Page 23
Defrost Control Timing Pins (P1)
Each timing pin selection provides a dierent accumulat-
ed compressor run time period for one defrost cycle. This
time period must occur before a defrost cycle is initiated.
The defrost interval can be adjusted to 30 (T1), 60 (T2),
or 90 (T3) minutes (see gure 17). The maximum defrost
period is 14 minutes and cannot be adjusted.
NOTE - Defrost control part number is listed near the P1
timing pins.
• Factory default is 90 minutes.
• If the timing selector jumper is missing, the defrost con-
trol defaults to a 90-minute defrost interval.
Compressor Delay (P5)
The defrost control has a eld-selectable function to re-
duce occasional sounds that may occur while the unit is
cycling in and out of the defrost mode.
The compressor will be cycled o for 30 seconds going in
and out of the defrost mode when the compressor delay
jumper is installed. (Factory default is jumper installed.)
NOTE - The 30-second compressor feature is ignored
when jumpering the TEST pins.
Time Delay
The timed-o delay is ve minutes long. The delay helps
to protect the compressor from short-cycling in case the
power to the unit is interrupted or a pressure switch opens.
The delay is bypassed by placing the timer select jumper
across the TEST pins for 0.5 seconds.
Test Mode
The TEST mode is activated by removing the jumper on
the defrost termination pins (30, 60 or 90) and placing the
jumper on the TEST pins after 24VAC is applied to the
control. The low pressure input is ignored in TEST mode.
IMPORTANT
The TEST pins are ignored and the TEST function is
locked out:
• If the jumper is applied on the TEST pin before 24VAC
is applied to the control.
• If there is a jumper on the 30 or 60 minute defrost
termination pins.
Bypass Anti-Short-Cycle Delay
The Y1 input must be active ON, the high pressure switch
must be closed or a jumper must be installed on the high
pressure terminals of the control.
Initiate a Force Defrost
The Y1 input must be active ON, the high pressure switch
must be closed or a jumper must be installed on the high
pressure terminals of the control, the defrost thermostat
must be closed or a jumper must be placed across the
DF terminals on the control and the O terminals must not
have 24VAC (no power to reversing valve) before control
will enter into a force defrost.
Test Mode Sequence / Clear Pressure Switch Lockout
Using the defrost termination pin, short the TEST pins for
a period of two seconds:
• Clear timed lockout / or pressure switch lockout function.
• Enter defrost mode.
After entering force defrost, if the jumper is removed be-
fore 5 seconds has elapsed, the unit will remain in forced
defrost mode until defrost thermostat opens or terminated
on maximum defrost time (14 minutes). If the jumper is not
removed, once 5 seconds has elapsed (7 seconds total),
the unit will terminate defrost and return to heat mode. The
TEST mode will then be lockedout and no further TEST
mode operation will be executed until the jumper on the
TEST pins is removed and reapplied to the applicable de-
frost termination pins.
IMPORTANT
After testing has been completed, properly reposition
test jumper across desired timing pins
Service Light Connection
The defrost control includes terminal connections for a
service light which provides a signal that activates the
room thermostat service light during periods of inecient
operation.
Defrost Control Diagnostic LEDs
The defrost board uses two LEDs for diagnostics. The
LEDs ash a specic sequence according to the condition.
TABLE 1
DEFROST CONTROL (CMC1) DIAGNOSTIC LEDs
Defrost Board Diagnostic LEDs
Green LED
(DS2)
Red LED
(DS1)
Condition
OFF OFF No Power to Control
Simultaneous slow
FLASH
Normal Operation /
Power to Control
Alternating Slow FLASH 5-min Anti-Short-Cycle Delay
ON
Slow
FLASH
Low Pressure Switch Ignored
(Low Ambient)
Fault & Lockout Codes
OFF
Slow
FLASH
Low Pressure Switch Fault
OFF ON Low Pressure Switch Lockout
Slow
FLASH
OFF High Pressure Switch Fault
ON OFF High Pressure Switch Lockout
Resetting Defrost Control High and Low Pressure
Switch Lockout
The defrost control will lock out the compressor if the
high or low pressure switch opens 5 times during a single
thermostat demand. To reset a 5-strike pressure switch
lockout, cycle 24V control power to the defrost control or
place the defrost control in the “TEST” mode by shorting
the “TEST” pins for 2 seconds.
IMPORTANT
After testing has been completed, properly reposition
test jumper across desired timing pins
To Next Page
Loading...
