A relative of mine was planning to install a generator transfer switch (or interlock kit) to serve his home in the country. The house is five years old and there are two main panels; one 200 amp and one 125 amp. Both are fed directly from the meter, and the 125 amp panel has no main switch and contains the well pump breaker (how convenient), so an interlock kit probably would not work.

The problem that arises with a transfer switch is the number of circuits; the local code seems rather strict (maximum 8 outlets per circuit, individual circuits for many appliances). This is what would need to be run:
-20 amp 240volt well circuit
-20 amp kitchen rec circuit
-20 amp 120 volt septic tank plug
-freezer circuit
-fridge circuit
-another 20 amp lighting/receptacle circuit
This is (frankly) the bare minimum that would suffice

The generator has a running load of 5000 watts, and a 240 volt 20 amp twistlock plug. Most 20A transfer switches only have 5 circuits.
Any recommendations?

Good morning Kyle.

Let me understand the feeds. You have one meter which in turn feeds a 125 Amp service and a 200 Amp service for the residence.

The type of transfer switch you are speaking of is a "Make/Break" switch. It is required to break the connection from the service feed and make the connection with the generator feed.

By definition, this will not work when two services are being interupted. Since the well pump is on the secondary feed, it also has to interrupt the feed from the meter to the pump otherwise you will still be putting a backchannel feed onto the POCO lines.

You would have to place the switch at the output of the meter and open all the feed lines. I do not know if this can be done. The only other alternative would be to use two generators and two transfer switches to open each feed from each meter.

I was thinking more towards the transfer switches that you wire to/from the panel to power individual circuits, and that have a designated number of circuits. I assume in this case I could pull circuits from either panel?

That's what I do not believe would work. You would have to be able open the feeds to both supplies or risk placing a backchannel amperage which would migrate back through the POCO's transformers and be amplified as it traveled along.

I would swap a couple of circuits for the pump, so all necessary loads are on the same Panel. An Interlockkit will work well on a Main Breaker Panel, you also need an Power inlet Box and Wiring, You won't need a Transfer switch with the interlock kit, it allows only Main Breaker or Generator Breaker to be on to prevent backfeeding.
DON'T get the small panel that allows 6-12 cicuits.
The interlockkit allows all 120 volt breakers to be ON, this allows turning on and off lights and fans everywhere(When needed)Turn OFF unused Lights, and unplug unnecessary electrical and electronics to prevent damage from low voltage as generator quits.
You will likely need a 50 Amp Power Inlet switch and wiring(2 #6's for the hots, a #8 for neutral and a Number 10 for Ground).
http://www.norwall.com/products/Gen%252dTran-50-Amp-Power-Inlet-Box.html?gdftrk=gdfV23267_a_7c1096_a_7c3304_a_7c63 652

http://www.interlockkit.com/

Thanks for the answers everyone. If I could get him to cut a little sheet rock, we might could try moving the well over to the main panel. (I don't know what that wasn't done in the first place... )

donf: I'm not sure I quite understand why it would be a problem, is it because there would be circuits from two separate panels going into the transfer switch? Or am I misreading your post? Maybe we're thinking about 2 different things.

Nonetheless, I think we'll see about moving the well over and just going with an interlock kit.

No, my concern is that the generator would be feeding two panelsm but only one would be disconnected from the service.

That would mean that one panel would still be on the feeder circuit from the POCO. If that is true, than the generator would be feeding the panel and its connection to the POCO equipment.