# Compressor trips breaker shortly after start up



## inspectweld (Jan 23, 2018)

My Quincy QT-10 trips the breaker a few seconds after start up.
I just do not know how to start troubleshooting, any help would be appreciated, thanks


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## motormonkey (Jul 10, 2016)

Turn off the power to the compressor and then release all the air in the tank down to zero pressure. Now turn the power back on. The compressor should start and run at normal speed with no abnormal noises, humming, or signs of overheating, and it should not trip the breaker. It should build up pressure in the tank until it reaches cut off pressure and then it should cut off. If it trips the breaker, or if you detect anything abnormal before it reaches cut off pressure, something is wrong with your motor or compressor.

If the compressor does build pressure and then cuts off, you should be able to hear a release of air when it cuts off. If not, something is wrong with your unloader valve. Starting up a compressor with a full head of pressure on it puts a huge strain on the motor, causing excessive current, which trips the breaker. The unloader valve, along with a check valve, releases this head of pressure on the compressor at cut off. When the motor starts up at cut on, it can get the compressor up to speed before any appreciable head of pressure develops ahead of the compressor.


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## inspectweld (Jan 23, 2018)

motormonkey said:


> Turn off the power to the compressor and then release all the air in the tank down to zero pressure. Now turn the power back on. The compressor should start and run at normal speed with no abnormal noises, humming, or signs of overheating, and it should not trip the breaker. It should build up pressure in the tank until it reaches cut off pressure and then it should cut off. If it trips the breaker, or if you detect anything abnormal before it reaches cut off pressure, something is wrong with your motor or compressor.
> 
> If the compressor does build pressure and then cuts off, you should be able to hear a release of air when it cuts off. If not, something is wrong with your unloader valve. Starting up a compressor with a full head of pressure on it puts a huge strain on the motor, causing excessive current, which trips the breaker. The unloader valve, along with a check valve, releases this head of pressure on the compressor at cut off. When the motor starts up at cut on, it can get the compressor up to speed before any appreciable head of pressure develops ahead of the compressor.


Thanks, The air tank is empty and I have also installed new air filters and still the same problem The breaker/reset located in my on off box is tripping. The dial next to the reset button is set at the max. of 18. I have been having this compressor for 3 years with no problems. Pic of on off box and white plastic reset button on bottom of pic


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## inspectweld (Jan 23, 2018)

from that box wiring goes to the pressure switch and the motor


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## iowagold (Jan 22, 2020)

check the start switch in the motor.
it maybe staying on the start winding or not coming up to cut out speed for the switch over.
also check the start caps. just to make sure that lightning has not trashed them.
pm me if you need parts.


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## motormonkey (Jul 10, 2016)

Check to confirm that the motor and compressor turn freely by hand WITH THE POWER OFF.
If the motor does not turn freely by hand, or turns with difficulty, there is likely something mechanical wrong, like a bad bearing or a seized part. (or a lack of lubrication. You did check the oil, didn't you?)
If the motor does turn freely by hand, apply power to it and note what it does.
If the motor does not move at all or moves slowly when power is applied, (It will likely hum, buzz, or show signs of overheating), I would suspect a bad start capacitor or a centrifugal cutout switch in the motor, or in some cases, something mechanical wrong, like a bad bearing or a seized part or a lack of lubrication.
Odds are that one of these things is what is causing the problem. The only other thing left is shorted windings in the motor.


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## inspectweld (Jan 23, 2018)

iowagold said:


> check the start switch in the motor.
> it maybe staying on the start winding or not coming up to cut out speed for the switch over.
> also check the start caps. just to make sure that lightning has not trashed them.
> pm me if you need parts.


this 10 hp. Baldor motor doesn`t have a start capacitor visible


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## iowagold (Jan 22, 2020)

ahh
BIG motor
I missed that.
pull the belt and see if it starts and runs ok.


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## motormonkey (Jul 10, 2016)

The photo is not clear, but it appears to be a single phase motor. Gotta have a start cap, and likely a run cap too.


