Hitachi RAD-25NH4, RAC-25NH4, RAD-40NH4, RAC-50NH4 Service Manual

NO. 0214E

SPECIFICATIONS AND PARTS ARE SUBJECT TO CHANGE FOR IMPROVEMENT

ROOM AIR CONDITIONER

INDOOR UNIT + OUTDOOR UNIT

JUNE 2004

Refrigeration & Air-Conditioning Division

SERVICE MANUAL

PM

REFER TO THE FOUNDATION MANUAL

TECHNICAL INFORMATION

FOR SERVICE PERSONNEL ONLY

(W)

(A)

(kW)

(B.T.U./h)

(W)

(A)

(kW)

(B.T.U./h)

W

H

D

(kg)

RAD-25NH4 RAC-25NH4

DC INVERTER (CEILING CASSETTE TYPE)

TYPE

MODEL

POWER SOURCE

TOTAL INPUT

TOTAL AMPERES

CAPACITY

TOTAL INPUT

TOTAL AMPERES

CAPACITY

DIMENSIONS
(mm)

NET WEIGHT

SPECIFICATIONS

750

235

400

19

RAD-25NH4
RAD-40NH4

CONTENTS

SPECIFICATIONS ------------------------------------------------------------------- 4

HOW TO USE ------------------------------------------------------------------------ 6

CONSTRUCTION AND DIMENSIONAL DIAGRAM ---------------------- 25

MAIN PARTS COMPONENT --------------------------------------------------- 27

WIRING DIAGRAM -----------------------------------------------------------------29

CIRCUIT DIAGRAM ---------------------------------------------------------------- 31

PRINTED WIRING BOARD LOCATION DIAGRAM ---------------------- 37

BLOCK DIAGRAM ------------------------------------------------------------------ 39

BASIC MODE ------------------------------------------------------------------------ 41

REFRIGERATING CYCLE DIAGRAM ---------------------------------------- 55

AUTO SWING FUNCTION ------------------------------------------------------- 57

DESCRIPTION OF MAIN CIRCUIT OPERATION ------------------------ 58

SERVICE CALL Q & A ----------------------------------------------------------- 89

TROUBLE SHOOTING ------------------------------------------------------------ 92

PARTS LIST AND DIAGRAM ------------------------------------------------- 112

RAD-25NH4/RAC-25NH4
RAD-40NH4/RAC-50NH4

RAC-25NH4
RAC-50NH4

COOLING

HEATING

INDOOR UNIT

OUTDOOR UNIT

INDOOR UNIT

OUTDOOR UNIT

1 PHASE, 50 Hz, 220-240V

720 (220~980)

3.31-3.03

2.50 (1.00 ~ 3.00)

8,540

1,000 (210 ~ 1,280)

4.59-4.21

3.80 (1.10 ~ 4.80)

12,980

750

570

280

38

750

235

400

19

850

650

298

60

1 PHASE, 50 Hz, 220-240V

1,400 (220~1,560)

6.43-5.89

4.00 (1.00 ~ 4.50)

13,660

1,770 (210 ~ 1,920)

8.13-7.45

5.20 (1.10 ~ 5.80)

17,750

RAD-40NH4 RAC-50NH4

SAFETY DURING REPAIR WORK

1. In order to disassemble and repair
the unit in question, be sure to
disconnect the power cord plug
from the power outlet before starting
the work.

2. If it is necessary to replace any parts, they should be replaced with respective genuine parts for the unit, and
the replacement must be effected in correct manner according to the instructions in the Service Manual of
the unit.

If the contacts of electrical parts
are defective, replace the
electrical parts without trying to
repair them.

3. After completion of repairs, the initial state
should be restored.

4. Lead wires should be connected and laid as
in the initial state.

5. Modification of the unit by user himself should
absolutely be prohibited.

6. Tools and measuring instruments for use in repairs or inspection should be accurately calibrated in advance.

7. In installing the unit having been repaired, be careful to prevent the occurence of any accident such as
electrical shock, leak of current, or bodily injury due to the drop of any part.

8. To check the insulation of the unit, measure the insulation resistance between the power cord plug and
grounding terminal of the unit. The insulation resistance should be 1M or more as measured by a 500V
DC megger.

9. The initial location of installation such as window, floor or the other should be checked for being and safe
enough to support the repaired unit again.
If it is found not so strong and safe, the unit should be installed at the initial location reinforced or at a new
location.

10. Any inflammable thing should never
be placed about the location of
installation.

11. Check the grounding to see whether
it is proper or not, and if it is found
improper, connect the grounding
terminal to the earth.

DANGER

First, I must disconnect
the power cord plug

from the power outlet.

– i –

WORKING STANDARDS FOR PREVENTING BREAKAGE OF SEMICONDUCTORS

1. Scope
The standards provide for items to be generally observed in carrying and handling semiconductors in relative
manufacturers during maintenance and handling thereof. (They apply the same to handling of abnormal goods
such as rejected goods being returned).

2. Object parts

(1) Micro computer
(2) Integrated circuits (IC)
(3) Field-effect transistors (FET)
(4) P.C. boards or the like on which the parts mentioned in (1) and (2) of this paragraph are equipped.

3. Items to be observed in handling

(1) Use a conductive container for carrying and storing of parts. (Even rejected goods should be handled in

the same way).

Fig. 1. Conductive Container

(2) When any part is handled uncovered (in counting, packing and the like), the handling person must always

use himself as a body earth. (Make yourself a body earth by passing one M ohm earth resistance through
a ring or bracelet).

(3) Be careful not to touch the parts with your clothing when you hold a part even if a body earth is being

taken.

(4) Be sure to place a part on a metal plate with grounding.

(5) Be careful not to fail to turn off power when you repair the printed circuit board. At the same time, try

to repair the printed circuit board on a grounded metal plate.

1M

Fig. 2. Body Earth

Body earth
(Elimik conductive band)

Clip for connection with a
grounding wire

IC

A conductive polyvinyl bag

IC

Conductive sponge

– 1 –

(6) Use a three wire type soldering iron including a grounding wire.

