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How-To

How to adjust belt tension?

To increase belt tension without an automatic belt tensioner:

Turn the lock nuts, on the side away from the motor, clockwise until the motor is loose.
Slide the motor, on mounting plate, away from the shaft until belt is properly tensioned while gradually tightening the lock nuts.
Proper belt tension is when the belt deflects approx. ¼” inch at the center when squeezed firmly on both sides.
Firmly re-tighten the locknuts.

To decrease belt tension, reverse the above procedure.

How to adjust discharge orientation on the Dynamo?

Make sure that the unit is not in operation that all power is disconnected to the unit. If the unit has a disconnect switch, make certain that required/adequate lockout is provided.
Remove nuts from eight (8) stud-bolts on the inlet side of scroll. Save these for re-assembly.
Once the nuts have been removed from the bolts, the inlet angle flange can be removed and set aside.
Support scroll housing from underneath, to support scroll weight for the remaining steps.
The short vertical inlet support must be removed.
If provided, the optional weather cover must be removed. Make certain that all hardware is saved for re-assembly.
Remove nuts from eight (8) stud-bolts on the bearing side of scroll. Save these for re-assembly.
Rotate scroll housing to the desired discharge position.
Replace nuts from eight (8) stud-bolts on the bearing side of scroll, and fasten.
The weather cover (if provided) can then be re-installed
The short vertical inlet support must be remounted.
Place inlet angle flange back into position.
Remove support from underneath scroll housing.
The eight (8) nuts used to hold the inlet assembly together can now be installed and fastened.
Spin the wheel by hand to unsure that the wheel does not rub against the wheel inlet or inlet cone.
Continue forward with unit installation to system and/or ductwork.

How to adjust the pulley?

The driven pulley (fan pulley) is not adjustable. However, the drive pulley (motor pulley) is a variable pitch pulley. The pitch diameter of the pulley is adjustable to allow speeding up or slowing down of the blower wheel within the adjustment range of the pulley. In order to perform such an adjustment:

First remove the fan “V” belt (see How to Replace a Belt).
Then loosen the allen screw at the hub of the pulley and remove the key.
Rotate the top of the pulley clockwise to close the belt groove ½ turn, 1 turn, 1-1/2 turn or 2 turns as required to obtain the desired adjustment.
Re-install the key and tighten set screw.
Re-install the “V” belt and adjust the belt tension.
Turn the fan “ON” and check the motor full load amps to verify that the motor is not overloaded.

How to align the pulley?

If the pulleys are not properly aligned, excessive belt wear will occur. It may cause fan vibration, and could cause the belt to “jump” off of the pulleys. The pulley alignment should be accomplished by laying a level or straight edge across the pulleys. Both pulleys should be level and aligned. If not:

Remove the belt (see How to replace a belt).
Loosen the driven pulley (shaft pulley), and adjust up and down to obtain level.
Firmly re-tighten the pulley.
Re-install and re-adjust the belt.

How to replace a belt-drive motor?

CAUTION - MAKE SURE POWER IS TURNED OFF AT THE DISCONNECT SWITCH PRIOR TO CHANGING THE MOTOR.

NOTE: This picture is just an example of a typical belt drive arrangement.

First remove the motor cover, if any.
Remove the motor junction box cover and disconnect the motor wiring.
Remove the fan “V” belt (see How to Replace a Belt).
Loosen the motor pulley set screw, remove the key (if applicable), and remove the pulley from the motor shaft.
Remove the four nuts, bolts, and washers securing the motor to the motor mounting plate, and remove the motor.
Install the new motor using the four nuts, bolts, and washers.
Place the key in the motor shaft (if applicable), re-install and align the pulley.
Tighten the pulley key set screw.
Reconnect the motor wiring, making sure the connections are made in compliance with the wiring diagram on the motor. (leave the junction box cover off at this time)
Re-install the belt and adjust the belt tension.
Turn the disconnect “ON” and momentarily energize the motor to verify correct rotation. (If rotation is incorrect, turn disconnect “OFF”, adjust wiring to reverse motor rotation, and Turn “ON” to verify rotation.)
Using motor leads in the junction box, take a correct reading with an appropriate instrument to verify that the motor is running within the nameplate amperage range and is not overloaded.
Re-install the junction box cover.
With fan “ON”, visually inspect that all is in proper working order.
Turn disconnect switch “OFF”, and replace the motor cover.
Turn disconnect switch “ON”.

How to replace a belt?

Turn the lock nuts, on the side away from the motor, clockwise to allow slack on the belt. Remove the old belt, install the new belt, and tighten see How to Adjust Belt Tension .

How to replace a direct-drive motor?