CG-PRC002A-EN
17
Controls
Operational Protection Measures and
Functions - The main operational
protection measures and functions
available are described below:
Compressor Internal Thermostats -
Trane compressors have internal
thermostats to protect the motor windings,
which are constantly monitored by the
controller.
Inversion and No Phase
The controller monitors the phase
sequence and the presence of current in
each phase by means of current sensors
installed in each of the supply phases.
Overload Relay
The supply for each compressor is via an
overload relay, which is constantly
monitored by the controller, which turns the
compressor off when an overload is
detected.
Balancing Starts / Operating Hours
The controller optimizes the start
sequence for the compressors by
balancing the number of starts and the
number of hours for each compressor, and
does not allow one compressor to have a
greater operating regime than the others.
Evaporator Water Flow
A suitable flow switch must be installed
and electrically connected to the controller
in order to report water flow in the
evaporator. This ensures that the
equipment either does not go into
operation or is shut down if there is no
water flow.
Anti-freeze Protection
The controller monitors the leaving water
temperature and will disable the
compressors when the water temperature
reaches the set cutout temperature.
High Pressure Protection
The controller constantly monitors the
pressure regulator installed in the
equipment discharge line and shuts the
circuit down when pressure greater than
the set maximum is detected.
.
Low Pressure Limit
The controller will restrict the operation of
the compressors, by switching them off or
not allowing other compressors to start,
when the suction pressure approaches
the set cutout pressure.
External Temperature Cutout - Operation
of the equipment can be controlled by the
temperature of the outdoor air, i.e. the
equipment will only go into operation when
the outdoor air temperature is above the
temperature set in the controller. If the
equipment is working, it will be switched
off when the outdoor air temperature
reaches the set temperature.
Automatic Adjustment of the Chilled
Water Setpoint - The controller can
provide automatic adjustment of the chilled
water temperature setpoint based on the
outdoor air temperature or on the return
temperature of the water.
This kind of adjustment offers better
ambient temperature comfort control, as
well as providing energy savings and
allowing the customer to find the best
system control point.
Capacity Limiting during Starting - When
the equipment goes into operation and the
leaving water temperature is above 19ºC,
the controller will not allow the second
compressor to go into operation until the
leaving water temperature drops below
19ºC. This prevents the equipment from
being switched off due to high discharge
pressure because of compressor
overload.
Starting in Cold Areas
When the equipment is installed in a
location where the ambient or outdoor
temperature is low, there is a possibility
that the equipment will be switched off
because of low pressure before there is
enough condensing pressure to send the
refrigerant back to the evaporator.
Therefore, cutout due to low pressure will
be ignored for a period; this period will vary
according to the outdoor temperature at
the location.
Operational Recovery and Service
Recovery
In equipment with reciprocating
compressors, recovery ensures that, when
started again, the liquid left in the
evaporator is not sucked in by the com-
pressor, thus damaging it.
Unlike reciprocating ones, scroll
compressors tolerate flood back. However,
when required, operational recovery of the
refrigerant after the equipment or circuit in
operation has stopped can be undertaken.
In order to be able to use this function the
equipment must be equipped with
solenoid valves in the liquid line. The
purpose of service recovery is to recover
the refrigerant into the condenser so that
maintenance work can be carried out. This
recovery can only be done manually from
the controller. Optional valves in the
compressors suction and discharge can
be requested.
Protections and
Operational Functions
