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I’d like to run power from a Uninterruptible Power Supply (UPS) in ROOM A to where a work computer is used in ROOM B. I was thinking of installing an outlet box in ROOM A near where the UPS is plugged in, then run wire under the house to another outlet in the other room. That way I could just plug the UPS power out into the receptacle in ROOM A and the computer into the outlet in ROOM B on the other side of the house. Of course this line would not be connected to a circuit breaker, only from outlet to outlet.

I want to run the UPS to be available for use in both rooms, that’s the reason for the additional line.

Would there be any problems with this from a code perspective? Would it require traditional wiring and hardware (e.g. Romex, outlet boxes) to accomplish it?

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    You refer to "the receptacle in ROOM A". If that's a receptacle (aka female, aka socket), how do you intend to "plug the UPS power out" into it? The UPS output is also via receptacles. – Doug Deden Jun 5 at 22:16
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    @staticGenerator, good thing you've decided not to use a male-male cord -- those are extremely dangerous, since when either end is plugged in, the exposed prongs on the other end are hot. This could easily kill someone who doesn't realize this cord is "special". – Nate Strickland Jun 5 at 23:25
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    The male-to-male cord is commonly nicknamed "suicide cord", for the reason Nate has given. – donjuedo Jun 6 at 11:39
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    Is this an infrastructure sized UPS? Seriously, if it's not a UPS you need a forklift to move then just buy another one for ROOM B. It will cost you more to do what you are planning and you'll be far less likely to kill yourself or others. – J... Jun 6 at 12:26
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    @Adonalsium 3000VA is not small (for a house). It's much too big to even run on a standard 15A branch circuit. OP apparently also has a generator and just needs these UPSes to ride through generator startup. For just a desktop computer a little 600VA job would generally be fine and would barely cost more than materials, to say nothing of the work of installing the extension. Don't know about you, here in Canada 30m (ie:100ft) of 14/2 runs almost $60, and that doesn't count boxes and incidentals, drywall mud, paint, etc. – J... Jun 6 at 15:29
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You need an inlet in Room A, not an outlet

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You'll need an outlet box with an inlet in it in Room A so that you can plug the output of the UPS into it with a proper cord (read: if you have to do weird crap to your cord to plug the output of the UPS into the wall, stop, because that's a sign you're doing it wrong!). From there, you can use a suitable chapter 3 wiring method (assuming the crawlspace is not wet, NM/Romex will do; use UF aka "outdoor Romex" instead if it is wet/damp, though) to connect the inlet box in Room A to an ordinary box+receptacle in Room B.

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    Thanks, yes my goal was to put a male connector on both ends of the cord (a.k.a. “Weird crap”), but later found receptacles with male connectors that could be used. Unfamiliar with UF cable but I’ll do the research. – staticGenerator Jun 5 at 23:29
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    @staticGenerator: think about the kinds of Bad Stuff that could happen if you (or someone else) accidentally used a male<->male cable to plug the UPS output into a live outlet! – Peter Cordes Jun 6 at 7:13
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    @staticGenerator In the UK, a power cord with male connectors on both ends is known as a "Jesus cable" - because if you use one, you'll be seeing him soon. – Martin Bonner Jun 6 at 7:32
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    @MartinBonner some people call it a suicide cord for similar reasons. – ratchet freak Jun 6 at 8:00
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    How not to do it: youtube.com/watch?v=At0advb9_fA – Tobias Mädel Jun 6 at 13:38
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I have a feeling you will find this to be quite a bit more involved than you originally expected. In addition to whatever other code issues involved in setting up a power "inlet" in Room A (as opposed to the normal receptacle = "outlet"), at a minimum you would need to use approved wiring methods to get from Room A to Room B. That means Romex properly installed - i.e., protected from damage, securely attached, etc. - or wires in conduit. As noted in another answer, regular Romex may not even be an option if the cable actually runs "under" the house as opposed to "through the basement". It means real junction boxes on both ends. It means a lot of work - for relatively little benefit.

My recommendation is "anything else". That includes:

  • If the UPS is relatively small (that's $ and capacity, which basically go together), just get a second UPS for Room B and you're done.

