Figure 4-15. Enclosure Heater Thermostat
To test the enclosure heater thermostat:
1. Apply ice to the tip of the thermostat to simulate cold air temperature.
2. Determine if the heater starts. If the heater does not start, first check the
circuitry, then replace the thermostat if necessary.
To replace the enclosure heater thermostat:
1. Switch off the main electrical power supply to Therma-Flow
®
Plus.
2. Open the thermostat unilet located above the enclosure heater.
3. Make note of the wire connections and disconnect the wires.
4. Remove the fitting that attaches the thermostat to the unilet.
5. Remove the thermostat and replace it with the new thermostat.
6. Wire the new thermostat in reverse order of removal.
7. Switch the electrical power on and test the thermostat by checking if the
heater starts when the temperature goes below the thermostat setting.
Enclosure Heater Contactor
The heater contactor is in the junction box located inside the enclosure (see Figure
4-16). When the thermostat reaches the set cold set point, the contactor closes the
circuit to start the heater. When the thermostat reaches the set hot point, the
contactor opens the circuit to stop the heater. If the contactor does not close or
open, the heater will not start or remains on indefinitely; if this hap-pens, the
contactor
may need to be replaced. Verify the heater thermostat is working properly
before replacing the contactor.
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