What wire for air compressor?

[19Vert64]

I know down the road I'll be getting a 2 stage air compressor but have not picked one out yet. I know where in the shop I want to put it and would like to get the wire run before the metal ceiling goes in. I figure it will be 55-60 feet run from the sub panel. Is 8-3 enough?
Thanks


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[Aceman]

I would recommend 8-2 Romex. That would cover a true 5HP compressor.

 

[zmaxmotorsports]

For that long of a run why not just run it in 6/2 ?

 

[matt_i]

#6 awg for a ~21FLA/5hp compressor seems like a lot of expense even with the distance.

 

[zmaxmotorsports]

It's not that much more money,for something that big running that far it's cheap insurance.

 

[toyotadriver]

Not enough info. 8ga probably be fine but 6ga be even more likely to meet the requirements of whatever you want to install. The cost difference is very little.

 

[wyliesdiesels]

HP first folks.

OP what is the HP rating?

 

[cj7jeep81]

8/2 should be perfectly fine. I just put in my 5hp (true HP) compressor, and wired it up with a 30 amp circuit and 10/2 wire. Haven't used it a ton, but hasn't tripped the breaker yet. If I was doing it from scratch, I'd run 8/2 just to be safe, but I already had some 10/2 laying around that was the perfect length for the ~50' run, so I went with that.

 

[19Vert64]

HP first folks.



OP what is the HP rating?

Don't have one yet so I don't know the hp. Just something I'd likely add in the future and would like to run wire for it before I close the ceiling and walls


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[19Vert64]

https://www.menards.com/main/electr...4442915871-c-6441.htm?tid=-698174916851824107

So this should work fine then? For 75 feet the price difference between 8 and 6 is minimal, like less than $30.

 

[matt_i]

There's a slight problem if attempting to use a 30A breaker and land a #6 awg on each pole see link...So if a #6 awg feed is desired then a larger breaker should be spec'd. Personally I don't like that because if you put a 60A breaker on a #6awg feeding a 21FLA motor...there is plenty of protection for the downstream conductor but not much protection for the motor...in my shop I'd size for 125% of the FLA and wire and breaker for that which would be a 30A breaker and a #10awg/thhn feed.

This link is for acceptable wire sizes to be landed on Square D - QO breakers, its not comprehensive for all styles but gives a data point. My wild guess is other manufacturers pretty much follow suit.
http://www.schneider-electric.us/en/faqs/FA237923/

 

[19Vert64]

There's a slight problem if attempting to use a 30A breaker and land a #6 awg on each pole see link...So if a #6 awg feed is desired then a larger breaker should be spec'd. Personally I don't like that because if you put a 60A breaker on a #6awg feeding a 21FLA motor...there is plenty of protection for the downstream conductor but not much protection for the motor...in my shop I'd size for 125% of the FLA and wire and breaker for that which would be a 30A breaker and a #10awg/thhn feed.

This link is for acceptable wire sizes to be landed on Square D - QO breakers, its not comprehensive for all styles but gives a data point. My wild guess is other manufacturers pretty much follow suit.
http://www.schneider-electric.us/en/faqs/FA237923/

Thanks for bringing this point up and posting the link. My sub panel is a QO panel.


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[lakeroadster]

HP first folks.

OP what is the HP rating?

Details.. Details..

 

[toyotadriver]

In order to do what you want, I would go with 6ga wire. That way it'll work regardless of the size of compressor you go with. But, 8ga should also be fine too. I run a 60 gallon air compressor and the motor is somewhere around 3 HP. I run it on a 30 amp breaker on 10ga wire.

 

[wyliesdiesels]

https://www.menards.com/main/electr...4442915871-c-6441.htm?tid=-698174916851824107

So this should work fine then? For 75 feet the price difference between 8 and 6 is minimal, like less than $30.

The problem with prewiring a motor circuit without knowing the HP rating is the wire is sized based on the HP.

But unless u get a huge compressor(larger than 7.5HP), #6/2 NM-b will be more than adequate.

There's a slight problem if attempting to use a 30A breaker and land a #6 awg on each pole see link...So if a #6 awg feed is desired then a larger breaker should be spec'd. Personally I don't like that because if you put a 60A breaker on a #6awg feeding a 21FLA motor...there is plenty of protection for the downstream conductor but not much protection for the motor...in my shop I'd size for 125% of the FLA and wire and breaker for that which would be a 30A breaker and a #10awg/thhn feed.

This link is for acceptable wire sizes to be landed on Square D - QO breakers, its not comprehensive for all styles but gives a data point. My wild guess is other manufacturers pretty much follow suit.
http://www.schneider-electric.us/en/faqs/FA237923/

That may be how u personally size things but the NEC says to size wire @ 125% of NEC table FLC NOT the motor nameplate FLA.

And breakers in motor circuits DO NOT provide overcurrent protection for the motor- only short circuit and ground fault protection.

Overcurrent protection is either provided by an overload relay in the starter(if equiped) or integral overload protection in the motor itself(red button on end of motor)

Also breakers for motor circuits can be sized max 250% of FLC.

 

[matt_i]

Its interesting that the NEC table is less conservative than using the actual printed FLA...

If you read this tabular summary (15 page .pdf) of NEC 430.250, a 5hp x 230vac motor is only good for 15.2A...and can be fed from a #14awg if 75deg C terminals and conductors can be achieved. That would make me a little nervous despite the supposedly intermittent duty...the thing can run a *long* time during a sandblast cabinet session.....

http://www.cooperindustries.com/con.../BUS_Ele_Tech_Lib_Motor_Protection_Tables.pdf

 

[wyliesdiesels]

Its interesting that the NEC table is less conservative than using the actual printed FLA...

If you read this tabular summary (15 page .pdf) of NEC 430.250, a 5hp x 230vac motor is only good for 15.2A...and can be fed from a #14awg if 75deg C terminals and conductors can be achieved. That would make me a little nervous despite the supposedly intermittent duty...the thing can run a *long* time during a sandblast cabinet session.....

http://www.cooperindustries.com/con.../BUS_Ele_Tech_Lib_Motor_Protection_Tables.pdf

You read the wrong chart. 15.2a is for 3phase 5HP 230v motor.

Scroll down to page 11(pg 155) and u will see 28a listed for 5HP single phase 230v.

 

[matt_i]

Maybe I need new glasses lol

 

[ard]

You could run EMT or conduit for now...pull what you need later. Even had room for additional circuits if needed. Not sure how straight things are, but an 'up, over, down' would be pretty easy.
FWIW