Air compressor wiring

[Robliepse]

I'm finalizing my shop wiring and adding the 220v circuit for the yet to be purchased air compressor. I understand the baisics of AC wiring and load ratings but I'm unclear if I should install a 3 prong outlet or a 4. I'll most likely purchase the 5A Ingersol compressor from Northern took andctheir specs are not very clear. Any advice will be appreciated

 

[Mike67]

3 ( 2 hots and a ground) are typically whats required unless you have one that has an intergrated 110v dryer, tank blowdown ect...

 

[Robliepse]

Thanks, I'm going around 100", will 10 gauge be enough ?

 

[mmissile]

http://wiresizecalculator.net/

 

[NJRR]

If it's 3-phase, you would use the 4 prong, but doubtful your house is wired for 3 phase. Also, I've always seen 3 phase wired directly into a fused safety switch.

 

[Beekeeper]

#10 would be the correct size for a 30 amp circuit. That will work great for the compressor. Use 10-3 with ground romex ,2 hots a neutral and ground

 

[Mike67]

I would use 8 on a 30 amp, theres a lot of inrush current at start up. Also something to consider depending on the size of the motor you may need a motor starter with heaters ( thermal overload motor protection). Breakers protect the wire not neccassarily the equipment...

 

[Beekeeper]

Most modern compressor motors have built in overload protection. If not it would need overload protection.

 

[747mopar]

I wired mine with a 3 prong and 6 gauge just incase I ever go really big but also because that's what I was running for welding outlets. 10 gauge and a 30amp circuit will handle most typical shop compressors.

 

[Mike67]

Most modern compressor motors have built in overload protection. If not it would need overload protection.

Our IR 80gal 5 Up didn't, I don't have my code book in front of me ends its been a while since I've looked at 430, but I think anything over 7.5 requires it. You can get free access to NFPA and look up 70.430...

 

[Beekeeper]

I have a code book. Have had since 1989 when I started as an IBEW apprentice

 

[vintage chromoly]

Hey beekeeper, local 38-cleveland Ohio
Inside wireman here!

 

[Beekeeper]

Hey beekeeper, local 38-cleveland Ohio
Inside wireman here!

Hey from local 760 Knoxville,tn
Journeyman wireman

 

[Robliepse]

Sounds like we have some good expierenced electricians here. Final question 10 or 8?

 

[Beekeeper]

If the compressor you buy has overload protection built in secondary protection isn't needed.
If not you will need overload protection for the motor.
You really need only 3 wires to the compressor 2 hots and a ground having a neutral there is
optional. You may want a tank heater there or some type of automatic tank drain if so then you would need the neutral. #10 will do the Job and do it well #8 would be
a un needed expense.

 

[vintage chromoly]

As has already been said, 10 AWG will meet code for a 30 amp circuit.
You are only going 100', so voltage drop will not be an issue.

 

[Mike67]

I know Bee is disagreeing but my opi ion if your compressor is rated for 24 amps or greater you need to run #8 which isn't really all that more expensive. Remember the code is the minimum requirement.
30 x 80%( % of the allowed loading of the breaker) = 24 amps. Or your breaker has to be sized 125% of the nameplate basically.
Also if the compressor you are choosing has marginal c.f.m rating for the the work you are going to be doing its going to run longer.
Ya I still have my NJATC Book from 93...I'm a Master Electrician from Tx LU 512 Austin, transfered my ticket to 716 before I retired from the field...whatever that's worth..
If you have a true 240volts at the panel & nameplate amperage of 24 and 100' distance, you are allowed a 7volt drop (3%), with a #10 you will have a 6volt drop, #8 you will be less than 4 volts...

 

[vintage chromoly]

at this point, we really need to know what the OP is buying.
It would have to be a monster to require more than a 220v, 30 amp feed.

 

[beanhead]

Just saw this thread...got some sparkys in fbbo land nice! Local 100 Fresno CA here..OP, probably a little overkill but if you can swing it use #8 it will avoid any issues later on..but yep motor full amps should determine.

 

[steve from staten island]

IBEW Local 3 -----23 year member.... Dont know much about wiring as i was just a millwright/welder in power generation. I do know A card holders union journeyman electricians are top skilled in there trade. Nobody else comes close