Lennox EL195DF SERIES User Manual page 15

Problem
Pressure switch stuck closed
Pressure switch does not close due to
obstruction in vent pipe.
Pressure switch does not close due to
incorrect routing of the pressure switch
tubing.
Pressure switch does not close due to
obstructions in the pressure switch line.
Pressure switch tubing damaged.
Condensate in pressure switch tubing.
Pressure switch does not close due to
a low differential pressure across the
pressure switch.
Wrong pressure switch installed in the
unit, or pressure switch is out of calibra-
tion
Miswiring of furnace or improper
connections at pressure switch.
Pressure switch failure.
Damaged condensate trap.
Cold end header box does not drain
properly.
Air leakage around the combustion air
inducer gasket.
Air leakage around the cold end header
box gasket.
Damaged cold end header box tubing.
TABLE 6
Pressure Switch Troubleshooting Guide
Corrective Action
Check that the pressure switch is open without the combustion air inducer operat-
ing. Replace if
defective.
Check for restricted vent. Remove all blockage.
Check for proper vent sizing. See table 10.
Check that the pressure switch tubing is correctly routed. Correctly route pressure
witch line.
Remove any obstructions from the the pressure switch line and/or taps
Check pressure switch tubing for leaks. Replace damaged tubing if necessary.
Check pressure switch tubing for condensate. Remove condensate from tubing.
Check the differential pressure across the pressure switch.
Check for restricted inlet vent. Remove all blockage.
Check for proper vent sizing and run length. See table 10.
Check that the correct pressure switch is installed in the unit. Replace pressure
switch if necessary.
Check for correct wiring and loose connections. Correct wiring and/or replace any
loose connections.
If all the above modes of failure have been checked, the pressure switch may have
failed. Replace pressure switch and determine if unit will operate.
Check trap for any cracks or damage and replace if necessary.
Check that the furnace is set properly with a slight tilt (0 − 1/2") towards the front
if necessary. See furnace installation instruction.
Check gasket and replace if necessary.
Check gasket and replace if necessary.
Check tubing and replace if necessary.
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