Panasonic U-8MF2E8 Service Manual page 14

3. Compressor Control
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.
1
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 the same pressure piping.
Definition of evaporation temperature and condensation temperature
Evaporation temperature (Te):
Shows the lowest temperature among the temperature sensors (E1 or E3) when the indoor unit heat exchanger
is functioning as an evaporator.
* When operating in mixed cooling/heating mode and the outdoor units are mixed evaporators, the outdoor unit
heat exchanger temperature is not recognized as "Te".
Condensation temperature (Tc):
Shows the highest temperature among the high-pressure saturated temperature in the system and indoor unit
heat exchanger's liquid tube temperature (E1) with the thermostat ON.
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.
Evaporation temperature area
*The evaporation temperature area changes depending on the maximum required level of each indoor unit as
shown in the right figure.
*C area is regarded as B area for 6 minutes after compressor starts.
*When the system operates in a minimum capacity, the system will continue operating for at least 6 minutes if the
evaporation temperature area is C area.
*The evaporation temperature is not adjusted while specially controlling defrosting and the oil recovery, etc.
*The evaporation temperature is not adjusted when there are one or more indoor units that select the test run.
If one or more indoor units are selected into test run, the system doesn't stop in all states except alarm appearing.
*The test run will finish automatically in about one hour.
deg
Compressor capacity can increase
6.5
Te_tgt_max. 6.0
Compressor capacity
cannot increase
Te_tgt_min. 3.0
2.5
Compressor capacity decreases
A area
B area
C area
1 - 6
3WAY SYSTEM
Control Functions
16.0
13.0
11.0
8.0
0
15 30
Max. required level
6.0
3.0