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XP21 SERIES
Y1 DEMAND
LOW
PRESSURE
SWITCH (S87)
COMPRESSOR
CONTACTOR
ENERGIZED
INITIAL TRIP
SWITCH IS
IGNORED FOR
90 SECONDS
LOW
PRESSURE
SWITCH (S87)
COMPRESSOR
CONTACTOR
DE−ENERGIZED
COMPRESSOR
ANTI−SHORT
CYCLE TIMER
BEGINS
INCREMENT
5−STRIKE
COUNTER
1
LED ALERT
CODE / OR
MODERATE
ALERT 410
DISPLAYED
ANTI−SHORT
CYCLE TIMER
ENDS
COMPRESSOR
CONTACTOR
ENERGIZED
LOW
PRESSURE
SWITCH (S87)
WAITING FOR
PRESSURE
SWITCH TO
CLOSE
SWITCH IS CLOSED OR OUTDOOR
AMBIENT TEMPERATURE IS 15ºF
OR BELOW
5−STRIKE
COUNTER
REACHES 5
WITHIN A SINGLE
Y1 DEMAND
LOW
PRESSURE
SWITCH (S87)
LOCKOUT
LED ALERT
CODE / OR
CRITICAL
ALERT 411
DISPLAYED
SERVICE
REQUIRED
2
LED ALERT
CODE / OR
MODERATE
ALERT 410
DISPLAYED
SERVICE
REQUIRED
2
NORMAL
OPERATION
CLOSED
CLOSED
OPEN
OPEN
1
If 5−strike counter has four or less strikes when Y1 demand is
terminated or satisfied, the strike counter will reset to zero. In a icomfort
Touch
®
thermostat enabled setup, the thermostat will terminate demand
when the compressor contactor is de−energized. If demand is satisfied
when alarm is not active, the 5−strike counter will reset.
2
Lockouts can be reset by either cycling power off to the heat pump
control’s (A175) R terminal, or placing a jumper on the field test pins
(E33) between 1 to 2 seconds.
OPEN
CLOSED
CLOSED
Figure 29. Low Pressure Switch (S87) Sequence of Operation
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