Air compressor quit running

[Matti]

I've got an old Curtis 5 hp single phase compressor that I was working hard today running the blasting cabinet. Everything was fine until it wouldn't start after the last cycle. I'm trying to do a few checks before I call an electrician assuming I can get one that knows motors and starters to come out. The motor looks to be a newer Leeson. Here is what I have done:

• I have confirmed that the compressor and motor turn.
• There is power to the magnetic starter and you can hear it pull in when I apply 120v to it. (an old Cutler Hammer size 1 C10CN3)
• There is a buzzing from the starter but the motor is quiet.
• The motor capacitors (big ones) look ok with no bulging and I did the resistance check....seem ok. (yes I confirmed there was no charge left)
• There is a reset button on the motor junction box. I didn't try to start the compressor after pressing this.

Are there any other checks I could do before calling an electrician?

 

[OccupantRJ]

After pressing the reset, try the unit again. It may have simply tripped from a long hot run.

 

[Jswain]

Yep hit the reset and try again. Check what the the magnetic starter is set to trip at and make sure it's set at the right cutout for the motor.

~ FLA x SF on the motor nameplate

 

[Matti]

I checked continuity across the starter contacts (button pushed) and its ok. I'm thinking its either the overload on the motor or the motor itself. I'm hoping the first one. I just checked the price on a new Leeson....$1000 USD! That's what I paid for the whole unit. I'll put the covers back on and push the button in the morning. I realized I might need a back up compressor. I can't use my 4 post lift without air.

 

[nadogail]

I checked continuity across the starter contacts (button pushed) and its ok. I'm thinking its either the overload on the motor or the motor itself. I'm hoping the first one. I just checked the price on a new Leeson....$1000 USD! That's what I paid for the whole unit. I'll put the covers back on and push the button in the morning. I realized I might need a back up compressor. I can't use my 4 post lift without air.

"No Guts,No Glory. You should try pressing the Reset button.

 

[Matti]

"No Guts,No Glory. You should try pressing the Reset button.

I didn't even know there was one until I started investigating.

 

[Jswain]

If you get it running by pushing the reset and have an amp clamp check the amp draw while it's running and close to cutout pressure.

 

[Matti]

If you get it running by pushing the reset and have an amp clamp check the amp draw while it's running and close to cutout pressure.

I've had this thing for at least 10 years and its never tripped. I put it in an enclosure last year and I think it got too hot. I have a temp gauge on it but it quit. It needs better ventilation for the big jobs.

 

[whateg01]

• There is a reset button on the motor junction box. I didn't try to start the compressor after pressing this.

Are there any other checks I could do before calling an electrician?

Was the overload tripped before you pressed it? Is there voltage on the output side of the contactor? Is the overload on the starter tripped? (Thinking it's not or the contactor wouldn't pull in)

 

[micromind]

Note; the red reset button will be hard to push after a trip.....really hard.

Is there 240 volt power at the bottom of the starter when it's pulled in?

Usually, when a motor burns up, it'll stink up the whole garage.....and even make its way into the house if it's attached to the garage.

 

[gizardlizard]

I've got an old Curtis 5 hp single phase compressor that I was working hard today running the blasting cabinet. Everything was fine until it wouldn't start after the last cycle. I'm trying to do a few checks before I call an electrician assuming I can get one that knows motors and starters to come out. The motor looks to be a newer Leeson. Here is what I have done:

• I have confirmed that the compressor and motor turn.
• There is power to the magnetic starter and you can hear it pull in when I apply 120v to it. (an old Cutler Hammer size 1 C10CN3)
• There is a buzzing from the starter but the motor is quiet.
• The motor capacitors (big ones) look ok with no bulging and I did the resistance check....seem ok. (yes I confirmed there was no charge left)
• There is a reset button on the motor junction box. I didn't try to start the compressor after pressing this.

Are there any other checks I could do before calling an electrician

You do not check capacitors using a resistance check. You actually need to measure capacitance. Not all multimeters can read capacitance. There will be a Farad number on the capacitor itself and they usually say plus or minus 5%. You mentioned capacitors as in plural. I assume it has both a start and run cap?

 

[Matti]

Pushing the reset on the motor jb did the trick….at least it works this morning. I’ve never had to do this on a motor before. I’ll have to work on installing a circ fan on the enclosure. The enclosure is great otherwise as it knocks the noise down 10 db.

 

[Matti]

You do not check capacitors using a resistance check. You actually need to measure capacitance. Not all multimeters can read capacitance. There will be a Farad number on the capacitor itself and they usually say plus or minus 5%. You mentioned capacitors as in plural. I assume it has both a start and run cap?

It seems to be a cursory check if your mm doesn’t have capacitance.

 

[gizardlizard]

It seems to be a cursory check if your mm doesn’t have capacitance.

You can try that but the results generally aren’t consistent and are easy to misinterpret. I would never trust that as a test.

 

[Matti]

You can try that but the results generally aren’t consistent and are easy to misinterpret. I would never trust that as a test.

It passed the test and they obviously weren't faulty so there is that. Depending on the issue perhaps they could pass the test but still be faulty....I don't know.

 

[gizardlizard]

It passed the test and they obviously weren't faulty so there is that. Depending on the issue perhaps they could pass the test but still be faulty....I don't know.

Buy a cheap meter that can do capacitance tests. Did you check the thermal overload in the motor with a meter to prove it’s closed?

 

[OccupantRJ]

Pushing the reset on the motor jb did the trick….at least it works this morning. I’ve never had to do this on a motor before. I’ll have to work on installing a circ fan on the enclosure. The enclosure is great otherwise as it knocks the noise down 10 db.

I have two 5 hp industrial compressors in an 8x20 insulated room on the rear of the shop. I installed a 6” through the wall vent fan above them with side wall louver, that runs automatically when temperature in the room exceeds 90*F until the room cools down. I only run one unit at a time, but it gets hot in there especially when running a blast cabinet.

 

[finn]

I think you’re correct. The motor overheated and tripped the reset

Get rid of the well intended enclosure. It’s causing the issue. An air inlet and outlet along with a power vent to outside the building might work.