"Jason" wrote in message
. com...
I have a 35 year old 100 amp service. I had my old furnance and AC replaced
with a geothermel unit about a year ago. When they did the install they
used all of the remaining free slots for new breakers. The issue is when
the unit comes on the lights dim for a second. Will upgrading to a 200 amp
service prevent the lights from dimming?

Depends on where the voltage drop is occuring. If it occurs inside your
house, then you need to use bigger wires. If it occurs outside your house,
then you call the power company.

To determine this, measure the voltage in your main panel while the dimming
is happening. If the voltage in the panel dropped alot (say more than 10V),
then call the power company. If the voltage in the panel doesn't drop much,
then the voltage drop is happening inside your house.

10V is something I pull off the top of my head. I'm sure NEC has a
recommended voltage drop limit somewhere.