Air Compressor Motor Upgrade Advice

[mycornerofthebarn]

So I have a Lux Air 5HP 60 gal 2-stage compressor and I think it needs a new motor. When it runs at no pressure it starts our fine, but when it runs around 75psi, it slows down and almost stops. It eventually picks back up, but a little slower. You can smell the motor a little bit when it happens. I've replaced the capacitors on the motor (Century 5HP SPL) and it doesn't help at all. My guess is a winding is opening up.

First, any advice on that?

If I'm getting a new motor, I was thinking about a little better motor than the SPL motor. The 5HP SPL motor is a 15 AMP 230V, that probably is really a 3HP motor in real life. I was looking at a real 5HP or a 6.4 WEG motor. Are there any others I should look at? I have a 30 Amp circuit currently powering the compressor. The issue is the Frame size. The current motor is a 56 frame, and the others all seem to be 56H or 184T.

Has anyone made brackets to convert motor frame sizes? I know they sell them for larger motors, but haven't seen one for a 56 Frame. I would make one, but am not really sure how to approach it. Looking for ideas.

 

[sberry]

You have checked the belt tension?

 

[mycornerofthebarn]

Yes. The belt and motor pulley were replaced about 3 months ago when I got the compressor. The original motor pulley had a broken woodruff key and was out of alignment. The weird thing is that it's intermittent as pressure increases, but eventually the motor gets back to full speed.

 

[iamrfixit]

Verify the check valve at the tank is holding? Maybe take it apart and clean or just replace it to rule it out.

I had the check valve fail on one of my compressors. It would only start with no pressure in the tank and then pump up to a point, about 60-70 psi, where it it would actually stall the motor.

Why does yours act up and then seem to come out of it, I don't know, maybe your CV is leaking back at lower pressure but reaches a point where it can actually seal off and work correctly?

I don't know, just ideas.

 

[mycornerofthebarn]

Thanks for the suggestion. I took the check valve apart and it looks clean and seems to be working. When I refilled the tank it slowed down at about 50psi this time. Eventually picked back up. I believe the pump is a PUMA. Could a stuck valve (don't really know compressors) cause this. It sounds normal so how would I test this? Appreciate all the ideas.

 

[Citation]

Have you verified the run cap in the motor is good? I'm not at all certain this is the problem but it would be a cheap check/fix.

 

[mycornerofthebarn]

Thanks for the suggestion. I replaced both the start and run capacitors but it didn't help. I suppose it's possible the new one is bad, but unlikely. The motor has wear and the bearings are slightly noisy, but that still doesn't explain the slow-down. Looking for ideas on what to try next.

 

[mycornerofthebarn]

I ran the compressor until it slowed down and stopped it. Pump turned freely even with belt on it. I pulled and examined check valve, it's clean and no sticking. Pulled the belt to run the motor solo, and no slow down. Put it all back together and it's working fine now. The belt wasn't loose, but I did tighten it a bit as I had the guard off. The belt never slipped or squealed, so that seems weird. Maybe the new belt (3 months old) stretched? Either way thanks for all of the suggestions and it looks like I just saved $200, at least for a while.