Troubleshooting guide

Third Procedure - Normally Open Switches (cont):
Pressure reading taken DOES NOT reach the activation pressure (cont):
Ensure the sensing tube is connected securely and not blocked with any debris or condensate. Ensure the tube
is not kinked or leaking. On residential power vent models check vent piping for excessive length or number of
elbows, check for obstructions in the vent pipe. On Cyclone BTH models ensure the minimum vent pipe length
requirement (7' BTH 120 - 250, 15' BTH 300/400) has been met. Ensure the blower wheel is clean on all models.
This can become dirty over time or during construction on new water heaters and cause operational problems.
Pressure reading taken DOES reach the activation pressure:
If the test results for the second procedure indicated the normally open switch contacts did not close and the
pressure reading taken during the third procedure indicated the pressure sensed by the switch did reach or
exceed the activation point (pressure value) for the switch, the switch is defective and should be replaced.
Normally Closed Switches: Current design residential power-vent/power direct-vent and commercial BTI/
BTN models are not equipped with normally closed air pressure switches. Cyclone BTH 120 – 400 models are
equipped with two normally closed air pressure switches; a blocked inlet and blocked exhaust switch (see pages
7 & 8). Normally closed switches should remain closed at all times unless there is an operational problem.
Pressure reading taken DOES NOT reach the activation pressure:
If the test results for the second procedure indicated a normally closed switches contacts were opening during
blower operation AND the pressure reading taken DOES NOT reach or exceed the activation point (pressure
value) for the switch, the switch is defective and should be replaced.
Pressure reading taken DOES reach the activation pressure:
If the test results for the second procedure indicated a normally closed switch contacts were opening during
blower operation AND the pressure reading taken DOES reach or exceeds the activation point for the switch DO
NOT replace the switch, it is not defective. Ensure the intake air or vent piping is not excessive and both are free
of obstructions. Always check the owner’s manual vent installation section for proper intake air and vent pipe
installation requirements.
Air Pressure Switch Testing
Blocked Exhaust Switch Pressure Test
Cyclone - BTH 120 - 250 Models
Blocked Exhaust Switch Pressure Test
Cyclone - BTH 300/400 Models
AHSA02307 6 of 8