Compressor Motor Capacitors Going Out?

[bfr57]

I have a Campbell-Hausfield 80 gal, 220VAC, twin cylinder, single stage compressor that's about 6 years old that's starting to trip the 20 amp breakers on startup. It doesn't do it all the time, but it's getting worse. I've ruled out faulty breakers by "un-poling" them; I removed the connector tying them together, and it's random which one trips. I know it's on startup as I've actual watched it happen at the breakers. The motor is an Emerson and has 2 external capacitors sitting at about the 11 and 1 o'clock positions looking at the motor. Are they the likely culprits? Anyway to test them?

On another note, I guess I've never paid attention that it has 2 capacitors; I haven't seen one like that before. I've just seen the single capacitor motors. Is having 2 just that much more juice for starting?

 

[rancherbill]

Yes it is probably causing your problem. One cap is a start cap and the other is a run cap.

 

[C96]

It’s possible the head unloader is not working and the pump is trying to start under tank pressure.

 

[bfr57]

When the breakers trip, there isn't a hint of motor turn, just a quick blink of lights in the garage and that's so slight you wouldn't notice it unless you were watching it all happen. Wouldn't a faulty unloader at least get a nudge from the motor?

 

[larry_g]

When the breakers trip, there isn't a hint of motor turn, just a quick blink of lights in the garage and that's so slight you wouldn't notice it unless you were watching it all happen. Wouldn't a faulty unloader at least get a nudge from the motor?

Caps are likely but to check the unloader, when the compressor fills and stops kill the power and then open the discharge line at the compressor head and check for air coming back to the head from the tank. Snap a small balloon over the line from the tank and if the balloon inflates then you have a bad check valve that is giving you head pressure.

lg
no neat sig line

 

[pattenp]

Better multimeters have a capacitance test setting. Look for this symbol on the tester.

 

[wyliesdiesels]

What is the HP rating of the motor?

 

[Mr. Fixer Upper]

Single phase motor?

If so disconnect the belt to the compressor
Turn on motor
If motor does not rotate, but you can get it to turn by giving the motor pulley a little spin then the cap is bad.

 

[Froggmann]

Sounds similar to what recently happened to my 40ish year old craftsman compressor. In my case the start switch was getting stuck and not allowing the motor to start or if it started it would go low RPM with high load and pop the breaker. What I found was a slightly gummy start switch that was covered in sawdust and rust. Essentially all my motor needed was a cleaning.

Here's the video I followed when I decided to just go for it.

It's been about 2 months now and the sucker cranks over as well as it did when I bought it.

 

[bfr57]

It's a 5HP, single phase.
Now I did a bunch of sandblasting and powder coating this weekend and it only tripped once, but other times it'll pop every other start-up.
So, is the larger cap the starter?

 

[pattenp]

Usually the start cap is brown plastic and the run is metal silver.

Start Cap

Run Cap

 

[wyliesdiesels]

OP did u figure it out?

 

[Badasssapper67]

Yeah OP would like to know if it was the start capacitor.