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Guidance on electrical wiring for new air compressor requested

16259 Views 14 Replies 9 Participants Last post by  emtnut
Hello,

New member here. I recently purchased a Porter Cable 60-gallon stationary air compressor (PXCMLC3706056) for use in my garage. The primary function will be to drive a rivet gun (and various other aircraft building tools) during my RV8 build project. I was given some advice by another RV8 builder to purchase a dryer cord and run the compressor from the same outlet my clothes dryer runs from since that's already wired for 240V. (The compressor is 230V / 15 AMP, according to the serial plate).

However, I think I would like to run a new line from my home panel in conduit to the garage so that I can also add a disconnect switch in the garage next to the compressor for safety. I don't know "a lot" about electrical wiring, but I would say I know enough to be dangerous?
My questions are:
1) What kind of breakers do I need to add to my panel?
2) What kind of wire to I need to buy? I'm guessing [email protected] 14-guage wires?
3) Do I only need 2 wires? There are only 2 terminals inside the pressure switch to wire to, so I think there is no ground required?
4) What kind of disconnect box should I get?
5) Depending on the size of the wire, is 1/2" conduit sufficient? The conduit will be run along the outside of the house attached near the bottom of the wall with straps screwed into stucco. I measured and the route I plan to take is 45 feet.

Thanks, in advance.
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1. A double pole 15 amp breaker that matches your panel.
2. 14/2 cable will be fine you don't need a neutral so the white can recoloured to black.
3. Yes only two wires are needed plus ground.
4. Does the compressor have a plug? That is all you need.
5. 1/2" will be fine for #14. You will want THWN wire not cable in the conduit. Get enough black for both runs or a red and black. You can't use white in this case.
You will need three conductors to the disconnect unless you are using metallic conduit from the house panel to the disconnect.
Two-pole 15 amp circuit breaker. two black, one green 14 guage THHN/THWN conductors. Two pole 30 amp disconnect, fused or unfused.
I am relatively sure there is a grounding location on the pressure switch.
Liquid-tite or MC cable from the disco to the pressure switch.
Is the compressor the only thing you want to run in there ?
I would consider using larger wire and running 4 wires,
2 x hots, 1 x neutral & 1 x earth.
That way you can add at a later date without
having to change/re-run your main feed.
Future proofing so to speak.
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Is the compressor the only thing you want to run in there ?
I would consider using larger wire and running 4 wires,
2 x hots, 1 x neutral & 1 x earth.
That way you can add at a later date without
having to change/re-run your main feed.
Future proofing so to speak.
The best advice is above:

But if not for the future, I would at least keep it off the edge. A 15 amp name plate, #14 wire, and 15 amp breaker is asking for trouble. It will cost very little more to do it right. I would upsize at the very least to #12 wire. I would also up size the OCPD to counter the locked rotor starting current. If you use, say, #12, you could upsize to at least a 30 amp OCPD. At 15 amps (sounds like you have 2-3 HP) FLA name plate, starting the compressor with a 15 amp OCPD could give nuisance trips.

I ended up installing an automatic drain valve on my big upright, and I have a small 240 volt air dryer as well. The neutral came in pretty handy for the drain valve.
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If it's a 15 amp name plate then a 15 amp circuit is probably too small. I thought you meant the unit required a 15 amp circuit. What does install directions say for circuit size?
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Hello,

New member here. I recently purchased a Porter Cable 60-gallon stationary air compressor (PXCMLC3706056) for use in my garage. The primary function will be to drive a rivet gun (and various other aircraft building tools) during my RV8 build project. I was given some advice by another RV8 builder to purchase a dryer cord and run the compressor from the same outlet my clothes dryer runs from since that's already wired for 240V. (The compressor is 230V / 15 AMP, according to the serial plate).

However, I think I would like to run a new line from my home panel in conduit to the garage so that I can also add a disconnect switch in the garage next to the compressor for safety. I don't know "a lot" about electrical wiring, but I would say I know enough to be dangerous?
My questions are:
1) What kind of breakers do I need to add to my panel?
2) What kind of wire to I need to buy? I'm guessing [email protected] 14-guage wires?
3) Do I only need 2 wires? There are only 2 terminals inside the pressure switch to wire to, so I think there is no ground required?
4) What kind of disconnect box should I get?
5) Depending on the size of the wire, is 1/2" conduit sufficient? The conduit will be run along the outside of the house attached near the bottom of the wall with straps screwed into stucco. I measured and the route I plan to take is 45 feet.

