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Service Manual -
HRG18xxS1P
508206-01
Issue 2140
Page 50 of 83
Y1 DEMAND
OR COOLING
DEMAND
LOW
PRESSURE
CLOSED
(S87)
CONTACTOR
ENERGIZED
SUCTION
PRESSURE
CUT-OUT IS
IGNORED FOR
90 SECONDS
LOW PRESSURE
(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
WAITING FOR
PRESSURE
TO RISE ABOVE
90 PSIG
OUTDOOR AMBIENT
TEMPERATURE IS 15ºF
OR BELOW
SWITCH IS CLOSED OR
3
5-STRIKE
COUNTER
REACHES 5
WITHIN A SINGLE
Y1 DEMAND
LOW
PRESSURE
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
OPEN
CLOSED
CLOSED
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.
LOW PRESSURE
SWITCH
S87
NO
Figure 22. Low Pressure Switch (S87) Sequence of Operation (All Units)