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## inspectweld (Jan 23, 2018)

motormonkey said:


> Check to confirm that the motor and compressor turn freely by hand WITH THE POWER OFF.
> If the motor does not turn freely by hand, or turns with difficulty, there is likely something mechanical wrong, like a bad bearing or a seized part. (or a lack of lubrication. You did check the oil, didn't you?)
> If the motor does turn freely by hand, apply power to it and note what it does.
> If the motor does not move at all or moves slowly when power is applied, (It will likely hum, buzz, or show signs of overheating), I would suspect a bad start capacitor or a centrifugal cutout switch in the motor, or in some cases, something mechanical wrong, like a bad bearing or a seized part or a lack of lubrication.
> Odds are that one of these things is what is causing the problem. The only other thing left is shorted windings in the motor.


thanks and I will try that tomorrow , I have full oil and it will turn over a few revolutions before tripping the breaker


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## inspectweld (Jan 23, 2018)

motormonkey said:


> The photo is not clear, but it appears to be a single phase motor. Gotta have a start cap, and likely a run cap too.


480v 3 phase sorry about the blurry pic


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## motormonkey (Jul 10, 2016)

Three phase is a whole different animal. Disregard the stuff about a start or run capacitor. Still could be something mechanical. Maybe one phase is open somewhere. Check any fuses in the circuit.


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## iowagold (Jan 22, 2020)

and remove the belt to see if the motor will come up to run speed!


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## iowagold (Jan 22, 2020)

yea at the same time try the turn just the compressor by hand with out the belt
like mm stated.


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## inspectweld (Jan 23, 2018)

inspectweld said:


> 480v 3 phase sorry about the blurry pic


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## inspectweld (Jan 23, 2018)

inspectweld said:


>


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## inspectweld (Jan 23, 2018)

iowagold said:


> ahh
> BIG motor
> I missed that.
> pull the belt and see if it starts and runs ok.


thanks i will try that tomorrow


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## inspectweld (Jan 23, 2018)

inspectweld said:


> thanks i will try that tomorrow


 its a QT-10 with a 10 hp. motor and 15 hp compressor and 120 gal tank


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## iowagold (Jan 22, 2020)

check the motor wiring... make sure it is set to the 480.


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## iowagold (Jan 22, 2020)

too big of compressor for the motor?


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## iowagold (Jan 22, 2020)

is this your unit
northern compressor 2021 version


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## inspectweld (Jan 23, 2018)

iowagold said:


> check the motor wiring... make sure it is set to the 480.





iowagold said:


> too big of compressor for the motor?


 no doubt it`s correct, been using it with no problem for 3 years, we checked that before initially firing it up


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## inspectweld (Jan 23, 2018)

iowagold said:


> too big of compressor for the motor?


that thought crossed my mind but I think that is the stock motor on there


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## inspectweld (Jan 23, 2018)

iowagold said:


> is this your unit
> northern compressor 2021 version


no mine is 2 cylinder and older, ill send a pic


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## inspectweld (Jan 23, 2018)

inspectweld said:


> no mine is 2 cylinder and older, ill send a pic


this link is not to my compressor but it is identical






Used QT-10 Quincy QT10 Reciprocating 2 Stage Air Compressor


Buy this used Quincy Compressor QT-10 or find other Quincy Compressor Air Compressors Related: Quincy QT10 Reciprocating 2 Stage Air Compressor




www.sigmaequipment.com


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## cammack (Mar 20, 2021)

motormonkey said:


> Turn off the power to the compressor and then release all the air in the tank down to zero pressure. Now turn the power back on. The compressor should start and run at normal speed with no abnormal noises, humming, or signs of overheating, and it should not trip the breaker. It should build up pressure in the tank until it reaches cut off pressure and then it should cut off. If it trips the breaker, or if you detect anything abnormal before it reaches cut off pressure, something is wrong with your motor or compressor.
> 
> If the compressor does build pressure and then cuts off, you should be able to hear a release of air when it cuts off. If not, something is wrong with your unloader valve. Starting up a compressor with a full head of pressure on it puts a huge strain on the motor, causing excessive current, which trips the breaker. The unloader valve, along with a check valve, releases this head of pressure on the compressor at cut off. When the motor starts up at cut on, it can get the compressor up to speed before any appreciable head of pressure develops ahead of the compressor.


