Start-up and Shut-down
88 CVHH-SVX001A-EN
occurs in the temperature of the purge refrigerant exiting
the coil. The compressor suction temperature sensor
monitors this temperature.
When sufficient non-condensables have accumulated in
the purge tank to decrease the compressor suction
temperature below the pump-out initiate value, a pump-
out cycle begins. The cycle is terminated when the
compressor suction temperature sensor increases above
the pump-out terminate value. The calculations for the
pump-out values are:
Pump-out initiate:
• (°C) = Purge liquid temperature (°C) – 10.0°C or -
17.8°C (whichever is higher)
• (°F) = Purge liquid temperature (°F) – 50°F or 0°F
(whichever is higher)
Pump-out terminate:
• (°C) = Purge liquid temper ature (°C) – 4.4°C or -
15.0°C (whichever is higher)
• (°F) = Purge liquid temperature (°F) – 40°F or 5°F
(whichever is higher)
The purge liquid temperature value comes from the
chiller’s saturated condenser temperature sensor when
the chiller is running, or the chiller’s saturated evaporator
temperature sensor when the chiller is off.
Non-condensable Pump-out cycle
A non-condensable pump-out cycle may be initiated as
described below only if the following two conditions are
met:
• A carbon regeneration cycle is NOT in process, and
• The refrigeration circuit is on.
If at any time, except as described above, the purge
refrigerant compressor suction temperature drops below
the pump-out initiate value, the following sequence is
initiated by the controls.
The controller starts the pump-out compressor and opens
the exhaust solenoid valve. After 5 seconds, the pump-out
solenoid valve opens and pulses at a rate of 20 seconds On
and 20 seconds Off. If, after two cycles, the purge
refrigerant compressor suction temperature has not
exceeded the pump-out terminate value, the pump-out
solenoid valve stays continuously open. If the pump-out
compressor runs for more than 10 consecutive minutes,
the controller recalculates the pump-out initiate and
pump-out terminate values as described.
The purge controls continue to operate the pump-out
solenoid valve and calculate values as described above
until the purge refrigerant compressor suction
temperature rises above the pump-out terminate value. At
this point, the controller will close the pump-out solenoid
valve and turn off the pump-out compressor and exhaust
solenoid valve.
Note: For purge systems equipped with standard pump-
out compressors, operation at low chiller
condenser saturation temperatures may result in a
system vacuum greater than the pump-out
compressor can overcome. If the chiller
experiences low condensing temperatures, then
the Tracer UC800 controller can be programmed to
inhibit the operation of the purge pump-out
compressor.
Carbon Tank and Regeneration Subsystem
The function of the carbon tank is to absorb refrigerant
molecules that may be entrained in the discharge of non-
condensables. In order to maintain effectiveness, the
carbon tank periodically regenerates.
Carbon Regeneration Algorithm
The controller uses the carbon regeneration algorithm to
determine when to initiate, control, and terminate a
carbon regeneration cycle. The carbon bed temperature
sensor serves as the feedback to this algorithm. In
addition, the controller uses a pump-out accumulation
timer to indicate the remaining carbon capacity in the
carbon tank. The carbon capacity is the capacity of the
carbon to adsorb refrigerant while maintaining acceptable
levels of refrigerant emission through the chiller vent line.
A capacity of 100 percent means the carbon bed has the
capacity to adsorb refrigerant and maintain acceptable
emission levels. A capacity of 0 percent means the carbon
bed has inadequate capacity to adsorb refrigerant and still
maintain acceptable emission levels.
The main objectives of the carbon regeneration algorithm
are to:
• Minimize the amount of refrigerant contained in the
carbon by performing a periodic regeneration.
• Regenerate to maintain low emissions levels.
• Minimize the regeneration time.
• Regenerate only when the chiller is at a minimum level
of purging activity.
• Allow regeneration to occur with the chiller On or Off.
Regeneration is preferable when the chiller is On to
ensure low carbon tank pressure, but regeneration is
also acceptable when the chiller is Off.
The remaining amount of absorption capacity within the
carbon tank is directly proportional to the number of purge
pump-out minutes that have accumulated, and is also a
function of the chiller refrigerant type. The purge carbon
tank on an R-1233
zd
(E)-equipped chiller is considered to be
fully saturated after the purge has accumulated
350 minutes of pump-out time. Because the relationship
between pump-out capacity and pump-out minutes is
directly proportional, it can be described by the following
equation within the regeneration algorithm:
Remaining carbon capacity% =
100 - (pump-out minutes since last regen/pump-out
minutes at 100% capacity)* 100
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