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SECTION 6. QUALIFIED TECHNICIAN - MAINTENANCE/SERVICING
Thermal control valve:
The front header also houses a thermal control valve. This
valve helps to control condensation off the heat exchanger by
not allowing water to ow throughout the heat exchanger until
the water reaches a temperature of 105°F. Very hard water may
leave deposits on the valve plunger causing the valve to stick.
If the valve sticks open, cold water can ow through the heat
exchanger causing condensation to occur. If the valve sticks
closed, very little water will ow through the by-pass hole which
will open the high limit contacts on the rear header.
To replace thermal control valve and/or bypass valve parts:
1. Turn pump, main gas valve and heater power off.
2. Remove drain plug and drain water out of heat exchanger.
3. Remove screws from right access panels and remove.
4. Remove wires from high limit switches on header.
5. Millivolt Heaters Only: Remove the thermostat bulb from the
header. Note: Using needle nose pliers to pull out copper strip
makes bulb removal easier.
6. Electronic Heaters Only: Unplug thermistor wire lead from
control board.
Figure 54: By-pass Valve
Figure 55: Thermal Control Valve
BY-PASS INSERT
THERMAL CONTROL
VALVE
ADAPTER
SHAFT
VALVE SPRING
BYPASS INSERT
VALVE
HEADER
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