Sorry, I meant the old analog meter. This True Value apparently doesn't sell analog meters anymore, so the new one is digital.

 

Anyway, that was a lot of anticipation just to prove pattenp right! With the new meter I get near 0 between the top 20A and the 15A and about 250V between the 15A and the lower 20A.

Someone asked about the label details. The top one says "Cir B 20A: Shop ceiling lights, shed south outlet, shop west outlets." The middle one says "Cir A 15A: shed overhead light, water softener (east) outlet." The bottom one says "Cir C 20A: North-south-east GFCIs, gate lights & GFCIs, shed north outlets." (The gate lights and GFCIs are out, I suspect ants in the outlets, but that's another post - the hurricane interrupted that project).

Really appreciate your help and patience.

 

Since the main panel is surface mounted doing a subpanel is very easy. Just mount it next to the main panel and connect with a conduit nipple.

 

Well the voltage check confirms what I thought. That means you do need to use a full size double pole breaker that will use up the two full spaces which you see as 4 circuit positions. One thing that might not make the subpanel a simple install is that it is an outside rated panel and may only have top and bottom knockouts for wire entry. So it may require more than a straight nipple from the side of one panel into the side of the other panel

 

It would be helpful if you knew exactly how the interlock kit fits to see if it would reach a half sized double pole breaker being mounted in the center two positions leaving the top position with a blank cover. That way you could move two of the single breakers to the other side and move the third single breaker to the bottom.

 

Here is my suggestion on how to do it assuming you have removed the cover and determined the interlock can be installed and will work:





Note you could move B and C to the top and bottom blank spaces on the left and just the center breaker on the right and 2-pole (pump) breaker on the left to the subpanel.



Note also there is only one space on each side for a 2 pole breaker and so the existing 2-pole breaker (pump) must be moved to the subpanel since one 2-pole space is used by the genny and one to supply the subpanel.

Terminology: Rereading the thread I see tandem breaker mentioned multiple times but GE does not use tandem breakers, that is two single pole breakers in one housing. They use half width breakers.

 

What I have on the interlock kit so far is photos and instructions from the mfr, InterlockKit.com, Model K-8410 (link below) and they've told me it will work with my GE Cat No TM420RMS panel. Beyond that I would have to order it and return within 30 days if it doesn't fit. I can see some wiggle room that might make it not work, for example if the handle on the generator breaker is too low for whatever reason. The description says it requires a "Two-handle breaker", I assume they mean the generator breaker. It attaches to the panel below the breaker slots, has a bar extension that runs up the middle 1/2" gap between the breakers, and slides up or down. There's an extension to the right at the top that locks either the main or the generator breaker in the OFF position.

Here's a link to the product page and installation instructions, for instructions scroll down the page a bit: https://www.interlockkit.com/Product...uctCode=K-8410.

 

I looked at the instructions and was having a hard time visualizing how it mounted. Now that you say it goes below the breakers I see how it works. So my thoughts about the Gen breaker being a half size with the top slot being a blank won't work because it seems to me that the "L" shaped end will be setting right at the top slot where the blank will be. Normally the flag end of the interlock sits down at the first slot when the Gen breaker is off blocking it from being turned on and then when the main is turned off the interlock can be pushed upward blocking the main allowing the Gen breaker to be turned on. So it boils down to as we said earlier a subpanel seems to be the best solution.

Ray's pictures clearly show the breaker configurations that you need.

 

For a sub panel look at the GE TL412R1. It's a 4 space/ 8 Circuit panel and is small enough that it should be able to fit next to your main panel, either beside or below depending on how you need to connect it.

 

I think I see a conduit from the bottom probably to the house subpanel so right side is best. There are a couple of communication cables that might need to be moved a couple of inches closer to the main panel to give room for the subpanel. The nipplel between the panels will be about ½" from the wall so the communication cables can run under it.

 

Are you guys seeing my photos, like the panel interior one with all the transfer switch connections? What I see now is that photo replaced by a message from Photobucket saying I have to start paying for Third Party Hosting. I guess I'll start attaching photos as files.

 

Here are a couple more interlock kit options. The mfr says he thinks this one might work but isn't sure although it looks promising to me and costs a lot less: Square D Homeline 200 amp panel Generator Interlock Kit | GenInterlock

This one is a little hard to figure out from the photo but it supposedly works with almost any double horizontal throw breakers. It rotates, looks kind of dicey to me: https://natramelec.com/genswitch/gen/gen2/gen2.htm

 

Neither of them are intended for GE panels. Also your panel isn't the same configuration as most panels. Your main is vertical on the side. Most panels it is horizontal centered across the top.

You need to throw the main breaker and pull the cover. You can't just guess.

 

Are you asking for a photo of the panel with the cover off?

 

And checking to see if the interlock fits.

 

I can't seem to get the photo to upload. It's only 3.4 MB. I'll try a different one.

 

Trying again (for about the fifth time) with the panel interior photo. The extra wires/connections are for a transfer switch I don't use, which is mounted on the inside of the wall.

 

Found the GE TL412R1. Looks good to me. $15 - seriously? That's the cheapest thing I've bought all week. My wife likes the color!

But I can't tell if it has side punchouts. You might have pointed that out previously. Just means I'll need a 90 in the nipple or conduit to go in from the bottom, right? Also doesn't specify for outdoor use, at least on Amazon. HD says yes, but says you need a ground kit.

 

Nema 3R panels are for outdoor use. Yes, you may need a LL or LR conduit body or 90 ell to connect. That TL412R1 panel only appears to have openings on top and possibly the bottom. And it probably does need a ground bar kit.

 

Or you can drill holes with a hole saw but on the existing panel you have a side hole right where you need it.

 

ray2047, many thanks for the diagrams.

