PREVOST X3-45 Multiplex, Maintenance Manual

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Section 22: HEATING AND AIR CONDITIONING
PA1562
10
when working on the heating system to remove
air pockets trapped in the system.
When performing an A/C cooling test and having
the water pump shut off in switch/sensor test
mode is required, just set the passenger set
point temperature to the minimum 64°F (18°C)
to shut off the pump.
5.2 HVAC SYSTEM AND TEST MODE FOR
ELECTRIC MOTORS
The test mode allows testing the motors and
electric contactors without the need to have the
engine running (see Section 06: ELECTRICAL
under "TEST MODE FOR ELECTRICAL
MOTORS" for complete information).
Use this test mode for testing of the condenser
motors, the A/C compressor clutch activation,
left and right unloaders, evaporator motor, water
pump, hot water solenoid valve and overhead
compartment air register fan.
5.3 PARTICULARITIES
Conditions for engaging the
2
nd
speed on the evaporator
motor (cooling demand).
The 2
nd
speed engages if the passenger's area temperature is 1
degree above the set point and it revert to speed 1 if the temperature
gets equal or below the set point.
Conditions for hot water
recirculating pump activation
(heating demand). The pump turns to OFF if the outside temperature is above 50°F
(10°C), when there is less demand for heating.
Note: To test a working pump, it is possible to keep it active even if
the outside temperature is above 50°F (10°C). See paragraph 5.2
HVAC SYSTEM AND TEST MODE FOR ELECTRIC MOTORS.
The compressor unloaders are
working based on pressure
and also on the difference
between the passenger's area
temperature and the set point. 2 left compressor cylinders:
Stop if: Passenger's area temperature is at less than 0.4°C degree
above the set point or if the compressor output is above 280 psi, or if
the compressor input is below 26 psi.
Restart if: Passenger's area temperature is 0.9°C or more above the
set point and the compressor pressure output is less than 220 psi and
the compressor pressure input is above 34 psi.
2 right compressor cylinders:
Stop if: Passenger's area temperature is at less than 0.2°C above the
set point or if the compressor input falls below 23 psi.
Restart if: Passenger's area temperature is 0.7°C or more above the
set point and the compressor input pressure is above 32 psi.
The A/C deactivation pressure
is 320 psi. In case of high pressure, the analog pressure sensor connected to
the Multiplex module deactivates the compressor.
There is also a « Pressure switch » adjusted to 350 PSI that acts to
stop the compressor in the instance that the Multiplex module fails.