# Compressor Upgrade Help...



## darita (Nov 19, 2019)

I currently have a 3.5hp Cobalt 60gal compressor. The unit above mine is a 5hp 80gal. Both are 2 stage. Looking up specs on both, I found they both use the same pump, rated for 5hp. If I want to upgrade in the future, can I simply use the 5hp motor, with appropriate pulley? Will that up my current 11 cfm?


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## stevon (Mar 5, 2019)

Yes it would if you increased the drive pulley size for the pump rpm to increase the pump RPM specified for that HP motor. Check the specs for the pump using the 5 HP motor and adjust motor drive size pulley accordingly. You could buy the pulley listed for the Kobalt 80 gal, 5 HP compressor model. May have to increase belt size to Accommodate the different size pulley. I have an old Sanborn compressor that uses the T-29 pump and the pump RPM listed is 1000 rpm with a 3 HP motor and 1400 with a 5 HP motor. When buying a modern efficient 5 HP motor make sure it draws 20 to 24 [email protected] 230 volt FLA. If not it may be a 3 HP marketed as a "5 HP motor" that draws 15 to 16 amps @ 230 volts, but in reality that is a 3 HP motor. Sure it can produce 5 HP at 19 amps for a very short period of time just before it overheats and trips it's thermal overload protection. Physics doesn't lie, there is no magic miracle electric motor that produces an actual 5 HP output at 230V @15 amps draw.

Stephen


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## darita (Nov 19, 2019)

Thanks for the reply. I actually went to Lowes this mornin and took a look at the two machines, side-by-side. Only difference I could see is that the 5hp motor uses a larger pulley and likely that different belt. Sure does seem like it would be a motor, pulley and belt replacement. The higher cfm would be nice to have.


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## stevon (Mar 5, 2019)

Darita,

I recently upgraded my compressor from a PoS Harbor Freight 3 HP (FLA 12.2 amps, actually a 2HP in reality) to a WEG 13521268 actual 5 HP 230V motor (20.5 FLA). I had to calculate the drive pulley size and bought a 7/8" bore x 5" sheave size. Pump RPM went from 1100 to 1350 RPM. Motor is marketed with some honesty and claims to be a "light duty" compressor motor. Meaning that it is designed to run 50% on and 50% off duty cycle. $214.00 on Ebay. I am very happy with my setup and pleased with the increased CFM output. Just make sure the pulley you buy has the same bore size as the motor's shaft you buy.

Stephen


darita said:


> Thanks for the reply. I actually went to Lowes this mornin and took a look at the two machines, side-by-side. Only difference I could see is that the 5hp motor uses a larger pulley and likely that different belt. Sure does seem like it would be a motor, pulley and belt replacement. The higher cfm would be nice to have.


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## stevon (Mar 5, 2019)

*extra speed*

Darita,

Increasing the pump speed slightly increases the wear on a pump and generates more heat in the air stream with more water in the compressed air and receiving tank. If the factory does this anyway, you should be good to go with the upgrade. Did they add or increase an after cooler (fins on copper tubing) on the 5 HP version? 

Stephen



darita said:


> Thanks for the reply. I actually went to Lowes this mornin and took a look at the two machines, side-by-side. Only difference I could see is that the 5hp motor uses a larger pulley and likely that different belt. Sure does seem like it would be a motor, pulley and belt replacement. The higher cfm would be nice to have.


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