52 AGR 055A through 100A IOMM AGR
Additional Global UNT Controller Features
Remote Stop/Start
When the remote stop/start switch is open, the controller will be in the unoccupied mode. The unit
will be enabled when the remote start / stop switch is closed and will control at the leaving water
temperature setpoint.
Unoccupied Mode
When the remote start / stop input is opened, the unoccupied mode is initiated. The chiller will
maintain a higher leaving water temperature setpoint (default 70°F) if the chilled water circulation
is maintained. The unoccupied leaving water setpoint can be changed from the Zone Terminal.
Soft Start
Soft loading limits the number of available stages when the unit is started to prevent excessive
power consumption and possible overshoot of the leaving water temperature set point. Soft loading
is in effect whenever the unit is started from an “off” cycle. When stage up starts, the controller
starts a countdown timer to indicate how long the unit has been in the cool stage mode. The number
of stages allowed during soft loading is determined by the Soft Start Capacity. The duration of the
soft load sequence is determined by the Soft Start Timer. If the Soft Start Timer is set to zero, no
soft loading will take place. The Zone Terminal is required to change the Soft Start values.
Compressor Staging
The AGR Reciprocating chiller has two refrigerant circuits and each circuit has one reciprocating
compressor. When the first stage of cooling is required, the #1 refrigerant circuit will start. This
circuit will be the first to start for the next ten starts. The Global UNT controller will then select the
#2 refrigerant circuit to start first for the next ten starts. This cycle will continue and balance the
number of starts between the refrigerant circuits. This is an automatic lead / lag control.
There are four or six stages of cooling capacity on the Global Reciprocating chiller unit. The
first stage of cooling will start the compressor of the lead refrigerant circuit. The second stage of
cooling will start the compressor of the lag refrigerant circuit. Cooling stage three will always be
compressor unloader head changing to loaded condition on the lead circuit. Cooling stage four will
always be loading of the lag refrigerant circuit.
Stage down is the reverse of the above paragraph.
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