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Discussion Starter #1
I have an upright Sanborn 60 gallon compressor. Model SLA 7006056 With a 755H pump. Running on 220. Older used compressor. I have had it a couple years. It is labled 10w30 synthetic and that is what I am using. Oil level is fine. It has been cold out the last couple months, under 30. The other day I went into the garage and the breaker was tripped. I reset it and the compressor built pressure and cycled fine several times. It does not struggle to start when cold. Nice quick torquey startup. After a while the compressor cycled, ran for a while, heard a clunk and then a belt squeal. I flipped off the breaker. Will look at it later. Well later came, I took the belt cover off and spin the pulley. It spins free. (normal) Turn the breaker on and it is running fine again. I am timid on using it. 2 strikes and all.... I guess I can take the pump apart and give it a once over. Ideas??
 

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B Mann,

Which breaker house or motor thermal overload? Do you have an ammeter handy? one of theses will work if you don't:


Stephen
 

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The house breaker tripped. I don't think it (technically) has to do with an over current. I think what happened is the compressor locked up and dramatically increased the load on the motor. Which caused the over current. I am not sure what would cause the compressor to randomly lock up. There are not a lot of parts in the pump. I just need to take it apart and look.

I do have an ammeter... It would not hurt to check the current draw anyway. I will try to remember to have a look before I take it apart.
 

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B Mann,

I have heard on this site about Ingersol Rand side by side cyl compressors with a defective head gasket locking up at like100 psi because pistons were fighting and locking each other up with the leak in the head gasket between the cylinders. Might be an issue to check out.

Stephen
 

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B Mann,

I found the post:
and:

Stephen
 

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Stephen, Thanks for the idea and link... I don't think that is my problem... But maybe. The one time I was there when it stopped, I heard a clunk or thud. I know the current reading will go up as the pressure increases... (As the load increases on the motor)... But if it increases substantially, That could be the problem. If I get time this weekend, I will give it a looking over.

It can't be to complicated. There are few moving parts.
 

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B Mann,

Circuit breakers work on overheating to trip and that takes time. Generally they trip in seconds not milliseconds. So if there is a problem, it may take a while for the breaker to react is all I'm saying. watching an ammeter under load will give more definitive answers.

Stephen
 

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Discussion Starter #8
I follow you completely.... Worked with breaker panels for decades. Seconds to minutes to get a breaker to trip depending on the overload current.

BTW Compressor empty, and cold. (right around freezing). 30 amp 220 breaker. Initial start up surge, hit the ammeter hard, about 40 amps. Well under a second. Normal. Running current... 7 amps at empty tank. 8 amps at 50 psi. 9 amps at 90 psi. Topped out 9.5 amps at 150 psi, when pressure switch kicked off. I would say normal. Current increase at higher pump pressure. (increased motor load) Gave me something else to do this morning. Full tank of air if I need it.

Thanks for the ideas!!!
 

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B Mann,

Sounds like the load is about 2 HP and a way undersize load for the wire and breaker. Nothing seems like it was overloading with this test. Definitely is a puzzle!

Stephen
 

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Discussion Starter #10
Interesting, I did a tear down and went over everything. Pistons and crank out. It could use a block flush. The block had some dirty oil in the bottom. Bearings look and feel great. I will pick up a gasket set and put it all back.

Only strange idea I have, when it was having problems, it was cold 0F or so. Possible ice build up?? Was it all a bad dream??

B
 

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B Mann,

Just as a thought...would install synthetic oil that is less sensitive to 0 degree days!

Stephen
 

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Discussion Starter #12
Yep, It says on the side of the compressor, synthetic 10w30. And that is what I was using. Hmm
 
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