SECTION C: Installation
Fig. 36: Air Pressure Switch
Blocked Vent Switch
This heater is equipped with a blocked vent pressure switch to prevent the operation of the heater when too much of the vent is blocked. This switch is located on the right side of the heater near the right rear corner.
Fig. 37: Blocked Vent Switch
UDB Diagnostic Board
This heater is equipped with a diagnostic board which will indicate faults as they occur. It has the ability to retain up to 256 faults in history. Refer to the Trouble- shooting section for instructions on accessing, reviewing and clearing these faults.
SW1 
SW2 
Fig. 38: UDB Diagnostic Board
37