Bare copper wire (for body earth)

Working
table

Resistor of 1 M (1/2W)

Earth wire

Fig. 3. Grounding of the working table

2

Screw stop at the screwed
part using a rag plate

Soldering iron

Grounding
wire

Fig. 4. Grounding a soldering iron

Use a high insulation mode (100V, 10M or higher) when ordinary iron is to be used.

(7) In checking circuits for maintenance, inspection or some others, be careful not to have the test probes of the

measuring instrument shortcircuit a load circuit or the like.

Metal plate (of aluminium, stainless steel, etc.)

Staple

– 2 –

1. In quiet operation or stopping the running, slight flowing noise of refrigerant in the refrigerating cycle is

heard occasionally, but this noise is not abnormal for the operation.

2. When it thunders near by, it is recommend to stop the operation and to disconnect the power cord plug

from the power outlet for safety.

3. The room air conditioner does not start automatically after recovery of the electric power failure for

preventing fuse blowing. Re-press START/STOP button after 3 minutes from when unit stopped.

4. If the room air conditioner is stopped by adjusting thermostat, or missoperation, and re-start in a moment,

there is occasion that the cooling and heating operation does not start for 3 minutes, it is not abnormal
and this is the result of the operation of IC delay circuit. This IC delay circuit ensures that there is no
danger of blowing fuse or damaging parts even if operation is restarted accidentally.

5. This room air conditioner should not be used at the cooling operation when the outside temperature is

below 10°C (50°F).

6. This room air conditioner (the reverse cycle) should not be used when the outside temperature is below

–15°C (5°F).
If the reverse cycle is used under this condition, the outside heat exchanger is frosted and efficiency falls.

7. When the outside heat exchanger is frosted, the frost is melted by operating the hot gas system, it is not

trouble that at this time fan stops and the vapour may rise from the outside heat exchanger.

!

CAUTION

– 3 –

SPECIFICATIONS

MODEL

FAN MOTOR

FAN MOTOR CAPACITOR

FAN MOTOR PROTECTOR

COMPRESSOR

COMPRESSOR MOTOR CAPACITOR

OVERLOAD PROTECTOR

OVERHEAT PROTECTOR

FUSE (for MICROPROCESSOR)

POWER RELAY

POWER SWITCH

TEMPORARY SWITCH

SERVICE SWITCH

TRANSFORMER

VARISTOR

NOISE SUPPRESSOR

THERMOSTAT

REMOTE CONTROL SWITCH (LIQUID CRYSTAL)

RAD-25NH4
RAD-40NH4

20W

NO

NO

–

NO

NO

NO

NO

NO

NO

YES

NO

NO

NO

NO

YES(IC)

YES

----------

40 W

NO

NO

NO

YES

YES

3.0A

G4A

NO

NO

YES

NO

450NR

YES

YES(IC)

NO

WITHOUT REFRIGERANT BECAUSE

COUPLING IS FLARE TYPE.

UNIT

PIPES (MAX. 20m)

REFRIGERANT CHARGING
VOLUME
(Refrigerant 410A)

RAC-25NH4 RAC-50NH4

JU1012D JU1013D

1400g1150g

– 4 –

– 5 –

CAUTION

Always install the indoor unit level.
Units not installed level may leak.

9

7

6

5

PLUG

Be sure to com­pletely seal any
gap with putty.

●

The indoor piping
should be insulated
with the enclosed
insulation pipe.
(If the insulator is
insufficient, please
use commercial
products.)

Drain pipe
Must be installed separately.
Insulate indoor part of pipe
to prevent condensation.

Adiabated pipes
must always be
used for both
large and small
diameter. Wrap
pipes with tape.
An adiabator
will weather
excessively if
not tape-wrapped.

●

Maximum pipe length 20m

Minimum pipe length 5m

above 200mm

above 700mm

above 200mm

above 50mm when
installed on the
ceiling of balcony

(

)

above 100mm

above 100mm
give clearance as

wide as possible

Use the holder
when the pipe
is drawn from
the left.

• If connect indoor unit “RAD-40NH4” with outdoor unit “RAC-50NH4”, opitional flare adaptor for piping is

necessary.
Flare adaptor for piping: ø9.52 (3/8”) → ø12.7 (1/2”)

{Parts number TA261D-4 001}

[Indoor unit installation]

– 6 –

– 7 –

– 8 –

FULL DUCT

SEMI DUCT

NON DUCT

– 9 –

– 10 –

an speed f

– 11 –

– 12 –

displa

– 13 –

– 14 –

– 15 –

– 16 –

(ON) mark b

(ON) mar

– 17 –

(ON) mar (RESER

A beep occurs and the (TIMER) lamp lights on the indoor unit.

The setting of the current time

The time indication star

lighting instead of flashing.

(OFF) mar

sign lights A beep occurs and the (TIMER) lamp lights on the indoor unit.

– 18 –

– 19 –

– 20 –

– 21 –

– 22 –

– 23 –

– 24 –

– 25 –

CONSTRUCTION AND DIMENSIONAL DIAGRAM

MODEL RAD-25NH4, RAD-40NH4

Cautions:

1. Use insulated pipes for both large and small diameters.

2. An connection cable.

15

148

235

216

Wide pipe

(

)

Narrow pipe

(

)

24

11

62177

750

20

790

35

70

319

75

40

5

400

Hanger

(

Use for hanging unit

)

28 347

Drain hose

53

Electric box

(

Possible to move,Right side

)

29

73

53

143

Indication panel

56

147

18

Wireless remote controller

Unit: mm

– 26 –

CONSTRUCTION AND DIMENSIONAL DIAGRAM FOR OUTDOOR

MODEL RAC-25NH4

MODEL RAC-50NH4

16556

28 750

852

76

570

95

166

559

2616 280

195

340

280

Handle

Air suction

grille

10464

26 850

955

79

650

96

169.5

638

1010

10

320

340

Air outlet

340

2022 298

201

Handle

Holes for anchor bolt

(2-ø12)

Fixing hole

507 198

57

12
37

Notch for anchor bolt

(2-ø12 Notchs)

More than

More than

More than

100

More than

700

100

100

Service space

– 27 –

MAIN PARTS COMPONENT

THERMOSTAT

Thermostat Specifications

FAN MOTOR

Fan Motor Specifications

CONNECTION

TEMPERATURE
°C (°F)

