Hitachi RAM-60QH4 Manuel De Service page 58

DEFROST
･Reversing valve defrost system is employed: it consists of balancing period →reversing cycle period → balancing period.
(1) Defrost start condition
･ When all the following conditions are established, defrost is executed:
①Normal operation
② Heat exchange temperature is within defrost range specified by outdoor temperature and heat exchange temperature.
③Defrost inhibit period linked to outdoor temperature has passed.
(2) Defrost release condition
･ If any one of the following conditions is established, defrost is released:
①Heat exchange temperature returns (heat exchange temperature ≧ DEFOFF).
② Defrost max time of 12 minutes has elapsed.
･Released by condition ① during balancing period: When remaining balancing period has elapsed, returned to initial
condition (ASTUS=0).
･ Released by condition ① or ② during reversing cycle period: [TDF415] Shifted to balancing period.
(3) Outputs during defrost
･Indoor defrost request: Transmitted to all units being operated in heating mode.
･Compressor : Balancing period for [TDF414] seconds → Starting of reversing cycle period by [SDRCT2] min
[TSKTM2] seconds → Accelerating by [DFSTEP]min
period until defrost MAX speed [DEFMAX] is reached → Balancing period for [TDF415] seconds
･Electric expansion valve
Unit being stopped : [FULL CLOSE] 30 seconds after balancing period has passed → [FULL CLOSE] during
Unit being operated : [DFCTPS] 30 seconds before balancing period is finished → Synchronized with step-up
reversing cycle period → [PCLOSH$] 15 seconds before balancing period is finished
of rotation speed of compressor, opened by [DFSPPS] pulses and reaches MAX opening
degree [DEFSMX] when rotation speed of compressor reaches [DEFMAX].
/[TDFSPT] seconds in remaining reversing cycle
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