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I exchanged my double pole 40 ampere breaker that supplied my sub panel for my garage with a single pole 40 ampere and now out of my six breakers in the sub panel only 1,3, and 5 have power. How do I resolve the issue to get power to all my breakers?

The reason I exchanged breakers is my sub panel has three lugs, and I had to completely disconnect it to do some work. When I wired it back up, even with the breakers in the sub panel in the off position, I had power to all my outlets and switches. I do not know what I did wrong as it was fine before.

To Harper, yes, there are only three wires supplying the sub panel.

Oh dear. This is a foogly mess.

First, you did the right thing by punching that main panel breaker down onto a single. The problem is with the subpanel; it is very badly misconfigured by a guy who cut a lot of shortcuts.

First, it is illegal to double-tap neutral bar screws like that, unless the panel's labeling or instructions say they are intended for that, and these aren't. A few panels will allow 3 grounds on a screw, but always one neutral.

Second, I see no cable clamps on the Romex cables entering this panel. Run down to the electrical supply house and grab a handful.

Separate neutrals and grounds

This sub panel has neutrals and grounds on the same bar. That is improper in a subpanel. Those neutrals and grounds need to be separated, and the grounds need to be attached to the subpanel chassis/frame. The ideal way to do this is to install an accessory ground bar for the panel - however the last guy didn't leave you much length to reach it.

Option 1: The panel may have factory drilled/tapped screw holes for accessory grounding bars. Fit them and buy a Square D brand grounding bar that lines up on those holes. Extend the ground wires down to it with wire nuts. There is a green grounding screw that connects the neutral bar to the box chassis; it appears to already be removed. Remove it.

Option 2: Squeeze a ground bar above the neutral bar, but it must be physically screwed down to the panel, it can't flop around. To bolt it down, either a) use any old metal screws to physically mount it, then run an actual #10++ (#8 would be great) ground wire to a suitable place on the chassis. Or b) mount the ground bar with fine-thread machine screws (bolts) of -32 or finer pitch, and then you can ground the bar through the screws.

Option 3: Convert the neutral bar to a ground bar only. You'll never find that green grounding screw, so just run a jumper wire from this bar to the panel chassis. Remove all the neutrals, and use wire nuts and a pigtail chain to attach supply neutral to the other neutrals. Inelegant, but effective.

Supplying the two hot terminals

The black hot wire coming in needs to be split to supply both hot terminals. (the last guy did a very ugly cheat he should not have done). For this, get about 2 feet of #8 copper wire, black will do, and make 2 pigtails off the solitary hot wire. One goes to where the black wire now is. The other goes to where the ground wire now is. Ideal's big blue wire nut is about right to join three #8s, crank it down HARD.

This converts the panel to a 120V panel. It is not legal to power this subpanel in 120/240V mode, with only 3 wires, as it was before - that would create a very dangerous situation, where if the neutral wire had a problem, everything that is supposed to be grounded would energize at 120V.

The panel will only able to supply 40A for all circuits added together, somewhat less than the 2 poles of 40 A that had been cheated in here. So you are at somewhat higher risk of tripping the supply breaker, but it probably won't be an issue.

Is it conduit? Add the 4th wire

If the route of the wire between subpanel and main panel is all conduit, a red wire of the same size should be added to the pipe. Then it can be hooked up like a normal panel.

While you're at this, maybe replace this panel.

Thinking about all the work needed here - ground bars, cable clamps, etc. - and the fact that this panel is already full - and that you may want to replace with a 4-wire cable which you might as well upsize too for more power...

-- well, given that, I'm thinking this might be a good time to just replace the whole panel with a much larger one.

For instance a 20 space would be a step in the right direction (ThreePhaseEel and myself would certainly go 30+, because spaces are cheap, and being out of space is expensive). By "space" I mean actual knockout, ignore that "20 space/40 circuit" baloney, that is a lie since nowadays most breakers must be GFCI or AFCI, and those require a full space each. (this requirement won't affect you since you are grandfathered; merely replacing a panel does not trigger the obligation to retrofit AFCI/GFCI).

If you want to keep the "sunk costs" you already have in those six breakers (we're talking $27 here) then you could stay in Square D Homeline - which is exactly what it says on the tin, a builder-grade cheapie (not unsafe, just not excellent). The way panels are marketed, there's hardly a price difference to get up into the industrial grade units like Square D's QO line, Eaton CH, GE or Siemens. Also, QO and CH are physically smaller.