  • If the UPS is relatively large then you could run a heavy duty extension cord. That isn't ideal - extension cords are supposed to be for temporary use. But indoors (at least no problems with weather and wild animals, etc.) and with a heavy duty UL-listed cord - e.g., 12 or even 10 AWG instead of the cheap 14 or 16 AWG that you find in the dollar stores - it would run just fine. But any time you use an extension cord you have to be aware of any possibility of damage - the cables buried inside your walls are safe, the cords outside your walls can be damaged by: kids, pets, furniture (e.g., rolling chairs), doors (I've seen people put extension cords under a door and not think about how it can get into the edge of the door and then get pinched with every open/close), etc. There are reasons extension cords are not supposed to be used for a permanent installation - but it is better than a non-compliant "permanent" installation.

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    Thanks! The goal was to avoid using an electrical cord. My wife will avoid tripping over it, but I will definitely face plant over it in the middle of the night. The secondary UPS is a fair option, although the main UPS will be plugged into a generator when extensive power outages occur, so being able to have it’s output accessible in the second room would be a real plus. Wish I could afford a more expensive option, but that will have to wait until later... – staticGenerator Jun 5 at 23:19
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    @staticGenerator - Have you tested the UPS on the generator? UPS's and small generators often don't work well together. If you've got a 20KVA whole house generator that'll probably work fine, but a small 5KVA "contractor special" generator may not provide a stable enough source for the UPS and it'll keep tripping over to battery. Even small inverter generators tend not to work well (I haven't had much luck with anything smaller than a 6500W inverter generator). Ironically, the auto-ranging power supplies found on most computers is more tolerant and can work even when the UPS doesn't. – Johnny Jun 6 at 0:54
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    @Johnny: It's not really "ironic"; the UPS cares about power "quality" (shape of the sine wave) but a computer power supply just rectifies to DC (and converts that to 12VDC with a switching power supply). Unlike an AC motor, it doesn't care much about power quality. Modern power supplies do have power-factor correction so they try to "look" like a resistive load where voltage and current are in phase, instead only drawing current from the voltage peaks of sine waves, but probably they'd still be fine with square wave or DC input. A simple bridge rectifier + capacitor would be. – Peter Cordes Jun 6 at 7:20
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    But yeah from the right POV it is ironic that the computer is fine, but the UPS that's supposed to protect the computer from power problems is itself having problems. – Peter Cordes Jun 6 at 7:22
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    That's the penultimate solution. The ultimate solution is a DC battery bank in the house, and server gear bought with power supplies that'll accept battery voltage. The battery is topped up by solar, wind, mains, or a generator. Nice thing here is, the room lighting can also be put on this. – Harper Jun 6 at 23:43
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Yes. You are allowed to use standard practices for in-wall wiring to build a "runt circuit" that goes A to B to C to D and does not actually go to any service panel.

You fit standard outlets in all locations but exactly one. Since there are no other inlets, you fit one inlet capable of taking an extension cord.

Every circuit needs some number of outlets and exactly one inlet. Normally the inlet is direct wiring to the service panel, but not today. If for some reason you want to have 2 possible inlets, you still install one inlet and simply move it as needed.

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    Would the wiring be required to be at least 12AWG to accommodate the possibility of a heavy-duty extension cord plugged into a 20A outlet? – supercat Jun 6 at 23:01
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    @supercat good point, I don't think Code actually calls that one out, but it's a good idea since NEMA 5-15 inlets will fit 5-20 cords. – Harper Jun 6 at 23:40
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To use a UPS located in one room for equipment located in another room, you need a UPS designed to be hardwired.

This is called a Structured Wiring UPS, and they are typically prohibitively expensive. They have internal wiring connections that an electrician would connect circuit breakers and then outlets to. They do not have normal outlets on them that you're used to seeing on a UPS.

An extension cord plugged into a normal UPS is the most you can do, and even that is against code if it's always going to be connected that way instead of just temporarily.

Putting outlets in the wall and connecting them to a normal UPS is not allowed as far a I know.

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    Citation needed on not being allowed to construct your own extension cords and wire outlets -- this definitely isn't true everywhere in the world. – Nate Strickland Jun 5 at 22:49
  • @NateStrickland I think you're right that it's allowed to make your own extension cords, I thought it was a NEC thing but it's just dumb OSHA guidelines which don't really apply here. – Dotes Jun 5 at 22:58
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    @Dotes -- can you give an OSHA or NEC cite on it being forbidden to have an inlet/outlet pair that's powered up by a cord-and-plug connection to a UPS? – ThreePhaseEel Jun 6 at 1:46
  • This is only needed on very long distances. On just a few meters, wiring everything yourself is perfectly fine. – Overmind Jun 7 at 7:55

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