Amp Draw: When increasing pulley size, always check amp draw immediately after making the change. Remember, Amps increase at the cube of airflow, so a 10% increase in airflow may increase the power the motor draws by more than 30%. Pulley adjustments can be hazardous to the health of your motor. Do not leave a motor operating at more than full load amps.

Always measure fan RPM. Check the fan speed against the manufacturer’s fan data to be certain you don’t go over the fan curve. Airflow may decrease with an increase in fan speed under certain conditions.

Adjusting the motor mount is accomplished by loosening the bolts that hold the motor onto the motor mount. Next, slide the motor closer to or farther away from the fan until the correct fan belt tightness is achieved, then tightening the bolts on the motor mount to hold the motor in place and keep the fan belt tight.

Pulley alignment: Sometimes you’ll need to loosen the set screws on the pulley and slide them along the shaft until the pulleys line up with each other. Alignment increases efficiency and prolongs the life of the fan belt and pulleys.

Belt tightness: How tight should the fan belt be adjusted? Too tight, and the power consumption may increase and equipment life could decrease. Too loose, and the fan belt squeals and slips. There are tools available to measure fan belt tension, I bought one once. I found it not worth the hassle.
The rule I use for fan belt tightness is that belt deflection with moderate pressure applied should be 1/32nd of the distance between the shafts of the fan and the motor. For example if there is 16” between shafts, fan belt deflection should be 16” divided by 32 or ½”.

One last tip: With blower motors over 10 hp, it’s recommended that a good quality fan belt changeout include a second visit a day or two later to tighten the stretched fan belt by adjusting the motor mount. The fan belts do stretch and need to be tightened to perform their best.

This article comes from contractingbusiness edit released