54
XC20
Y1 DEMAND
LOW
PRESSURE
SWITCH (S87)
CONTACTOR
ENERGIZED
INITIAL TRIP
SWITCH IS
IGNORED FOR
90 SECONDS
LOW
PRESSURE
SWITCH (S87)
CONTACTOR
DE-ENERGIZED
ANTI-SHORT
CYCLE TIMER
BEGINS
INCREMENT
5-STRIKE
COUNTER
1
LED ALERT
CODE / OR
MODERATE
ALERT 410
DISPLAYED
ANTI-SHORT
CYCLE TIMER
ENDS
CONTACTOR
ENERGIZED
LOW
PRESSURE
SWITCH (S87)
WAITING FOR
PRESSURE
SWITCH TO
CLOSE
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. 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.
OPEN
CLOSED
CLOSED
SWITCH IS CLOSED OR OUTDOOR
AMBIENT TEMPERATURE IS 15ºF
OR BELOW
3
3. The low pressure switch is ignored by the system when the outdoor
temperature is below 15°F.
Figure 31. Low Pressure Switch (S87) Sequence of Operation (All Versions)
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