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Fig. 35 —
Defrost Control Board Arrangement
Reversing valve control
The DFB has two outputs for unit reversing valve control. Opera
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tion of the reversing valves is based on internal logic; this applica
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tion does not use an “O” or “B” signal to determine reversing
valve position. Reversing valves are energized during the cooling
stages and the defrost cycle and de-energized during heating cy
-
cles. Once energized at the start of a cooling stage, the reversing
valve will remain energized until the next heating cycle demand is
received. Once de-energized at the start of a Heating cycle, the re
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versing valves will remain de-energized until the next cooling
stage is initiated.
Compressor control
The DFB receives inputs indicating Stage 1 Cooling, Stage 2
Cooling and Stage 1 Heating from the space thermostat or unit
control system (PremierLink™ controller or RTU Open control
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ler); it generates commands to start compressors with or without
reversing valve operation to produce Stage 1 Cooling (one com
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pressor runs), Stage 2 Cooling (both compressors run) or Stage 1
Heating (both compressors run).
Auxiliary (Electric) Heat control
The 50HCQ unit can be equipped with one or two auxiliary elec
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tric heaters, to provide a second stage of heating. The DFB will
energize this Heating System for a Stage 2 Heating Command
(heaters operate concurrently with compressor(s) in the Stage 1
Heating cycle), for an Emergency Heating sequence (compressors
are off and only the electric heaters are energized) and also during
the Defrost cycle (to eliminate a “cold blow” condition in the
space).
Fig. 36 —
Defrost Control Board Location
DIP
SWITCHES
SPEED-UP
JUMPERS
Summary of Contents for 50HCQ12
Page 4: ...4 Fig 2 Unit Dimensional Drawing Size 12 Units ...
Page 5: ...5 Fig 2 Unit Dimensional Drawing Size 12 Units cont ...
Page 9: ...9 Fig 6 Roof Curb Details REV 50TM500827 ...
Page 25: ...25 Fig 42 Typical 50HCQ Control Wiring Diagram ...
Page 26: ...26 Fig 43 Typical 50HCQ Power Wiring Diagram 208 230 3 60 unit shown ...
Page 27: ...27 Fig 44 PremierLink Controller Wiring Schematic ...
Page 28: ...28 Fig 45 RTU Open Controller System Wiring Diagram ...