INDICATION

16

INDICATION

24

INDICATION

32

MODEL RAD-25NH4/RAD-40NH4

THERMOSTAT MODEL IC

OPERATION MODE COOL HEAT

ON 14.9 (59.3) 20.4 (68.8)

OFF 14.3 (58.3) 21.0 (69.1)

ON 22.9 (73.7) 28.4 (83.1)

OFF 22.3 (72.7) 29.0 (84.1)

ON 30.9 (88.1) 36.4 (97.7)

OFF

30.3 (87.1) 37.0 (98.8)

M

RED

YEL

BLU

5V

0~35V

MODEL

RAD-25NH4
RAD-40NH4

POWER SOURCE DC: 0 ~ 35V

DC360V

OUTPUT 20W

40W

BLU : BLUE YEL : YELLOW BRN : BROWN WHT : WHITE

GRY : GRAY ORN : ORANGE GRN : GREEN RED : RED

BLK : BLACK PNK : PINK VIO : VIOLET

RED

360V

BLK

0V

WHT

15V

M

YEL

0~6V

BLU

0~15V

RAC-25NH4
RAC-50NH4

– 28 –

WHITE

RED

YELLOW

MODEL

COMPRESSOR MODEL

PHASE SINGLE

RATED VOLTAGE AC 220 ~ 240 V

RATED FREQUENCY 50 Hz

POLE NUMBER 4

COMPRESSOR MOTOR

Compressor Motor Specifications

CONNECTION

20°C

(68°F)

75°C

(167°F)

( )

RESISTANCE VALUE

!

CAUTION

When the refrigerating cycle has been operated for a long time with the capillary tubes clogged or crushed
or with too little refrigerant, check the color of the refrigerating machine oil inside the compressor. If the
color has been changed conspicuously, replace the compressor.

2M = 1.05

2M = 1.28

(U)

(V)

(W)

M

M

M

WHITE

YELLOW

RED

RAC-25NH4 RAC-40NH4

JU1012D JU1013D

MODEL RAD-25NH4 / RAC-25NH4

RAD-40NH4 / RAC-40NH4

WIRING DIAGRAM

– 29 –

SYSTEM POWER

MODULE 2

RED

BLK

WHT
YEL
BLU

GRN

BLK
BLK

REVERSING
VALVE

FAN
MOTOR

M

BLU : BLUE YEL : YELLOW BRN : BROWN WHT : WHITE
GRY : GRAY ORN : ORANGE GRN : GREEN RED : RED
BLK : BLACK PNK : PINK VIO : VIOLET

INDOOR UNIT

C

RED

BRN

(

BRN

)

(

RED

)

TERMINAL

BOARD

D

BLU

YEL

BLU

YEL

CN16

RED

MAIN
P. W . B .

BLK

WHT

WHT

REMOTE CONTROL

WIRELESS

LIGHT
RECEIVING
UNIT

BLK

BLK

RED

RED

GRY

GRY

CN12

CN8

CN10

EXCHANGER
THERMISTOR

HEAT

THERMISTOR

ROOM TEMP.

BLK

BLK

BLK

M

RED

INDOOR
FAN MOTOR

AUTO SWEEP

(STEPPING MOTOR)

MOTOR(RAD-BD

)

FLOAT SW

M

M

6

WHT

WHT

WHT

WHT

DRAIN
PUMP
M OTOR

CN11A

CN3

CN1

1

HA

CN9

C1 C2 M1 M2

1234

TEST

2

CN5

3 45678

OUTDOOR UNIT

COMPRESSOR

WHT

L2

L1

YEL

RED

WHT

UVW

YEL

YEL

YEL

YEL

R008

C006

C003

L001

CT1

DIODE
STACK

VARISTOR3

MAIN P.W.B.

VARISTOR

C001

C002

R001

R007

COIL

NF
COIL 1

25A
FUSE

SURGE ABSORBER

BRN

C

D

L

RED

BLK

WHT

GRN

N

AC 220-240V

50Hz

CONNECTING

CORD

GREEN &
YELLOW

GREEN &
YELLOW

GREEN &
YELLOW

POWER
RELAY

3A FUSE

ICP

RELAY

REACTOR

RED

C501 C502 C503

CN14 CN14

10

5

5

CN11 CN11

CN12

CN12

2A FUSE

BLU

RED

GRY

DIODE
STACK

CN13 CN13

C011

C010

R002

C007
C012
C014

C008

VARISTOR2

L002

CN6
WHT

C013
C015

R011

CN2
RED

POWER
CIRCUIT

R010

GRY

OUTDOOR
TEMPERATURE
THERMISTOR

DEFROST
THERMISTOR

OH
THERMISTOR

ELECTRIC EXPANSION
VAVLE

CN10

RED

CN9
BLU

CN8
WHT

CN15

WHT

GRY

GRY

GRY

RED

RED

Remote Control

CIRCUIT DIAGRAM

– 31 –

1
2
3
4
5
6
7
8

10
11

13
14
15
16
17

19
20

9

12

18

SEG19
SEG18
SEG17
SEG16
SEG21
SEG24
SEG25
SEG26
SEG27
SEG28

NC
NC
NC
NC
NC
NC
NC
NC
NC

SEG20

SEG5
SEG0

SEG1

SEG2
SEG3
SEG4
SEG5
SEG6

SEG7
COM3
COM2
COM1
COM0

SEG14

SEG13

SEG12

SEG11

SEG13

SEG9

SEG8

40
39
38
37
36
35
34
33

31
30

28
27
26
25
24

22
21

32

29

23

40
39
38
37
36
35
34
33

31
30

28
27
26
25

32

29

64

63

62

61

60

59

58

57

56

55

54

53

52

51

50

49

48 47

46

45

44

43

41

42

65
66
67
68
69
70
71
72

74
75

77
78
79
80

73

76

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17 18

19

20

21

22

24

23

SEG20
SEG21
SEG22
SEG23
SEG24
SEG25
SEG26
SEG27
SEG28
SEG29
SEG30
SEG31
SEG32

SEG33
SEG34

SEG35

SEG19

SEG18

SEG17

SEG16

SEG15

SEG14

SEG13

SEG12

SEG11

SEG10

SEG9

SEG8

SEG7

SEG6

SEG5

SEG4

SEG3

SEG2

SEG1

SEG0

SEG43

SEG42

SEG41

SEG40

P40

P41

P42

P43

P00

P01

P02

P03

P10

P11

P12

P13

D0

D1

D2

D3

D4

D5

D6

D7

D8

D9

BEEP

P20

P30
P31

NCVL C1

VL C2
VL C3

XC IN

XC OUT

VDD

X OUT

X IN

RESET

CARR

P23
P22

P21

VSS

IC 1
M3455OM6A-504FP

LCD 1

C8

50v/1u

K 1
D3
RB425D(1/2)