Thanks, in advance.

How many horsepower is the motor on the compressor?
Is the compressor the only thing you want to run in there ?
I would consider using larger wire and running 4 wires,
2 x hots, 1 x neutral & 1 x earth.
That way you can add at a later date without
having to change/re-run your main feed.
Future proofing so to speak.
Yes, the air compressor is the only thing I want to run there. It needs a dedicated circuit. There are other normal outlets in the garage i can use for smaller / non-pneumatic tools. :)
How many horsepower is the motor on the compressor?
The motor is rated at 3.7 HP
If it's a 15 amp name plate then a 15 amp circuit is probably too small. I thought you meant the unit required a 15 amp circuit. What does install directions say for circuit size?
I am also worried the 15 amp is too small... the instructions dont give much guidance other than "ask a licensed electrician". :) It does say the motor will draw several times the rated amount when it first starts up and recommends a time-delay fuse if fuses are used. Not sure the difference between a fuse and a breaker beyond a fuse being a one-time burn out thing and a breaker being reuseable after it is tripped...

Any suggestion on sizing the circuit? The compressor is 230V, 15 amp, single phase rated with a 3.7 HP motor. The wire distance from the unit to the panel is roughly 45 feet.
I am also worried the 15 amp is too small... the instructions dont give much guidance other than "ask a licensed electrician". :) It does say the motor will draw several times the rated amount when it first starts up and recommends a time-delay fuse if fuses are used. Not sure the difference between a fuse and a breaker beyond a fuse being a one-time burn out thing and a breaker being reuseable after it is tripped...

Any suggestion on sizing the circuit? The compressor is 230V, 15 amp, single phase rated with a 3.7 HP motor. The wire distance from the unit to the panel is roughly 45 feet.
At least #12 wire should be used, but I think a #10 would be better considering the starting load. A circuit breaker has a built-in time delay. You might want to install a manual motor starter to protect the motor from overload.
the instructions dont give much guidance other than "ask a licensed electrician"
No, what the instructions say is:

"Ensure that all wiring is done by a licensed electrician, in accordance with the National Electrical Code.. "
Code requires a minimum #12 wire and a maximum 45 amp breaker for a 3HP single phase motor operating on 230 volts.

If it were mine, I'd use #10 and a 30 amp breaker. If it trips on starting, go with a 40 and keep the #10s.

The reason for using #10 is because it is a 3.7HP motor. #12 may very well be compliant, I'm too tired and lazy to figure it exactly.

Lol.

Rob
If your nameplate FLA is actually 15 amps, you must have one of those creative "peak" horsepower rated motors. A single phase 2 Hp is rated @12 amps; 3Hp is rated @17 amps (@230 VAC). It is unlikely to be almost 4 true horsepower.

Read post #5 and #13 again. And I still maintain that a neutral will come in handy someday, especially after you have to lay on the floor to drain the tank multiple times (you WILL drain the water out won't you?).

http://www.amazon.com/iiMash®-AC110...id=1455073076&sr=1-3&keywords=automatic+drain

Just an example.
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Hello,

I think I would like to run a new line from my home panel in conduit to the garage so that I can also add a disconnect switch in the garage next to the compressor for safety. I don't know "a lot" about electrical wiring, but I would say I know enough to be dangerous?
My questions are:
1) What kind of breakers do I need to add to my panel?
2) What kind of wire to I need to buy? I'm guessing [email protected] 14-guage wires?
3) Do I only need 2 wires? There are only 2 terminals inside the pressure switch to wire to, so I think there is no ground required?
4) What kind of disconnect box should I get?
5) Depending on the size of the wire, is 1/2" conduit sufficient?
Thanks, in advance.
I installed the same setup (Dewalt, but same compressor)for a guys home garage.
Calculations came up as
20A ocpd , #12 wire
Home depot has a cheap disconnect, about $25. 30A. Use 30A slow blow fuses.
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