1--9
©
2012 Mobile Climate Control
T-348 Rev. 07/2012
1.7 ELECTRICAL SPECIFICATIONS - SENSORS AND
TRANSDUCERS
a. Suction and Discharge Pressure Transducer
Supply Voltage: 4.5 to 5.5 vdc (5 vdc nominal)
Supply current: 8 mA maximum
Output Range: 8K ohms minimum
Input Range: -6.7 to 450 psig (-0.46 to 30.62 bar)
b. Temperature Sensors
Input Range: -52.6 to 158
°
F (-47 to 70
°
C
)
Output: NTC 10K ohms at 77
°
F (25
°
C
)
1.8 SAFETY DEVICES
System components are protected from damage
caused by unsafe operating conditions with safety
devices. Safety devices with Mobile Climate Control
supplied equipment include high pressure switch
(HPS), low pressure switch (LPS), circuit breakers
and fuses.
a. Pressure Switches
High Pressure Switch (HPS)
During the A/C mode, compressor operation will
automatically stop if the HPS switch contacts open
due to an unsafe operating condition. Opening HPS
contacts de-energizes the compressor clutch
shutting down the compressor. The high pressure
switch (HPS) is installed in the center head of the
compressor.
Low Pressure Switch (LPS)
The low pressure switch is installed in the
compressor and opens on a pressure drop to shut
down the system when a low pressure condition
occurs. In addition, if the microprocessor monitors a
pressure less than 10 psig (0.68 bar)by the suction
pressure transducer mounted in the evaporator
section, the system will be shut down for at least one
minute.
b. Fuses and Circuit Breakers
The system is protected against high current by an
OEM supplied 125 amp fuse or circuit breaker.
Independent fuses or circuit breakers protect each
evaporator blower motor and condenser motor
assembly. 5 amp fuses protect each relay board
output, 10 amp fuses protect ignition circuit output.
c. Ambient Lockout
The ambient temperature sensor located in the
condenser section measures the condenser inlet air
temperature. When the temperature has fallen below
the cut out set point the compressor is locked out
until the temperature rises above the cut in setting.
The set points will be programmed to cut out at 45
°
F
〈
7.2
°
C) and cut in at 50
°
F
〈
10
°
C). This setting
protects the compressor from damage caused by
operation at low pressures.
d. Water Temperature Switch (WTS)
When the the engine coolant temperature has fallen
below the cut out set point, the evaporator fans are
locked out until the temperature rises above the cut
in set point. The set point will be programmed to cut
in at 105
°
F (41
°
C).
