Compressor motor Hp question

[BareBones]

I have a Baldor electric motor to turn my Gardner-Denver compressor. The compressor looks old but the electric motor looks relatively new. I am trying to find a new safety switch and called Grainger and gave them my info they said that my electric motor is not big enough for the compressor. Is this true?

Motor Info: Baldor 1.5 HP 1725 RPM 19.5A@115V or 9.5A@230V, I will be running it at 220 volts.

Compressor Info: Gardner-Denver, Bore 3.5, Stroke 5, 850RPM

Thanks,
Bob

 

[nissan_crawler]

unless I'm missing something, my calculation shows that would be putting out 23.7 cfm? That's not counting any losses, of course. If that's right, that motor isn't close to big enough.

 

[BareBones]

I bought this from a thrift store for construction materials so I have never personally run it. I can tell that the electric motor is not original.

 

[bmwguru]

unless I'm missing something, my calculation shows that would be putting out 23.7 cfm? That's not counting any losses, of course. If that's right, that motor isn't close to big enough.

I agree. Not near enough motor. My new Eaton puts out 26cfm@175psi and uses a true 7.5 hp running motor. It draws 32amps at 220v and requires a 50amp 220v breaker. Heck the motor itself weighs 180lbs!! 1.5hp, 220v or not aint gonna cut it.....Sorry.

 

[Torque1st]

Assuming it is a single stage compressor moving 23.7 scfm would require an approx 5HP motor to compress that air to 125PSI. That would assume the other calculations are correct.

 

[BareBones]

So I should be looking for a motor with at least 5Hp and preferably 7.5?

Bob

 

[Torque1st]

bmw's compressor is a two stage compressor so the HP required is quite different. Contact a Gardner-Denver service rep and get their recommendation for a motor.

 

[larry4406]

I would google the compressor model number. That should then lead you to the packaged unit which will likely be 5hp or 7 hp.

 

[BareBones]

What are the formulas that you guys are using to figure this out. I would like to be able to figure this out myself next time. Also which has more influence HP or RPM.

Bob

 

[Torque1st]

There are formulas in the Machinery Handbook available at bookstores and libraries. Just call the G-D rep for your compressor motor requirements and don't try to re-engineer your compressor.

 

[Aceman]

There are formulas in the Machinery Handbook available at bookstores and libraries. Just call the G-D rep for your compressor motor requirements and don't try to re-engineer your compressor.

I agree.