Service Reference Manual | UNIT COMPONENTS |
The measured static pressure reading should be compared to the pres- sure switch specifications. If the measured static pressure meets or exceeds the specifications and switch contacts will not transfer, check the following items:
•Switch out of calibration
•Defective pressure switch
•Moisture in pressure switch tubing
•Incorrect switch installed
WARNING
DO NOT try to repair a pressure switch. Use an identical replacement. The use of an improperly repaired or malfunctioning pressure switch could result in property damage, personal injury or death.
WARNING
Never try to adjust a pressure switch or jumper the switch to allow the furnace to operate. Doing so could allow the furnace to operate under hazardous conditions, potentially causing property damage, personal injury or death.
Blocked Intake
Blocked intake is any condition that blocks or restricts the flow of intake (combustion) air to a point where the pressure fall reaches the calibrated open setting of the pressure switch.
Potential Causes:
•Rodents
•Spiders
•Nest building in the intake opening
•Debris or trash that has been pulled into the intake opening
Symptoms:
•Excessive negative pressure in the burner box area. The furnace cycles on and off quite frequently, typically within 60 seconds or so.
•Inability of unit to stay on for a complete call for heat.
For a blocked intake or blocked flue, connect the incline manometer as shown on in Figure
