Daikin ComfortNet DX18TC Service Instructions Manual page 27

SYSTEM OPERATION
EXPANSION VALVE/CHECK VALVE ASSEMBLY EXPANSION VALVE/CHECK VALVE ASSEMBLY
IN COOLING OPERATION
IN HEATING OPERATION
Most expansion valves used in current Daikin Brand Heat Pump products
use an internally checked expansion valve.
This type of expansion valve does not require an external check valve as shown above.
However, the principle of operation is the same.
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