Panasonic U-8ME1E81 Service Manual page 14

3. Compressor Control
3-4. Operating frequency range of inverter compressor
- When one of the constant speed compressor mounted in the outdoor unit do not operate:
The inverter compressor can operate between 15Hz and 95Hz.
- When all constant speed compressors mounted in the outdoor unit operate:
The inverter compressor can operate within the range shown in the table below.
Outdoor Unit Capacity
Min.frequency
1
Max.frequency
*The inverter frequency during operation may be lower than the frequency listed above due to overload current
protection control.
3-5. Forced Compressor Stop
Once a compressor stops, it will not start for a period of 3 minutes (3-minute forced OFF). However, this does
not apply when the compressor was forced to stop as the result of a control operation during the special controls
(start control, defrost control, refrigerant oil recovery control, etc.)
3-6. Capacity Control (Roadmap control)
The capacity control by the compressors is performed according to the pressure sensor attached to the outdoor
unit and temperature thermistor attached to the indoor / outdoor unit heat exchanger.
* With roadmap control, the pressure detected by the pressure sensor is converted to saturation temperature
before it is used by microcomputer. This converted temperature is called "pressure sensor temperature".
This control is performed every 30 seconds.
- Required level of each indoor unit
Required level of indoor unit is calculated by difference between preset temperature in remote controller and
intake temperature of indoor unit (that is called "DTi"), difference between preset discharge air temperature in
EEPROM on indoor unit PCB and discharge air temperature of indoor unit (that is called "DTo").
Required level has "0" to "30" phases. This level becomes "31" at the test run.
The target temperature of indoor unit heat exchanger is decided according to the maximum required level.
*Target temperature of all indoor units heat exchanger is same value because all indoor units are connected with
same pressure piping.
- Definition of evaporation temperature and condensation temperature
Evaporation temperature (Te): The lowest temperature of heat exchangers (E1, E3) in all indoor units including
Condensation temperature (TC): This depends on the operating mode.
3-6-1. Evaporation temperature adjustment by roadmap control
The cooling capacity is adjusted with this control. It prevents freezing of the indoor unit's heat exchanger and the
dew to the outside panel of the indoor unit. The capacity is adjusted according to the following figure.
8HP 10HP 12HP 14HP 16HP 18HP 20HP
15
68.8 82.0 66.1 71.7
stopped indoor units.
Cooling mode: The highest temperature of high pressure sensor temperature in outdoor
units.
Heating mode: The highest temperature of high pressure sensor temperature in outdoor
units and the indoor unit heat exchanger liquid temperatures (E1)
excluding stopped indoor units.
* The E3 in indoor heat exchanger may indicate superheated gas temperature. Therefore it
is not included for detection of Tc.
Control Functions - Outdoor Unit
16
79.0 67.4 67.4
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2WAY SYSTEM