Wiring new shop compressor

[mksj]

Often you will find the same compressor air pump used with different Hp versions of the compressors, typically with dual stage compressors the upper and lower limit PSI settings remain the same, the difference is the drive ratio to achieve the desired pump speed for the Hp.This effects the CFM output, which is a function of the compressor speed and PSI. I have a Champion 2-stage compressor which uses the R15B pump, it can be used with 3, 5 and 7.5 Hp motors, the pump speed range is 440-990 depending on the motor Hp. The pump RPM for the Quincy QT-7.5 is ~1026 at 175 PSI, air pump RPM is depending on the pressure. You should be able to adjust the motor pulley for a pump speed of around 700 RPM @175 PSI for 5 Hp, you could monitor the motor current or if it trips the overload relay you could reduce the upper pressure cutoff. By maintaining a wider on - off pressure the compressor will cycle less frequently, but if one needed maximum CFM at lower PSI than one might get by lowering the maximum pressure. My compressor uses an on pressure of 125 PSI and off at 175 PSI, I run my primary air regulator at 125 PSI through 3/4" lines and then have separate air regulators at each drop.