Air compressors

[Former Member]

I am no electrical expert by any means, but any motor starting (other than VFD driven) has inrush current and this is caused as the AC motor comes up to operating speed this only lasts a couple of seconds, at which point motor under operating load will pull he rated current (VFD actual ramp speed and set up correctly stay extremely close to the operating current).

This is why most manufacturing facilities are slowly going to VFD's as it reduced the "spare" current required for those few seconds.

 

[Chris Cramer]

The problem did turn out to be the circuit. I took a look at the breaker panel and how many wires went to the breaker that kept tripping. The breaker I was using also had a light connected to it and it is only 15A. I wanted to switch the breaker to a 20A breaker, but the wires are not thick enough. I moved it to a receptacle that had its own breaker and the motor kept running from 60 psi. I could still tell that it was struggling to start, but drawed enough currently to speed up.

 

[RobinHood]

There should be some sort of check valve between the compressor and tank maybe in the unloader valve assembly. Check to see if working and holding pressure. If not the compressor will be trying to start under load, resulting in high current draw.

Have a small pancake compressor with exactly that problem. Replaced the pressure switch/unloader - did not fix it. Have not bothered to repair the leaky check valve as it only gets used in “portable mode” (it is empty when not in use and starts from 0 psi - so all is fine) since I now have a GD, 5hp shop compressor. That is on a dedicated 30A, 240V circuit.

The note about extension cords in the manuals is because folks run too small of a wire gauge. My cords start at 12ga and all the way to 6ga. Never had any problem with running motors away from a panel.

 

[Chris Cramer]

The compressor has a 120v cable for power, so I need to make a 120v to 220v adapter cable to use my 220v outlet. However, like Degen said, that would need a long extension cable for me to plug it into the panel I made to use multiple 240v machines off the same main outlet. I may contact one of my coworkers who is a master electrician to add another outlet with 12 gauge wire for a 20A breaker.

 

[Susquatch]

The compressor has a 120v cable for power, so I need to make a 120v to 220v adapter cable to use my 220v outlet. However, like Degen said, that would need a long extension cable for me to plug it into the panel I made to use multiple 240v machines off the same main outlet. I may contact one of my coworkers who is a master electrician to add another outlet with 12 gauge wire for a 20A breaker.

I certainly was not advocating an adapter to use 110 on half of the 220 - assuming the neutral is even there.

If that's what you had in mind, then a 20A dedicated 110V circuit is clearly the way to go.

 

[phaxtris]

Air hose is way cheaper than a breaker and BX, and has the advantage of cooling the air before it gets to your water trap

Would it be easier and cheaper to just plug you compressor into where your 220 outlet is and run more air hose?

Don't forget you will need to change the wiring in the motor to run it on 220, don't just go plugging it into 220 as is

 

[curmudgeon]

The compressor has a 120v cable for power, so I need to make a 120v to 220v adapter cable to use my 220v outlet.

As @Susquatch almost says, this is a very bad idea.... Your future self or someone else will misuse that adapter cable for a 120V load.

To run your compressor on 220V:
- rewire the motor, see page 8 of your manual
- replace cord (or at least the plug) with 6-15P plug
- install 220v 6-15P receptacle (since we use our compressors with other equipment, a dedicated circuit is advised)
- install double 15 amp breaker
- run 14/2 cable from beaker to receptacle
- IMO, there is no need for 20 amp breaker, 12/2 cable, and 6-20P plug & receptacle for this 7.5 amp @ 240V compressor, but lots of us feel better by spending more to oversize stuff

 

[Susquatch]

As @Susquatch almost says, this is a very bad idea.... Your future self or someone else will misuse that adapter cable for a 120V load.

To run your compressor on 220V:
- rewire the motor, see page 8 of your manual
- replace cord (or at least the plug) with 6-15P plug
- install 220v 6-15P receptacle (since we use our compressors with other equipment, a dedicated circuit is advised)
- install double 15 amp breaker
- run 14/2 cable from beaker to receptacle
- IMO, there is no need for 20 amp breaker, 12/2 cable, and 6-20P plug & receptacle for this 7.5 amp @ 240V compressor, but lots of us feel better by spending more to oversize stuff

Well said.

 

[Chicken lights]

I have my compressor on its own circuit, 14/3 220v 15 amp breaker, it’s never given me any problems

 

[Chris Cramer]

I didn't have in mind to use 14 gauge wire for the cable to use my 220v outlet. I can't permanently remove the straight blade plug from the compressor in case my dad still wants to use it somewhere else. In that case I will have to rewire the motor with 12 Guage wire first to the straight blade male plug, and then make an extension cable with 12 or 10 gauge wire, a female straight blade receptacle, and a nema 6 male plug.

 

[Susquatch]

I didn't have in mind to use 14 gauge wire for the cable to use my 220v outlet. I can't permanently remove the straight blade plug from the compressor in case my dad still wants to use it somewhere else. In that case I will have to rewire the motor with 12 Guage wire first to the straight blade male plug, and then make an extension cable with 12 or 10 gauge wire, a female straight blade receptacle, and a nema 6 male plug.

It's not really clear to me what you are planning to do there Chris. With electrical, it's always good to be crystal clear. Don't be afraid to make it a long post.

 

[Ironman]

Aliva has the answer.
Especially if your compressor is in an unheated space. I have started mine at -35 without a problem.
I rebuilt an old 1932 Quincy 325 compressor ten years back, and it has air unloader valves. I have wired in a solenoid and a delay relay set for 10 seconds. So when my compressor starts it remains unloaded while the motor comes up to speed and oil is distributed. After 10 seconds of running free, the solenoid opens and vents the air pressure holding the unloaders open and it begins to pump.

 

[Hruul]

Breakers are typically only rated for 80% of their labeled rating for continuous loads. So 15 amp would be good for 12 amps continuous load. Anything above that is questionable.