A friend's service panel is getting power from somewhere, but their power is shut off. They're in the process of getting a voltage detector and trying to use that to figure it out but they're super new at this.

In the meantime, if anyone has thoughts on where to look or how to tell where the power could be coming from, we'd love some suggestions.

All I was able to tell them so far is figure out if the mains are hot or not.

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UPDATE: To answer the question below, yes it is single family. I don't think anyone else uses it? I hope? I tried having him turn them off one by one. That seemed to show that all the power was coming from the one left main, but then we ended up going round and round still seeming to find contraindications to that answer.

Eventually he just took the whole thing apart and put it back together without the water heater, just treating it as if it's only getting 110V service. That seems to be working for now. Occam's razor, probably power is coming from that one left main. Assuming maybe the electric company person only turned off one of the mains instead of both on accident?

Wondering if there's anything else that we could be missing? Things still seem to defy sense. He says that the hot breakers are not alternating, they're consecutive. So the left main seems to be serving the entire right side of the panel instead of every other one. Could there be damage to the panel itself? Also seems like the 200A main breaker might not be stopping power to the hot bus, so that's concerning. Just another thing that seems super weird.

So the above part was just a miscommunication -- they do alternate like normal and the 200A breaker does turn off the whole thing. My bad-- one more mystery solved.

  • 1
    Have you tried flipping that 200A breaker into the off position? There could be residual power coming through that line.
    – MonkeyZeus
    Feb 4, 2020 at 16:20
  • 1
    When shutting off a breaker - make sure it actually disconnects ie if the contacts are stuck together...
    – Solar Mike
    Feb 4, 2020 at 16:27
  • Here's an update: Both mains are hot when the 200A breaker is on. When they shut that breaker off, the left main is still hot. When the 200A breaker is on, we think the left side is supplying power to the right side via a 220V circuit for the hot water heater that's back feeding the right side. When they turn the 200A breaker off it still has power on the left but not the right. How can we figure out how the left side is getting power? Is it getting power from the main or could it be coming from one of the other circuits on that side?
    – Sarah
    Feb 4, 2020 at 16:56
  • 1
    @Sarah, as stated in my answer below, turn off each breaker until the power is no longer present. Also note that not all the breakers on the left connect to the left leg. Every other breaker connects to the left leg in both rows.
    – JPhi1618
    Feb 4, 2020 at 17:28
  • Is this in a single family structure? Who uses the water heater besides your friend? Feb 4, 2020 at 20:29

2 Answers 2


You will just need to shut off breakers to isolate each wire and check it for voltage.

Turn the main breaker off, and check the incoming lugs for voltage. If present, then the power has not been "shut off". With the breaker still off, check the lugs that attach to the sliver bars in the back of the panel.

If there is voltage on the bars, one of the breakers is "back feeding" voltage. Turn the breakers off one at a time to see which breaker it is coming from.


About two years ago, a landlord came on here and said "I want to get my 2 tenants to split the cost of running the dryer. I want to tap the red wire from tenant 1's panel, and the black wire from tenant 2's panel, so it rolls half on each electric bill. Make sense?" Of course, we had to take our shoes off to count the number of ways that violates the Electrical Code.

When the 200A breaker is on, we think the left side is supplying power to the right side via a 220V circuit for the hot water heater that's back feeding the right side.

Look at the red wire, lower left

All the circuits which are attached look to be in reasonable order, except that one. It goes onto half a 30A 2-pole breaker, and there's no partner black wire.

Now if you follow it to where it exits the box, it kinda disappears in the lower left corner. There is a same-size black wire which exits the picture out through where the panel cover is supposed to be, off to parts unknown. I assume that is the red's partner in the cable? And somewhere back there a white wire goes up and hits the neutral bar.

I suspect that this (presumably) 10/3 cable goes to a utility room, where it may have powered a water heater dedicated to this unit, until the landlord got the bright idea and decided to have one commons water heater.