K2K3

K4

K5

P10

P11

P12

K6

K7 K8

K9 K10

K11K12

K18

K17

K15 K16

K13 K14

D0

D1

D2

D3

R1

100k

SW1

R2

P

100k

R3

100k

R4

100k

R5

Q1
2SC3443
or 2SC2982

R6

R7

R9

D2D1

D1 D2

EL-1L7

D3

(1/2)

RB425D

R10
12M

K19

X1

C9

R11

R15

R16

R13

R14

910kHz

105

104

104

150k

X2

kHz

C4

C5

C6

C7

18p

22p

R12
220k

220K

220k

100k

100k

32.768

C1

C2

C3

220p

220p

334

R6 R9

24(1/8W)

R8

330

SW-187-2P

Key matrix table

Input

D3D2D1

D0

Output

Door open Automatic swingFan speed selectionOperation selectionStart/Stop

Door shut ––Automatic swingStart/Stop

Door open Day

• present timeHour downHour upOn timer

Door shut Fan speedRoom temperature downRoom temperature up–

Door open CancelReservation–Off timer

Door shut –––Sleep

P10

P11

P12

CIRCUIT DIAGRAM

MODEL RAD-25NH4

RAD-40NH4

– 33 –

CIRCUIT DIAGRAM

MODEL RAC-25NH4

RAC-50NH4

– 35 –

– 37 –

PRINTED WIRING BOARD LOCATION DIAGRAM

MODEL RAD-25NH4, RAD-40NH4

MAIN P.W.B.

Marking on P.W.B.

COMPONENT SIDE

SOLDERING SIDE

– 38 –

MODEL RAC-25NH4, RAC-50NH4

MAIN P.W.B. Marking on P.W.B

COMPONENT SIDE

– 39 –

Wireless receive
circuit

Operation.
Timer.

Auto sweep motor for
Air deflector

Drain Pump Motor

LCD wireless

Heat exchanger
thermistor

Room temperature
thermistor

Reset circuit

Initial setting circuit

Temporary switch

Electric Expansion valve
drive circuit

Electric

Expansion

valve

Outdoor microcomputer / HIC (AX-8N00)

Trip signal
synthesis circuit

L

N

RAD-25NH4 / RAC-25NH4
RAD-40NH4 / RAC-50NH4

SPM2

Outdoor
unit
Terminal
board

Indoor microcomputer (AX-7R11)

– 41 –

47.

RAD-25NH4, RAD-40NH4

27
16

25

25

25

16

27

– 43 –

Table 1 Mode data file

RAD-25NH4 RAD-40NH4

LABEL NAME VALUE

WMAX 4400 min

–1

5400 min

–1

WMAX2 4500 min

–1

5400 min

–1

WSTD 3500 min

–1

4700 min

–1

WBEMAX 2800 min

–1

3500 min

–1

CMAX 2700 min

–1

4700 min

–1

CMAX2 2800 min

–1

4700 min

–1

CSTD 2450 min

–1

4300 min

–1

CKYMAX 2200 min

–1

3500 min

–1

CJKMAX 1800 min

–1

2700 min

–1

CBEMAX 1600 min

–1

2000 min

–1

WMIN 1500 min

–1

1800 min

–1

CMIN 1500 min

–1

1800 min

–1

STARTMC 60 Seconds 60 Seconds

DWNRATEW 80% 80%

DWNRATEC 80% 80%

SHIFTW 5.00°C 5.00°C

SHIFTC 1.66°C 1.66°C

CLMXTP 30.00°C 30.00°C

YNEOF 20.00°C 20.00°C

TEION 2.00°C 2.00°C

TEIOF 9.00°C 9.00°C

SFTDSW 2.00°C 2.00°C

DFTIM1 50 Minutes 55 Minutes

DFTIM2 60 Minutes 60 Minutes

DFTIM3 90 Minutes 90 Minutes

– 45 –

Reversing valve (heating “on” mode)

NOTE (9)

Notes:
(1) Condition for entering into Cool Dashed mode. When fan set to “Hi” or “Auto mode” and temperature difference between indoor temperature and set temperature has a

corresponding compressor rpm (calculated value in Table 7) larger than WMAX.

(2) Cool Dashed will release when i) a maximum 25 minutes is lapsed and ii) room temperature is lower than set temperature –3°C (thermo off) and iii) when room temperature

has achieved setting temperature –1°C then maximum Cool Dashed time will be revised to 20 minutes. And iv) indoor fan is set to Lo and Med fan mode and v) change operation

mode.
(3) During Cool Dashed operation, thermo off temperature is set temperature (with shift value) –3°C. After thermo off, operation continue in Fuzzy control mode.
(4) Compressor minimum “ON” time and “OFF” time is 3 minutes.
(5) During normal cooling mode, compressor maximum rpm CMAX will maintain for 60 minutes if indoor temperature is lower than CLMXTP. No time constrain if indoor temperature

is higher than CLMXTP.
(6) When fan is set to “Hi”, compressor rpm will be limited to CKYMAX.
(7) When fan is set to “Med”, compressor rpm will be limited to CJKMAX.
(8) When fan is set to “Lo”, compressor rpm will be limited to CBEMAX.
(9) During Cool Dashed, when room temperature reaches set temperature –1°C compressor rpm is actual rpm x DWNRATEC.

