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Liquid Level Sensor
The liquid level sensor is a binary input used to indicate the
presence of a high level of liquid refrigerant in the primary
purge tank. The switch is a normally closed float switch,
open for high liquid level (in which case a diagnostic is
called), closed for acceptable level.
Explanation:
During certain failure modes of the purge
system, liquid refrigerant can fill the tank. A pumpout cycle
would then discharge large quantities of refrigerant water.
In such a circumstance, it is necessary to generate a
diagnostic and discontinue operation of the purge.
Service Pumpout Setpoint
If the pumpout rate timer exceeds the maximum pumpout
rate setpoint while the service pumpout switch is in the
service position, a non-latching diagnostic will be set. When
this diagnostic is cleared, the pumpout rate timer will be
reset to zero. Since pumpout time is also accumulated in
the daily timer, no data loss occurs because of this reset.
Design: The Purge Module has as a binary input labeled
Service Pumpout Switch. This input is unused for
production; however, if module communications were lost
and a service person wanted to pumpout, this input could
be jumpered to enter the Service Pumpout mode.
Outputs
Purge Refrigerant Compressor Relay
This relay is used to activate and deactivate the purge
refrigerant system. The purge refrigerant system includes
the purge refrigerant compressor and purge refrigerant
condenser fan. The compressor relay will be deactivated
when purge saturation temperature falls below 30 degrees
F. The compressor relay is reactivated when saturation
temperature is above the pumpout termination
temperature.
Purge Pumpout Compressor Relay
This relay is used to activate and deactivate the purge
pumpout compressor. The purge pumpout compressor
pumps the air out of the primary purge tank and into the
chiller vent line.
Tank Valve Relay
This relay is used to control the tank valve. The tank valve
controls the flow of purge tank exhaust from the primary
purge tank to the pumpout pump.
Alarm Relay
This relay will be energized in the presence of latching
purge diagnostics. It will be de-energized at all other times.
It is anticipated that a customer supplied alarming device
will be controlled by this relay.
Purge System Operating Modes
The purge system operating modes are dictated by the
purge operating mode set point. They are in effect as long
as there are no purge diagnostics that preclude operation
currently true. If a latching diagnostic exists, all outputs are
turned off with the exception of the alarm relay.
The purge-operating mode indicates the desired mode of
operation.
These operating modes are: Stop, On, Service Pumpout.
The default set point is on.
Stop
In this mode the purge system is not running. All relays are
turned off.
On
This mode is the normal operation state. On mode
corresponds to continuously running the Compressor
Relay, and vacuum pump. Pumpout is initiated via the
refrigerant suction temperature.
Service Pumpout
The service pumpout status is intended to aid the
serviceman in accomplishing certain mechanical repairs.
Service Pumpout mode initiates the pumpout sequence
regardless of the chiller running state OR the refrigerant
suction temperature.
Purge Status of Operation
The purge status indicates the current operating status.
Values of operating status are:
Ready to Pumpout - Condensing Unit is On, Pump is On)
Pumping Out - (Temperature initiated Pumpout)
Service Pumpout - (Pumpout initiated by the Service Setpoint)
Diagnostic Alarm - (Purge is idle unless mode is Service Pumpout)
Standby - (Condensing Unit is Off, Pump is on unless Mode is Stop)
Above values are explained on the following page.
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