The blower wheel is a critical component of any oil burner and provides the necessary air for burning the atomized fuel. R. W. Beckett is issuing this technical bulletin to help the service technician identify and correct problems with the CF1400 blower wheel, part 21268.
BLOWER WHEEL FAILURE
The CF1400 blower wheel is a 28-blade fan that provides high static pressure. High static pressure is valuable in many of today’s commercial appliances. The blower wheel is attached to the CF1400 motor shaft using a ¼” cup point set screw. Older 21268 blower wheels used a 5/16” setscrew which was later changed to the recent ¼” set screw. The blower wheels were installed at R. W. Beckett at a setscrew torque of approximately 40 in-lbs.
We have received reports of some blower wheel failures. Therefore, we have conducted extensive research on this problem and enlisted the help of the wheel manufacturer. Typically, we have found that the failure involves separation of the blower wheel hub from the backplate. Examination of the blower wheels and motors from these failures has lead to the discovery that the cup point ¼” set screws can loosen and back out of the hub. The loosening of the setscrew causes the blower wheel to become unbalanced. The unbalanced wheel can either slide up or down on the motor shaft causing the wheel to rub inside the burner housing or it can vibrate and cause the hub to separate from the blower wheel. Inspection of the motor shaft will reveal the movement of the setscrew if done early. If the screw is loose, it may cold work the shaft material opposite of the shaft rotation at the contact point between the setscrew and shaft.
If a wheel fails and a new wheel is installed, the second wheel could also have the potential of failing. The failure of the second wheel could be caused by the new setscrew quickly working loose due to the damage incurred by the first setscrew.
REPAIRING THE PROBLEM
R. W. Beckett is taking measures to prevent this failure. Effective April 2002, all new burners have set screws with serrations which will lock the setscrew into the shaft surface and prevent loosening. The set screws are installed with 80 in-lbs of torque to supply sufficient holding force. For burners in the field, the following steps should be taken:
- Disconnect electrical power to the burner and motor.
- Remove the motor/blower wheel/coupling assembly.
- Remove coupling.
- If setscrew is 5/16”, reinstall assembly in burner.
- If setscrew is ¼”, remove setscrew and apply drop of Loctite 571™ or equivalent thread locking compound.
- When tightening screw, if torque wrench is available, torque to 70 to 80 in-lbs.
- Inspect motor shaft for damage. If severely damaged, contact R. W. Beckett.
- Replace blower wheel ensuring 3/32” gap between motor face and blower wheel.
- Reinstall coupling and place assembly into burner.
- Restore power and test burner for correct CO2 and smoke level.