help with compressor (1 Viewer)

workingdog

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A local thrift store was shutting down and we bought a large Sanborn 500b compressor (5hp) they had - we thought we were getting a deal, but we weren't really. It was virtually used, but soon after we got it hooked up, the pump section froze.

We bought a replacement pump for $200

But, the thing will not fill the tank from empty. It overheats and we have to unplug it (it has no on off switch), let it cool, and start it up again. I'm guessing this is a 50% duty cycle pump - but the compressor has no way to limit run time to 50%, so it just cooks.

If we wanted to replace this pump with a decent 100% duty cycle pump appropriate for 5hp motor, what would I get. They are available all over at a wide variety of prices.
 

e9999

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Maybe the flywheel is intended to provide air flow, that is pretty common. There is no added shield or anything that would impede cooling, is there?

Anyway, I've not seen a compressor system that stops to rest by design before the desired pressure is reached. Then again, I've not seen that many. But the notion that the compressor itself can not sustain running until the max pressure is reached seems strange to me for normal operating conditions. I would suspect something else going on besides the compressor itself.

How do you conclude that the compressor is overheating?
 
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Did you match the RPM of motor to pump of course taking the ratio of pulley sizes into to account? Spinning the correct direction? The pulley on the compressor pump is the fan. Has to be blowing towards the cylinders.

YouTuber Mustie1 has an excellent video where he replaced the pump on an air compressor. Initially he had the replacement pump spinning too fast and overheated it. Lots of things to consider.
 

Eyedaho

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Did you match the RPM of motor to pump of course taking the ratio of pulley sizes into to account? Spinning the correct direction? The pulley on the compressor pump is the fan. Has to be blowing towards the cylinders.

YouTuber Mustie1 has an excellent video where he replaced the pump on an air compressor. Initially he had the replacement pump spinning too fast and overheated it. Lots of things to consider.
I guess one thing to double check would be that the flywheel is installed in the right direction to blow at the housing. The compressor has to be rotating in the correct direction, since he's pressurizing the tank instead of pulling a vacuum. But if the pulley shaft isn't tapered, it would be easy to put it on backwards when swapping it from the old compressor, so the fan would be blowing away from the housing. Just a thought.
 

workingdog

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The shaft is tapered and keyed, no way to put it on backwards. it moves a lot of air. It's the spec'd pump for this set up, it's a 5hp pump and a 5hp motor.
 
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A local thrift store was shutting down and we bought a large Sanborn 500b compressor (5hp) they had - we thought we were getting a deal, but we weren't really. It was virtually used, but soon after we got it hooked up, the pump section froze.

We bought a replacement pump for $200

But, the thing will not fill the tank from empty. It overheats and we have to unplug it (it has no on off switch), let it cool, and start it up again. I'm guessing this is a 50% duty cycle pump - but the compressor has no way to limit run time to 50%, so it just cooks.

If we wanted to replace this pump with a decent 100% duty cycle pump appropriate for 5hp motor, what would I get. They are available all over at a wide variety of prices.
Try to stay away from compressors that are aluminum casing you want to buy the compressors that are made out of cast iron.
 

workingdog

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Any recommendations. there are cheaper ones at Harbor freight, and ones that cost more than the entire compressor online. I was confused by all the options. It seems the mounting plate on top of the tank will take just about anything. and it seems all the 5hp compressors are sized for motors and use the same flywheel.
 

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