Lennox Signature XP21 Series Installation And Service Procedure page 77

PRESSURE
Y1 DEMAND
SWITCH (S87)
COMPRESSOR
CONTACTOR
DE−ENERGIZED
OPEN
COMPRESSOR
ANTI−SHORT
CYCLE TIMER
BEGINS
INCREMENT
5−STRIKE
COUNTER
LED ALERT
CODE / OR
MODERATE
ALERT 410
DISPLAYED
ANTI−SHORT
CYCLE TIMER
ENDS
COMPRESSOR
CONTACTOR
ENERGIZED
PRESSURE
SWITCH (S87)
SERVICE
2
REQUIRED
WAITING FOR
PRESSURE
OPEN
SWITCH TO
CLOSE
Figure 43. Low Pressure Switch (S87) Sequence of Operation (All Versions)
LOW
CLOSED
LOW
PRESSURE
OPEN
SWITCH (S87)
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 icomfortt 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.
REACHES 5
WITHIN A SINGLE
1
Y1 DEMAND
SWITCH (S87)
LOW
CLOSED
CLOSED
COMPRESSOR
CONTACTOR
ENERGIZED
CLOSED
5−STRIKE
COUNTER
LOW
PRESSURE
LOCKOUT
LED ALERT
CODE / OR
CRITICAL
REQUIRED
ALERT 411
DISPLAYED
LED ALERT
CODE / OR
MODERATE
ALERT 410
DISPLAYED
Page 77
INITIAL TRIP
SWITCH IS
IGNORED FOR
90 SECONDS
SWITCH IS CLOSED OR OUTDOOR
AMBIENT TEMPERATURE IS 15ºF
OR BELOW
SERVICE
2
NORMAL
OPERATION
XP21