Heating Mode - Carrier 40MAQ Series Service Manual

Compressor Operation in Cooling Mode:
In cooling mode, the maximum operation frequency (Fmax) of the
compressor, after it starts running, depends on the outdoor ambient
temperature (T4).
Once the system starts running, the compressor will run at the Fmax
frequency for 7 minutes at a specific T4. During this time, the
frequency limitation is active, therefore the compressor will continue
running even if the set point condition is satisfied. The compressor
running frequency will then be controlled based on the difference
between the room temperature and the temperature set point (T1- Ts).
Outdoor Fan Operation in Cooling Mode:
When in cooling mode, the outdoor fan motor cycles based on the
outdoor ambient temperature as shown below:
°F °F
72
68
Fig. 27 – Outdoor Fan Motor Cycles
Indoor Fan Operation in Cooling Mode:
When in cooling mode, the indoor fan runs continuously either at
the chosen set speed (high, medium, or low), or in Auto mode,
where the speed is determined by the microprocessor based on the
difference between the room temperature and the temperature set
point as shown below:
4
High
3
1.5
1
Fig. 28 – Indoor Fan Operation

HEATING MODE

In this mode, the system heats the room air with the indoor fan
running at either the selected speed or on Auto. As in the cooling
mode, the indoor fan will run continuously unless interrupted by
the cold blow algorithm. This algorithm will not allow the fan to
run if the indoor coil temperature drops below a preset value.
Defrost is controlled by the on- board microprocessor.
High
Low
Medium
Low
Compressor Operation in Heating Mode
In heating mode, the maximum operation frequency (Fmax) of the
compressor, after it starts running, depends on the outdoor ambient
temperature (T4).
Once the system starts running, the compressor will run at the
Fmax frequency for 7 minutes at a specific outdoor ambient
temperature (T4). During this time, the frequency limitation is
active, therefore the compressor will continue running even if the
set point condition is satisfied. The compressor running frequency
will then be controlled based on the difference between the room
temperature, the temperature set point, and a temperature difference
that takes a default value of 32_F (T1- Ts- ΔT).
Outdoor Fan Operation in Heating Mode
When in heating mode, the outdoor fan motor cycles based on the
outdoor ambient temperature as shown below:
°F
63
59
Fig. 29 – Indoor Fan Motor Cycles
Indoor Fan Operation in Heating Mode
In heating mode, the indoor fan runs depending on the evaporator
coil temperature (T2).
If the set point conditions are satisfied and the compressor stops,
the indoor fan will be forced to run for two minutes with breeze.
During this period, the anti- cold- wind is disabled.
If the machine is running at the rated capacity test mode, the indoor
fan will run at the rated speed and the anti- cold- wind function is
disabled.
Auto Mode in Heating Mode
In heating mode, when the fan speed is set to Auto, the fan will run
at a speed determined by the microprocessor based on the
difference between the room temperature and the temperature set
point as shown below:
2.5
2
1.5
1
Fig. 30 – Auto Mode
26
Low
High
Low
Medium
High