Troubleshooting a compressor motor

[Skyking1992]

My BIL was given a Ingersoll Rand 7.5 HP, 80 gal single phase compressor. He does some side work for a small shop; they had trouble with the compressor and just decided to get a new one. Nice looking compressor with an electric auto-drain and a large radiator type cooler next to the belt guard.

The cover on the motor box was off and the capacitors have been removed. I think the first thing I could do is check resistance of the windings. I think there should be some resistance - infinite resistance would indicate an open winding, zero would indicate a short. Then pull the rear cover and look for a centrifugal switch. I should be able to mechanically activate the switch and check resistance of the starter and run windings. Am I on the right track so far?

I have no clue how the caps go back in. With the compressor were six caps, four look to be the same and two a little different. One of the two definitely is bad - melted through the side. There were 7 short jumpers laying in the box. Even if I check the caps and replace any bad ones (or just replace all of them), I have no clue on how to wire them. I have been doing a little google searching.

Of course, one more option would be to buy a new motor. A quick glace an flea bay looks like he could get one around $500. I think this was a $2500 dollar compressor when new.

Any hints or tips would be appreciated.

 

[Bert_]

Pictures would help. Pulling all the capacitors out was a major mistake. They are very difficult to get connected correctly unless you are familiar with that particular motor.

What were the symptoms when the compressor was pulled from service.

Best place to start is get the capacitors put back. Then we can do some troubleshooting. You could pop an end bell off and look for visibly burnt windings.

 

[metalmagpie]

I'm sorry to say this, but I consider those motors to be ****. And it's really hard and super expensive to replace one.

If I were you, I'd put a 5 horse motor on it, use a bit smaller drive pulley and accept less air. The silver lining is it would also run quieter.

metalmagpie

 

[evintho]

What he said^^^^

I replaced the motor on my IR 5hp 80gal compressor last year. The original actually lasted for 12 years. Paid $250 for a decent one off fleabay.
The easiest route would probably be to just replace the motor.

 

[brownbagg]

smell the motor winding, has it been smoked, if so just shitcan everything

 

[Bert_]

I'm sure there are some deals out there but a 7.5 hp motor retails for like $800. I would at least figure out what is wrong with the current motor before deciding it's scrap.

 

[joe_padavano]

I'm sure there are some deals out there but a 7.5 hp motor retails for like $800. I would at least figure out what is wrong with the current motor before deciding it's scrap.

I recently bought a brand new Leeson 7.5 HP single phase 1725 RPM motor for about $600 delivered from a vendor on ebay. Works great on my compressor.

 

[like2wheel]

Where are you located?
I have a 7.5 Baldor motor that came off an Atlas Copco that was in service less than 2 years.
I recently bought a 5hp 3ph Quincy compressor thinking i could use this but sizes/rpm is wrong.

 

[Skyking1992]

Thanks for all the help and suggestions. I'll post some pics when I can.

The story as I know it (second hand) is that the compressor was in use at a shop and started giving trouble. I think the owner said it was still running but not at full speed or power. He had someone troubleshoot it (probably who took out the capacitors) and they wanted a $1000 to fix it (I'm guessing that's the price of a new motor installed). The owner of the shop just decided to buy a new compressor. So my BIL, who is a packrat, hauled the old one away.

I don't think my BIL wants to keep this for his own, I think he wants to flip it for a few dollars. If the motor is shot, it may make more sense to sell as a project. Personally, I think this looks like a very impressive compressor - I might be interested myself if I could get it for the right price.

 

[kbs2244]

Find the local motor repair shop.
Take it in and set it on the counter and see what they say.
One that has been taken apart needs experienced eyes looking at it to see what is missing.
Most likely they will have a rebuilt one on the self you can trade in what you have for.

 

[sld961]

Where are you located?
I have a 7.5 Baldor motor that came off an Atlas Copco that was in service less than 2 years.
I recently bought a 5hp 3ph Quincy compressor thinking i could use this but sizes/rpm is wrong.

You can adjust for different rpm with a new pulley on the motor.

 

[sld961]

What brand is the motor? I've found that a lot of equipment companies have good technical support that can give you a lot of good information over the phone if you call and explain your problem.

 

[23ford]

Took mine to motor repair shop they had it a week and cost $125.00 with a warranty

 

[nadogail]

Took mine to motor repair shop they had it a week and cost $125.00 with a warranty

That would be my suggestion.