Mitsubishi Electric PU(H)Y-P250YGM-A, Service Handbook

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[
VII
Control ]
-7- Capacity Control of Outdoor Fan and Heat Exchanger
(1) Control method
ΠThe outdoor fan air flow rate is controlled to keep constant evaporation temperature during cooling operation and to keep
constant condensing temperature during heating operation.
ΠThe 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
ΠOutdoor unit fan stops while the compressor is stopped (except in the presence of input from snow sensor).
ΠThe fan operates at full speed for 5 seconds after start-up.
ΠThe outdoor unit fan stops during defrost operation.
(3) Capacity control of outdoor heat exchanger
Notes:
ΠThe unit runs a cooling cycle when 21S4b and 21S4c are not powered and runs a heating cycle when it is powered.
ΠSV5b and SV5c are open when it is not powered and is closed when it is powered.
ΠWhile 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>)
ΠThe amount of super heat is controlled and kept constant based on the bypass outlet temperature (TH8) of subcool coil
every 30 seconds.
ΠThe 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.
ΠThe LEV stays open at 480 during defrost operation.
[P500 model]
Operation
mode
Heat exchanger
capacity
Number of fans Inverter control Notes
Cooling 50% 1 5-100% 21S4b ON, 21S4c OFF
SV5b ON, SV5c OFF
100% 2 10-100% 21S4b OFF, 21S4c OFF
SV5b OFF, SV5c OFF
Heating 100% 2 10-100% 21S4b ON,21S4 ON
SV5b OFF, SV5c OFF
Defrost 100% 0 0% 21S4b OFF, 21S4c OFF
SV5b OFF, SV5c OFF