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COMMERCIAL DEFROST CONTROL
On 50FCQ units equipped with electro-mechanical controls or the
optional factory-installed RTU Open controller the Defrost Con-
trol Board (DFB) coordinates thermostat demands for supply fan
control, 1 or 2 stage cooling, 2 stage heating, emergency heating
and defrost control with unit operating sequences. The DFB also
provides an indoor fan off delay feature (user selectable). See
Fig. 30 for board arrangement.
The DFB is located in the main control box of the 50FCQ unit (see
Fig. 31). All connections are factory-made through harnesses to
the UCB (unit control board) to the ECM (direct-drive motor), re-
versing valve solenoids and to defrost thermostats. Refer to
Table 3 for details of DFB Inputs and Outputs.
NOTE: The Defrost Control Board is not used on units equipped
with the factory-installed SystemVu™ controller option.
Fig. 31 — Defrost Control Board Location - 50FCQ 04-07 Electro-Mechanical Units
Fig. 30 — Defrost Control Board Arrangement
18
DIP
SWITCHES
SPEED-UP
JUMPERS
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