[MikeLocke]

Hello. Something does not look right with this run capacitor. I am going to replace it. This 60 gal air unit has been poorly maintained by me over the last 10 years. I will also be changing the oil for the first time and filter. Do you think there is a reason this went
bad...maybe the pump is bad as well?

 

[motormonkey]

Capacitors are probably the most common parts to fail in an induction motor. It would be a good idea to check the resistance of the motor windings anyway. I would expect them to be somewhere in the range of five to fifty ohms. You'll want to clean up all of the stuff that that capacitor barfed out too.

 

[MikeLocke]

Thanks for the reply and ideas. I may research the ohm reading and check that out. I might see what happens when I just put that new cap on there, it is a $15 risk. Thing is, this motor was still running but I guess it wasn't running too good. Not sure how long that was going on.

 

[stevon]

motormonkey,

Another forum user Phatteus is having a similar problem See:

Is anyone interested in a 1955 Brunner two stage air...

It is a Model 75SH8 two stage Brunner air compressor with the original tank and possibly the original motor, a WEG 10 HP 220v. (Probably not the original motor. I reached out to WEG for info and was told that this motor is too old for them to have any info on it.) See attached photos of the...

www.powerequipmentforum.com

Stephen

Capacitors are probably the most common parts to fail in an induction motor. It would be a good idea to check the resistance of the motor windings anyway. I would expect them to be somewhere in the range of five to fifty ohms. You'll want to clean up all of the stuff that that capacitor barfed out too.

 

[motormonkey]

Hmm. I wasn't paying attention. The OP said, "run capacitor," and I didn't question it. It is indeed likely that this is a start capacitor, and thus, the motor has a centrifugal start winding cutout switch, a likely point of failure that needs to be checked. Good call Stephen.

 

[MikeLocke]

@motormonkey I did replace that capacitor. Now I think I have a bad pump. Then I thought maybe a bad motor. Now I don't know. The pump spins fine when I wheel it with my hand. The motor seems to run fine when I take the belt off but there is no load of course. When plugged up, it really struggles to get going (see video). Once it does get going, seems to build pressure. I don't want to throw too much $ at this, like buy a new motor and a new pump. I would rather put that money into a new better unit. Let me know if you have any clues please. Never mind, couldn't get the video to attach. It just shows it struggling to start to move then gets going.

 

[stevon]

MikeLocke,

If you can turn the pump by hand, the pump is probably OK. Your exploded capacitor shown is the run cap, the low uF and high voltage rating is the tip off. Well you did the right thing to go the capacitor replacement route first. You still haven't mentioned the amps while running under load. A cheap ammeter on one leg of the power will tell you a lot. What are the winding resistances? Sounds like the motor is toast but you won't know for sure without diagnosing it properly. The HP listed on your motor is "SPL" meaning a 2 to 3 actual HP output based on the 230 volts and amps drawn. Was this the original motor that came with the compressor? I bought a used compressor that had a bogus motor with "3HP" listed on it (Harbor Freight) It showed 12 amps FLA at 240 volts on the nameplate which means it actually only produces 2 HP of usable power. The previous owner went cheap with this inexpensive replacement motor to replace the original 240 volt/ 23 amp real 5HP motor. What he did not replace was the original 5 HP sized drive pulley and the overloaded compressor motor would overheat, trip thermal overload and shut off within 2 minutes running. I got a used WEG real 5HP motor and correctly sized drive pully to fix my compressor problem. Tell us the pump model so we can figure out the required motor and pulley size to use with it. That could explain the slow running issue.

Stephen

@motormonkey I did replace that capacitor. Now I think I have a bad pump. Then I thought maybe a bad motor. Now I don't know. The pump spins fine when I wheel it with my hand. The motor seems to run fine when I take the belt off but there is no load of course. When plugged up, it really struggles to get going (see video). Once it does get going, seems to build pressure. I don't want to throw too much $ at this, like buy a new motor and a new pump. I would rather put that money into a new better unit. Let me know if you have any clues please. Never mind, couldn't get the video to attach. It just shows it struggling to start to move then gets going.

@motormonkey I did replace that capacitor. Now I think I have a bad pump. Then I thought maybe a bad motor. Now I don't know. The pump spins fine when I wheel it with my hand. The motor seems to run fine when I take the belt off but there is no load of course. When plugged up, it really struggles to get going (see video). Once it does get going, seems to build pressure. I don't want to throw too much $ at this, like buy a new motor and a new pump. I would rather put that money into a new better unit. Let me know if you have any clues please. Never mind, couldn't get the video to attach. It just shows it struggling to start to move then gets going.

