Tom - Thanks so much for the detailed reply. If I haven't worn you out,
here are more details and pictures.
Re: "Can you tell me the size of the wires in that feeder and the type
of conduit that was installed for the 2&1/2 inch raceway to your main
The wires say THHN 4/0 AWG and measure 0.61" diameter with the
insulation. They are copper. I had the old aluminum upgraded about 3
years ago. All I can read off the conduit is "AHF 42040635". Does this
help? Even if I could only run 50A or 60A sub
back through that conduit, I would settle for that, since it is simpler
than what's discussed below.
Re: "Some listed breaker assemblies are actually two common trip,
double pole, 100 ampere, circuit breakers assembled in parallel using a
handle tie. If the breaker handles are not labeled 400 amps then you
do not have a four hundred ampere service."
I took a picture of the main breaker:
The breaker has four sections and reads 200A twice. The red and black
pairs on the load side are paralleled, so I assumed 400A, but I think I
may be wrong. The fine print on the breaker label also shows it's
outputs paralleled. Do I have 200A service?
Re: "Presuming that the service is in fact 200 amperes, a one hundred
ampere panel could be located up to twenty five wire feet away from the
tap point to its main breaker as long as the conductors are in
My subpanel would be less than 4 feet away on the other side of the
wall. The open box (open for pic only) in this pic is just opposite the
main breaker. The main feed to the house comes straight thru the wall
into this box and then goes out the top.
Re: "Alternatively you could consult the manufacturer of the meter
mains assembly and install multi barreled terminal lugs on the load
side of your main breaker."
Something like this was already done: The 4 wires leaving the main
breaker in the photo are paralleled down to two with lugs that look
like what you describe. I may not have another space availalble in them
however. I can't tell because they are wrapped with tape.
If I tapped the main feed for a new panel, you are saying I could not
run this feed through the same hole where the main feed comes through
to the house? It is an 8 inch long conduit through the wall into the
big box in the inside_gar_crop picture. I could poke my tap through the
same hole and mount the sub-panel to the right of that box. The total
run would be less than 4 feet so I don't care about wastefully
oversized wire. Would I still have to poke a new hole in the wall and
run a new pipe? Or could I connect IDTs to main feed wires, but do it
in the box on the INSIDE of the house (shown in inside_gar_crop)?