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## iowagold (Jan 22, 2020)

inspectweld said:


> this link is not to my compressor but it is identical
> 
> 
> 
> ...


is this a 2 or 4 piston design?

yea disconnect the belt and see if it runs up to speed ok. and check the bearings on both with the belt off.


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## stevon (Mar 5, 2019)

inspectweld,

Looks like a 2-stage, 4 cylinder, what are the amps on each leg at startup?

Stephen


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## inspectweld (Jan 23, 2018)

it turns free and smooth by hand and in the 2 or 3 seconds that it tries to run it builds a little pressure. I made sure all the wire contacts are tight There is a 1 - 1/4" pipe about 10" long and looks lile a breather cap on top connected to the top of the compressor and it looks like some sort of breather, what is that, I was thinking maybe it`s clogged. trying to get a picture of it sent here. Do you think it`s maybe the reset/breaker is bad?


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## inspectweld (Jan 23, 2018)

inspectweld said:


> it turns free and smooth by hand and in the 2 or 3 seconds that it tries to run it builds a little pressure. I made sure all the wire contacts are tight There is a 1 - 1/4" pipe about 10" long and looks lile a breather cap on top connected to the top of the compressor and it looks like some sort of breather, what is that, I was thinking maybe it`s clogged. trying to get a picture of it sent here. Do you think it`s maybe the reset/breaker is bad?


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## inspectweld (Jan 23, 2018)

i took the cap off that pipe and its not clogged and there is a pin that runs across the pipe and there is a ball in the pipe, maybe a check valve there. Is it possible that the reset/breaker is bad and if so how would i check it?


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## inspectweld (Jan 23, 2018)

inspectweld said:


> i took the cap off that pipe and its not clogged and there is a pin that runs across the pipe and there is a ball in the pipe, maybe a check valve there. Is it possible that the reset/breaker is bad and if so how would i check it?


Well I have it running now, I dont know for how long LOL but what I did was tapped on that reset/ breaker quite a few times with the power off of course,,,,and it running now what do you think?


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## inspectweld (Jan 23, 2018)

inspectweld said:


> Well I have it running now, I dont know for how long LOL but what I did was tapped on that reset/ breaker quite a few times with the power off of course,,,,and it running now what do you think?


I let it cycle through 3 times by bleeding it down and it restarts good


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## stevon (Mar 5, 2019)

inspectweld,

What are the amps drawn? do you have a clamp on ammeter?

Stephen


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## inspectweld (Jan 23, 2018)

stevon said:


> inspectweld,
> 
> What are the amps drawn? do you have a clamp on ammeter?
> 
> Stephen


No but it must be less than the 18 setting on the reset and I have a 25 amp fuse disconnect that has not blown


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## iowagold (Jan 22, 2020)

inspectweld said:


> it turns free and smooth by hand and in the 2 or 3 seconds that it tries to run it builds a little pressure. I made sure all the wire contacts are tight There is a 1 - 1/4" pipe about 10" long and looks lile a breather cap on top connected to the top of the compressor and it looks like some sort of breather, what is that, I was thinking maybe it`s clogged. trying to get a picture of it sent here. Do you think it`s maybe the reset/breaker is bad?


crank case breather on the long or tall stand pipe between the heads.


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## inspectweld (Jan 23, 2018)

still runnin, and like they say "if it aint broke dont fix it"


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## motormonkey (Jul 10, 2016)

inspectweld said:


> what I did was tapped on that reset/ breaker quite a few times


Well there you are. You found the problem. There is likely a loose connection or damaged contacts in that reset/breaker, and it's only a matter of time until the problem recurs. It would be wise to disassemble that reset/breaker and look for the problem.


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## iowagold (Jan 22, 2020)

just replace the components on the reset assy.
get the numbers and go ebay shopping!


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