, the circuits cannot be independent if you do.

210.7 Multiple Branch Circuits. Where two or more branch circuits supply devices or equipment on the same yoke, a means to simultaneously disconnect the ungrounded conductors supplying those devices shall be provided at the point at which the branch circuits originate.

When 2 separate circuits serve the same yoke, again they must be handle tied, and again this defeats your purpose.

There's a very good reason for the handle-tie requirement. Someone servicing the wiring will typically plug a radio into one of the sockets, and trip off breakers until the radio goes silent. Then turn everything else back on, and go to work on the wiring. Think about it. That procedure will leave one of the sockets "hot", unbeknownst to the maintainer. So again those 2 circuits must be handle-tied.

Why would anyone ever put 2 independent circuits on the same yoke, when the MWBC approach does that better? AFCI/GFCI. They don't make 2-pole AFCIs and 2-pole GFCIs are expensive. Often the only way to provision GFCI/AFCI to such a split recep is to have separate neutrals.

Socket size must exactly match breaker size if there is 1 socket

As manassehkatz noticed, you are speccing a 20A breaker that is feeding exactly one 15A socket. Nope. Breaker size and socket size must exactly match, NEC 210.21(B), so you must use a 20A socket or a 15A breaker.

"But people use 15A sockets on 20A breakers all the time!" Because there is an exception for 15A sockets when 2 or more sockets exist on a circuit, which is the usual situation.

You have no option that will allow you to split a yoke.

and maintain independent trip (in practice). Further, you wouldn't want to anyway, because anyone looking at your setup would think you made a mistake by putting both power supplies on the same yoke. (and they'd be right if you followed Code).

Your only option is to fit a 2-gang junction box so you will have 2 yokes, and run 2 independent circuits with either dual /2 cable or /2/2 cable. (can't use /4 cable since you can't re-mark blue to be neutral). At that point you'll have 2 sockets per circuit and 15A duplex receps are fine. If you really want 1 socket per circuit you can get 20A simplex receps, but their rarity means cost.

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  • Excellent answer as always. One small correction: in 2020, 2-pole AFCIs aren't quite the unicorn they once were -- Siemens and Square D (QO & HOM) ones are both available at my local home depot. Eaton (BR & CH) ones don't seem to be stocked at big boxes near me, but they do seem to exist at electrical distributors and on Amazon. It's true that I don't think GE makes one, and all of them except Siemens do seem excessively expensive, but for most brands, if you really need it it can be found. It's the two-pole DFCIs that are the unicorn today. – Nate S. Sep 3 at 17:31
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    @Nate GE has a neat trick where their AFCIs don't need neutral. Their selling point is you can just handle-tie 2 of them for MWBCs. – Harper - Reinstate Monica Sep 3 at 17:42
  • Oh very cool. So in that case, it's once again possible to use shared neutral MWBCs on any modern panel, unless the circuit requires both AFCI and GFCI, and GFCI at the receptacle after splitting the neutrals isn't an option. Nice! – Nate S. Sep 3 at 17:46
  • MFG instructions must be followed 110.3.b no reason for dual supplies if tied. Taking power from different points with separate wires that makes no difference they could be on the same leg or opposite and would function the same with 4 wire + ground – Ed Beal Sep 3 at 18:15
  • I haven’t worked there for 10 years so I no longer have access. – Ed Beal Sep 3 at 18:37
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As described in some other answers, a Multi Wire Branch Circuit (MWBC), can do exactly what you want, with one exception.

  • An MWBC lets you get 2 x 120V on 3 wires instead of 4, because the two 120V circuits share neutral.
  • Assuming this duplex receptacle is the only thing on the circuit, it must be a 20A receptacle as each 120V section will only have one receptacle. There is an exception for an ordinary 120V circuit where both receptacles are on the same (single) 20A breaker. Once you split it, each receptacle (unless you have more daisy-chained) is the only receptacle on the circuit, so it has to be a 20A receptacle to match the 20A breaker. But a 20A duplex receptacle basically costs the same as a 15A duplex receptacle - just get the right item.
  • While an MWBC does not need common trip, it does need handle tie for common maintenance shutoff. But the usual way to get common maintenance shutoff is a double breaker == common trip, since MWBCs are required to be on breakers next to each other. So if you really want to make sure that an overload of one does not affect the other, you need two totally separate circuits.

The exception is: What are you trying to protect against? Power supply failure/replacement or overload?

If the main concern is a passive non-breaker-trip failure of the power supply, then an MWBC will do just fine. This is also the case if you want to put in two UPSes, one in line on each power supply. With an MWBC (or any other method of providing 2 120V power sources), this will allow replacement of a UPS (e.g., battery degraded and needs replacement) while letting the other circuit continue powering the server.

On the other hand, if you are concerned about catastrophic power supply failure (blaze of glory/magic smoke), then a momentary overload often comes with the failure, resulting in a breaker trip that, on an MWBC, may trip the power going to the other side as well.

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If you split the neutral jumper on the receptacle and hot receptacle so you feed the receptacles like you want each having a hot , neutral and pigtailed ground they are 2 separate circuits and not required to be handle tied . You can have multiple circuits as long as the hot and neutral are separate 210.4 requiring a handle tie is because of the common grounded or neutral conductor. This is more common in server rooms Where each receptacle is utilized at its limit note this requires a 20 amp receptacle on a duplex outlet because there is only 1 receptacle.

Edit I just remembered the receptacle was required to be labeled fed from more than 1 source.

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    Even if the circuits were independent with separate neutrals, they still need to be handle-tied, because they are on the same yoke. If you use the usual method of "plug in a radio and flip off breakers til the radio goes silent", the yoke would still be energized. – Harper - Reinstate Monica Sep 3 at 16:44
  • No check our Hp bulletin for dual power servers they are required to be split and the receptacle labeled fed from 2 sources. – Ed Beal Sep 3 at 16:48
  • Where each receptacle is utilized at its limit note this requires a 20 amp receptacle on a duplex outlet because there is only 1 receptacle This sounds ambiguous. What is "at its limit" in this context, and what circumstance are you describing that requires anything but a receptacle rated to match the breaker? – J... Sep 3 at 16:49
  • @j... 15 amps on a 20 amp circuit is at its limit actually 16 amps is the limit but both power supplies could not be on the same circuit. – Ed Beal Sep 3 at 16:51
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    HP says the servers are required to be on independent circuits, but I guarantee you HP doesn't say anything about putting both circuits on a single receptacle yoke. – Harper - Reinstate Monica Sep 3 at 17:18

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