SECTION 22: HEATING AND AIR CONDITIONING
DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Final Version – Rev.2 April 2016)
15
5.4 MODES
OF
OPERATION
COOLING DEMAND
Conditions for engaging the 2
nd
speed on the evaporator motor
The 2
nd
speed engages if the passengers' 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.
HEATING DEMAND
Conditions for hot water
circulating pump activation
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
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.
The compressor unloader
operation is based on pressure
and on the difference between
the passengers’ area
temperature and set point.
right compressor cylinders
Stop if: The passengers’ area decreasing temperature becomes less
than 0.4°F above the set point (68°F) or if compressor discharge
pressure is above 280 psi, or if 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 220 psi
and compressor suction pressure is above 32 psi.
A/C compressor deactivation
pressure
320 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.
Compressor turns on
automatically if (2 required
conditions)
outside temperature is above 32°F
and
return air temperature in passengers’ area is 61°F or above (
∆
T=7°
with set point)
passengers’ area temperature
set point
68°F
