I have a 10 breaker transfer switch (reliance), and I want to pair up two more breakers from my breaker panel to the one breaker on the transfer switch. The two breakers just are for lights from the panel to lights on the transfer switch and all are 20 amps. This won't all be used at the same time. Is this against code? The amp draw will be minimal.
Electrical – Breaker panel to transfer switch
electrical-panel
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Lucky you
Your panels are set up very advantageously to put in a generator transfer switch. All the loads you want to switch (but one) are already in a subpanel. This makes this super easy. It's almost like somebody planned it... Except the guy who put the pump circuit in the main panel did not get the memo.
You need to put a different transfer switch in between the two boxes. There are a couple ways to do this.
One is fit the subpanel with a manual interlock switch. This is a listed (offically tested) modification to the subpanel where it puts two breakers opposite from each other with a sliding plate so they can't both be on. Simple and cheap, and you may even be able to retrofit your existing panel. Must be thrown manually.
The other way is to pick a spot along the cable between the panels (or elsewhere if you don't mind rerouting cable), cut the cable, and insert the transfer switch inline. This will work with any kind of transfer switch, including automatic. You'll need to cut the cable on one side with enough slack to work, and the other side will be too short so you will have to replace that "half" of the run. So choose location and cut point very carefully to your advantage.
That one breaker in the wrong panel
The stuff you are imagining, you cannot do anything like that. In that approach, the options are break the law, backfeed the grid and kill linemen; or spend a king's ransom on more heavy cables than the underside of an NYC subway car, in a veritable Gordian knot of transfer switch wiring that nobody will be able to figure out after the fact. And the power company and inspector will absolutely hate it.
The right way is easy, if annoying: move the circuit to the subpanel. Extend the pump circuit, all wires, to the subpanel and land it on a double breaker, ground bar, and neutral if used. Do not continue to use the ground in the main panel, in fact if you make this splice inside the main panel, tape the ground wire with green tape to insulate it from the main panel. It's not the end of the world if it grounds accidentally, but grounds must go to the same panel the hots do.
I know that's a pain, but it's way less of a pain than anything else you could do legally.
Not room in the subpanel?
This happens a lot, some guy drove back from the subpanel store slapping himself on the back for saving $30... by buying barely enough spaces. Don't be that guy. You're going to need 6 right off the bat - 4 for the transfer switch and 2 for the well pump.
Worst case you may need to replace the subpanel, and fortujately that is DIY-possible because you can entirely shut off the panel at the main breaker. Also a great time to be looking for transfer switch friendly panels if you want to go that way. Don't scrimp - slap yourself on the back for buying twice as many spaces as you need today. The bigger panels often come with "bonus breakers" which save you some money too.
No, you can't do that
A 100A manual transfer panel has a 100A breaker for the utility-side input; as a result, it would be a "bottleneck" if you put it inline with your service, restricting the whole service to 100A. However, this does not mean that you have the wrong transfer switch, so do not go running back to the store before you read the rest of this answer!
But, you probably don't want to transfer the entire house
Whole-house transfer sounds good at first, but especially for folks with smaller generators, its not nearly as good a plan in practice as it is in theory. Many of your larger loads, even on a smaller service, are rather large for a generator, and are not nearly as important to have on a generator unless you are dealing with a situation where the power regularly goes out for days on end. (Do you really need your dryer on a generator, or your range for that matter?) Furthermore, you will have to flip a zillion breakers in order to not overload the generator when you transfer to generator power -- probably not the easiest thing to do in the dark!
As a result, what I would do is put a 30A, 2-pole branch breaker in the main panel to provide the utility-mains-side feed to the transfer switch, and then put a subpanel in off the standby side that only has breakers in it for the critical loads -- the ability to have heat so the house doesn't freeze (with a 125A service, I can tell you do not have electric resistance heat), the ability to run a small cooking appliance (such as a plug-in electric griddle or a microwave), your refrigerator (if it's not on the aforementioned small appliance branch circuit, that is), 1-2 circuits for standby lighting + the smoke alarms and selected receptacles, and perhaps the ability to run the hot water heater as well (an electric tank-type heater can be half-volted for use on a generator at the cost of very slow recovery, as well as an extra transfer switch and some clever wiring), as well as any sump or well pumps the house may have.
Related Topic
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Best Answer
Never. You cannot splice the output of 2 breakers together, EVER.
North American wiring is done in a "tree" topology, with unlimited branches permitted. I mention this because most of the time, you see a "vine" topology, and people think that is somehow required.
What this means for you is that your FORMER 2 circuits can be rearranged to be branches of 1 circuit. The 1 circuit lands on 1 circuit breaker. The other breaker then goes unused, leave it in place so you don't have a gaping hole in your panel.
With this conversion done, the way to work it with your transfer switch becomes obvious.
Since you got a huge transfer gang-switch, and even 10 circuits is not enough for you, I must honestly say you would've been better off going another way: a subpanel. You get a $130 subpanel, two "main" breakers for $9 each, a $30-60 interlock kit, and each generatable circuit lands on the subpanel instead of the main using regular breakers in the normal way. No restrictions on number of 120 vs 240 circuits, and as many circuits as your panel has spaces, minus 4 for the interlock.