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I have a woodworking shop with 3 - 240V outlets. I recently had some electrical work done in the house and now one of the outlets doesn't work. Testing the 2 working outlets (see below) I get 120V between ground and both legs and 240V between the two legs. But if I test the non-working outlet I do not get the 240V between the legs. Is this something I could fix easily or should I get an electrician to come back out and fix it?

outlet readings

Edit:

Electrical panel, I switched the two 240V circuits off to better highlight which circuits I'm talking about. The bottom right breakers go to a second panel...

panel

Edit 2:

Dead panel and info sheet. Sadly it looks like the info sheet needs some updating.

dead panel more

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    You're leaving us hanging. What exactly did the electrical work entail? Was anything done in the panel? Was the panel full before work started? A photo of the panel (door open, cover on is fine) may help. Also, if you unplug all 240V appliances, do you still get that same reading? – Harper - Reinstate Monica Jan 1 at 20:10
  • What sort of electrical work was done? Can you post photos of the panel please? – ThreePhaseEel Jan 1 at 21:26
  • Hope the panel photo helps – joegtp Jan 2 at 19:51
  • @joegtp -- can you provide us with a shot of the panel with the deadfront on please, as well as a photo of the label on the inside of the panel's door? I think I know what went wrong here... – ThreePhaseEel Jan 2 at 20:40
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    Thank you all I swapped 14B and 16B and I now have 240V. – joegtp Jan 3 at 15:30
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This panel has 20 spaces/40 circuits. The spaces alternate (by row) between the 2 hot legs. The "A" and "B" within each space are on the same leg.

The functioning 240V circuit is on 12B + 14A.

The dead 240V circuit is on 16A + 16B.

All the voltage readings you've made and the pictures match.

The simple solution, is to swap 14B and 16B. That would make the 240V circuit 14B + 16A, and it would work properly.

The problem likely happened when the electrician moved something else and did not realize these two breakers needed to be a pair on opposite legs. Why didn't they realize it? That's a good question. They should have figured it out by looking at looking at the wires, but since they are loose wires in conduit rather than cables, that is not immediately obvious. They should have figured it out from the panel labels, but those are often wrong. So that just leaves the breakers themselves.

Key question, since I can't tell from the picture: Are the "dead circuit" breakers (16A + 16B) actually a double-breaker or two breakers tied together? Or are they two entirely separate breakers (i.e., you can flip each one independently)? If they are a double-breaker or handle-tied pair then the electrician should have known better. Seriously. If they are not a double-breaker or handle-tied pair then you should either replace them with a double-breaker or get a proper handle-tie.

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Hmmm. Are the working and non-working outlets on different circuits? If so, it sounds like your alleged "electrician" put the 2 hot wires for the non-working outlet on the same phase. If so, I'd have a different qualified electrician check out his other work.

To fix this, if the non-working outlet hots are on the same phase, you need to move one to an opposite phase. In fact, if that's the case, it's a major screw-up. Both hots on a 240 volt circuit need to be on the same double pole breaker. Lots of speculation on my part here. Pictures of the panel with the cover removed would help. I probably should have posted this as a comment, but I had too much to say!

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    This can happen when 1 feeder leg is open and a load is connected. to ground both sides read 120. Nothing from leg to leg. – Ed Beal Jan 1 at 20:01
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    @EdBeal Good point. If a hot wire simply became disconnected, then any 240V load attached, even a tiny standby vampire load (pilot light etc.) would connect the 2 poles so they both read 120V. OP needs to unplug everything to get a straight reading. – Harper - Reinstate Monica Jan 1 at 20:14
  • @EdBeal Agreeing with you and Harp. That's a great point. It would have been easy to lose a hot leg when working in the panel, simpler explanation than mine. – George Anderson Jan 1 at 20:56
  • Sounds like I need to get an electrician in, thanks for all the help – joegtp Jan 2 at 0:16
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Your electrician must have moved breakers around so that the "bad" ones are now on the same phase.

240 Volt circuits must be on opposite phases. When you run down one side of the panel, alternate breakers are on opposite phases so any 240V are usually placed on adjacent breakers and Ta Da you get it right.

However, all your breakers except the four at the bottom are "tandem" breakers, they are half-height breakers that occupy the space meant for 1 breaker. There is nothing wrong with this, except that the rule of thumb to use adjacent breakers for 240V is based on full-height breakers. You can clearly see the problem in the following picture.

enter image description here The single half-height breaker located between your good and bad 240 circuits throws off the pattern.

The solution is to move the bad ones up a half-position, and the intervening one down next to the sub-panel breaker.

Also, the two breakers on a 240V circuit must be bound together so they both trip together. I think I see a pin joining the two "working" ones. Harder to see with the "not working" ones but please double check that every pair of breakers controlling a single circuit are joined up that way. The one feeding the sub panel is much more obviously joined with a clip.

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  • Yup, they somehow crammed a THQP2xx 2-pole double-stuff breaker in so that both poles are on the same bus stab (leg). Dunno how they pulled it off...but it explains the OP's symptoms for sure – ThreePhaseEel Jan 3 at 4:26
  • @ThreePhaseEel are you sure it's a THQP220 and not two THQP120 breakers? Doing this with a pair of breakers would be stupid and wrong. Doing it with a double pole breaker would defy understanding as you suggest. I'm not familiar with this panel, would it physically prevent installing a double pole breaker that way? – jay613 Jan 26 at 13:58
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    It could be two handle-tied THQP120s, which'd make defeating the rejection feature easier, but at the same time make the mistake much more...deliberate in that someone would have had to know to put the handle-tie on the breakers – ThreePhaseEel Jan 26 at 22:27
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Whoever was fidding in the panel last really didn't know what they were doingscrewing up

Whoever was last doing electrical work on this panel probably shouldn't be invited to return for more, given what they managed to screw up with your shop circuit. Your GE panel, instead of using tandem breakers (2 breaker mechanisms in a single pole frame) for "double-stuffing" the panel, uses a half-width breaker frame instead, and your panel is indeed loaded mostly with THQP half-width breakers.

This is fine as long as you're dealing with 120V circuits; however, a 240V circuit requires two breaker poles that land on adjacent bus stabs. For full-width breakers like the 90A subpanel breaker in the bottom-right, this is trivial. However, half-width two-pole breakers like the ones used for the two 20A circuits for your shop require a bit of care to ensure that they end up straddling two bus stabs, as the breaker for the working circuit is doing, instead of being crammed onto a single bus stab in the fashion that was done for the breaker feeding your broken circuit.

GE CTL panels such as yours, furthermore, have a rejection feature in them that should prevent the last installer from doing what they did. As a result, either your faulty 240V circuit was fed by a pair of handle-tied single-pole half-width breakers (which the rejection feature can't stop from being mis-inserted), or the installer must have done something sketchy to get the breaker to fit where it didn't belong.

So, I would ask the electrician to pack a couple of THQP120s, a TQLFP1, and a THQP220, and have them move the faulty 240V circuit over to the bottom-left of the panel between the two existing 20A 120V circuits there, replacing the existing 20A breakers in the process. They then can plug the hole left by removing the old breaker with said filler plate since we don't know if that bus stab's even usable any longer after potentially being abused by the prior installer.

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