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2 − Dual Capacitor C12
The compressor and fan in XP13 series units use permanent
split capacitor motors. The capacitor is located inside the unit
control box (see figure 2). A single dual" capacitor (C12) is
used for both the fan motor and the compressor (see unit wir-
ing diagram). The fan side and the compressor side of the ca-
pacitor have different MFD ratings. See side of capacitor for
ratings.
3 − Defrost Control
The XP13 defrost system includes two components: a de-
frost thermostat and a defrost control.
Defrost Thermostat (Defrost Switch S6)
The defrost thermostat is located on the liquid line between
the check/expansion valve and the distributor. When de-
frost thermostat senses 42°F (5.5°C) or cooler, the thermo-
stat contacts close and send a signal to the defrost control
board to start the defrost timing. It also terminates defrost
when the liquid line warms up to 70°F (21°C).
Defrost Control
The defrost control board includes the combined functions
of a time/temperature defrost control, defrost relay, diag-
nostic LEDs and terminal strip for field wiring connections.
The control provides automatic switching from normal heat-
ing operation to defrost mode and back. During compressor
cycle (call for defrost), the control accumulates compressor
run times at 30-, 60-, or 90-minute field−adjustable inter-
vals. If the defrost thermostat is closed when the selected
compressor run time interval ends, the defrost relay is ener-
gized and defrost begins.
XP13 Outdoor Unit Defrost Control Board
24V TERMINAL
STRIP
CONNECTIONS
DIAGNOSTIC
LEDS
HIGH PRESSURE
SWITCH
TEST
PINS
FIELD SELECT
TIMING PINS
REVERSING
VALVE
DEFROST
THERMOSTAT
LOW PRESSURE
SWITCH
COMPRESSOR
DELAY PINS
S4
S87
FIGURE 4
Defrost Control Timing Pins
Each timing pin selection provides a different accumu-
lated compressor run time period for one defrost cycle.
This time period must occur before a defrost cycle is initi-
ated. The defrost interval can be adjusted to 30, 60 or 90
minutes (see figure 4). The defrost timing jumper is facto-
ry−installed to provide a 60−minute defrost interval. If the
timing selector jumper is not in place, the control defaults
to a 90−minute defrost interval. The maximum defrost pe-
riod is 14 minutes and cannot be adjusted.
A TEST option is provided for troubleshooting.
The TEST
mode may be started any time the unit is in the heating
mode and the defrost thermostat is closed or jump-
ered.
If the jumper is in the TEST position at power-up, the
control will ignore the test pins. When the jumper is placed
across the TEST pins for two seconds, the control will enter
the defrost mode. If the jumper is removed before an addi-
tional 5−second period has elapsed (7 seconds total), the
unit will remain in defrost mode until the defrost thermostat
opens or 14 minutes have passed. If the jumper is not re-
moved until after the additional 5−second period has
elapsed, the defrost will terminate and the test option will
not function again until the jumper is removed and re−ap-
plied.
Compressor Delay
The defrost board has a field−selectable function to reduce
occasional sounds that may occur while the unit is cycling in
and out of the defrost mode. The compressor will be cycled
off for 30 seconds going in and out of the defrost mode
when the compressor delay jumper is removed.
NOTE − The 30-second compressor feature is ignored
when the defrost test pins are jumpered.
Time Delay
The timed-off delay is five minutes long. The delay helps to
protect the compressor from short-cycling in case the pow-
er 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.
Pressure Switch Circuit
The defrost control incorporates two pressure switch cir-
cuits. The high pressure switch (S4) is factory-connected to
the board’s HI PS terminals (see figure 4). The board also
includes a low pressure, or loss-of-charge-pressure, switch
(S87). Switches are shown in the unit wiring diagram. Dur-
ing a single demand cycle, the defrost control will lock out
the unit 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 Table 1). The unit 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.
Some XP13 units will be equipped with an optional by−pass
switch wired in parallel with the low pressure switch (S87).
This by−pass switch prevents nuisance trips when ambient
conditions drop below 15° F.
NOTE − The defrost control board ignores input from the
low-pressure switch terminals as follows:
during the TEST mode,
during the defrost cycle,
during the 90-second start-up period,
and for the first 90 seconds each time the reversing valve
switches heat/cool modes.
Diagnostic LEDs
The defrost board uses two LEDs for diagnostics. The LEDs
flash a specific sequence according to the condition.
