Air compressor reset

[David]

My 60 gallon Sanborn compressor is in a lean-to on the outside of my shop, fully enclosed, and insulated for noise abatement. Wired to a 30A, 220v circuit.
Sometimes it starts fine, other times for some reason the reset button on the motor will have tripped and I have to manually reset it.
Yesterday it started fine, tonight the button was tripped.
It will run fine once started but I have no idea why the motor reset is tripping. Is it getting too hot?

 

[Doggggboy]

Does the bleed off valve work properly to allow the compressor to start without a load?
Had that problem with mine when the valve was sticky.

 

[David]

Does the bleed off valve work properly to allow the compressor to start without a load?
Had that problem with mine when the valve was sticky.

It seems to work fine as I can hear the air bleed off when it hits pressure and shuts off.

 

[Elektrishun]

@David

Do you mean that the motor's thermal overload relay is sometimes in the tripped position before starting?

Or it sometimes trips during operation?

If it's tripping during operation then the thermal overload relay is working properly due to prolonged excessive current draw.

 

[skippyelwell]

I had that same thing happen to me a few yrs back on my 80gal tank, couldn't figure it out so shut off the power and tore down the starter.
Can't find my pics atm but basically all the contacts had some corrosion and pitting, cleaned everything, smoothed out the contact surfaces, lubricated and everything has been good now for about 4yrs.

 

[slow-poke]

Might want to check the capacitor(s)

Just take all safety precautions; lockout the power, and then discharge the caps, both before you disconnect them and then just before you measure them.

I'm always extra electrically cautious when working outside and especially with a 240V, 30A source.

 

[David]

@David

Do you mean that the motor's thermal overload relay is sometimes in the tripped position before starting?

Or it sometimes trips during operation?

If it's tripping during operation then the thermal overload relay is working properly due to prolonged excessive current draw.

Last night I flipped the switch to energize the compressor plug and it didn't start. So I went outside and the overload was tripped. But the night before it started just fine. So sometime between the two start attempts the overload tripped.
I don't leave it powered on when I'm not in the shop. I'll check to day to see whether it's stopping because it's hitting full pressure or because the overload is tripping. I suspect the overload is tripping.

 

[slow-poke]

I would get someone to activate the power while you observe the startup and run.

A bad run capacitor in an AC motor can lead to several issues, including reduced motor performance, overheating, and even motor failure. The motor may run slower, vibrate, hum, or have trouble starting. It can also cause the motor to cycle on and off frequently or stop working altogether.

A bad start capacitor will likely prevent the motor from starting, or cause it to hum and struggle to turn, possibly even tripping a circuit breaker. The motor might start if physically pushed, but it won't run efficiently or at full speed. The start capacitor is crucial for providing the initial torque needed to get the motor spinning.

Capacitors often fail, usually in stock at Amazon. I have changed many over the years. When it happens on your furnace or A/C the repair guys almost always replaces the motor and charges you $500 when the $10 capacitor is all that is required

 

[David]

Good idea @slow-poke I'll do that today.

 

[jcdammeyer]

Verify that your 220vac wiring is solid and the capacity is there for the compressor.
If the black or red phase has a bad connection the motor may have trouble.
Make sure the circuit breaker is solidly connected.

 

[Elektrishun]

Last night I flipped the switch to energize the compressor plug and it didn't start. So I went outside and the overload was tripped. But the night before it started just fine. So sometime between the two start attempts the overload tripped.
I don't leave it powered on when I'm not in the shop. I'll check to day to see whether it's stopping because it's hitting full pressure or because the overload is tripping. I suspect the overload is tripping.

Ok
That it is some unfortunate timing to have those circumstances happen more than once.

Lot of good troubleshooting ideas already given.

 

[YotaBota]

You've probably already done this but check the wiring connections are tight right from the breaker panel to the motor and all in between. I believe 30amp on the backbone would be #10 wire.

 

[David]

You've probably already done this but check the wiring connections are tight right from the breaker panel to the motor and all in between. I believe 30amp on the backbone would be #10 wire.

I think everything is tight but I will double check to be sure.

 

[David]

I just checked everything again and it ran up to pressure (135PSI), I bled it down to 50 psi and it would not restart because the thermal protector had tripped. The motor is warm but not hot to the touch.

 

[Elektrishun]

I just checked everything again and it ran up to pressure (135PSI), I bled it down to 50 psi and it would not restart because the thermal protector had tripped. The motor is warm but not hot to the touch.

If you could get an ammeter involved to see what the current is while the motor is running it would help.

If the current isn't excessive at any point then you may have a faulty relay.

 

[David]

If you could get an ammeter involved to see what the current is while the motor is running it would help.

If the current isn't excessive at any point then you may have a faulty relay.

I assume the relay is internal to the motor?

 

[Elektrishun]

I assume the relay is internal to the motor?

I assume yours looks something like this?

 

[slow-poke]

I'm still betting on the capacitors.

 

[David]

I assume yours looks something like this?

View attachment 66296

Pretty much exactly like that.

 

[David]

I'm still betting on the capacitors

Will the size be marked on the them?
Is there a way to test them?