Belt drive compressor blows breaker

[trexmonkey]

Ok so its a belt drive, with a 1.5hp marathon motor on it. The power plug, 1 of the prongs has the very tip burnt off. Could just be people plugging it in while its already turned on.

Anyways i just got the compressor used so i have no idea if it would have normally ran on my garage outlet without problems.

When turned out it seems to run fine, until it hits about 60 to 80 psi, then it blows the house breaker.

What ive tried:
I blew the motor out with compressed air, it was pretty dusty. No change

I took the check valve out, took it apart, not sure if theres supposed to be any kind of rubber gasket in there or not? Couldnt find one anyway. I thought maybe the spring was a little soft so i put a stronger spring in and put it back together. No change.

Edit: oh and i ran it with the drain open and it ran for over 5 mins, didnt blow the breaker, so i turned it off.

So now im here, any ideas

 

[#6 Hill]

Use an inductive ammeter to see if what it's drawing is within spec. Could be a faulty breaker or something else

 

[micromind]

An air compressor motor draws more current with higher pressure.

a 1.5HP motor very likely won't be able to pump up a tank on a 15 amp breaker and some 20 amp ones won't hold.

It could be a weak breaker, try it on a kitchen or laundry room outlet.

 

[The Cobbler]

a true 1-1/2 motor is close to using 15 amps, a weak breaker is possible as mentioned. someone may have changed motor pulley to a larger one, so that would increase amp draw & higher pressures.
the motor could be on it's way out, drawing more amps .

 

[trexmonkey]

An air compressor motor draws more current with higher pressure.

a 1.5HP motor very likely won't be able to pump up a tank on a 15 amp breaker and some 20 amp ones won't hold.

It could be a weak breaker, try it on a kitchen or laundry room outlet.

So it says 13ish amps on the sticker, dont have a meter to check actual draw. My breaker is a 20. I opened the lids and checked the capacitors. The starting capacitor my meter wouldnt read. But the running cap showed 50 and its a 50uf 240v cap so that checked out. Only catch is someone had clearly been inside there and may have changed the capacitors. Is there anyway to find out what caps originally came with this motor? I looked for over and hour and couldnt find anything.

I also did a cfm calculation. I could only test it up to 40psi which is easier....so the cfm is probably way lower, but the number i got was around 4.4cfm. This compressor is supposed to do 7.3cfm at 90psi

 

[micromind]

Generally speaking, there's no way to find what the caps should be. Sometimes you can call the manufacturer but often this doesn't work.

If the start cap is bad, it won't start or it'll have a hard time starting.

If the run cap is bad or the wrong size, it'll start ok but draw too much current while running.

The only way to know for sure is to measure actual current while it's running.

Given the low air output, I wouldn't be surprised if there's something wrong with the pump and the motor is ok.

This'll sound dumb but is there oil in the pump? And if so, is it all black and icky or does it look ok? Too thick of oil will cause low output and overload the motor.

 

[The Cobbler]

also, is the motor wired for the correct voltage you're plugging it in to?

 

[#6 Hill]

So it says 13ish amps on the sticker, dont have a meter to check actual draw. My breaker is a 20. I opened the lids and checked the capacitors. The starting capacitor my meter wouldnt read. But the running cap showed 50 and its a 50uf 240v cap so that checked out. Only catch is someone had clearly been inside there and may have changed the capacitors. Is there anyway to find out what caps originally came with this motor? I looked for over and hour and couldnt find anything.

I also did a cfm calculation. I could only test it up to 40psi which is easier....so the cfm is probably way lower, but the number i got was around 4.4cfm. This compressor is supposed to do 7.3cfm at 90psi

Try here for the specs. Capacitor sizes are listed for some

Regal Rexnord Literature

regalrexnordliterature.callmss.com

Regal Rexnord Literature

regalrexnordliterature.callmss.com

There isn't any kind of long extension cord involved is there? Too much voltage drop will allow the motor RPM to get pulled down under load and then the current will go up. Does that motor have a thermal overload with a red reset button?

 

[trexmonkey]

This'll sound dumb but is there oil in the pump? And if so, is it all black and icky or does it look ok? Too thick of oil will cause low output and overload the motor.

I think the guy i bought it from went through it a bit, to try and fix it before giving up. It looks like brand new oil in the pump, granted who knows what kind of oil they put in.

For greater context, the guy didnt mention anything about the compressor popping breakers. His problem was it wouldnt build air quick enough to run his jobsite tools. Obviously its possible it was tripping his breakers too and he just didnt tell me. But he was probably using much beefier power. i feel like this machine should still work on a 20amp breaker.

 

[trexmonkey]

also, is the motor wired for the correct voltage you're plugging it in to?

Ive never worked with electric motors much, i wouldnt know where to begin. But i assume if it was rigged for 220v it would just instantly either fry the motor or the wires in my wall. Like i said tho with the drain plug open the motor seems to run with no problems

 

[trexmonkey]

There isn't any kind of long extension cord involved is there? Too much voltage drop will allow the motor RPM to get pulled down under load and then the current will go up. Does that motor have a thermal overload with a red reset button?

no extention cord, just one of the prongs is burnt a bit. The power cord on this thing is beefy. A replacement is $90. The motor does have a red switch. Ive pressed it a few times thinking it might help somehow, maybe it was half engaged or something, no luck.

 

[#6 Hill]

Ive never worked with electric motors much, i wouldnt know where to begin. But i assume if it was rigged for 220v it would just instantly either fry the motor or the wires in my wall. Like i said tho with the drain plug open the motor seems to run with no problems

Should be a diagram on the cover for the peckerhead showing high and low voltage connections

 

[#6 Hill]

no extention cord, just one of the prongs is burnt a bit. The power cord on this thing is beefy. A replacement is $90. The motor does have a red switch. Ive pressed it a few times thinking it might help somehow, maybe it was half engaged or something, no luck.

If it is seriously overloaded it should be tripping that thermal. You know an amp clamp type ammeter is really cheap at places like harbor freight. If you say it's 13 amp full load that is really kind of pushing a 15 amp circuit. You say a 20 amp breaker? Is there anything else on the circuit? For continuous loads you are only supposed to use 80% of the circuit's rating. An air compressor really isn't continuous but it could be if you used a lot of air.

Who made your panel? Is the wire tight on the breaker? Does the breaker fit tight on the buss? This isn't something like an old Zinsco panel , is it?

 

[micromind]

If the motor were connected for 230 volts and operated on 115, it would start slower than usual, run ok and draw low current with low load then as the load increased (higher air pressure), the current draw would go up rapidly. In this case, there's a fair chance that the breaker would trip before the built-in motor overload.

 

[cosmokenney]

Change the oil anyway. I went through this this winter. In the sight glass the oil looked perfectly fine. But I was still popping the breaker. I changed from the Quincy oil to a lighter synthetic compressor oil and no more popped breakers. When I drained the oil to put in the synth, it was obviously dirty.