Attic Fan Belt Deflection

Adjust the motor back until there is approximately 1 2 1 3 cm to 3 4 1 9 cm deflection at the center of the belt with light pressure.

Attic fan belt deflection.

Pull one end of the old fan belt off from around the hub connected to the motor shaft. So for a 32 span the deflection amount would be 32 64 or 1 2. Dispose of the broken fan belt or pieces of the belt in the trash. Lift the belt out of the fan if the fan belt is broken in half pull the two sections off the hubs and lift them out of the fan.

For example if the span length is 32 inches the desired belt deflection is inch. A space between the belts should be about 1 3 4 at proper belt tension. Conversely an improperly tensioned belt can cause a host of easily preventable problems including noise vibration poor fan performance bearing wear and shortened fan motor life. Test belt tension with power off squeeze belt together with light force.

Desired belt deflection is 1 64 of an inch for every inch of belt span. Set the small o ring on the tensiometer to the zero mark. To deflect the belt 1 64 for each 1 of belt span q. The force shown in the table is per rib.

You can then use an app or a chart like this one to find the proper force to generate this deflection. The correct tension method is to get the belt close to the correct tension by feel with a deflection of 1 64 of an inch for every 1 of distance between the two pulley centers. Set the large o ring on the tensiometer to the desired deflection determined in step 2. The force f to apply is shown per belt in the table to the left.

A properly tensioned belt ensures smooth operation and extends the service life of fans and motors.