"Mark or Sue" wrote in message
news:HdCub.183851$275.602329@attbi_s53...

For what you want, you will need a 200A service and perhaps more (you'll
have no expansion to grow w/200A). You may want to go with a 320A service
if
you're going to the trouble of replacing your service. Both options 1 and
2
are NEC compliant except that 6/3 can only support a 60A panel. If you
really want a 200A indoor subpanel, you'll need a 2/0 copper feeder with 4
wires which is huge, and the main panel must have feed through lugs
(uncommon). I would lean towards option 2, but it may look ugly on the
outside of your house with all the feeders coming out of it. If you have
an
outside main disconnect (breaker), all the inside panels must have their
ground and neutral busses separated. Only the ground bus can touch the
chassis on a subpanel, the neutral must remain insulated. If your existing
100A inside panel is not isolated like this, it could be difficult to make
it compliant (wires too short).

The central heat and A/C need disconnects, but not necessarily subpanels.
If
this is a heat pump, the part with resistance heat will need a lot of
amps.
Best to run a circuit from the main panel to just handle this load (which
will probably have to be #4 or #2 copper).

The wires in the attic are sized by the size breaker protecting them and
not
necessarily length. But with a 60' length, I'd be inclined to stay with
the
larger choice if a borderline wire size is needed. Wires do not have to be
in conduit if a cable type wire is used, but must be protected from
physical
damage. Your low attic sounds like you may just be able to fish the cable
through and staple it down where you can.

When you ask about an inside "main" I'm not sure what you mean. It is OK
to
have a subpanel inside with its own main breaker, but a main breaker is
not
required in a subpanel inside your house. If you want a "service rated
panel" inside, it usually must have a main. Only problem is, all your
"service rated" disconnects must be grouped near each other (can't have
one
outside and one inside). If you have an outside disconnect, that is the
only
main you need, and all other should be subpanels. You could have another
panel next to that outside disconnect that is also a "service rated"
panel,
but you usually only do this when you have a larger service than the panel
is rated for (e.g. 300A service with a 100A and 200A panel side by side).

Hopefully this helped and didn't confuse you too much. You may want to
post
again with new questions. I'd recommend talking to an electrical
contractor
to see what they recommend. Be sure you know the amp requirements of the
new
heat pump (both inside and outside units) and anything else you want to
add
that is power intensive (larger range, hot tub, welder,...). Sometimes,
HVAC
contractors can do some really weird things with power, but then so can
lame
electrical contractors. Be prepared for the electrical costs to top $1000
for all of this, and even more if your electric utility company charges to
upgrade the service drop and/or transformer to your house.

--
Mark
Kent, WA


First,
*Thank you* for reading this and taking your time to reply, Mark!

I hired an electrician to come out and give a consult since I wrote the
questions.
He suggested option 1 at first (200A inside panel for heater and addition,
60' away from outside disconnect)
After he left, I checked the ampacity of the wire needed to feed option 1
and was told I'd need 4/0 feeder wire (at $7.50 a foot!) to carry
potentially 200amps.

After reading your analysis and calling the electrician back, he said I
could optionally run 2 wires (one dedicated to inside heater, one to a
100amp panel) instead of 1 wire to do both.
That way I could run 4/3 copper 60' through the attic directly to the
heater (heater only) and 2/3 copper 60' through the attic to a 100amp panel
for the addition (lights, sockets, stove, dryer, sewerage pump) (instead of
a 200amp panel as per option 1), and have an outside breaker for each
seperate circuit (total of 4 circuits - old inside panel, new inside panel,
central air heater, outside compressor).
It intuitively seems to be a better solution to distribute the load over 2
wires instead of 1.

I rechecked my old inside main, and there is indeed a 100amp single throw
double breaker for the stove. At least when I throw it, the stove is off,
but other lights are on. The stove consists of a separate oven and rangetop.
Have no idea why the original homeowners installed a 100amp breaker, but
it's there. I'm guessing the wire coming from it is a #6.

BTW, the new central air and electric heater is a Goodman 4 ton 13 SEER
conventional unit (not a heat pump)
According to option 2 (which is what I'm tending towards now), the heater
will have it's own dedicated circuit from the outside meter base and
breaker.
Should I also have an second inside breaker/disconnect for the heater at the
heater location (which is right above the new panel, in the new attic)?

I appreciate your mention of separating the ground and neutral busses on the
subpanel.
I don't know if the exisiting inside panel is able to be ground and netural
separated. I do know that most of the wires going through the exisiting
structure do not have a ground wire. It is also good to know that a subpanel
can have a main breaker (that was a hard one to find an answer to). Home
Repo suggested that a subpanel without a main breaker (main lug?) had to be
used if the distance was 10 feet.

I want to be NEC-compliant and am very interested in doing it as properly as
I can (and hoping to leave the existing inside panel untouched, minus
transferring some of the existing panel's load - stove, dryer, sewerage
pump - to the new panel)

Thank you!