Hitachi RAM-68NP3B, Service Manual, Page: 38 / 79

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DEFROST
(2) Defrost release condition
(2) Output during defrost
degree [DFPSMX_d] when rotation speed of compressor reaches [DEFMAX]
of rotation speed of compressor, opened by [DFSPPS_d] pulse and reaches MAX opening
Unit being operated : [DFCTPS_d] 30sec before balancing period is finish →Synchronized with step-up
cycle period → [PCLOSH_d] 15 sec before balancing period is finished.
Unit being stopped : [FULL CLOSE] 30sec after balancing period has passed → [FULL CLOSE] during reverse
* indicate number of operating indoor unit
• Compressor: Balancing period for [TDF414_*U] (min-1) → Star;ng of reverse cycle period by [SDRCT2] (min-1) for
• Indoor defrost request: Transmitted to all units being operated in heating mode.
• Released by condition ① or ② during reverse cycle period: [TDF415_*U] shifted to balancing period.
• Electric expansion valve
period until defrost MAX speed [DEFMAX] is reached → Balancing period for [TDF415_*U](sec).
[TSKTM2] (sec) → Accelera;ng by [DFSTEP](min-1) for dura;on [TDFSPT](sec) in remaining reverse cycle
③ Defrost inhibit period linked to outdoor temperature has elapsed.
condition (ASTUS = 0).
• Released by condition ① during balancing period: When remaining balancing period has elapsed, returned to initial
② Defrost max time of 12 minutes has elapsed.
① Heat exchange temperature returns (heat exchange temperature ≥ DEFOFF).
• If any of the following conditions is established, defrost is released:
(1) Defrost start condition
Reversing valve defrost system is employed: it consists of balancing period → reversing cycle period → balancing period.
① Normal operation
• When all the following conditions are established defrost is executed:
② Heat exchange temperature is within defrost range specified by outdoor temperature and heat exchange temperature.
(Defrost signal occurred).
RAM-68NP3B