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COMMERCIAL DEFROST CONTROL
On RHW units equipped with electro-mechanical controls
the Defrost Control Board (DFB) coordinates thermostat de-
mands for supply fan control, 1 or 2 stage cooling, 2 stage
heating, emergency heating and defrost control with unit op-
erating sequences. The DFB also provides an indoor fan off
delay feature (user selectable). The DFB also provides an
indoor fan off delay feature (user selectable). See Fig. 29 for
board arrangement.
The DFB is located in the main control box of the RHW unit
(see Fig. 30). All connections are factory-made through har-
nesses to the UCB (unit control board) to the ECM (direct-
drive motor), reversing valve solenoids and to defrost
thermostats. Refer to Table 3 for details of DFB Inputs and
Outputs.
Fig. 30 — Defrost Control Board Location - RHW036-060 Electro-Mechanical Units
18
Specifications subject to change without notice.
Fig. 29 — Defrost Control Board Arrangement
DIP
SWITCHES
SPEED-UP
JUMPERS
18
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