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Fig. 30 — Defrost Control Board Location — RHV090-102 Electro-Mechanical Units Shown
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
COMP2
HEAT 2
COM
CONFIGURATION
Select Jumper
SPEED-UP CONFIGURATION
Speed-Up Jumper
Speed-Up Jumper
NOTES:
1. 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).
2. 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.
Operation of the reversing valves is based on internal logic;
this application does not use an "O" or "B" signal to deter-
mine reversing valve position. Reversing valves are ener-
gized 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 ener-
gized until the next heating cycle demand is received. Once
de-energized at the start of a Heating cycle, the reversing
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; it
generates commands to start compressors with or without
reversing 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 RHV unit can be equipped with one or two auxiliary
electric heaters, to provide a second stage of heating. The
RHV-090-120-01SI
Table 4 — RHV Defrost Board I/O and Jumper Configurations
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
—
—
Specifications subject to change without notice.
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
DFB will energize this Heating System for a Stage 2 Heating
Command
(heaters
compressor(s) in the Stage 1 Heating cycle), for an Emer-
gency 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).
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 compo-
nent is provided by Defrost Thermostat 1 and 2 (DFT1 and
DFT2) mounted on the outdoor coil.
The continuous run period is a fixed time period between
the end of the last defrost cycle (or start of the current Heat-
ing cycle) during which no defrost will be permitted. This pe-
riod can be set at 30, 60, 90 or 120 minutes by changing the
positions of DIP switches SW1 and SW2 (see Fig. 31 and
Table 5). The default run period is 30 minutes.
Shorting the jumpers for a period of 5 to 20 seconds by-
passes the remaining continuous run period and places the
unit in a Forced Defrost mode. If the controlling DFT is
closed when this mode is initiated, the unit will complete a
normal defrost period that will terminate when the controlling
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
—
—
—
operate
concurrently
NOTE
with
21
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