Inspection and Maintenance
8-12
750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
8.12 — Forced Draft Fan
The position of the fan housing and the clearance between it and the fan (impeller) is extremely important to the
output capacity of the fan.
To install and adjust:
1. Bolt the motor securely to the head.
2. Slide the fan onto the shaft, but do not tighten the setscrews.
3. Turn the spacers on the studs until they contact the headplate.
4. Place external tooth lockwashers next to the spacers and install the fan housing on the studs.
5. Hold the fan housing in place with nuts and lockwashers. Tighten the nuts by hand.
6. Slide the impeller outward until its vanes contact the fan housing. The housing must be parallel to the impeller.
Adjust the spacers as necessary to align the housing with the impeller.
7. Slide the impeller toward the motor. Use a feeler gauge to obtain a .030” - .050” clearance between the impeller
and the housing.
8. Secure the key and then tighten the impeller hub setscrews.
9. Using a selected vane, rotate the impeller while checking to see that the clearance between the impeller and the
housing remains constant and within the specified .030” - .050” clearance.
10. Install the air duct assembly through the head opening. Tighten the screws securing the air duct to the fan hous-
ing only enough to create a seal between the neoprene gasket and the housing.
11. After connecting the motor leads, verify that the impeller rotation is counterclockwise when viewed from the
motor end.
NOTE: If the boiler is installed in a dusty location, check the vanes occasionally for deposits of dust or dirt. These
buildups can cause a decrease in air capacity, or lead to an unbalanced condition or cause damage to the equipment.
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