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2
INSTALLATION
2.15 Thermostat Wiring:
One Two-Stage Thermostat and
Multiple Two-Stage Series Heaters
The Burner box contains a 24 volt transformer that
operates the control circuits. When more than one
heater is operated with a single thermostat, the 24
volt control circuit of each heater must be isolated.
A factory supplied isolation relay HL-RB must be
installed. See Figure 2.15.1 for internal wiring.
Heaters with factory installed relay boards are
labeled "Equipped with HL-RB". See Figure 2.15.2.
The thermostat is not part of the burner control
circuit, therefore an external (installer-supplied) 24
volt transformer will be required to operate all
HL-RB's. Each HL-RB draws .03 amps. All heaters
equipped with the HL-RB will use three wires to
operate the relays:
- Connect Line 24 volt from installer supplied
transformer to thermostat terminal (R).
- Connect common 24 volt from installer supplied
transformer to the 24 volt spade on the heater.
- 1st stage 24 volt from the thermostat (W1) to
heater number 1 low.
- 2nd stage 24 volt from the thermostat (W2) to
heater number 2 high.
See Figure 2.15.2.
Wiring from thermostat to heater does not change
due to thermostat type. Wiring from external
transformer to thermostat may change. Refer to
thermostat installation instructions.
Figure 2.15.1
Figure 2.15.2
25
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