A.O. Smith FPS 75, FPSE50, fps50, FPS40 manual AIR FOR COMBUSTION cont

FPS/FPSE/FPDTECHNICAL TRAINING AND SERVICE WORKBOOK

AIR FOR COMBUSTION cont.

CONDITION

Excessive heat build-up in PVC

venting

Intermittent fan cycling without burner

operation (Propane Only)

CAUSE

Inlet air damper not

opening completely

Blower does not run when main burner fires

Wrong main burner orifice size

Build up of pressure in the main burner tube between thermostat gas valve and solenoid qas valve

SOLUTION

Free air damper

Replace entire blower assembly

Install correct orifice

If cycling occurs

more than twice per hour, see troubleshooting

procedures.

A malfunctioning vent damper may also cause excessive unable to free the damper, replace the entire combustion

heat buildup in the PVC vent piping If control tee.

If blower does not run when the main burner fires, replace the control box. Also check burner orifice for correct size.

Intermittent cycling of the fan, without main burner operation, indicates a build-up of pressure in the main burner tube between the thermostatic gas valve and solenoid gas valve.