Air Compressor Starting ?

[Serial # 19781010]

I gave my son a 220V 2 HP. air compressor and it has always run well. The compressor is in his unheated garage which is about with a temperature of around 0 degrees F. The motor trys to turn and trips the breaker because it does not have enough torque. With the belt removed the motor runs fine. Turning the flywheel by hand does not seem abnormal. Could this be a faulty capacitor on the motor or has the compressor casing shrink a bit because of the cold and there is not enough clearence for the pistons. How can a capacitor be checked to see if it is all right? Putting up walls in his basement and we really need the compressor to run the framing nailer Thanks.

Vic

[Mike Marlow]

If the motor runs without the belt on the cap is ok. There is a blow by valve that lets the motor spin the compressor up without working against the air pressure until it gets a little head up. Make sure the valve is working freely. Try this - drain the tank and leave the petcock on the tank open. Then try to start the compressor. It's not the same as the pressure relief valve, but it might give you an indication if the valve is the culprit.

[Tyke]

I agree. The line between the outlet of the compressor and the tank needs to be de-pressurized when the motor starts, otherwise the motor will pull too many amps and trip the breaker.

I had this happen on my old 2 HP unit. The check valve had a spring which rusted, and the result was the line did not de-pressurize after the unit turned off. In this case I merely had to replace the spring.

Look for a 1/8in size line coming off the compressor discharge and see where the de-pressurization device is located.

Dave Paine.

[eganders]

I have a compressor that had this problem. I think it is a typical problem due to the high torque required when the oil is cold and the V-belt is stiff. I changed the belt from an old style V-belt to a thinner, more flexible one and after that I could put a larger pully on the motor and still get it to start in a cold garage. A cold, stiff V-belt sucks a lot of power. Also, the line from the breaker panel to the garage is usually quite long and in a 115V line, probably not the heaviest gauge. Since you have a 220 V line, I would think that that might not be as big a problem, especially with just a 2 HP motor. As Mike said above, the pressure relief valve could cause the problem. When I had the problem, I often held the valve open manually (not all can do this) and that would allow the motor to come up to speed unloaded and warm the parts up so it would run normally. Not the best solution I will admit.

[Edwin Pawlowski]

There is the problem Porter Cable recommends SAE10 oil for extreme winter running. IR says to never operate below 20 degrees.

[DJ Delorie]

Along with all the others, a side thought... Make sure it's getting the power it needs from your outlet. I found that one outlet in my garage is just far enough away from the breaker panel that the compressor won't start reliably, but a different outlet (wiring? connections? outlet? who knows) works just fine.

[Tim and Steph]

Agreed - I've got an oil-lubed compressor that complains a lot this time of year unless I switch out the oil for a lighter grade. Just don't forget to put something a tad thicker in when the weather warms up again.

[Carl Stigers]

air compressors that use oil for lube need a thin oil if run outside in an unheated area. I service all makes and models up to and including 400HP units. You need a thin 10 weight non detergetn oil in the unit. The oil is thickening up and preventing the unit from running. If the unit is still having problems look at the tank check. Graingers sells them in various styles. The most common one is a 6X209.

Carl Stigers