Hitachi RAM-40QH5 Service Manual page 30

DEFROST
Reversing valve defrost system is employed: it consists of balancing period → reversing cycle period →
G
balancing period.
(1) Defrost start condition
When all the following conditions are established, defrost is executed:
G
Normal operation
1
Heat exchange temperature is within defrost range specified by outdoor temperature and heat exchange
2
temperature.
Defrost inhibit period linked to outdoor temperature has passed.
3
(2) Defrost release condition
If any one of the following conditions is established, defrost is released:
G
Heat exchange temperature returns (heat exchange temperature
1
Defrost max time of 12 minutes has elapsed.
2
Released by condition
G
to initial condition (ASTUS = 0).
Released by condition
G
(3) Outputs during defrost
Indoor defrost request: Transmitted to all units being operated in heating mode.
G
Compressor: Balancing period for [TDF414] seconds → Starting of reversing cycle period by [SDRCT2]
G
min
remaining reversing cycle period until defrost MAX speed [DEFMAX] is reached →
Balancing period for [TDF415] seconds
Electric expansion valve
G
Unit being stopped : [FULL CLOSE] 30 seconds after balancing period has passed →
Unit being operated : [DFCTPS] 30 seconds before balancing period is finished →
during balancing period: When remaining balancing period has elapsed, returned
1
or during reversing cycle period: Shifted to balancing period.
1 2
for [TSKTM2] seconds → Accelerating by [DFCTEP] min
–1
[FULL CLOSE] during reversing cycle period → [PCLOSH] 15 seconds
before balancing period is finished.
Synchronized with step-up of rotation speed of compressor, opened
by [DFSPPS] pulses and reaches MAX opening degree [DEFSMX]
when rotation speed of compressor reaches [DEFMAX].
DEFOFF).
– 36 –
–1 / [TDFSPT] seconds in