Question on wiring 220v air compressor.

[mroneeyedboh]

So as Im looking for a 110v AC for the shed, I see that since I already have a decent feed going out to the shed, I could use 220v. But one reason I didnt want to go 220v was because I thought I needed to pull 12/3 wiring to use 220v. I did some reading online and it seems that I would NOT need 12/3 and I can just not hook up the neutral ( not needed in a 220v circuit if there isnt a need for 120v too. Like a stove has a 220v heating element but a 120v light ) and use that as my second 120v leg.

Im understanding this correctly, right?

 

[crbnfbr]

Yeah, 12/2 should be fine depending on the run length. That's what I plan on doing someday in my shed since I already have a 90A 240V sub panel in there already.

 

[mroneeyedboh]

I think the run is like 35 feet, max

 

[crbnfbr]

Mind you I'm no electrician, but imho I say you are good to go unless the compressor has a massive motor with a huge current draw.

 

[TheGrooveking]

Find what your amperage needs are and work backwards from there. If more than 30 feet you need to factor in voltage loss which will require an increase in wire size.

TheGrooveking

 

[md21722]

What HP is the compressor?

2 HP requires wiring for 15A 230V (#14 THHN or #12 Romex)
(if you tried to wire a 2HP for 115V, you would need to wire for 30A and use #12 TTHN or #10 Romex and then increase wire size for voltage drop as needed)

3 HP requires wiring for 22A 230V (#12 THHN or #10 Romex)

5 HP requires wiring for 35A 230V (#10 THHN or #8 Romex)

7.5 HP requires wiring for 50A 230V (#8 THHN or #6 Romex)

Run the motor the highest voltage you can. Voltage drop will be better and wire size can be smaller.

At 230V, the air compressor does not need a neutral, just two hots and a ground.

(At 35 feet from the main panel and running 230V you should be fine with the sizes listed above).

By locating the compressor remotely in the shed you will likely need to upsize air line size to account for pressure drop running it back to where you will use the air.

 

[Woodworker99]

I think you mean 12/4 not 12/3. In a 12/3 cable you have a black (hot) wire, a white (neutral) wire, and a green (ground) wire. A 12/3 cable is for 120 volt 20 amp max tool. A 12/4 cable is the same as a 12/3 cable except there is an additional hot wire maybe red color. So the black wire and the red wire EACH carries electricity. The white wire is for equipment that are rated 120V/240V such as a stove as you stated. If you use metallic conduit and not cable then you would have only two wires (240V equipment) one black and one red. No separate ground (green or bare) since the metallic conduit/boxes serves as the ground. Wire size depends on amperage, voltage, distance, and phase. If your particular equipment can run on 120 volt single phase OR 240 volt single phase, remember that for example a single phase 240 volt motor rated for 10 amps if re-wired for 120 volt would draw 20 amps. If you have 3 phase power then there will be 3 hot wires (black, red, blue) plus a ground in a 240 volt delta or wye system. A 3 phase motor draws less amps than a similiar size single phase motor.

 

[mroneeyedboh]

Thanks guys. Ideally I'd only use what a 120 portable Ac can put out. But for the SAME cost, I can just use a 230v Ac and be even BETTER off...