Hitachi RAM-52QH5, Service Manual

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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.
When all the following conditions are established, auto-fresh is executed:
Defrost request signal is present.
Start conditions for auto-fresh (1)
15 minutes of auto-fresh inhibit period has elapsed.
All indoor units are stopped.
1
3
2
Compressor delay command is sent from indoor unit when operation is stopped.
Compressor is ON when operation is stopped.
5
4
If any one of following conditions is established, auto-fresh is released:
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
reaches MAX opening degree [DEFSMX] when rotation speed of compressor reaches [DEFMAX].
Heat exchange temperature returns (heat exchange temperature
≥
DEFOFF)
Release condition of auto-fresh (2)
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
-1
/TDFSPT seconds and reaches defrost MAX speed [DEFMAX].
[Electric expansion valve]:
(3)
Failure occurred.
12 minutes of defrost MAX time has elapsed.
1
3
2
Shifted to auto-fresh in defrost mode when operation is stopped.
Note (4)
All indoor units must be stopped to fulfill condition for auto-fresh.
If signal is delayed, auto-fresh condition will not be established.
Either unit 1 or unit 2 or unit 3 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. 4
Unit 1
Unit 2
Unit 3
Unit 1
Unit 2
Unit 3
Unit 1
Unit 2
Unit 3
Compressor
rotation speed
Outdoor fan
Heating output
Cooling output
Defrosting signal
R
equest
R
ev
er
sing
valv
e
Oper
a
tion
Compressor
Turns on for
cooling
Balancing period 3min.
Balancing period [TDF414] sec. Auto-fresh inhibit period 15min.
DEFMAX
Reverse cycle period (max. 12 minutes)
TSKTM2
SDRCT2 WMAX1
WMAX2
WMAX3
30sec.
30sec.
80sec.
Hold
Hold
DFCTPS$
DFPSMX$
DFSPPS$ Pulse
30sec.
15sec.
Defrosting sequence
DFSTEP min
-1 /
TDFSPT sec.
Defrosting request Balancing request
Balancing request
Balancing request
Unit 1
Unit 2
Unit 3
Electric e
xpansion valv
e
480
0
480
0
480
520
520
520
0
MODEL RAM-53QH5