Carrier Aquasnap 30RAP010, Product Data

Page: 59 / 76

59
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 for space temperature reset is required. The
energy management module (EMM) is only required for
temperature 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.
Electronic expansion valve (EXV) — The EXV con-
trols refrigerant flow to the cooler for different operating
conditions by moving an orifice to increase or decrease the
flow area through the valve based on microprocessor
input. The orifice is positioned by a stepper motor and is
monitored every 3 seconds. The EXV maintains approxi-
mately 9° F (5° C) refrigerant superheat entering the
compressor.
Diagnostics — The microprocessor may be put through
a service test (see Controls, Operation, and Troubleshoot-
ing literature). Service test confirms microprocessor is
functional, informs observer through display 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, 30RAP
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. 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.