Hitachi RAM-60QH4 Manuel De Service page 62

AUTO-FRESH DEFROST
• During heating operation is stopped, and when auto-fresh condition is established, defrost operation will be performed while
operation is stopped.
Auto-fresh consists of balancing period at start of defrost for [TDF414] seconds → Reverse cycle period for MAX 12
minutes.
(1) Start conditions for auto-fresh
• When all the following conditions are established, auto-fresh is executed:
①Defrost request signal is present.
②All indoor units are stopped.
③15 minutes of auto-fresh inhibit period has elapsed.
④ Compressor is ON when operation is stopped.
⑤Compressor delay command is sent from indoor unit when operation is stopped.
(2) Release condition of auto-fresh
• If any one of following conditions is established, auto-fresh is released:
①Heat exchange temperature returns (heat exchange temperature ≧ DEFOFF)
②12 minutes of defrost MAX time has elapsed.
③Failure occurred.
④ Either unit 1 or unit 2 started operation.
※ Released during start of balancing period : Stopped or started after remaining balancing period has elapsed.
Released during reverse cycle period : Stopped or started after balancing for 3 minutes.
(3) Outputs during auto-fresh
[Indoor unit defrost request]: Transmitted only to unit to which auto-fresh is applied (indoor unit stopped last).
[Compressor]: Accelerated by DFSTEP min
[Electric expansion valve]:
Unit auto-fresh not applied: FULL CLOSE when balancing for 30 seconds has elapsed at start of defrost.
Unit auto-fresh applied : Synchronized with step-up of rotation speed of compressor, opened by [DFSPPS] pulses and
(4) Note
• Shifted to auto-fresh in defrost mode when operation is stopped.
• All indoor units must be stopped to fulfill condition for auto-fresh.
If signal is delayed, auto-fresh condition will not be established.
Defrosting signal
Unit 1
Unit 2
Unit 1
Unit 2
Unit 1
Unit 2
Turns on for
cooling
Cooling output
Heating output
Outdoor fan
Auto-fresh inhibit period 15min.
WMAX2
Compressor
rotation speed
520
480
Unit 1
0
520
480
Unit 2
＋100rpm
0
-1 /TDFSPT seconds and reaches defrost MAX speed [DEFMAX].
reaches MAX opening degree [DEFSMX] when rotation speed of compressor reaches [DEFMAX].
15sec.
Balancing period [TDF414] sec.
WMAX1
30sec.
60sec.
Hold
Hold PCLOSH$
Defrosting request
Reverse cycle period (max. 12 minutes)
Defrosting sequence
30sec. TSKTM2
DFSTEP min
TDFSPT sec.
SDRCT2
DFSPPS$ Pulse
Hold
DFCTPS$
Hold
– 74 –
Balancing request
Balancing request
Balancing period 3min.
DEFMAX
-1 /
80sec.
DFPSMX$
30sec.