Hi,

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?

Sorry to be so long-winded, but I wanted to be thorough.
I would *greatly* appreciate any expert help in this matter.

Thank you!