Features
The ComfortMiser Chiller Control
System
- Temperature Control is designed to operate a
parallel, multiple staged compressor rack or group of
parallel reciprocating or scroll compressors based upon
a single temperature sensor.
Temperature
Control - The CMCC Control
Systems will maintain the
temperature of a single space by staging the operation compressor and the unloaders.
The CMCC Control
System will initially
start the compressors in the fully unloaded (lowest
capacity) configurations. Should additional capacity be
required, the CMCC Control System, after a calculated delay, will turn
off (add capacity) the next available unloader. Each
unloader will be staged sequentially, in a First On-Last
Off (FILO) sequence. If all the unloaders assigned
to the running compressors have been turned off, then
the CMCC will turn on the next compressor.
If the temperature is below
the Cut-Out setpoint, after a calculated delay, the
CMCC
will turn on (reduce capacity) the next unloader
assigned to the running compressor. If all the unloaders
on the running compressors have been turned on, then it
will turn off the next compressor. The delay time is
calculated automatically using the temperature differential
and the rate of change of the temperature.
A minimum runtime can be
adjusted at the Compressor Cycling Speed menu.
Monitor
Suction
Pressure
Head pressure monitoring is
optional. The CMCC will monitor a Suction Pressure transducer. The
CMCC will
go into alarm stage and cycle the alarm relay when
the suction pressure exceeds a high alarm limit for more
than 30 minutes or the suction pressure is below its low
alarm limit for more than six minutes.
Monitor Head
Pressure
Head pressure monitoring is
optional. The CMCC will monitor a 0-500PSIG
Head/Discharge Pressure transducer. The CMCC will
go into alarm stage and turn off the alarm relay when
the head pressure exceeds a high alarm limit for more
than 90 seconds or the head pressure is below its low
alarm limit for more than six minutes.
The Head Pressure input can
be used as high side suction input on split suction
system with high side and low side interlock.
Compressor/Unloader Staging Methods
Sequential - The stages will be activated and
deactivated in a First In and Last Out method. The
first compressor will have the longest runtime and the
last compressor has the least runtime. The method is
suitable for those rack design requires first
compressor running most of time for proper oil
distribution.
Round Robin - The stages will be
activated and deactivated in a First In and First Out
method. These This will maintain even run times on
participate compressors. It also prevent the
lubrication oil from migrating out of the compressors.
Combination of
Sequential and Round-Robin - For parallel racks with
two different sizes of compressors or one compressor
with an unloader. Will activate the sequential
compressors via the FILO format, then will activate
the round-robin compressors randomly. The sequential
compressors will be de-activated last.
Mix Match - On parallel racks with
different compressor sizes. The user sets the order of
which the compressors will activate and de-activate in
order to smooth the rack operating step sizes.
Unloaders - The CMCC can operate
up to six unloaders per rack. Each unloader can be
assigned to any of the parallel compressors. The
unloaders will operate on an accelerated algorithm as
compared to the compressor algorithm. When a
compressor with an assigned unloader is activated, the
compressor will initially start unloaded. If the CMCC
requires an increase in the rack load, the compressor
will then be fully loaded before an additional
compressor is activated.
Compressor 1 Swing
Staging - When
the rack is set up to run in a combination of one
sequential compressor and more than one round-robin
compressor mode, the first sequential compressor will
operate as the swing compressor. This compressor,
usually a smaller compressor, will swing in / swing
out (turned on / turned off) between activation of the
round-robin (bigger) compressors. The smaller
compressor will act as a half step, smoothing out the
performance of the rack.
Unloader 1 Swing
Staging - The
first unloader can be activated as a Swing Unloader.
It will swing in / swing out (Load / Unload) between
compressor staging steps, effectively adding a half
step to the staging, smoothing out the performance of
the rack.
Monitoring
and Alarming
The CMCC monitors six
separate sensors and activates alarms based upon user
definable alarm setpoints. These alarms include:
Low Suction Pressure - The CMCC
will shutdown all compressor operations and activate
alarms when the suction pressure is below the Low
Suction Alarm Setpoint for a user defined delay period
High Suction Pressure - The CMCC
will shutdown all compressor operations and activate
alarms when the suction pressure exceeds the High
Suction Alarm Setpoint for a user defined delay period
Low Oil Pressure
Differential - The CMCC monitors an oil
pressure transducer and calculates the pressure
differential. The CMCC will shutdown the compressor
operation and activate an alarm when the oil pressure
differential is below the Low Oil Pressure
Differential Alarm Setpoint for a user defined delay
period
High Head Pressure - The CMCC
monitors the Head/Discharge Pressure Transducer and
will shutdown the compressor operation and activate an
alarm when the head pressure exceeds the High Head
Pressure Alarm Setpoint for a user defined delay
period
Low Head Pressure - The CMCC monitors
the Head/Discharge Pressure Transducer and activates
an alarm when the head pressure is below the Low Head
Pressure Alarm Setpoint for a user defined delay
period
High/Low Room Temperature
- The CMCC
can monitor up to two temperature sensors located in a
refrigerated spaces. The CMCC activates an alarm when
the space temperatures exceeds the High
Temperature Alarm Setpoint for a user defined delay
period or goes below the Low Temperature Alarm
Setpoint for a user defined delay period
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