er valve/regulator performance. The low gas pressure switch automatically shuts down the heater if gas sup- ply drops below the factory setting of 3.0 in. WC for natural gas or propane gas.
The optional high gas pressure switch connection mounts
Operation of either the High or Low Gas Pressure Switch will turn on an LED inside the switch housing. Push the top of the plastic switch housing as shown in Fig. 44 to reset a tripped pressure switch. The white LED will go out when the switch is reset.
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. 46: Blocked Vent Switch
Fig. 44: High/Low Gas Pressure Switch
Air Pressure Switch
This heater is equipped with an air pressure switch to prove the operation of the blower before allowing the ignition control to begin a Call for Heat. It is located on the right side of the lower flange of the blower mount- ing assembly, directly behind the junction box.
UDB Diagnostic Board
This heater is equipped with a diagnostic board which will indicate faults as they occur. Refer to the Trouble- shooting section for instructions on accessing, reviewing and clearing these faults.
Fig. 47: UDB Diagnostic Board
Fig. 45: Air Pressure Switch
NOTE: The wiring diagrams in this manual show all standard options. Refer to the large wiring diagram provided with your heater for options installed on your specific unit(s).
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