14
Pressure Switch Circuit
The defrost control includes LO-PS terminals to connect an
optional low pressure (loss of charge pressure) switch. A high
pressure switch (optional) can be connected to the HI PS
terminals. See “Defrost Control Board” in the “Adjust Defrost
System” section.
During a single demand cycle, the defrost control will lock out
the heat pump after the fifth time that the circuit is interrupted by
any pressure switch wired to the control board. In addition,
the diagnostic LEDs will indicate a locked-out pressure switch
after the fifth occurrence of an open pressure switch. See
Defrost Control Board Diagnostic LEDs chart later in this section.
The heat pump will remain locked out until power to the board is
interrupted, then re-established, or until the jumper is applied to
the TEST pins for 0.5 seconds.
NOTE: The defrost control board ignores input from the low
pressure switch terminals during:
■
TEST mode
■
Defrost cycle
■
90-second start-up period
■
First 90 seconds after the reversing valve switches heat/cool
modes
NOTE: If the TEST pins are jumpered and the 5-minute delay is
being bypassed, the LO PS terminal signal is not ignored during
the 90-second start-up period.
Adjust Defrost System
Defrost Control Board
Optional high pressure switch safety circuit connections
NOTE: To add the pressure switch, remove the factory-installed
jumper.
Adjust Time Between Defrost Cycles
1. Disconnect power.
2. Remove the heater compartment access panel.
3. Adjust the time period between defrost cycles by placing the
defrost time plug in the proper position. See “Defrost Control
Board.”
■
For 30-minute intervals between defrost cycles, connect
the Defrost Time Setting Plug to the pins corresponding
to 30.
■
For 60-minute intervals between defrost cycles, connect
the Defrost Time Setting Plug to the pins corresponding
to 60 (this setting is the factory preset setting).
■
For 90-minute intervals between defrost cycles, connect
the Defrost Time Setting Plug to the pins corresponding
to 90.
4. Replace the heater compartment access panel.
5. Reconnect power.
Defrost Control Board Diagnostic LEDs
Mode
Green LED
(DS2)
Red LED
(DS1)
No Power to Board
Off
Off
Normal Operation/Power to Board
Simultaneous Slow Flash
Short Cycle Lockout
Alternating Slow Flash
Low Pressure Switch Fault
Off
Slow Flash
Low Pressure Switch Lockout
Off
On
High Pressure Switch Fault
Slow Flash
Off
High Pressure Switch Lockout
On
Off
A. Defrost time setting pins
B. Test pins
C. Compressor delay pins
D. Reversing valve
E. Low pressure switch (optional)
F. Defrost thermostat
G. High pressure switch (optional)
H. Diagnostic LEDs
I. Low voltage terminal strip
connections
K1 Relay
K2 Relay
FAN
DS1
L
24V
P2
P5
O-OUT
DF
Y1-OUT
HI-PS
U1
U2
DS2
K3 Relay
P6
TST PS DF C
R
O Y1
C5
LO-PS
C2
P1
30
60
90
TEST
W1
C
L
R
Y1
O
H
I
A
B
C
D
E
F
G
WARNING
Electrical Shock Hazard
Disconnect power before servicing.
Replace all parts and panels before operating.
Failure to do so can result in death or electrical shock.
