Reversing Valve Control; Compressor Control; Auxiliary (Electric) Heat Control - Carrier 50GCQ Series Service And Maintenance Instructions

Fig. 31 — Defrost Control Board Location — 50GCQ*04-06 Electro-Mechanical Units
Table 7 — 50GCQ Defrost Board I/O and Jumper Configurations
POINT NAME
INPUTS
G Fan
Y1 Cool 1
Y2 Cool 2
W1 Heat 1
W2 Heat 2
R Power
C Common
DFT 1
DFT 2
OUTPUTS
IFO Fan On
OF OD Fan On
RVS1
RVS2
COMP 1
COMP 2
HEAT 2
COM
CONFIGURATION
Select Jumper
SPEED-UP CONFIGURATION
Speed-Up Jumper
Speed-Up Jumper
NOTE(S):
a. Jumper for 1-3 seconds: Factory Test — The defrost interval timing is reduced by a factor of 0.1 seconds/minute based on the positions of DIP switches SW1 and SW2
(i.e., 90 minutes will be reduced to 9 seconds).
b. Jumper for 5-20 seconds: Forced Defrost — Defrost runs for 30 seconds if DFT2 is open.

Reversing Valve Control

The DFB has 2 outputs for unit reversing valve control. Operation
of the reversing valves is based on internal logic; this application
does not use an "O" or "B" signal to determine reversing valve po-
sition. Reversing valves are energized during the cooling stages
and the defrost cycle and de-energized during heating cycles.
Once energized at the start of a cooling stage, the reversing valve
will remain energized until the next heating cycle demand is re-
ceived. Once de-energized at the start of a Heating cycle, the re-
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 (SystemVu ™
TYPE OF I/O CONNECTION PIN NUMBER
DI, 24 vac
DI, 24 vac
DI, 24 vac
DI, 24 vac
DI, 24 vac
24 vac
24 vac
DI, 24 vac
DI, 24 vac
DO, 24 vac
DO, 24 vac
DO, 24 vac
DO, 24 vac
DO, 24 vac
DO, 24 vac
DO, 24 vac
24 vac
24 vac
—
—
controller or RTU Open controller); it
UNIT CONNECTION
P2-3
P2-5
P2-4
P2-7
P2-6
P3-1
P3-2
DFT-1 to DFT-1
DFT-2 to DFT-2
P3-9
OF
P3-7 to P3-5
P3-6 to P3-4
P3-10 FPT1-REHEAT/HP-6
P3-8 FPT2-REHEAT/HP-8
E-HEAT
P3-3
P1-1
JMP17
JMP18
generates commands to start compressors with or without revers-
ing valve operation to produce Stage 1 Cooling (one compressor
runs), Stage 2 Cooling (both compressors run) or Stage 1 Heating
(both compressors run).

Auxiliary (Electric) Heat Control

The 50GCQ unit can be equipped with one or 2 auxiliary electric
heaters, to provide a second stage of heating. The DFB will ener-
gize 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 De-
frost cycle (to eliminate a "cold blow" condition in the space).
21
a,b
CTB-G
CTB-Y1
CTB-Y2
CTB-W1
CTB-W2
CONTL BRD-8
CONTL BRD-4
—
—
REHEAT/HP-2
OFR
— Energize in COOL
— Energize in COOL
TB4-1
TB4-3
—
—
—
NOTE