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3. Compressor Control
3-6-2. Condensation Temperature (Tc) Control:
Control when there are indoor units operating in Heating mode
PX = 125.6 ˚F
PX
*
Depending on the maximum requirement level
of the indoor unit, the judgment temperatures
for each area may vary as shown in the figure
(example).
(1) For indoor units which are operating in Heating mode, if one unit is selected for a test run, the air intake
temperature difference is ignored, however Tc control is performed according to the figure above in order to
prevent excessive load. (This is used for test run checks, etc.)
(2) Even within the same area, the compressor capacity varies depending on the refrigerant temperature.
(3) Temperature PX is the coefficient value used to correct for any deviation with the high pressure or condensation
temperature. It may vary. (At the time of shipment it is 125°F.)
(4) If the condensation temperature (Tc) enters area D and the thermostat turns OFF, the next time the compressor
starts it may restart from a lower capacity.
(5) When the area changes to area C, area C is considered to be area B for control purposes for the first 6
minutes, even if the horsepower is the minimum value within the range where capacity control is possible
(operation with inverter frequency of 25 Hz only). Subsequently if C area continues, the thermostat turns OFF.
3-6-3. Control of condensation temperature and evaporation temperature during mixed cooling/heating
operation
During mixed cooling/heating operation, the control maintains a heat balance with a target evaporation temperature
(Te) for the Cooling mode indoor units of 35 ~ 42°F and a target condensation temperature (Tc) for the Heating
mode indoor units of 116 ~ 118°F.
Heat balance control is performed by varying the compressor capacity and heat discharge (heat intake) of the heat
exchanger.
(1) Increasing/decreasing the compressor capacity
• When evaporation temperature (Te) is high and condensation temperature (Tc) is low
This occurs when both the cooling capacity (heat intake) and the heating capacity (heat discharge) are low.
The compressor capacity and the circulation flow of refrigerant are increased in order to lower the evaporation
temperature (Te) and raise the condensation temperature (Tc).
• When evaporation temperature (Te) is low and condensation temperature (Tc) is high
This occurs when both the cooling capacity (heat intake) and the heating capacity (heat discharge) are
high. The compressor capacity and the circulation flow of refrigerant are decreased in order to raise the
evaporation temperature (Te) and lower the condensation temperature (Tc).
* Under conditions other than those listed above, the capacity of the outdoor unit heat exchanger is adjusted.
In some cases the heat exchanger capacity may also be adjusted at the same time when the compressor
capacity is varied.
Thermostat OFF
–0.1
Horsepower decrease
118.5
118.4
Horsepower increase
prohibited
116.6
116.4
Horsepower increase
permitted
113.0
112.8
Horsepower increase
permitted
Area D
Area C
Area B
Area AB
100.4
Area A
98.6
0
15
Maximum requirement level [L]
1 - 7
3-WAY ECO-i SYSTEM
Control Functions
118.4
116.6
109.4
107.6
30
1
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