I would like to run a sub panel out to my garage to run an 80 gal (4hp) compressor. — I have a 200 amp shut-off panel on the outside of my house which runs to a 200 amp breaker panel in the house. I was told to think of the outside box as the "main" panel and the one in the house as a "sub-panel." So, I am essentially running a sub panel from a sub panel. – Any problems with that?
I'm thinking I'd do a 60 amp panel in the garage. The compressor would need a "dual 30A" breaker – correct? Can I still have another circuit in that panel for a 20A outlet and or a lighting circuit? Or would that require a larger sub-panel?
How many wires of what awg would I need to run from the house panel to the garage in each case?
In response to question – Total distance from indoor panel to garage panel is about 100 feet.
and, the plate on the motor says 230 volts — 16.5 amps….
I also use a welder very intermittently that "works" on a 20a circuit.
As I continue to browse on this subject… I've learned that I can have four 6 awg wires in my 3/4" conduit… Am I correct that I will need 2 hots, a neutral and a ground running to my sub panel? At just under 100 feet, will 6 awg suffice for a 60 amp sub panel? Then the question becomes, what circuits will I be able to run out of that sub panel? My compressor, plus what?
Best Answer
You can run the sub for the barrage to the house sub panel. As far as the garage panel size I would go bigger, put at least a 100/125 amp panel in this way if later you need more power you only need to upsize the breaker in the house feeding the garrage and the wire gauge. Larger panels are not much more and I have never been asked to down size a panel but have upsized many over the years. For the breaker size on the compressor get the specs off the compressor. Compressor motors may not have "true power ratings" they use locked rotor current. Not FLA + for disconnect and wire size.(note your 16.5 amp size would work on a 20 amp circuit but the mfg instructions need to be followed). For example I have an 7 or 8 horse compressor that only requires a 30 amp breaker on 10awg wire but a true 5 horse compressor that draws more. The only way to know for sure is to check the mfg install instructions. At 100' usually the the wire size won't be needed to be upsized for compressors and welders because they are not continuous loads. With that 240v compressor 4 each 120v 20 amp circuits would be fine possibly more in a 60 amp panel but I would install a larger panel just in case of future needs.