When I start my air compressor up cold and with air in the tank. The motor buzzes(acts as if it is bound up) and in 10-20 seconds trips my 20amp breaker. When I let the air out of the tank the motor starts up and builds pressure to 130psi. Seems to run fine with no air in the tank at start up. Please help
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Re: Start up problem
The problem that you describe is caused by the in-tank check valve and/ or the unloader at the pressure switch. When the compressor cycles off the pressure switch releases the air that remains in the air line thru a small valve. There is a 1/4 " plastic tube extending from the check valve to the switch. Listen for the release of air as soon as the compressor stops. There is a small metal tab that pushes on the unloader valve that may need to be adjusted. The motor does not have enough power to start pumping if there is air/backpressure in the air line. If these parts are working correctly then check the value of the start capacitor and use meter to measure. The cap should test within 95 % of stated value. Parts are available at www.chpower.com. Enjoy
Your compressor's un loader valve is damaged , thus cause a air buildup in line .
When start up occurs the pressure buildup causes the piston of the compressor to stick .
Solution is to renew the un loader valve . If the pressure reaches 8bar of whatever its set to it should cutout with a " hiss sound " indicating the air is unloaded from the system and release the pressure from the compressor pistons to start new with no pressure strain on the motor .
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Re: Start up problem
YOUR IN TANK CHECK VALVES ARE BAD. THERE IS AIR TRAPPED ON TOP OF YOUR PISTON WHEN IT IS TRYING TO START UP. DRAIN TANK AND REMOVE THE BRASS VALVE WHERE THE AIR GOES INTO THE TANK FROM THE HEAD (FOLLOW COPPER LINE). THERE IS A PEICE OF TRASH OR THE SEAT THE DISC SEALS ON IS DAMAGED. PART SHOULD COST $10.00 - 20.00. TAKE THE OLD VALVE WITH YOU TO MATCH SIZES. WHEN THE COMPRESSOR CUTS OFF AT FULL PRESSURE YOU SHOULD HEAR IT UNLOAD THE TRAPPED AIR.
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Small, easy to transport air compressors have become very popular over the last 25 years. However they do have their drawbacks. The motors on these small compressors generate alot of heat as they cycle, especially under higher tank pressures (PSI's) and air volume usage (CFM's). They work very hard and run more frequently. In time, this heat creates increased resistance in the rotating armature windings (which act as quickly reversing magnets against magnets in the outer case of the motor for thrust to rotate). The magnetic force weakens, the motor gets weaker and hotter and has to work harder to do the same job. When an air compressor motor seizes in it's cycle and hums or buzzes, it is over heating to a point where a thermostactic relay will break electrical contact (to prevent Fire) and the motor will have to cool before it will run again. each time this happens you are reducing the life of the motor by several hours.
To maximize the life of your compressor, use the following guidelines:
1.Always use the shortest possible cord and plug directly into a 20 amp cicuit when possible,no extension cords! SHORT WIRE+LONG AIRHOSE- electrical current is lost through longer wire and requires a larger gauge (diameter) to carry the current.
2.Make sure the plug contacts are clean- as with automobile batteries:CORROSION=RESISTANCE=HEAT=WEAR.
3. Should your compressor begin to stall during its cycle, attempt to turn it off or quickly or reduce the pressure in the air tank to reduce the load on the motor- while the motor is moving a fan blows air through it to cool it.
4.Should the motor overheat, let it cool untill you can touch it with your hand and bleed most of the air from the tank to minimize the start-up work load.
5.Remember to try to drain the tank after each use to minimize corrosion due to moisture and minimize load the next time you start it up.
Following these guidelines will increase the life of your compressor motor several months if not years.
-Remember- BROKEN TOOLS CAN'T HELP YOU BUILD OR FIX ANYTHING
One thing mine does, If it is plugged into a 15 amp circuit , it will do the same thing. It needs a 20 amp circuit to run, the start up motor on those things draw 16+ amps, and then run on 13. If it is cold, full of air, it won't run, if it has a cord of any length, forget it, It needs a big cord, 20 amp circuit, or no air in the tank and be warm. In the winter time we all had our compressors in the bathroom with the heat on, I though it was for us to warm up in, but it was for the compressors. I thought mine was the only that did it.
one of a few things possible, first is that the start capacitor is faulty, second could be the start switch inside the motor, and the third that the pump is not unloaded ( if only happens when the tank has air in it) or the pump and or motor is locked up.
Most likely it is the unloader valve. This is inline with the air filltube from compressor to tank. Somestimes the unloader valve is screwed into the tank and air tube is attached to it. This device takes the pressure out of the tube so the compressor can start without the back pressure from in the tank. Other possibility, the start capacitors of the motor. The capacitors must give a kickstart upon startup or the motor will just hum for a couple seconds and overload the breaker. A tempoary solution is to turn off the power to compressor when it reaches 120psi, then allow the pressure to drop to 40 or less, then turn power on and mostlikey compressor will start with a load of 40psi or less. It is a nuisance but it works until you replace the bad part. Goodluck,Macgivor
My first thought was that the check valve is allowing pressure back into the compressor and preventing the motor from turning. That's still my best guess right now.
I think the cold weather start symptom is what you would see with any engine/motor -- it requires more torque to get it going. In this scenario, if the check valve weren't leaking, it would start okay when cold.
It is a good sign that the motor turns freely with and without air. That indicates that you have good bearings and that the intank check valve is in good condition. Next you should check the capacitors and the condition of the windings. Some motors have start and run capacitors and others only have run cap. Remove from the circuit and test with meter having cap. test setting. Most shops will test them for free. The cap should test within 95% of stated ( uf ) value. Replace as needed. Finally check that the flyball switch at rear inside of motor is functioning correctly. At rest, switch is at start winding, then a split second after start, it shifts to run winding. Check contacts are not stuck and that switch is working and lastly that the winding are the color of new penny. Good luck.