Temperature Calculated

difference compressor rpm

1.66 2265 min

–1

2 2435 min

–1

2.33 2600 min

–1

2.66 2765 min

–1

3 2935 min

–1

3.33 3100 min

–1

3.66 3265 min

–1

4 3435 min

–1

4.33 3600 min

–1

4.66 3765 min

–1

5 3935 min

–1

5.33 4100 min

–1

5.66 4265 min

–1

6 4435 min

–1

6.33 4600 min

–1

6.66 4765 min

–1

7 4935 min

–1

7.33 5100 min

–1

7.66 5265 min

–1

8 5435 min

–1

8.33 5600 min

–1

8.66 5765 min

–1

9 5935 min

–1

9.33 6100 min

–1

9.66 6265 min

–1

10 6435 min

–1

10.33 6600 min

–1

10.66 6765 min

–1

11 6935 min

–1

Table 2 ∆TCMAX

Note:

1. See the data in Table 1 on
page 43 for each constant in
capital letters in the diagrams.

– 47 –

Notes:

(1) The sleep operation starts when the sleep key is pressed.
(2) When the sleep key is set, the maximum compressor speed is limited, and the indoor fan is set to “sleep Lo”.
(3) 30 minutes after the sleep key is set, the sleep shift of temperature starts, and upper shift is made at least 6 times. If 25˚C

is not reached after 6 shifts, shifts repeat unit 25˚C is reached.
(4) The sleep shift upper value of set temperature is 28˚C.
(5) After 6 hours, a shift down to the initial set temperature is made at a rate of 0.33˚C/5 min.
(6) If the operation mode is changed during sleep operation, the set temperature is cleared, and shift starts from the point when

switching is made.
(7) The indoor fan speed does not change even when the fan speed mode is changed.
(8) When operation is stopped during sleep operation, the set temperature when stopped, as well as the time, continue to be

counted.
(9) If the set lime is changed during sleep operation, all data including set temperature, time, etc. is cleared and restarted.
(10) If sleep operation is canceled by the cancel key or sleep key, all data is cleared.

Cooling Sleep Operation

Compressor speed

Horizontal air
deflector

Shut

Horizontal

Facing down

Maximum speed

Indoor fan

Outdoor fan

Timer lamp

Operation lamp

Sleep key

(Cooling/dehumidifying set
temperature = Remote control set
temperature (+) SHIFTC)

Final set temperature
(Cooling/dehumidifying set
temperature (+) sleep shift)

Set to 7 hours

0.5hr

1.5hr

3hr

P1

2.5hr 3.5hr 6hr 7hr

Hi

See basic operation

Med

Lo (sleep)

Lo

+

+

Delay

–1.33˚C

–0.66˚C

– 49 –

Notes:

(1) If the room temperature is (cooling preset temperature) - (1.33°C) or less after 30 seconds from starting the operation, the operation is done assuming

as the preset temperature = (room temperature at the time) - (2°C).
(2) The indoor fan is operated in the “Lo” mode. During thermo OFF indoor fan will be OFF for 5 minutes and ON for 1 minute.
(3) When the operation is started by the themostat turning ON, the start of the indoor fan is delayed 32 seconds after the start of compressor operation.
(4) The compressor is operated forcedly for 3 minutes after operation is started.
(5) The minimum ON time and OFF time of the compressor are 3 minutes.

– 51 –

1.33˚C.

SFTDSW

0.66˚C.

Fan speed set to "auto"

1 min.

Hi

Lo Hi Hi Hi

ultra Hi

Basic Heating Operation

Start

Stop Star t Start StopStop

Thermo

OFF

Thermo

OFF

Heating set temperature

(remote control set temperature

(+))

Start/stop switch

Thermo judgment

Indoor fan

Ultra-Hi

Hi

Med

Lo

Ultra-Lo

Operation lamp

Max.

Rating

3000

0

Compressor speed

Outdoor fan

Reversing valve (heating "on" model)

Thermo OFF

Dash period

TWMAX

Wtd

Defrost signal

Preheating judgment

30sec. 30sec.

10sec.

15sec. 15sec.

15sec. 15sec. 15sec.

10sec.

15sec.

15sec.

150sec. Delay

150sec. Delay150sec. Delay

3min.

Max. 3 min.

Preheating released

Control by
heat exchanger temperature

Control by
heat exchanger temperature

15sec.

Control by
heat exchanger temperature

Control by
heat exchanger temperature

Control by
heat exchanger temperature

18˚C

10sec.

30sec. 30sec.

10sec.

30sec. 30sec.30sec. 30sec. 30sec. 30sec.

10sec.

Preheat released

WMIN

(WSTD)

(WMAX)

NOTE (11)

WMAX2

Notes:
(1) Condition for entering into Hot Dashed mode. When fan set to “Hi” or “Auto mode” and i) Indoor temperature is lower than 18°C, and ii) outdoor temperature is lower than 10°C,

and iii) Temperature difference between indoor temperature and set temperature has a corresponding compressor rpm (calculated value in Table 3) larger than WMAX.
(2) Hot Dashed will release when i) Room temperature has achieved the set temperature + SFTDSW. ii) Thermo off.
(3) During Hot Dashed operation, thermo off temperature is set temperature (with shift value) +3°C. After thermo off, operation continue in Fuzzy control mode.
(4) Compressor minimum “ON” time and “OFF” time is 3 minutes.
(5) During normal heating mode, compressor maximum rpm WMAX will maintain for 120 minutes if indoor temperature is higher than 18°C. No time limit constrain if indoor temperature

is lower than 18°C and outdoor temperature is lower than 2°C.
(6) During Hotkeep or Defrost mode, indoor operation lamp will blink at interval of 3 seconds “ON” and 0.5 second “OFF”.
(7) When heating mode starts, it will enter into Hotkeep mode if indoor heat exchanger temperature is lower than YNEOF + 0.33°C.
(8) When fan is set to “Med” or “Lo”, compressor rpm will be limited to WBEMAX.
(9) In “Ultra-Lo” fan mode, if indoor temperature is lower than 18°C, indoor fan will stop. If indoor temperature is higher than 18°C + 0.33°C, fan will continue in “Ultra-Lo” mode.

