Air compressor electric motor

[bslayter]

I have a60 gallon air compressor that I had changed the pump a while ago with a 5 HP 145 PSI Twin Cylinder Air Compressor Pump from Harbor freight. Now the electric motor is out and was wondering if the same version of electric motor was good enough to power this newer pump if I bought the exact same one that was originally on the air compressor.

It was originally a Campbell Hausfeld set up with a 5HP pump that went bad and I have been told the electric motor isn't a true 5HP motor due to it listing it as SPL motor. The electric motor part is 8-173719-20 which come back as a 5 HP SPL 3450 RPM Air Compressor 60Hz Electric Motor 208-230 Volts B385 on Ebay.

Will this electric motor be good enough to run this newer pump or do I need a better motor? Money is an issue for me to be buying a higher priced electric motor if needed. So I hope its good enough o run this newer pump. Also does the pulley size on the newer pump matter? I believe its a14 1/2 inch pully. The pump seems to be going counter-clockwise according to the arrow on the wheel.

Any help would great. Thanks in advance

 

[The Cobbler]

for that pump I think you want a true 5 hp motor
what is the amp draw on your 5HP SPL motor?

 

[plinker]

Those "SPL" motors draw about 15a and are actually around about 3hp IIRC, a 22a draw motor would be considered 5hp. Both using 220v.

This would be a true 5hp motor,
https://www.surpluscenter.com/Electrical/AC-Motors/Air-Compressor-Motors/5-HP-Special-Compressor-Duty-230-Volt-AC-3450-RPM-US-Motors-Air-Compressor-Motor-10-2621.axd

This would be comparable what you have,
https://www.surpluscenter.com/Air-Pneumatics/Air-Compressors-Vacuum-Pumps/Air-Compressor-Motors/5-HP-Special-Duty-230-Volt-AC-3450-RPM-Leeson-Air-Compressor-Motor-10-2530.axd

 

[Mick56]

You could try a smaller pulley on the original motor, that would be like "gearing it down".

 

[Citation]

What failed on the motor? Did it over heat?

I'm going to agree with those who say it was probably a 15amp motor. That motor would pair nicely with the cheaper 3hp HF pump (which seems like a decent pump based on my limited working with one).

If the motor isn't damaged the OP would just need to change the pulley ratio to keep the motor from being overloaded. To verify the motor isn't overloaded the OP would need to measure motor RPM under load. I'm not sure that HF provides the information needed to estimate the correct pulley size.

If the motor isn't really bad I would buy the HF 3hp pump since it will be the right size for the current motor.

 

[bslayter]

The original electric motor all of sudden just started smoking and *******. Was the 5HP original pump from Campbell Hausfeld, not a true 5HP pump?

What failed on the motor? Did it over heat?

I'm going to agree with those who say it was probably a 15amp motor. That motor would pair nicely with the cheaper 3hp HF pump (which seems like a decent pump based on my limited working with one).

If the motor isn't damaged the OP would just need to change the pulley ratio to keep the motor from being overloaded. To verify the motor isn't overloaded the OP would need to measure motor RPM under load. I'm not sure that HF provides the information needed to estimate the correct pulley size.

If the motor isn't really bad I would buy the HF 3hp pump since it will be the right size for the current motor.

 

[bslayter]

15 amp

for that pump i think you want a true 5 hp motor
what is the amp draw on your 5hp spl motor?

 

[bslayter]

I already have the 5HP version of the Harbor fright pump and can't return it now.

What failed on the motor? Did it over heat?

I'm going to agree with those who say it was probably a 15amp motor. That motor would pair nicely with the cheaper 3hp HF pump (which seems like a decent pump based on my limited working with one).

If the motor isn't damaged the OP would just need to change the pulley ratio to keep the motor from being overloaded. To verify the motor isn't overloaded the OP would need to measure motor RPM under load. I'm not sure that HF provides the information needed to estimate the correct pulley size.

If the motor isn't really bad I would buy the HF 3hp pump since it will be the right size for the current motor.

 

[bslayter]

HF does provide the information needed to estimate the correct pulley size and I estimated it would need a 4.5-inch pulley. But is it going to ruin the electric motor because it is undersized?

What failed on the motor? Did it over heat?

I'm going to agree with those who say it was probably a 15amp motor. That motor would pair nicely with the cheaper 3hp HF pump (which seems like a decent pump based on my limited working with one).

If the motor isn't damaged the OP would just need to change the pulley ratio to keep the motor from being overloaded. To verify the motor isn't overloaded the OP would need to measure motor RPM under load. I'm not sure that HF provides the information needed to estimate the correct pulley size.

If the motor isn't really bad I would buy the HF 3hp pump since it will be the right size for the current motor.

 

[bslayter]

The true 5HP motor you listed has a 7/8 shaft and I believe mine had a 5/8 shaft.

Those "SPL" motors draw about 15a and are actually around about 3hp IIRC, a 22a draw motor would be considered 5hp. Both using 220v.

This would be a true 5hp motor,
https://www.surpluscenter.com/Electrical/AC-Motors/Air-Compressor-Motors/5-HP-Special-Compressor-Duty-230-Volt-AC-3450-RPM-US-Motors-Air-Compressor-Motor-10-2621.axd

This would be comparable what you have,
https://www.surpluscenter.com/Air-Pneumatics/Air-Compressors-Vacuum-Pumps/Air-Compressor-Motors/5-HP-Special-Duty-230-Volt-AC-3450-RPM-Leeson-Air-Compressor-Motor-10-2530.axd

 

[Citation]

I think the problem was the "5hp" motor was actually more like 3hp and that's why the motor died. It was just over loaded.

I see two options going forward. The first would be get a true 5hp motor. However, that might overload the motor switch on your compressor. Up to about 5hp it seems the industry uses the all in one pressure switch
https://www.amazon.com/dp/B008JVM45G/?tag=atomicindus08-20

Once you get to true 5 hp and above they switch to using a starter circuit.
https://www.amazon.com/dp/B079TMKPTT/?tag=atomicindus08-20
The pressure switch would feed into the magnetic starter. This adds a level of complexity that you probably don't want to mess with.

The next option would be to get something like a 15-20 amp motor (3-4hp) and change the pulley on the motor to run the pump a bit slower. That's not all bad as it will make the compressor quieter. I think that 5hp pump can be run at lower RPM off a 3hp motor (I was looking at that pump a while back).
https://manuals.harborfreight.com/manuals/67000-67999/67698.pdf

The manual says it can run at 655 RPM. Well 1050 rpm at 5hp so assume that scales to 630 rpm at 3hp (probably close enough to 655 RPM and it's probably not a perfect linear scale). So next would be calculate the pulley size. So based on the instructions you have 14.5"*655 RPM/3450RPM=2.75" pulley for a 3 hp motor. (I don't guarantee my math)

 

[James-W]

You really should get a 5hp electric motor to do the job right. Putting a smaller pulley on the motor will certainly work out for you, but then the pump will turn slower and you won't get the cfm that the pump is suppose to put out. It is your compressor and you can do what you feel is best, but my vote is to replace the burned out motor with a high quality 5hp motor. That way you will get the cfm output the pump was rated for.