Capacity Control Of Outdoor Fan And Heat Exchanger; Subcool Coil Control (Linear Expansion Valve) - Mitsubishi Electric PU(H)Y-P250YGM-A Service Handbook

[ VII Control ]

-7- Capacity Control of Outdoor Fan and Heat Exchanger

(1) Control method
The outdoor fan air flow rate is controlled to keep constant evaporation temperature during cooling operation and to keep
constant condensing temperature during heating operation.
The capacity of the heat exchanger on the P500 model of outdoors is controlled by the 4-way valve (21S4b) or the sole-
noid valve (SV5b).
(2) Control
Outdoor unit fan stops while the compressor is stopped (except in the presence of input from snow sensor).
The fan operates at full speed for 5 seconds after start-up.
The outdoor unit fan stops during defrost operation.
(3) Capacity control of outdoor heat exchanger
[P500 model]
Operation
mode
Cooling
Heating
Defrost
Notes:
The unit runs a cooling cycle when 21S4b and 21S4c are not powered and runs a heating cycle when it is powered.
SV5b and SV5c are open when it is not powered and is closed when it is powered.
While the unit is stopped, 21S4b and 21S4c are not powered cooling cycle, and SV5b and SV5c are open.
-8- Subcool Coil Control (Linear Expansion Valve <LEV1>)
The amount of super heat is controlled and kept constant based on the bypass outlet temperature (TH8) of subcool coil
every 30 seconds.
The degree of opening is controlled based on the subcool coil outlet/inlet temperature (TH5, TH7), high pressure (Pd), and
discharge temperature. The LEV will be closed (0) during heating operation and when the compressor is stopped, and it
will be open during cooling operation with Thermo off.
The LEV stays open at 480 during defrost operation.
Heat exchanger Number of fans
capacity
50%
100%
100%
100%
Inverter control
1 5-100%
2 10-100%
2 10-100%
0 0%
- 84 -
Notes
21S4b ON, 21S4c OFF
SV5b ON, SV5c OFF
21S4b OFF, 21S4c OFF
SV5b OFF, SV5c OFF
21S4b ON,21S4 ON
SV5b OFF, SV5c OFF
21S4b OFF, 21S4c OFF
SV5b OFF, SV5c OFF