However, I could be wrong for 2 reasons, and this may instead be happening with the 30A MP-T breaker above it, or the 50A breaker above that. I think that because first the breaker is off, and second parallax may be confusing me, but it looks like the red wire is attached to the right side bus not the left.

The dead giveaway would be if you switched the breaker off and the spook voltage went away.

Why does the water heater backfeed? Don't all electrical appliances work like diodes and block current flowing backwards through them? No, they're not, not at all. A water heater simply has a heating element of about 10 ohms in line with a thermostat, so when the thermostat is on, it's similar to a wire of long length.

This panel is the poster child for NEC 110.12

Aka "Neat and workmanlike". Which makes this kind of slop not a surprise, and casts shade on all the electrical work done in the building. First, don't misinterpret 110.12 as a call to runt back excess cable length; you actually want enough length for hots and neutral to reach any breaker in the panel. The problems are elsewhere:

  • Alien breakers. This is a Murray/Siemens panel, and that Square D breaker definitely doesn't belong and will not clamp the power bus correctly, causing arcing and damage. I would also look carefully at the black breakers near that double-stuff breaker.
  • "Enough length to reach any breaker in the panel" is correct! But that yellow cable is taking it a bit too far and should be shortened somewhat. Other than that, it's perfectly OK for the cable to remain in sheath for a distance inside the panel; all the better to letter it with a Sharpie saying what it is.
  • The way the neural wires have floppy-dopped out of the bottom of the panel, makes me think this panel spends a lot of time with its cover off. The cover should be reinstalled when the servicer walks away from it (2 corner screws loosely set is fine; but you must stop curious fingers!) I've probably taken my panel covers off hundreds of times.
  • The abandoned cables entering the top should have their conductors grouped by cable, lightly twisted together so they can be identified as related, tucked away from the panel, and their bare copper ends capped or taped off. The grounds don't need to be disconnected.
  • All hot wires from the same cable must land on the same breaker, unless you know for sure the usage is correct (e.g. a MWBC with half held in reserve,
  • Cables coming in through bare knockouts with no strain relief or cable clamps. They make donut adapters to reduce that huge opening to one that matches a cable clamp for whatever cable is coming in that hole.
  • The loose Romex below the panel has no physical protection and needs that.
  • +1 for workmanship separating neutrals and grounds. The wire-nut splices are fine.

Other than that, it's a perfectly fine panel if properly fit.

Can't work on a rental unit yourself

All work on any rental unit must be done by a licensed electrician, to assure quality work and no slumlord shortcutting (and this panel looks like it's full of that). Second, any work requires landlord permission. The only way you get away with self-repair in a rental unit is if you a) own it, b) are genuinely living there (meet the criteria for an owner-move-in eviction), and c) the type of unit is typically owner-occupied, i.e. a 2-unit duplex or 3-unit flat, but not a 12-unit apartment building.

  • Yes, this is an owner occupied situation. All the wiring was ripped out by thieves prior to the purchase by the current owner. They hired someone to do the wiring, but he did a bad job and also didn't finish, so they're doing it themselves now. I will definitely let them know about the Square D breaker and try and go back through your post and re-read for more stuff. They also have a link to this post too but I have slightly more experience talking and thinking through this stuff.
    – Sarah
    Feb 4, 2020 at 23:39
  • 2
    @sarah that's a terrifying situation. I'd recommend a qualified, licensed, INSURED, and competent electrician be retained to (at bare-minimum) give the installation a complete check.
    – Criggie
    Feb 5, 2020 at 0:57
  • Yeah, if someone took money for electrical work, they need to be licensed, and licensure requires years of apprenticeship. . I'd be all over TaskRabbit if that wasn't the case. Feb 5, 2020 at 0:59
  • That yellow wire is so excessively long at first I thought it was two different wires that exited from where the cover should be implying that it was impossible to close the panel properly. Feb 5, 2020 at 20:26

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