Hitachi RPI-0.8FSG1 Service Manual page 367

[Countermeasure]
Perform the heat load calculation with the decreased capacity as shown in the graph in page 5-8.
Do not install the unit in such a place where temperature difference among rooms is big and the heat
load when cooling and heating is excessively big during simultaneous COOL/HEAT operation.
(2) Influence by ON/OFF Operation of Other Rooms:
[Phenomenon]
During the simultaneous cooling and heating operation, the actual capacity of the indoor units in
operation is decreased for a short time due to the influence of heat balance when the cooling or
heating operation when some other indoor units is started or stopped, or thermo-ON/OFF.
[Countermeasure]
The following conditions and the system as shown below are not appropriate for FXG/FX3 series,
since other indoor units may be influenced by the indoor unit.
Therefore, it is recommended that different air conditioning systems be selected.
(a) There is a room where the heat load change is big and ON/OFF operation of indoor unit is
excessively frequent.
(b) where capacity decrease for a short time according to ON/OFF operation of other rooms is not
allowed. However, this system can be applied to a room where gradual heat load change is given,
such as a heating operation in the morning, cooling operation during daytime and heating operation
in the evening.
[Example]
In case that the mainly cooling operation is changed to the mainly heating operation especially when
the big capacity indoor unit (ex.: 5HP) is stopped at cooling operation or thermo-OFF, the outdoor heat
exchanger is changed from condenser to evaporator functions and the cooling capacity of other indoor
units in continuous cooling operation is excessively decreased.
10HP Outdoor Unit
Indoor Unit 5HP
Cooling
ON / OFF
Mainly Mainly
Cooling Heating
ON OFF ON
100%
Approx. 10min.
100%
80%
FIELD WORK INSTRUCTION
CH Unit
3HP 1HP
Heating Cooling
(Continuous) (Continuous)
OFF ON
5HP Cooling Unit
Thermo ON /OFF
1HP Cooling Unit
Continuous Operation
5-7