Here's the Home Depot shopping list, not counting nipples, conduit if needed, wire. I'll put all the existing breakers in the subpanel as you suggested.

pattenp, the panel (from Home Depot) has a "P" at the end of the model # compared to the model # you gave me (TL412R1). Not sure what the P denotes

• GE PowerMark Gold 125 Amp 4-Space 8-Circuit Outdoor Single-Phase Main Lug Circuit Breaker Panel Model #TL412R1P $35.00
• GE Load Center Equipment Ground Kit Model #TGL1P $3.29
• GE Q-Line 30 Amp 2 in. Double Pole Circuit Breaker Model #THQL2130 $8.98 (generator)
• GE Q-Line 50 Amp 1 in. Double Pole Circuit Breaker Model #THQP250 $8.98 (subpanel)

I'll keep you all posted and hope you won't mind additional dumb questions if they come up.

 

Just make sure the interlock works before buying anything.

 

The TL412R1 is just the base number. I'm not sure what the "P" means. There is a GE chart and there's a reference to the knockout sizes on the panels and "P" list 1", 1.25" 2" and 2.25". So may be the panel can take those size of conduits connections. I don't think the "P" is something that's an issue and the panel will work for what you need.

 

Good plan, but how would I do that without buying at least the $150 interlock and the generator breaker? Am I missing something?

 

You could probably tell without buying the breaker just by buying it but be sure you have in writing you can return it at no charge.

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It wasn't entirely the cost (up to a point), it's also having to decide in advance (when you buy then wire in the xfer switch) which circuits you'll be able to use, and also having to buy an xfer switch that can handle all the circuits you might need even though you won't use them all at once. With an interlock you turn circuits off, switch from service to the generator, then use the breaker panels to choose what circuits to use. An xfer switch almost seems like a completely redundant (and expensive) set of switches. They really run into some $$ for many circuits. An interlock just seems a lot more flexible to me. Especially if you anticipate say using a refrigerator a few hours a day when you don't need lights, hot water heater every day or two to take warm showers, or a window A/C unit in the bedroom only at night, but none of these big wattage items at the same time. 'Cause we're talking about your basic 5500 W generators here, not a whole-house setup.

 

That said, I've discovered a big flaw in my plan for the main panel. Thinking through ray2047's question made me realize that the house is on a subpanel after the main panel (the one we've been talking about), so switching from service to a generator at the main panel would mean no power to the house. For some reason I was thinking the house would have power and I would choose circuits to use in the house subpanel. All I'd be able to power from a generator with this setup is the circuits in the shop.

Am I wrong? If not, I'll have to rethink this project to put an interlock on the house subpanel service breaker instead.

 

The house will have power because the Gen is back feeding the bus that the house sub panel is hooked to. You'll be good to go using the interlock. Doesn't throwing the outside main breaker kill the inside house panel along with the outside breakers? After taking a look at the picture if those lugs are pass-thru and you have another main disconnect I may have to eat my words.

 

Yes throwing the outside main breaker kills the house panel.

You mean I would have to eat your words! Any way to determine that? I'm pretty sure there's no other main disconnect. The house subpanel only switches off the house feed, not the shop. Another subpanel in an inlaw apartment only switches off power there, not in the house or shop. That's all panels except the unused transfer switch.

I'll double check tomorrow. Would doing that resolve the question about pass-through, just checking where power is turned off by each panel main switch?

 

If the outside main kills the house subpanel then you are okay. When I said pass-thru lugs, I'm not even sure if there is a main disconnect panel that has unprotected pass-thru lugs that can be used to pass power to another main disconnect panel. To satisfy your own uncertainty, turn off the outside main and check that there is not power to anything.

 

WIll do. Thanks for your persistence on this.

 

This is my interpretation of what you have but as Pat suggested verify.

 

Nice, many thanks.

<more words to make it 25>

 

One more thing you need to check is does your jurisdiction allow the use of an interlock. If they allow an interlock do they allow one that attaches to the inside cover. If not does the interlock mount internally or to the cover. Interlocks that mount to the inner cover are easily defeated by removing the cover so are sometimes not allowed.

I know you posted the interlock you plan to use but I haven't really studied it.

 

Another issue could be that this interlock is not UL Listed.

 

It attaches to the outer surface of the inside cover, bolted in from the back. So the sliding metal part goes on the outer surface of the inside cover between the switch handles of the breakers that protrude through the inner cover.

I guess you're right. There's a rather misleading statement (that they were tested in UL-listed panels) here: https://www.interlockkit.com/SearchResults.asp?Cat=1837. Kinda sneaky, huh.

But frankly I don't see the big deal. It's a metal thing that slides to physically prevent two breakers from being on at the same time, not really an electrical component per se. It's a light-years improvement over my redneck neighbors who routinely plug the gen into their dryer outlets and continue like that for days or weeks. And they recommend the method highly to anyone who will listen. They think I'm insane.

I'll check with an inspector by phone. Hopefully he'll be cool and it won't set off a $200 permit. Although it would be nice to have the assurance, I have other house expenses this year.

Venting alert! The real-world options for multi-day power outages are: (a) a dryer plug backfeed or (b) a total rats-nest of evolving 50-100 foot extension cords or (c) $1500 and up for an electrician or (e) do nothing and hope it never happens and suffer when it does or (e) a straightforward DIY project that only costs a few hundred dollars.

 

Never an option.

You might look for a UL approved interlock. Check with the manufacturer to see if they sell one.

 

I agree 100%. <more words>

 

InterLockKits.com interlocks are tested and certified. That's one reason they cost so much.

 

But whether it will be accepted and pass inspection is up to the AHJ (your local inspector). It's always best to ask before purchasing anything that may in the least bit be questionable. Being tested in UL Listed panels is a far cry from being tested and listed by UL.