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3.3.3 - The evaporator pumps
The controller can regulate one or two evaporator pumps, with
automatic changeover between the two pumps.
3.3.4 - The condenser pump
In appropriate cases the controller can regulate a condenser
pump (for water-cooled units or air-cooled units with heat
reclaim option). This control does not require an additional
board.
3.3.5 - Pressure sensors
These are used to measure the following pressures in each
circuit:
• Discharge gas pressure (high pressure type)
• Suction pressure (low pressure type)
• Oil pressure (option)
These electronic sensors deliver 0 to 5 V d.c. to the main board
or to a 4xAI-2xAO slave board. Two sensor versions are used;
one is calibrated for high pressure and the other for low
pressure and oil pressure.
Discharge pressure sensors
These are on the high pressure side of the lead compressor in
each circuit. They replace the usual discharge gas pressure
gauges and can be used to control head pressure or by the high
pressure load shedding option.
Oil pressure sensors
If installed, these sensors are used to measure the compressor
oil pressure on the oil pressure discharge side. The suction
pressure is subtracted from the oil pressure value to arrive at
the differential oil pressure.
Suction pressure sensors
They are located in the low-pressure side of the unit on the lead
compressor of each circuit. The suction pressure sensor reading
is used to control the electronic expansion devices EXV. They
permit replacement of the low-pressure switches, low-pressure
gauges and possibly of the oil pressure safety switch.
3.3.6 - Thermistors
These all have similar characteristics.
Evaporator entering water temperature sensor
The evaporator entering water temperature sensor is installed in
the evaporator wall in the free space at the side of the tube
bundle.
Evaporator leaving water temperature sensor
The evaporator leaving water temperature sensor is installed in
evaporator leaving water piping: The sensor bulb is directly
immersed in the water.
Compressor suction sensor
This is located in the lead compressor of each circuit in the
suction gas line situated between the motor and the cylinders
above the oil pump.
Condenser entering and leaving water temperature sensors
These are used to control the heating capacity on heat pumps.
In cooling only units they have no control function. They are
installed in the common condenser entering and leaving line.
Heat reclaim condenser entering/leaving water temperatures
These sensors measure the entering and leaving water tempera-
tures of heat reclaim condensers and are used on air-cooled
units equipped with the heat reclaim option. If not, they may be
fitted as options. In this case they only have informative
character.
Temperature setpoint reset sensor
This is an optional 0-10 V sensor which can be installed
remotely from the unit. It is used to reset the cooling and
heating setpoint on the unit as a function of either the outdoor
air temperature or ambient room temperature. The sensor is not
supplied by Carrier, and must be configured by the User Menu.
Outdoor temperature sensor
Mounted on the control box. It is used for start-up, setpoint
temperature reset and frost protection control.
Master/slave assembly temperature control
The optional water temperature sensor can be used for master/
slave assembly control.