A.O. Smith 120 through 250 Series User Manual
Page 75
is
Instruction manual BFC
75
Air pressure switch fails
to close during pre-
purge.
Air pressure switch
leads
1. Check the wiring between the air pressure switch and the
controller. Rectify any defect:
-
if any wires are damaged, replace the wiring harness
-
properly connect loose or detached hoses
2. Reset appliance controller
Loose air pressure
switch hoses
1. Check hoses between air pressure switch and burner/fan.
Rectify any defect:
-
if any wires are damaged, replace the wiring harness
-
properly connect loose or detached hoses
2. Reset appliance controller
Heat exchanger and/or
chimney flue is blocked
3. Measure the pressure differential across the air pressure switch
4. Check the values
5. Check heat exchanger, condensation drainage and/or chimney
flue for blockages
6. Clear any blockage that may be present.
7. Reset appliance controller
Defective controller
1. Check that the controller is receiving power
2. Check that the controller is correctly connected
3. If there is no electrical power, check the power supply to the
terminal block, or replace the controller.
4. Rectify any incorrect connections.
5. Reset appliance controller
Code + Description
Cause
Solution
Remark