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VZ-VZH-VZT-IOM (08-24) 1047121-A
Figure 37. Model VZT Components
Pressure Switch
The pressure switch is a pressure-sensitive switch that monitors air pressure to ensure that proper combustion airflow
is available. If the sensing pressure is outside the pressure switch setpoint, the switch functions to shut off the burner.
Combination Gas Valve
⚠ WARNING ⚠
The combination gas valve is the prime safety shutoff. All gas supply lines must be free of dirt or
scale before connecting them to the unit to ensure positive closure.
The combination gas valve is powered by the 24V control circuit and is a diaphragm-type valve that is factory-set
to provide regulated gas flow.
Ignition Control Module
The ignition control module controls the operation of the combination gas valve and ignition system. The display’s
codes are listed and described in the Troubleshooting Using Ignition Control Module section.
Door Safe Switch (Model VZH)
The door safe switch prevents the heater from operating when the burner cabinet’s access door panel is open.
⚠ CAUTION ⚠
Verify that the door safe switch operates when opening the access door panel. While a temporary
bypass of the switch may be required for troubleshooting, always return the switch to normal
operation once troubleshooting is complete. Do not permanently bypass the switch.
SIDE VIEW BOTTOM VIEW
BLOWER AND
MOTOR ASSEMBLY
BLOWER
OUTLET
GASKET
IGNITION
CONTROL
MODULE
PRESSURE
SWITCH
COMBINATION GAS VALVEIGNITOR
TRANSFORMER
VIEWPORT
ELECTRODE
BURNER ASSEMBLY
BURNER STATUS INDICATOR LIGHTS
RELAY
CONTROLS—CONTINUED
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