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Y1 DEMAND
LOW
OR COOLING
PRESSURE
DEMAND
CLOSED
(S87)
CONTACTOR
DE-ENERGIZED
OPEN
ANTI-SHORT
CYCLE TIMER
BEGINS
INCREMENT
5-STRIKE
COUNTER
LED ALERT
CODE / OR
SERVICE SOON
ALERT 410
DISPLAYED
ANTI-SHORT
CYCLE TIMER
ENDS
CONTACTOR
ENERGIZED
LOW PRESSURE
SWITCH
S87
SERVICE
2
REQUIRED
WAITING FOR
PRESSURE
OPEN
TO RISE ABOVE
40 PSIG
Figure 26. Low Pressure Switch (S87) Sequence of Operation (All Units)
CLOSED
LOW PRESSURE
OPEN
(S87)
1.
The thermostat terminates demand when the contactor
is de-energized. If demand is satisfied when alarm is
not active, the 5-strike counter resets.
2.
door control (A175) R terminal.
3.
The low pressure switch is ignored when
the outdoor temperature is below 15°F.
5-STRIKE
COUNTER
REACHES 5
WITHIN A SINGLE
1
Y1 DEMAND
PRESSURE
LOCKOUT
LED ALERT
CODE / OR
SERVICE URGENT
ALERT 411
DISPLAYED
CLOSED
CLOSED
NO
CONTACTOR
ENERGIZED
CLOSED
LOW
SERVICE
REQUIRED
LED ALERT
CODE / OR
SERVICE SOON
ALERT 410
DISPLAYED
SUCTION
PRESSURE
CUT-OUT IS
IGNORED FOR
90 SECONDS
SWITCH IS CLOSED OR
OUTDOOR AMBIENT
TEMPERATURE IS 15ºF
3
OR BELOW
2
NORMAL
OPERATION
31-5000750 Rev. 1
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