Reversing Valve Control; Compressor Control; Auxiliary (Electric) Heat Control; Defrost - Carrier WeatherMaker 50KCQ A04 Series Service And Maintenance Instructions

POINT NAME
G Fan
Y1 Cool 1
Y2 Cool 2
W1 Heat 1
W2 Heat 2
R Power
C Common
DFT1
DFT2
IFO Fan On
OF OD Fan On
RVS1
RVS2
COMP 1
COMP 2
HEAT 2
COM
Select Jumper
Speed-Up Jumper
Speed-Up Jumper
Jumper for 1-3 seconds: Factory Test, defrost runs for 9 seconds
Jumper for 5-20 seconds: Forced Defrost, defrost runs for 30 seconds if
DFT2 is open

Reversing Valve Control

The DFB has two outputs for unit reversing valve control. Op-
eration of the reversing valves is based on internal logic; this
application does not use an "O" or "B" signal to determine re-
versing valve position. 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 received. Once de-energized at the
start of a Heating cycle, the reversing valves will remain de-en-
ergized until the next cooling stage is initiated.

Compressor Control

The DFB receives inputs indicating Stage 1 Cooling and Stage
1 Heating from the space thermostat or unit control system
(PremierLink ® or RTU-OPEN); it generates commands to start
compressors with or without reversing valve operation to pro-
duce Stage 1 Cooling or Stage 1 Heating. The 04-06 systems
have one compressor).

Auxiliary (Electric) Heat Control

The 50KCQ unit can be equipped with one or two auxiliary
electric heaters, to provide a second stage of heating. The DFB
will energize this Heating System for a Stage 2 Heating Com-
mand (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 ener-
gized) and also during the Defrost cycle (to eliminate a "cold
blow" condition in the space).

Defrost

The defrost control mode is a time/temperature sequence.
There are two time components: The continuous run period
and the test/defrost cycle period. The temperature component
is provided by Defrost Thermostat 1 mounted on the outdoor
coil.
Table 8 — 50KCQ Defrost Board I/O and Jumper Configurations
TYPE OF I/O
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
SPEED-UP CONFIGURATION
CONNECTION
UNIT CONNECTION
PIN NUMBER
INPUTS
P2-3
P2-5
P2-4
P2-7
P2-6
P3-1
P3-2
DFT-1 to DFT-1
DFT-2 to DFT-2
OUTPUTS
P3-9
OF
P3-7 to P3-5
P3-6 to P3-4
P3-10
P3-8
E-HEAT
P3-3
CONFIGURATION
P1-1
JMP17
JMP18
The continuous run period is a fixed time period between the
end of the last defrost cycle (or start of the current Heating cy-
cle) during which no defrost will be permitted. This period can
be set at 30, 60, 90 or 120 minutes by changing the positions of
DIP switches SW1 and SW2 (see Fig. 29 and Table 9). The de-
fault run periods are 60 minutes for unit sizes 04-06.
Fig. 29 — DIP Switch Settings - Defrost Board
At the end of the continuous run period, the defrost control will
test for a need to defrost. On unit sizes 04-06 (single compres-
sor designs), DFT1 controls the start and termination of the de-
frost cycle. If DFT1 is still open, the defrost test/run window is
closed and the control repeats the continuous run period. If
DFT1 is closed, the defrost cycle is initiated. The defrost peri-
od will end when DFT1 opens (indicating the outdoor coil has
been cleared of frost and ice) or a 10 minute elapsed period ex-
pires, whichever comes first.
At the end of the unit defrost cycle, the unit will be returned to
Heating cycle for a full continuous run period. If the space
heating load is satisfied and compressor operation is terminat-
ed, the defrost control will remember where the run period was
interrupted. On restart in Heating, the defrost control will re-
sume unit operation at the point in the run period where it was
last operating.
23
LCTB-G
LCTB-Y1
LCTB-Y2
LCTB-W1
LCTB-W2
CONTL BRD-8
CONTL BRD-4
REHEAT
OFR
Energize in COOL
Energize in COOL
FPT-REHEAT-6
REHEAT-8
HC-1 (TB4-1)
HC-1 (TB4-3)
NOTE