During Hotkeep or Defrost mode, fan will continue in “Ultra-Lo” mode.
(10) During Hot Dashed or outdoor temperature is lower than –5°C, compressor rpm is WMAX2.
(11) During Hot Dashed, when room temperature reaches set temperature + SFTDSW compressor rpm is actual rpm x DWNRATEW.

Temperature Calculated

difference compressor rpm

1.66 1965 min

–1

2 2135 min

–1

2.33 2300 min

–1

2.66 2465 min

–1

3 2635 min

–1

3.33 2800 min

–1

3.66 2965 min

–1

4 3135 min

–1

4.33 3300 min

–1

4.66 3465 min

–1

5 3635 min

–1

5.33 3800 min

–1

5.66 3965 min

–1

6 4135 min

–1

6.33 4300 min

–1

6.66 4465 min

–1

7 4635 min

–1

7.33 4800 min

–1

7.66 4965 min

–1

8 5135 min

–1

8.33 5300 min

–1

8.66 5465 min

–1

9 5635 min

–1

9.33 5800 min

–1

9.66 5965 min

–1

10 6135 min

–1

10.33 6300 min

–1

10.66 6465 min

–1

11 6635 min

–1

Table 3 ∆TWMAX

Notes:

1. See the data in Table 1 on
page 43 for each constant in
capital letters in the diagrams.

– 53 –

1 min

WMIN

TDF TDF TDF

TDF

TDF

TDF

Notes:
(1) The sleep operation starts when the sleep key is pressed.
(2) When the sleep key is set, the maximum compressor speed is limited to WSTD+2000/2, and the indoor fan is set

to “sleep Lo”.
(3) 30 minutes after the sleep key is set, the sleep shift of set temperature starts.
(4) The maximum sleep shift of set temperature is 5°C, and the minimum is 12°C.
(5) If the operation mode is changed during sleep operation, the changed operation mode is set and sleep control

starts.
(6) The indoor fan speed does not change even when the fan speed mode is changed. (Lo)
(7) When defrosting is to be set during sleep operation, defrosting is engaged and sleep operation is restored after

defrosting.
(8) When operation is stopped during sleep operation, the set temperature when stopped, as well as the time, continue

to be counted.
(9) If the set time is changed during sleep operation, all data including set temperature, time, etc. is cleared and

restarted.
(10) If sleep operation is canceled by the cancel key or sleep key, all data is cleared.

Setting Defrosting Inhibit Period

D F T I M 3

D F T I M 2

Time

Outdoor temperature

– 1 0 – 5˚C0˚C

D F T I M 1

Notes:
(1) The first inhibit time after operation start is set to DFTIM1.
(2) From the second time onwards, the inhibit time is set according to the time required for

defrosting.
Reverse cycle operation time ≥ [DEFCOL] : DFTIM1 is set.
Reverse cycle operation time < [DEFCOL] : The time corresponding to outdoor tempera­ture is set.

– 55 –

REFRIGERATING CYCLE DIAGRAM

MODEL RAD-25NH4

RAC-25NH4

COOLING, DEHUMIDIFYING, DEFROSTING

OUTDOOR UNIT

REVERSING
VALV E

SUCTION
TAN K

SERVICE VALVE

(3/8)

INDOOR UNIT

SINGLE-ENDED
UNION (3/8)

COMPRESSOR

SINGLE-ENDED
UNION (1/4)

SERVICE VALVE

(1/4)

ELECTRIC
EXPANSION VALVE

STRAINER

STRAINER

CHARGING PIPE

HEATING

OUTDOOR UNIT

REVERSING
VALV E

SUCTION
TAN K

SERVICE VALVE

(3/8)

INDOOR UNIT

SINGLE-ENDED
UNION (3/8)

COMPRESSOR

SINGLE-ENDED
UNION (1/4)

SERVICE VALVE

(1/4)

ELECTRIC
EXPANSION VALVE

STRAINER

STRAINER

CHARGING PIPE

– 56 –

REFRIGERATING CYCLE DIAGRAM

MODEL RAD-40NH4

RAC-50NH4

COOLING, DEHUMIDIFYING, DEFROSTING

OUTDOOR UNIT

REVERSING
VALV E

SUCTION
TANK

SERVICE VALVE

(1/2)

INDOOR UNIT

SINGLE-ENDED
UNION (3/8)

COMPRESSOR

SINGLE-ENDED
UNION (1/4)

SERVICE VALVE

(1/4)

ELECTRIC
EXPANSION VALVE

STRAINER

STRAINER

HEATING

OUTDOOR UNIT

REVERSING
VALV E

SUCTION
TANK

SERVICE VALVE

(1/2)

INDOOR UNIT

SINGLE-ENDED
UNION (3/8)

COMPRESSOR

SINGLE-ENDED
UNION (1/4)

SERVICE VALVE

(1/4)

ELECTRIC
EXPANSION VALVE

STRAINER

STRAINER

ADAPTOR

ADAPTOR

12.7

– 57 –

OPERATING SPECIFICATION

REFERENCE

OPERATION OPERATION MODE AIR DEFLECTOR

PRESENT CONDITION

KEY INPUT

THERMO. ON

(INTERNAL FAN

ON)

THERMO. ON

(INTERNAL FAN

OFF)

MAIN SWITCH

ON

MAIN SWITCH

OFF

CHANGE OF

OPERATION

STOP

DURING

OPERATION

DURING

OPERATION

STOP

DURING

OPERATION

DURING

OPERATION

EACH MODE

AUTO COOL

COOL

FAN

AUTO DRY

DRY

AUTO HEAT

HEAT

CIRCULATOR

AUTO DRY

DRY

AUTO HAET

HEAT

CIRCULATOR

COOL

FAN

DRY

HEAT

CIRCULATOR

EACH MODE

EACH MODE

STOP SWINGING AND MODE BECOMES INITIALIZING

CONDITION.

INITIALIZING CONDITION OF EACH MODE.

ONE SWING (CLOSING AIR DEFLECTOR)

1 DOWNWARD

2 UPWARD

INITIALIZE

1 DOWNWARD

INITIALIZE

1 DOWNWARD

2 UPWARD

STOP AT THE MOMENT.

