Lennox XC25-024-230-01 Installation And Service Procedure page 51

LOW
PRESSURE
Y1 DEMAND
SWITCH (S87)
CONTACTOR
DE-ENERGIZED
OPEN
ANTI-SHORT
CYCLE TIMER
BEGINS
INCREMENT
5-STRIKE
COUNTER
LED ALERT
CODE / OR
MODERATE
ALERT 410
DISPLAYED
ANTI-SHORT
CYCLE TIMER
ENDS
CONTACTOR
ENERGIZED
LOW
PRESSURE
SWITCH (S87)
SERVICE
2
REQUIRED
WAITING FOR
PRESSURE
OPEN
SWITCH TO
CLOSE
Figure 32. Low Pressure Switch (S87) Sequence of Operation (All Versions)
CLOSED
LOW
PRESSURE
OPEN
SWITCH (S87)
1. The thermostat will terminate demand when the 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 cycling power off to the outdoor control's
(A175) R terminal.
3. The low pressure switch is ignored by the system when the outdoor
temperature is below 15°F.
5-STRIKE
COUNTER
REACHES 5
WITHIN A SINGLE
1
Y1 DEMAND
LOW
PRESSURE
SWITCH (S87)
LOCKOUT
LED ALERT
CODE / OR
CRITICAL
ALERT 411
DISPLAYED
CLOSED
CLOSED
51
CONTACTOR
ENERGIZED
CLOSED
SERVICE
REQUIRED
LED ALERT
CODE / OR
MODERATE
ALERT 410
DISPLAYED
INITIAL TRIP
SWITCH IS
IGNORED FOR
90 SECONDS
SWITCH IS CLOSED OR OUTDOOR
AMBIENT TEMPERATURE IS 15ºF
3
OR BELOW
2
NORMAL
OPERATION
XC25