"major domo" wrote in message
.. .
I have an electrical service question and have gotten 2 or 3 different
answers.
You can probably tell, but I am a novice. Maybe someone here can help.

I have a 1000 sq ft brick/slab foundation house in the U.S. (electric
water
heater, electric dryer, electric stove, no central air) that is 40 years
old
(grey cloth-covered copper wire).

Outside the house is a meter and separate breaker box with a two 30amp and
two 20 amp breakers. Two circuits from this outside box run along the
outside of the house to an electric dryer and private sewer system.

Inside the house directly through the brick wall is an inside main with no
main breaker visible.
In the inside box (12 slot), there are 8 breakers: One 100 amp double
throw
(stove), one 60 amp double throw (electric water heater - which will be
probably be replaced with a LP unit during the remodel), one 30 amp double
throw (?), and a mixture of 20 amp single and double throws.
One slot is empty.

I am adding a 600 sq ft addition to this house, and adding electric
central
air heating and cooling. It is a 4 ton unit. (60 to 80 amp heater?)

Here are the two options suggested to me already.

1) The HVAC installer recommended upgrading the outside meter and breaker
combination ("meter main") to 200 amps and then feeding the old inside
main
from one larger outside breaker.
He then suggested running a wire (presumably from another outside breaker)
the 60 foot distance through the attic to a new 200 amp inside main
underneath the central air heater (which is in the attic). This main would
also serve the new addition. I will probably move the electric stove to
use
this new service, since the wiring in the area is now exposed. I assume he
would power the outside air conditioning compressor (40 feet away) with a
third breaker from the new 200 amp outside main. He suggested 6/3 wire for
the 60 foot run through the attic.

After some consideration, I began to think that the single line to the new
200 amp inside main would be overloaded unless it was very large.

2) A suggestion from another individual involved the following layout:
Upgrade the outside main ("meter main") to a 200 amp unit. Run one breaker
to the old inside main. Run another outside breaker and wire directly to
the
central heater through the attic (60 feet). Run a third outside breaker
and
wire through the attic to the new inside main (60 feet), which could be
now
be 100 amp (20 circuit), since the central heater has it's own circuit.
Run
the fourth breaker and wire outside the house to the air conditioning
compressor (40 feet). He suggested using 4/3 or 2/3 wire for the 60 foot
runs through the attic.

Here are my questions:

a) Which arrangement would you use that meets NEC code? Are there more
options?
b) I would prefer not to change out the old inside main, unless it's of
great advantage.
c) Also, do I need subpanels for the central heater and air conditioning
compressor?
d) What gauge of wire is acceptable to use for 60 foot runs through the
attic? Should it be enclosed in a pipe? (the attic is vaulted ceiling with
very little (2 feet) crawling room)
e) Last, is it okay to have a single main breaker/smaller breaker box on
the
new inside main (60 feet away from outside service) or should it be a
subpanel as well?

What you've posted seems confused, as parts don't make sense. I'm hoping you
have your breakers labeled wrong, and am guessing what you have is the
following in the inside panel:

100A main
60A for stove
30A water heater
misc 15A and 20A branch circuits

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