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Standard
Comfort
Link™ controls with scrolling
marquee display module —
A four-digit alphanumeric
display shows all of the
Comfort
Link control codes (with
60-character expandable clear language), plus set points,
time of day, temperatures, pressures, and superheat. Addi-
tional information can be displayed all at once with the
accessory Navigator™ display.
Low-temperature override —
This feature prevents
LCWT (leaving chilled fluid temperature) from overshoot-
ing the set point and possibly causing a nuisance trip-out
by the freeze protection.
High-temperature override —
This feature allows
chiller to add capacity quickly during rapid load variations.
Abnormal conditions —
All control safeties in chiller
operate through compressor protection board or control
relay and microprocessor.
Loss of feedback signal to the MBB will cause the com-
pressor(s) to shut down. For other safeties, microprocessor
makes appropriate decision to shut down a compressor
due to a safety trip or bad sensor reading and displays
appropriate failure code on the display. Chiller holds in
safety mode until reset. It then reverts to normal control
when unit is reset.
Low-pressure safety —
Safety cuts out if system pres-
sure drops below minimum.
High-pressure cutout —
Switch shuts down compres-
sors if compressor discharge pressure increases to
426 psig (2937 kPa).
Compressor anti-cycling —
This feature limits com-
pressor cycling.
Loss of flow protection —
Proof of flow switches are
standard and installed on all 30RA chillers.
Sensor failures —
Failures are detected by the
microprocessor.
Dual chiller control —
The
Comfort
Link controller
allows 2 chillers (piped in parallel) to operate as a single
chilled water plant with standard control functions coordi-
nated through the master chiller controller. This standard
Comfort
Link feature requires a communication link
between the 2 chillers and an additional thermistor and
well in the common supply line.
Temperature reset —
If applied, microprocessor com-
pares either return fluid, space temperature, or outdoor-air
temperature with the accessory board settings, and adjusts
LCWT appropriately. The energy management module
can also be added for 4 to 20 mA reset.
Accessory controls —
Demand can be limited by con-
trolling the chiller capacity through the demand limit
control (the energy management module is required for
this function). This FIOP/accessory interfaces with micro-
processor to control unit so that chiller’s kW demand does
not exceed its setting. It is activated from an external
switch or a 4 to 20 mA signal.
The standard
Comfort
Link control is programmed to
accept various accessory temperature reset options (based
on outdoor-air temperature [std], return-fluid temperature,
or space temperature), that reset the LCWT. An accessory
thermistor (T10) is required if outdoor-air temperature or
space temperature reset is selected. The energy
management module (EMM) is only required for tempera-
ture reset that is initiated by a 4 to 20 mA signal.
Demand limit —
If applied, the demand limit function
limits the total power draw of unit to selected point by con-
trolling number of operational compressors during periods
of peak electrical demand.
The energy management module is required for either 2-
stage or 4 to 20 mA demand limit.
Navigator display module —
An optional 4-line,
20-character per line display an also available as a field-
installed accessory.
Thermostatic expansion valve (TXV) —
The TXV
controls refrigerant flow to the cooler for different operat-
ing conditions. An equalization line and temperature-
controlled sensing bulb are used to maintain a fixed setting
of super-heated refrigerant leaving the cooler.
Diagnostics —
The microprocessor may be put through
a service test (see Controls, Start-Up, Operation, Service,
and Troubleshooting literature). Service test confirms
microprocessor is functional, informs observer through dis-
play the condition of each sensor and switch in chiller, and
allows observer to check for proper operation of fans and
compressors.
Default settings —
To facilitate quick start-ups, 30RA
chillers with
Comfort
Link controls are pre-configured with
a default setting that assumes stand-alone operation sup-
plying 44 F (6.7 C) chilled water.
Configuration settings will be based on any options
or accessories included with the unit at the time of
manufacturing.
Date and time are set to U.S.A. Eastern Time zone and
will need reconfiguring based on location and local time
zone. If operation based on occupancy scheduling is
desired, this will also need to be set during installation.
Ice duty —
Comfort
Link controls have the capability of
reduced leaving fluid temperature operation for thermal
storage, or ice duty. The optional energy management
module includes input contacts for the “ice done” signal
generated by the thermal storage control system. The ice
duty feature may be configured to start on an external
input command or by the
Comfort
Link standard internal
scheduling function. The ice duty function requires brine
modification for leaving fluid temperatures below 40 F
(4.4 C). Ice duty may be used in combination with any
other standard features offered by the energy management
module and
Comfort
Link controls.
The production of ice, which is stored for peak cooling
demands, can significantly decrease energy costs. The unit
produces ice (normally at night) by supplying ice storage
tanks with low temperature cooling fluid. The chiller takes
advantage of reduced ambient conditions at night for ice-
making mode, so the capacity suffers a lower penalty for
the low leaving fluid temperatures.
At peak cooling demands the chiller and the stored ice
may share the cooling load to reduce operating costs. The
thermal storage system may potentially reduce the size of
the chiller plant required to meet demand loads.
Controls (cont)