START SWINGING

1 DOWNWARD

2 UPWARD

3 DOWNWARD

STOP AT THE MOMENT.

START SWINGING

1 DOWNWARD

2 UPWARD

3 DOWNWARD

STOP AT THE MOMENT.

ONE SWING (CLOSING AIR DEFLECTOR)

1 DOWNWARD

2 UPWARD

INITIALIZE AT NEXT

OPERATION.

INITIALIZE AT NEXT

OPERATION.

STOP

DURING ONE SWING

STOP

DURING SWINGING

STOP

DURING SWINGING

TEMPORARY STOP

DURING SWINGING

STOP

DURING ONE SWING

STOP

DURING ONE SWING

STOP

DURING SWINGING

DURING

INITIALIZING

STOP

DURING SWINGING

AUTO SWING FUNCTION

MODEL: RAD-25NH4, RAD-40NH4

STOP SWINGING TEMPORARILY.

(SWING MODE IS CLEARED IF SWING COMMAND IS

TRANSMITTED DURING TEMPORARY STOP.)

START SWING AGAIN.

INPUT SIGNAL

– 58 –

● The reset circuit initializes the microcomputer program when power is ON or OFF.

● Low voltage at pin 7 resets the microcomputer and Hi activates the microcomputer.

● When power “ON” 5V voltage rises and reaches 4.4V, pin 1 of IC521 is set to “Hi”. At this time the

microcomputer starts operation.

● When power “OFF” voltage drops and reaches 4.2V, pin 1 of IC521 is set to “Low”. This will RESET the

microcomputer.

DESCRIPTION OF MAIN CIRCUIT OPERATION

MODEL RAD-25NH4, RAD-40NH4

1. Reset Circuit

Fig. 1-1

Fig. 1-2

2

1

5

3

7

NORMAL : HI
RESET : LO

RES

Microcomputer

C524

R521

C522

C521

R522

5V

0V

IC521

Voltage

5.0V

Reset enter at 4.2V

Reset release at 4.4V

voltage

5.0V

Voltage at pin

7

of microcomputer

Voltage supply to
pin

2

of IC521

– 59 –

2. Receiver Circuit

● The light receiver unit receives the infrared signal from the wireless remote control. The receiver amplifies

and shapes the signal and outputs it.

3. Buzzer Circuit

Fig. 3-1 Buzzer Circuit

Sound wave

Metal diaphragm

V

Pizoelectric element

V

Fig. 3-2 Buzzer Operation

Microcomputer

Buzzer output

BZ

12V

0V

R722

Q722

30

BZ

● When the buzzer sounds, an approx.

3.9kHz square signal is output from buzzer
output pin of the microcomputer. After
the amplitude of this signal has been set
to 12Vp-p by a transistor, it is applied to
the buzzer. The piezoelectric element in
the buzzer oscillates to generate the
buzzer’s sound.

Fig. 2-1

30

0V

0V

13

RECEIVER I/P

Microcomputer

R419 R611

C405

IRR

GND

V

out

V

DD

5V

C611

– 60 –

4. Auto Sweep Motor Circuit

● Fig. 4-1 shows the Auto sweep motor drive circuit; the signals shown in Fig.4-2 are output from pins

15 – 18 of microcomputer.

● As the microcomputer’s outputs change as shown in Fig.4-2, the core of the auto sweep motor is excited

to turn the rotor. Table 4-1 shows the rotation angle of horizontal air deflectors.

Table 4-1 Auto sweep Motor Rotation

Rotation angle per step (˚ ) Time per step (ms.)

0.0882 10Horizontal air deflectors

Microcomputer pins Step width

Horizontal air

deflectors: 10ms.

Horizontal air deflectors

15

16

17

18

1234 5678

Fig.4-2 Microcomputer Output Signals

Fig.4-1

Microcomputer

18

17

16

15

IC711

C711

9

7

10

11

12

13

15

16

P.W.B. MAIN

14

6

5

4

3

2

1

8

0V

CN8

M

12V

1

2

3

4

5

6

7

8

9

10

AUTO SWEEP
MOTOR FOR
HORIZONTAL
AIR DEFLECTOR

● The air deflectors are driven by the stepping motors, which are instructed by the microcomputer.

● The air deflectors on the left and right are each driven by two stepping motors.

● The stepping motors and main unit are connected via relay connectors. The air deflectors will not operate

unless the relay connectors are connected: Securely connect the relay connectors identified by colors
when attaching the panel.

● Before removing the panel for servicing, be sure to disconnect the relay connector to protect the lead

wires.

– 61 –

5. Room Temperature Thermistor Circuit

● Fig. 5-1 shows the room temperature

thermistor circuit.

5

4

3

2

1

0

010

Room temperature (˚C)

Fig. 5-2

20 30 40

0V

Room
temperature
thermistor

0V

5V

Fig. 5-1

62

A

R305

C302

Microcomputer

Room
temp. input

Voltage at

(V)

R301

0V

Heat exchanger
temperature thermistor

0V

5V

Fig. 6-1

61

A

R306

C303

Microcomputer

Heat
exchanger
temperature
input

R302

A

5

4

3

2

1

0

010

-10

Heat exchanger temperature (˚C)

Fig. 6-2

20 30 40

Voltage at

(V)A

6. Heat exchanger temperature thermistor circuit

● The voltage at depends on the room

temperature as shown in Fig. 5-2.

● The circuit detects the indoor heat

exchanger temperature and controls
the following.

(1) Preheating.

(2) Low-temperature defrosting
during cooling and dehumidifying
operation.

(3) Detection of the reversing valve
non-operation or heat exchanger
temperature thermistor open.

The voltage at depends on the
heat exchanger temperature as shown
in Fig. 6-2.

A

A

– 62 –

7. Initial Setting Circuit (IC401)

● When power is supplied, the microcomputer reads the data in IC401 (E

2

PROM) and sets the preheating

activation value and the rating and maximum speed of the compressor, etc. to their initial values.

● Data of self-diagnosis mode is stored in IC401; data will not be erased even when power is turned off.

