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UEZ-IOM (07-23) 1034347-I
Figure 36. Replaceable Components
Interlock Door Switch Maintenance
⚠ CAUTION ⚠
Verify that the interlock door switch operates when opening the cabinet. 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.
If it is determined that the interlock door switch (see Figure 36) needs replacing, use only a factory-authorized
replacement part that is designed for the heater. For the approximate door switch location, see Figure 27.
Transformer Maintenance
Use a voltmeter to verify that there are 24V output from the transformer (see Figure 36). If the transformer is not
functioning, it must be replaced. Use a replacement transformer identical to the factory-installed model. For the
transformer location, see Figure 27.
HIGH TEMPERATURE
LIMIT CONTROL
INTERLOCK DOOR
SWITCH
TRANSFORMER VENT TEMPERATURE
LIMIT SWITCH
DISCONNECT SWITCH
Inspect the combination gas valve, carefully remove any external dirt accumulation, and check wiring connections.
Check the valve annually to ensure that the valve is shutting off gas flow completely as follows:
1. Close manual shutoff valve to prevent flow to combination gas valve.
NOTE: Use a water column manometer that is readable to the nearest tenth of an inch.
2. Connect manometer to 1/8-inch outlet pressure tap on combination gas valve (see Figure 30).
3. Open manual shutoff and combination gas valves.
4. Use finger to fully block main burner orifice for several seconds.
5. Observe manometer with orifice blocked. If any pressure is indicated, combination gas valve is leaking and must
be replaced before heater is restored to operation.
Pressure Switch Maintenance
If it is determined that the pressure switch (see Figure 29) needs replacing, use only the factory-authorized replacement
part that is designed for the model and size of heater being serviced. Replace the switch in accordance with the
Pressure Switch Replacement section.
NOTE: A unit operating above 6,000 feet (1,830 meters) in elevation requires a high-elevation
pressure switch (refer to Pressure Switch Replacement section).
High Temperature Limit Control Maintenance
If it is determined that the high temperature limit control (see Figure 36) needs replacing, use only a factory-authorized
replacement part that is designed for the size of heater. For the approximate limit control location, see Figure 27.
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