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Hurricane season is already here ... planning to put in a transfer switch for my Westinghouse 7500DF generator However my home electric panels is not a regular panel like I see in the videos.

The main panel is in the exterior wall there are 2 main switches in the main panel to disconnect service from the main lines. Unfortunately no one makes an Interlock kit for this Square D panel.

This main panels then drive 2 sub panels inside and the circuits I want to run in an emergency are unfortunately scattered between the 2 sub panels.

Question is can I just use a single 6-switch transfer switch and route the wires to the 2 sub-panels inside to choose the circuits I want to run in an emergency with generator power?


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Install two of those 6 switch transfer panels, one for each large load center (sub)panel..

Construct an extension cord with two female ends to go into the transfer switch box' inlet receptacles respectively and one male end to go into the generator.

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Oh heavens no, don't contaminate that beautiful system with a hokey-dokey 6/8 switch transfer switch panel. They do all the wrong things with neutral, which also means they don't play well with AFCIs and GFCIs! That poos the scrooch for you: you cannot use that thing at all.

Since you're already willing to bring the 6 circuits to one single location, continue onward with that plan. But we'll use a much better transfer switch made out of quality QO parts, supporting many more circuits, supporting your AFCI/GFCI breakers, and we'll do it for half the price!

So we get a QO 18-space main lug panel ($57ish).
- And a 60A breaker ($12, I picked it because it's cheap).
- And a breaker appropriate for the gen ($12)
- And A QO2DTI interlock kit ($27).

The two breakers mount on the left side top 4 spaces. We fit the QO2DTI interlock kit so they can't both be on at the same time. The 60A breaker is fed from one of the subpanels. (#6 wire and done). The generator breaker is fed from a generator inlet ($60ish) which you install wherever you please that is convenient for you. Run a /3 cable from that inlet location to this "generator" breaker.

Then, you simply reroute each circuit to this new panel, and move its breaker (e.g. AFCI/GFCI). Any number of 120V circuits and any number of 240V circuits until the panel fills up. Which may take awhile if you got the linked 24-space :)

The procedure is a little more complex.

1. Turn OFF all the non-main breakers in this new panel.
2. Turn OFF whatever interlocked breaker is on.
3. Turn ON the other interlocked breaker.
4. Turn ON the loads you need, one at a time so the generator isn't bogged.

Hold on. Can't I do that same thing in the subpanels I already have?

By golly, you can! What was I thinking!!

Pick one of the 2 subpanels to be your generator panel. Either:

a) If these panels are upgradeable to main-breaker panels, and QO or somebody makes a generator interlock (such as QOCGK2C) that fits that, then yeah, just go ahead and use that. Otherwise

b) Use the side-by-side arrangement with the QO2DTI interlock, and reroute the panel's supply so it uses the backfed breaker instead of the main lugs.

I expect you can probably do a) but consult with an electrical supply house who is a Square D dealer.

Then yes, fit an appropriate size generator backfeed breaker. Run your cable to your inlet. Now, your entire original subpanel is a transfer switch, and you didn't have to move a single circuit. (well, maybe to get the gen breaker into the top left etc.)

Then simply move the circuits now in the other panel, that you want on generator, to this panel. And done!

Wait. Can I do that for both subpanels at once? Then I don't have to move any circuits.

Hmm, no, that wouldn't work unless your generator interlock switched neutral (as Canadian panels do in fact do). Neutral is not switched (or breakered!), and you don't want a loop/redundant path. If the utility neutral failed in one panel, it would try to pull neutral from the other panel *via* the generator wiring (even if the switches are on utility). If you ran a #10 cable for 30A, your system could be pulling 100A of neutral via that #10 wiring, and who would ever know?
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