I'm planning on pulling a permit to install a branch circuit to drive a new
refrigerated A/C compressor. Before I go to the inspector's office I'd
like your opinions on my plan.
I currently have a 125A (rated) panel feeding the house with a 100A Main
breaker. I plan to check the feeders on this to see if I can bump the Main
up to a 125A breaker. I can change a few breaker's around and get room for
a 220 double breaker. I should be ok from a total amperage standpoint as I
don't use the dryer circuit and am on a gas range but by bumping up to the
125A, I'd be able to leave those intact, I believe. The electrical specs on
the compressor say the RLA (Rated Load Amps) is 20.2, the LRA (Locked Rotor
Amps) is 137 A, the Fuse or HACR Breaker Min is 35 A and Max is 45 A. I
figure I'll put in a 40 A/220V breaker and run a 6/3 THHN feeder via conduit
to the location of the compressor approx. 40 ft. away. I understand I
could probably use 8/3 but just in case I ever want to upsize, I figure the
extra cost of the 6/3 is minimal for the length of run. The feeder would
terminate in a fused disconnect mounted on a unistrut frame with Double
Element fuses sized at 175% of RLA (Time Delay fuses) so they would be 35 A.
From there, I'd continue with the feeder to the equipment via flex. Does
this sound like I'm on the right track? I still have to figure what size
conduit (1/2" would prolly work as there will minimal 90's but 3/4 might
just be easier to deal with) and I'm still a little shaky on the fuse size.
I didn't count the Fan Motor Full Load Amps (1.2A) so that would move the
fuse up to 37.45A so I'd probably have to stick with the 35A fuses. Am I
figuring this correctly?
I've given myself a headache searching all the articles in the codebook but
hope I'm on the right track here. Ultimately, the inspector will be the
judge but I appreciate any advice you may have.