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Theoutdoor u nitandindoor b lower c ycleondemand from
theroomthermostat. Whenthethermostat blower s witch
is in the ON position,the indoor bloweroperates
continuously.
FILTER DRIER
Theunitisequipped w itha bi-fiow filterdrier. S eefigure 18.
If replacement is necessary, orderanother o f likedesign.
CRANKCASE H EATER
A IMPORTANT
EMERGENCY
HEAT FUNCTION (ROOM
THERMOSTAT)
An emergency heat function is designed into some room
thermostats. This feature is applicable when isolation of
outdoor unit is required or when auxiliary electric heat is
staged by outdoor thermostats. When the room thermostat
is placed in the emergency heat position, the outdoor unit
control circuit is isolated from power and field-provided
relays
bypass
the
outdoor
thermostats.
An
amber
indicating light simultaneously
comes on to remind the
homeowner that he is operating in the emergency heat
mode.
Emergency
heat
is usually
used during
an outdoor
shutdown, but it should also be used following a power
outage if power has been off for over an hour and the
outdoor temperature is below 50°F (10°C). System should
be left in the emergency heat mode at least six hours to
allow the crankcase
heater sufficient
time to prevent
compressor slugging.
The HP13 defrost system includes two components:
a
defrost thermostat and a defrost control.
DEFROST THERMOSTAT
The defrost thermostat is located on the liquid line between
the check expansion
valve and the distributor.
When
defrost thermostat
senses 42°F (5.5°C) or cooler, the
thermostat 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,
diagnostic
LEDs
and terminal
strip
for field
wiring
connections. See figure 22.
The control provides automatic
switching from normal
heating operation
to defrost
mode and back.
During
compressor
cycle
(call
for
defrost),
the
control
accumulates
compressor
run times
at
30-, 60-,
or
g0-minute
field-adjustable
intervals.
If
the
defrost
thermostat is closed when the selected compressor run
time interval ends, the defrost relay is energized
and
defrost begins.
FIELD SELECT
TIMING PINS
TEST
PINS
COMPRESSOR
DELAY PINS
REVERSING
VALVE
LOW PRESSURE
SWITCH
(OPTIONAL)
_
DEFROST
THERMOSTAT
HIGH PRESSURE
SWITCH
(OPTIONAL)
PI
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FAN
::,
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(_
OBSI
O_S2
P2
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0-0UT
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fl-OIJT
DIAGNOSTIC
LEDS
24V TERMINAL
STRIP
CONNECTIONS
SERVICE
LIGHT
CONNECTIONS
Figure 22. HP13 Outdoor Unit Defrost
Control Board
DEFROST CONTROL TIMING PINS
Each
timing
pin
selection
provides
a
different
accumulated
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 figure 22). The
defrost timing jumper
is factory-installed
to provide a
90-minute defrost interval. If the timing selector jumper
is not in place, the control defaults to a 90-minute defrost
interval. The maximum defrost period 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
jumpered.
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 additional
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 removed 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-applied.
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.
Page 15
HP13
SERIES
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