Tools, Sharpening and Power Machinery - Compressor pops 20A breaker

Looking at other posts, I guess a key suspect is the unloader valve. But I think not in my case. I've seen mine start with 0 pressure in the tank, sometimes with difficulty. Usually blows breaker with high pressure in the tank, warm or cold head. Now, in cold weather, won't start with 0 pressure. Haven't pulled the cover to see what the FLA and LRA ratings are. Don't know what weight oil in it. Suggestions? Thanks,
Don

Welcome to the forums! Give us a little more information. Size tank, size motor, single head or double head compressor, stand up, lateral, 120 volt or 240 volt set up, required amperage per tag on motor.

I'm guessing a capacitor start! Is the capacitor working?

I agree, Mike, mine don't like cold starts, but they do start. If it hums and trips a breaker, it could be a cap.

Larry

Wow, what quick comments from you guys. Yes, it hums, and seems to try to turn, and if it doesn't spin the bkr pops. I pulled the discharge copper tube and still couldn't get the cover all the way off to see the fan end of the motor; have to pull wiring and switch to see behind the fan.
Barrel of the motor has no info, is cast aluminum finned. Vertical head compressor on top of steel tank, 12" d. 30"l. single ph.
Decals and plates on tank: NAPA 1993 82-115-PAT, s/n 00L627
Sticker on motor cover: 79H0068 / GR.COMPR.BASE / B1800 FL/1,5 115 / ord. 142708 N.08
How do I know if capacitor IS working? :o

It is not a safe way to do it, but if you care careful, once the motor energizes, try to spin the pulley in the way it wants to go. If it starts successfully, it is definitely the capacitor. No more expensive than they are, you could just replace the cap and save taking a chance on getting hurt by the pulley. Unplug the compressor and ground the capacitor before you grab it with your hands.

I'm guessing this is a direct drive unit, no belts or pulleys, correct? Can you get to the capacitor at all? If you can, take it off, deenergize it and put some current through it with a multimeter. If it does not charge - it's bad, change it. If it's good, your next step will be to check the motor start windings for continuity.

I have an old Energair 2 HP horizontal compressor with a GE motor. Says 115/240 V 12.1 amp. Had no wire to the switch. Belt seemed good and pulley turned freely. I put a cord on it and plugged it in. Pulley turned and ran for about a minute (very quiet, no unusual humming or anything) but seemed to be running slower than I would have expected. Then eventually tripped a breaker.
I would have thought breaker would have tripped quicker if it were the same capacitor problem. Could it be that the motor is wired to 240? How would I tell? Would this cause this problem? If so, how can I correct this?

Looking at other posts, I guess a key suspect is the unloader valve. But I think not in my case. I've seen mine start with 0 pressure in the tank, sometimes with difficulty. Usually blows breaker with high pressure in the tank, warm or cold head. Now, in cold weather, won't start with 0 pressure. Haven't pulled the cover to see what the FLA and LRA ratings are. Don't know what weight oil in it. Suggestions? Thanks,
Don

Did you check the brushes in the motor for wear?? dislocated?? broken/frayed wire???