System Operating Controls And Components; Switches And Controls; Water Temperature Sensor (Wts) - Carrier Supra 950MT Operation & Service Manual

2.6

SYSTEM OPERATING CONTROLS AND COMPONENTS

The unit is furnished with a microprocessor control system (Refer to Section 3.1). Once the desired set point is
entered at the Cab Command in the truck, the unit will operate automatically to maintain the desired temperature
within very close limits. The control system automatically selects Loaded and Unloaded Cooling or Loaded and
Unloaded Heating as necessary to maintain the desired temperature.
The microprocessor has an Auto Start/Stop feature. The Auto Start/Stop operation provides automatic cycling of the
diesel engine, which in turn offers an energy efficient alternative to continuous operation of the engine. Temperatures
are maintained by alternate cooling and heating of the supply air (evaporator outlet air).
A remote standby receptacle is standard with all units.
2.6.1

Switches And Controls

Manual control switches are located on the side of the electrical box. Components required for monitoring and con-
trolling the diesel engine and refrigeration system are located on the engine, compressor, or system piping.
Run/Stop Switch (RSS)
The RSS controls the supply of power to the microprocessor and cab command. The switch is placed in the ON
position to allow manual or automatic unit operation. With the switch in the OFF position, the unit will be shut down,
and neither manual or automatic starting is allowed.
Oil Pressure Safety Switch (OP)
The Oil Pressure Safety switch automatically stops the engine upon loss of oil pressure. The switch is preset to
open when the pressure drops below 15 ± °3 psig (1.0 ± 0.2 bar).

Water Temperature Sensor (WTS)

Located on top of the engine, the WTS senses engine water temperature. The microprocessor stops the unit when
the temperature exceeds 230°F ± 5F (110°F ± 3C). The sensor is located near the thermostat housing in the cylin-
der head.
High Pressure Cutout Switch (HP1)
This switch will automatically stop the engine when compressor discharge pressure exceeds cut out The switch is
located on the compressor cylinder head.
Compressor Discharge Temperature Sensor (CDT)
The microprocessor will stop the unit when this sensor signals a high discharge temperature condition. The sensor
is located on the compressor center head.
Compressor Suction Pressure Transducer (SPT)
The Compressor Suction Pressure Transducer signal is used by the microprocessor in the compressor protection
logic to protect the compressor under excessive suction pressure conditions and under excessively low suction
pressure conditions. The sensor is located on the compressor body.
Ambient Temperature Sensor (ATS)
The Ambient Temperature Sensor signal is used by the microprocessor in the compressor protection logic to deter-
mine expected conditions. It is located between the condenser and the front grille.
Temperature Control Sensors
Compartment temperature is monitored and controlled by the Return Air Sensor (RAS), which measures return air
temperature to the remote evaporators.
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