My Porter-Cable Air Compressor is drawing too many amps

Question

I recently was given a 6hp 25 gal Porter-Cable Air Compressor (CPF6025VP) that kicks out my 20 amp breaker at around 80psi and will not restart with even 20 psi in the tank.

I measured the amp draw on it and initial start was very high then leveled out around 7 amps and kept rising above 15 until the breaker tripped at around 80 psi. Amp rating for the motor is 15A (GE motor model is 5kcr49tn2403x). I read through other posts and was planning on replacing both run and start capacitors but I'm having trouble finding the right ones.

I cannot find original replacements and the ones with matching ratings have different terminals on them and I cannot find them that come with a wiring diagram. My run capacitor has 2 red and a brown and start has two black. run capacitor model M40FY33 -40uF -370VAC 50/60Hz start capacitor 52A103967-1 -400-480MFD -165VAC -50/60Hz

Anyone that could point me in the right direction of some capacitors and how they should be wired would be greatly appreciated

Please Let me know if any other info would be helpful. Thank in advance!

-John

p.s. -unloader and check valve are working

-motor spins free

Answer 1

At 15A, that is a 3HP motor (assuming 240V single phase here), the "6HP" is a marketing term that means WHEN the motor is slowed down by a change in the load to it's "Break Down Torque" speed, it will develop 220% of rated torque, VERY briefly, in attempting to get the motor back to speed, so 220% torque at a just slightly lower speed results in 200% HP for that brief moment, and they are allowed to present it that way (which I think is a shame). the operative issue however is that during that moment, which for a compressor will be when the pressure is highest, that motor can actually be pulling 33A, not 15A. Most likely your meter is averaging and/or too slow (not enough samples) to be giving you the correct current at the moment the breaker is tripping, but of course, the thermal element on the breaker is seeing and reacting to it. That would also explain why you can't reset it when the pressure drops, because at that point it has nothing to do with pressure any more, it's a thermal cool-down time frame and thoise are specifically designed around the time it will take the rest of the equipment to cool down too.

Changing the caps will not fix this. You need a bigger circuit. a 20A breaker can only be used at 16A continuously (80%). Upgrade to a 30A breaker and #10 wire.