I have a two year old A/C compressor. They wired it with 10/2 with
ground to my inside 125A box. The outside box is 200A and has space
for more breakers. When the a/c comes on my lights dim slightly. I
can run the line for the compressor to the outside 200A box. My
question is, would this be any better? Would it help at all with the
dimming? Should I run it with larger guage wire? (13 seer, 2 ton(I
think)) Should it be 3 wire (with ground) or is the 2 (using bare as
common) that they wired ok?

If the 125 has a substantial load on it, including the lights in question
dimming would be expected and would very likely be diminished by connecting
directly to the main panel, unless the entire 200 amp service is already
near capacity. They didn't use bare as common, they used it as ground which
is proper. If the run of cable isn't to long and the condenser doesn't draw
more than 24 amps, the cable size is fine



"Shad" wrote in message
ups.com...
I have a two year old A/C compressor. They wired it with 10/2 with
ground to my inside 125A box. The outside box is 200A and has space
for more breakers. When the a/c comes on my lights dim slightly. I
can run the line for the compressor to the outside 200A box. My
question is, would this be any better? Would it help at all with the
dimming? Should I run it with larger guage wire? (13 seer, 2 ton(I
think)) Should it be 3 wire (with ground) or is the 2 (using bare as
common) that they wired ok?

"Shad" wrote in message
ups.com...
I have a two year old A/C compressor. They wired it with 10/2 with
ground to my inside 125A box. The outside box is 200A and has space
for more breakers. When the a/c comes on my lights dim slightly. I
can run the line for the compressor to the outside 200A box. My
question is, would this be any better? Would it help at all with the
dimming? Should I run it with larger guage wire? (13 seer, 2 ton(I
think)) Should it be 3 wire (with ground) or is the 2 (using bare as
common) that they wired ok?

Everything electrical should be grounded. 10/2 is usually 3 wires, one of
which is bare or ground.
The other two wires carry the 240v load. "Common" is not the correct term
for a/c distribution.

Wire should be sized to the load and distance. I can not answer your
question
http://www.electrician.com/vd_calculator.html

If the lights are dimming I would begin by checking all of the electrical
connections. Then measuring the voltage at the service with a decent VOM
meter. Do any of your neighbors have the same problem? If so then may be
call the power company. There is a slight chance that they have anything to
do with the problem.

Hard to say what is wrong with out seeing the installation.