 

[MikeLocke]

Thanks Stephen. I appreciate the help and your time explaining things. You have some good understanding of this, and I do not. Rather, I know a little about everything but not all about anything. It's the original motor, yes. I will go out there later and check those things mentioned.

 

[stevon]

MikeLocke,

I'm older and forget sometimes that not everyone studied electrical engineering in college or played with cars, he, he. Like to tinker and take on challenges and repairs. Raised in the sixties to be a man you had to fix the car, the water heater, the furnas, the TV etc. today to be a man you just need a good credit rating lol. things are harder to fix these days and parts are even harder to find. Good luck with your repair, sounds like you'll solve this one, kudos for the effort!

Stephen

Thanks Stephen. I appreciate the help and your time explaining things. You have some good understanding of this, and I do not. Rather, I know a little about everything but not all about anything. It's the original motor, yes. I will go out there later and check those things mentioned.

 

[MikeLocke]

I told my boys to either pay attention to what I'm doing and learn how to fix things...or make a lot of money so you can pay someone else to do your man work. So far, they haven't done either one and didn't listen to a thing I said. Back to the issue...about 9.5 -10A on each side with inductive. Comes to maybe 3 or so if I am close. Matches up. I found a motor that looks like it should work perfect. I'll give that as try! I think I screwed the motor up years ago when I did some very improper wiring just to get it up temporarily...involving a couple regular extension cords running to a couple different 15A circuits and maybe a generator. I just remembered that. I remember it smoking some at the time periodically.

 

[stevon]

MikeLocke,

A generator needs to be 3 to 4 times more wattage than the compressor load so with a 15amp electric motor at start (LRA) will draw 6 to 10 times it's FLA listed on the motor. So a generator that can steadily put out 50 to 60 amps is required to start the 15 FLA motor under load. If you get a replacement motor make sure its the same volts, FLA (full load amps) and RPM. A lower RPM motor can be used but the drive pulley and belt has to be changed.
a 240 volt only "SPL HP" motor usually is sold as a "5 to 6HP" marketed compressor by Loews, Sears or Sanborn, they usually draw 15 amps at 240 volts and produce an actual 3HP output. At 9.5 to 10 amps measured under load that translates to about 1.5 HP actual motor output. your motor sounds a bit weak for a compressor unless it was originally a 1.5 HP dual voltage model 120/240 volts. Running a compressor at 120 volt at 20 amps is not very useful, pops breakers, overheats plugs, melts outlets, etc. Your model and make of compressor will narrow down your selection of replacement motors and the cost as well.
My kid asks me questions all of the time, I never say "that's a dumb question". Gave her my old cell phone and when stumped with some question I just say "honey, I don't know everything in the world, Google search on your phone" I try to reward her curiosity not discourage it!

Stephen

I told my boys to either pay attention to what I'm doing and learn how to fix things...or make a lot of money so you can pay someone else to do your man work. So far, they haven't done either one and didn't listen to a thing I said. Back to the issue...about 9.5 -10A on each side with inductive. Comes to maybe 3 or so if I am close. Matches up. I found a motor that looks like it should work perfect. I'll give that as try! I think I screwed the motor up years ago when I did some very improper wiring just to get it up temporarily...involving a couple regular extension cords running to a couple different 15A circuits and maybe a generator. I just remembered that. I remember it smoking some at the time periodically.

 

[MikeLocke]

Thanks. Well I may have checked the amps incorrectly. I just used an inductive meter and clamped on to the first hot lead (~120) and then the second 120. Each showed about 10A.

 

[stevon]

MikeLocke,

I didn't see the FLA on your motor picture but I bet its 15 or 16 FLA amps a leg or a 3 HP actual output motor. 10 amps is just too low unless there is 0 psi in the tank. You reach the FLA listed on the motor at the end of a fill cycle just before the pressure switch cuts off. Measuring either leg works, they are 180 electrical degrees of each other so both should be the same amps. Sounds like you are learning a lot!

Stephen

Thanks. Well I may have checked the amps incorrectly. I just used an inductive meter and clamped on to the first hot lead (~120) and then the second 120. Each showed about 10A.

 

[MikeLocke]

Thanks for your help. All is working now. I purchased a new motor and installed. Hooked it all up and the pump was struggling really hard. Bought a new pump. Then noticed the belt was dry rotted...ordered that next. Then, I just decided to replace the switch so I could adjust my cut in PSI better. Now it all works. Around $400+ later. I guess I could have bought a new one, but this is half the cost and all new except the tank. I will maintain it this time and not use it for 10 years before I change pump oil / filter. Best I can tell...my poorly maintained pump messed up the motor.

 

[iowagold]

one of the ways to save life is to slave the power off the light switch for the shop.
that way the compressor power is off when the lights are off in the shop.