I want to install a generator interlock switch on my main panel with a 30A breaker for the generator to power selected switches on the subpanel that powers the house. GE makes an interlock kit for my existing main breaker panel. The existing panel is shown in Photo 1 but to install it I need to move breakers to accommodate the new generator breaker, which has to be under the service disconnect breaker. Can I move the two breakers for circuits B and A (20A and 15A) as indicated by the red arrows in Photo 1?

The generator breaker will be 30A, as will the generator inlet box. The new 30A breaker for the generator would be in the B/A slots.

If you're curious the interlock kit is shown in Photo 2 and the panel requirements for it are shown in Photo 3.

 

You can move those two breakers to any open spot. The two spots across from the main may be unusable because of the main breaker.

 

You're saying the main disconnect may extend over to that double slot? I'll open and check. The only other option would be the one above it.

 

Nope, both of the knockouts across from the main are most likely unusable because of the way the main breaker attaches. The two arrows are pointing to just one space. The breaker you have is a tandem or 2 half space and uses one space. You have some blank covers there that can be removed for the two breaker to move to.

 

If I'm not mistaken.... breakers A & B are in one full size space on one leg. C and the blank below it are the opposite leg. That means a two pole breaker needs A & B & C & the blank space.

 

So the 30A gen breaker would take up the 4 spaces on the right side and I would come up 1 space short?

Is there a simple solution other than giving up a circuit or installing a new box?

 

If you have the 30A breaker just hold it there to see how wide it is.

 

No I don't have it yet.

By wide I assume you mean top to bottom in the photo (narrow direction), right?

Should I look for a 30A with a specific configuration that would make this work?

 

Breakers are not interchangeable between different panels. The breaker you use must be the one specific to the panel. That isn't a GE panel is it?

 

Yes, it's GE. Cat no. TM420RMS I think it says.

 

Here are photos of label and panel from a google search on TM420RMS:

 

Looks like you need to move those breakers to a subpanel. Then you'd have space for a full size 30A DP for the generator and a second full size DP to feed the subpanel from the meter main panel

 

So a new subpanel is the only way to do this and keep the three circuits that are currently on the right side? That will run into some money. There are no other options?

I'm not finding on the label where it says whether or not tandem breakers are allowed. This would be for the generator.

I can't use this GE?
GE Q-Line 30 Amp 1/2 in. Single Pole Circuit Breaker-THQP130 - The Home Depot

Or this one?
GE Q-Line 30 Amp 1 in. Double Pole Circuit Breaker-THQP230 - The Home Depot

 

I believe that interlock only works with a full size double pole. You need to verify that before buying a tandem breaker. That tandem needs to use A&C to get 240V.

 

This is the breaker most likely to work: GE Q-Line 30 Amp 2 in. Double Pole Circuit Breaker-THQL2130 - The Home Depot Notice that is a full size 2" breaker.

Probably around $100 and it can be a DIY. Tell us more about the existing panel. Inside or outside. Flush or surface mounted?

A half size breaker can be used for the 240 breaker to supply the subpanel so you need six half spaces if the panel is full.

If you use a GE for the subpanel a 12 space 100 amp main lug panel would be $50-$60 and you could reuse the single pole breakers you are moving. A 30 amp 2-pole half size breaker at $8-$10 and a bit of hardware and you'd be good to go.

 

This is all speculative because I don't know the layout of your meter panel as to physical room around it. But if you can mount a new small subpanel next to the main panel connected together with a short nipple so you can extend all the circuits for the existing breakers through the nipple to the new subpanel. For the generator you will then install a 30A full size double pole breaker in the spots on the right side below the main breaker which will fill up the space currently used by the 3 half size breakers and the one blank cover. Then install a 50A or 60A full size double pole breaker in the left side spots which will fill the space used by the 2 half size breakers and the two blank covers which will feed the new subpanel through the connecting nipple. Use the largest size nipple that will fit to connect the panels, such as 1.5" or larger if possible. This is just a thought based on guessing what you may have.

 

To add my post was also only a guess. Answer my previous questions on your panel and we will go from there.I disagree slightly. A half size 2-pole breaker should work for the sub panel supply. A 50 or 60 amp supply to the sub would be better but I suggested 30 amp to keep the wire size easier to work with.

A not recommended suggestion would be to double up two lightly use circuits on one breaker but only if you could verify the actual loads. Then you wouldn't need a subpanel.

 

The reason I said 50A or 60A for the sub is not knowing what the actual concurrent loads are on the existing breakers. Also the half size DP breaker will work fine for the sub feed and leave two half spaces open.

 

And your suggestion of higher amps is better than mine. I was focusing on four 15 amp circuits but that is only a guess and leaves no room for future loads on the subs.

 

The meter is above the main panel, both are on an exterior garage/shop wall (photo). So there's plenty of room for a subpanel if I understand what's being asked.

But I wanted to confirm that there's a consensus that the simpler, moving-breakers-around option is completely out. According to the manufacturer of the interlock (https://www.interlockkit.com/v/vspfi...10GENewDsn.pdf), the generator breaker mounts in "slots 2 and 4 (top 2 spaces under main breaker) utilizing piggyback breakers as necessary to create the needed spaces." . I think they're saying a 1 inch generator breaker is what the interlock is designed to work with. Should I check with GE (not an easy task) if 1" breakers will work with the panel?

