Test Mode For Electric Motors; Modes Of Operation - PREVOST H3-41 Maintenance Manual

display. This feature can be used when the
vehicle is traveling to check the A/C compressor
pressure values.
In test mode, with the parking brake applied and
the passenger set point set to a value higher
than 64°F (18°C), the hot water circulating pump
is not set to OFF as it would normally do when
the outside temperature gets above 50°F (10°C).
This feature allows verification of the pump
when inside a garage. This is also useful 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.
5.6

MODES OF OPERATION

COOLING DEMAND
Conditions for engaging the
2 speed on the evaporator
nd
motor
HEATING DEMAND
Conditions for hot
circulating pump activation
The compressor unloader
operation is based
pressure and on
difference between
passengers'
temperature and set point.
A/C compressor deactivation
pressure
Compressor turns
automatically if (2 required
conditions)
- The 2 speed engages if the passengers' area temperature is
nd
1 degree above the set point and it revert to speed 1 if the
temperature gets equal or below the set point.
- The pump turns ON if the outside temperature is equal or less
than 50°F (10°C), when heating is more likely to be needed
water
Note: To test pump operation, it is possible to keep it active
even if the outside temperature is above 50°F (10°C). See
paragraph 5.2 ON DEMAND ACTIVATION OF HOT WATER
CIRCULATING PUMP.
Right compressor cylinders
on
- Stop if: The passengers' area decreasing temperature
the
becomes less than 0.4°F above the set point (68°F) or if
the
compressor discharge pressure is above 290 psi, or if
area
compressor suction pressure is below 23 psi.
- Restart if: The Passengers' area temperature is 1.3°F or more
above the set point and compressor discharge pressure is less
than 250 psi and compressor suction pressure is above 32 psi.
- 310 psi
- In case of high pressure, the high pressure transducer
connected to the multiplex module deactivates the compressor
- There is also a 350 psi pressure switch that acts to stop the
compressor in the instance that the multiplex module fails.
on outside temperature is above 32°F
and
return air temperature in passengers' area is 61°F or above
(∆T=7° with set point)
PA1621 Maintenance Manual All Series | Revised February 2019
SECTION 22: HEATING AND AIR CONDITIONING
5.5 TEST MODE FOR ELECTRIC
MOTORS
The test mode allows testing the motors and
electric contactors without the need to have the
engine running.
Use this test mode for testing of the condenser
fans, evaporator fans, overhead compartment
fans, A/C compressor clutch activation, A/C
compressor unloader activation, driver's unit hot
water solenoid valve and refrigerant solenoid
valve, passengers' unit hot water solenoid valve
and refrigerant solenoid valve, water circulating
pump. Refer to Section 06: ELECTRICAL under
"TEST MODE FOR ELECTRICAL MOTORS" for
complete information.
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