So you might shop for a panel that will fit, has plenty of extra spaces, and where the neutral and ground wires will reach the bar without extending (we already must split the hot wire). Any type will do; a main breaker is unnecessary here. Some panels come with "bonus breakers".

Edit: I wrote this answer before the photo was added. I will defer to Harper’s answer that goes into much detail about the problems.

You have a 240 volt sub panel which was fed from a 240 volt breaker. Now you’re feeding only half of the sub panel with a 120 volt breaker. Sorry, what did you think would happen?

Maybe you don’t understand how dual-leg 240 volt systems work. The incoming 240 volts comes in as two 120 volt legs which are 180 degrees out of phase. You get 120 volt between either hot and neutral and 240 volts between the two hots. Most breaker panels are designed so that the even numbered slots connect to one leg and the odd to the other. Therefore, a full-sized dual breaker connects to both legs to give 240 volts. Combine this with neutral to also give 120 volts.

Assuming you have no 240 loads (dual breakers) in the sub, you could use a pigtail wire to connect both hot wires (that were previously connected to the 240 you removed) to the new 120 volt breaker. However, this would give you half the total amperage in the sub (40 amps instead of 80).

Otherwise, you really need a dual (240 volt) breaker there.

You need a double pole breaker. More specifically, you need a breaker that supplies power from both phases on the main panel.

Half your breakers in the sub are now not powered because they were connected to the second phase. It’s not clear what they are tied to now.

As others have stated, there are multiple problems with your panel. I would like to point out a few things that have not already been covered.

1. The reason you had power to switches and outlets even when the circuit breakers were turned off is that you swapped places with the white conductor and the bare ground conductor when you reconnected the feeder (supply cable for the subpanel). The white conductor is connected to the neutral bar in the picture. That conductor was originally connected to the 40 amp double pole breaker. Therefore, when the double pole breaker was turned on, power was arriving at the neutral bar and then was distributed to all of the circuits via the white neutral conductors (and grounds!).




2. I can not determine from the picture if the feeder is 10/2 UF or 8/2 UF. If the black and white conductors are made up of smaller copper conductors, then it is 8/2. If they are single solid conductors, then it is most likely 10/2. If so, then you need to downsize the circuit breaker supply power to the subpanel to 30 amps.

Options on what to do:

1. As an electrician, I can not recommend putting this panel back to its original configuration. But I will tell you how to do it because correctly. Exchange places with the white feeder conductor and feeder ground. Also, there is a place in the neutral bar where a long green screw is supposed to go. This screw connects the metal body of the panel with the neutral bar. If you can not find that screw, then you need to tap a 10/32 threaded hole into the panel, screw a 10/32 green ground screw partially into the hole, hook a 10 awg bare (or green insulated) copper wire around that screw and tighten the screw down, and connect the other end of the bare copper to the neutral bar. Then reinstall the double pole breaker. This is not up to current electrical code, but it is safer than the current configuration and is how older houses are wired.




2. (I believe the following method has been detailed above) Disconnect the feeder ground wire from the right hand lug. Install a small ground bar in the upper portion of the panel (must be screwed to the body of the panel via tapped holes). Connect all of the grounds to this ground bar. Disconnect the black conductor and connect two short pieces of black conductor of the same size to it. Connect these two "pigtails" to the left and right lugs. Leave the single pole breaker in the main panel. This is the correct method for the existing feeder. Connecting the pigtails may be difficult for you if the feeder is 8 gauge wire, but it is important the connection is solidly done.




3. Install a 4 wire feeder and a ground bar (8/3 copper UF minimum). Connect black and red conductors to the left and right lugs, white conductor to the neutral lug, and all grounds to the ground bar.




4. Hire a reputable licensed electrician to perform option 2 or option 3 for you and also fix the problem with the cable entries.

I highly recommend option 4.

The reason why you are only getting power to only breakers 1 3 5 is because u eliminated the other phase on your breaker when u turn it into a single pole breaker so basically u only have a 120 volt going to one bar in your your sub panel. If you take all your breaker out your sub panel you'll see that breakers 1,3,5 are all connected so u don't have power to the other bar. So put your double pole breaker back in for it to work correctly.