A question about breaker sizes. "Half" = 1 inch (requires 2 slots)? "Full" = 2 inch (requires 4 slots)? So the breaker described in the interlock instructions assumes a half or 1 inch breaker for the generator. And is a half-size breaker a "tandem" breaker?

 

You panel has four 1" spaces/slots. A half size breaker allows two breakers to use one space/slot. I believe when InterLock says spaces 2 and 4 that is the 2 spaces used by your three breakers and blank. The only way to know for sure is to pull the cover and look at the stabs. Based on the panel paper diagram there are only four 1" spaces. If the A & B breakers are using the same leg then placing a half size double pole breaker in that position will not work. Look at Pjmax's picture. The breaker for the Gen needs to be full size and use 2A,2B,4A,4B in order to pick up both legs. A 2" DP breaker is what I believe you need. A 1" DP breaker will need to straddle two spaces to pickup both legs. As an example look at the well pump breaker, it crosses two knock-outs so to pickup both legs. Using Pjmax's picture if you use a half size DP breaker it will need to be mounted in 2B,4A position leaving 2A blank or with a single breaker in it and that's where the problem is if the interlock plate will work with the DP breaker not being fully at the top. It may work if leaving 2A blank.

 

OK, will look inside and get back to you for more expert opinions! I'm just looking for the simplest solution to safely connect a generator.

Assuming it's getting more complicated (new subpanel), any other options I should consider? I came across this, and they seem to make in 200A but not as easy to find Eaton 100 Amp 120/240-Volt 24,000-Watt Non-Fused General-Duty Double-Throw Safety Switch-DT223URH-N - The Home Depot

 

You are going down a completely different road when you get into using a transfer switch which may end up being more costly than just adding a small subpanel and the interlock on the main. Remove cover and take some pictures so we can see what's inside. Also, if you can, check the voltage across the top 20A and 15A breakers to see if you get 0V or 240V. Then check across the 15A and the lower 20A to see if 0V or 240V

 

Just checking on how to do this test with a multimeter, i.e., what you mean by checking the voltage "across" the top 20A and 15A breakers and across the 15A and the lower 20A breakers? Doesn't sound like the usual breaker voltage test. Are you saying to test both breakers in each pair separately, or to somehow test both breakers in each pair together?

 

Take the probes of your multimeter and put one to the top 20A breaker at the wire connection and put the other probe to the 15A breaker at the wire connection to see what the voltage is. If the reading is 0 then the two breakers are on the same leg, if 240V then the breakers are on opposite legs. Then do the same on the 15A to the 20A under the 15A. I suspect you'll see 0 between the top 20A to the 15A and will see 240V between the 15A and the lower 20A. This is to confirm that a half size DP breaker will or will not work in the same positions as the top two half size breakers.

 

Gotcha. Will do once it stops raining.

 

OK, I'm not sure this makes any sense, but both give 0 volts. I tried two different multimeters, both of which worked with a 9V battery. I also tried them both with the red probe at the breaker screw and the black probe at ground, nothing.

The only twist is there's a generator transfer switch that I've never used because it is connected only to the garage/shed (the circuits at the bottom of the main panel). The house has a separate subpanel and the way it's set up the house would need a separate xfer switch and separate generator. The transfer switch is switched to Line and everything in the garage/shed works.

Photo in a moment.

 

Photo of panel interior. The extra wires are the tranfer switch

 

Trying again with the panel interior photo. The extra wiring is the transfer switch, which I plan to remove.

 

I assume photos take a little while to upload.

 

It does not make any sense that you get no voltage at any point. You need to verify the meter reads voltage and is set to the correct setting for up to at least 300V.

You are taking readings between your A & B breakers and then A & C, correct? What is the detailed label saying by A,B & C breakers? Sounds like there is a lot we don't know about the set up you have which is making it very difficult to help you.

 

That's right, as you specified earlier. Meters were set for 300v and both worked on a new 9v battery, reading about 9v. Maybe by coincidence they're both failing at higher voltage? Maybe I need a new multimeter?

Are you seeing the photo? I'm seeing nothing.

 

Panel interior. The connectors are for the transfer switch that will be eliminated.

 

Test the multimeter on a 120 volt receptacle? Turn the main breaker off then on and test the breakers again.

 

You say testing the meter on a 9V battery gives you a correct reading of 9V. So now for the dumb question. Are you setting the meter to AC and not DC voltage when testing the panel?

 

I'm gonna make a run to the local hardware store to buy a grossly overpriced but new multimeter. Will reply later. One of the meters is dead now after changing the battery. The other is reading nothing from an outlet that works.

 

Get a cheap analog multimeter not a digital. Under $15 is good.

 

That's actually a good question, but yes I did switch to AC for the panel and outlets. Off to True Value.

 

Yes it was the Greenlee digital that died altho the cheap analog is also acting screwy.

 

In what way is it screwy? Post a picture of the new meter.