Fig. 7-1

Microcomputer

External ROM

SCL
SDA

0V

0V

0V

5V

5V 5V

C401

IC401 (E

2

PROM)

R404

R403

27
26

1

2

3

4

8

7

6

5

}

– 63 –

Model RAC-25NH4, RAC-50NH4

1. Power Circuit

● This circuit full-wave rectifies 220-240V AC applied between terminals L and N, and boosts it to a required

voltage with the active module, to create a DC voltage.

The voltage becomes 260-360V when the compressor is operated

(1) Active module

The active filter, consisting of a reactor and
switching element, eliminates higher
harmonic components contained in the
current generated when the compressor is
operated, and improves the power-factor.

(2) Diode stacks

These rectify the 220-240V AC from
terminals L and N to a DC power supply.

< Reference >

● In case of malfunction or defective connection:

Immediately after the compressor starts, it may stop
due to “abnormally low speed” active error, etc.

The compressor may continue to operate normally,
but the power-factor will decrease, the operation
current will increase, and the overcurrent breaker
of the household power board will probably activate.

● In case of active module faulty or defective

connection:

Although the compressor continues to operate
normally, the power-factor will decrease, the
operation current will increase, and the overcurrent
breaker of the household power board will probably
activate.

< Reference >

● If diode stack 1 is faulty, the compressor may stop

due to “lp”, “anbormally low speed”, etc. immediately
after it starts, or it may not operate at all because
no DC voltage is generated between the positive e
and negative d terminals.

If diode stack 1 is faulty, be aware that the 25A
fuse might also have blown.

● If diode stack 2 is faulty, DC voltage may not be

generated and the compressor may not operate at
all. Also, be aware that the 3A fuse might have
blown.

L

25A FUSE

SURGE­ABSORBER

VARISTOR1

VARISTOR3

CT1

C009

L001

C001

C004C005

C006

R007

L002

JW6

R008

ICP RELAY

TB2

TB8

TB7 TB6

TB10
TB11
TB12

U
V
W

N1

L1 L2

3A FUSE

R002

C008

C007

C012

C013

C014

C015

DIODE

STACK 2 (RC2)

DIODE

STACK 1

(D25VB60)

VARISTOR2

C011

POWER CIRCUIT

R010R011

C002

C003

R001

0V

0V

NF COIL1

COIL

POWER RELAY

TERMINAL

BOARD

N

REACTOR

C010

SPM2

P1

Vdba

Fig. 1-1

– 64 –

(3) Smoothing capacitor (C501, C502, C503)

This smoothes (averages) the voltage rectified by the diode stacks.

<Notes> Smoothing capacitor C501 is not available for model RAC-25NH4 and RAC-35NH4.

(4) Smoothing capacitor (C010, C011)

This smoothes (averages) the voltage rectified by the diode
stack2. A DC voltage is generated in the same way as in
Fig. 1-3.
Voltage between + side of C010 and – side of C011 is about
330V.

(5) C001 to C003, C012 to C015, C007, C008, NF COIL1, COIL,

absorb electrical noise generated during operation of
compressor, and also absorb external noise entering from
power line to protect electronic parts.

(6) Surge absorber, Varistor 1, 2, 3,

absorbs external power surge.

(7) Inrush protective resistor (R007, R008)

This works to protect from overcurrent when power is turned
on.

< Reference >

● When inrush protective resistor is

defective, diode stack may
malfunction. As a result, DC voltage
is not generated and no operation can
be done.

● Be careful to avoid an electric shock as a

high voltage is generated. Also take care

not to cause a short-circuit through incorrect

connection of test equipment terminals. The

circuit board could be damaged.

Fig. 1-3

Fig. 1-2

a

b

OV

OV

OV

Vd

DC voltage
(approx. 260-360V during operation)

Smoothing Capacitors

SPM2

– 65 –

2. Indoor/Outdoor Interface Circuit

● The interface circuit superimposes an interface signal on the DC 35V line supplied from the outdoor unit

to perform communications between indoor and outdoor units. This circuit consists of a transmiting circuit
which superimposes an interface signal transmit from the microcomputer on the DC 35V line and a
transmiting circuit which detects the interface signal on the DC 35V line and outputs it to the microcomputer.

● Communications are performed by mutually transmiting and receiving the 4-frame outdoor request signal

one frame of which consists of a leader of approx. 100 ms., start bit, 8-bit data and stop bit and the
command signal with the same format transmit from the indoor unit.

● Communication signal from outdoor microcomputer to indoor microcomputer. At first outdoor microcomputer

will send a request signal (SDO) to indoor microcomputer. A high-frequency IF signal approx. 38 KHz is
generated and modulated by the request signal (SDO) inside the outdoor microcomputer then output to
pin 11 of microcomputer. This modulated IF signal is output to pin 30 of HIC and amplified by amp. This
signal is superimposed to DC 35V line via C801 and L801.
To prevent erroneous reception, the outdoor microcomputer is designed so that it cannot receive a signal
while it is outputting a request signal.
The receiving circuit in the indoor unit consists of a comparator and transistor. The interface signal from
the outdoor unit on the DC 35V line is supplied to C821, where DC components are eliminated, and is
then shaped by the comparator. The shaped signal is detected by diode, amplified by amp, and output
to pin 49 of the indoor microcomputer.
Fig. 2-2 shows the voltages at each component when data is transferred from the outdoor microcomputer
to the indoor microcomputer.

● Communication signal from indoor microcomputer to outdoor microcomputer. The request signal (SDO)

generates by indoor microcomputer is output to pin 50 , and amplifies by C801. IF signal approx. 38 kHz
is generated by comparator, then modulate by the request signal from pin 50 of indoor microprocessor.
This modulated IF signal is then amplified and superimposed to DC 35V line via L801 and C802 of indoor
interface circuit.
Fig. 2-3 shows the voltages at each component when data is transferred from outdoor microcomputer to
indoor microcomputer.
The circuit operation of the outdoor receiving circuit is same as indoor receiving circuit.

– 66 –

● Fig. 2-1 shows the interface circuit used for the indoor and outdoor microcomputers to communicate with

each other.

Indoor P.W.B.

Outdoor P.W.B.

Terminal board

Terminal board

CD

CD

D101

I/F 0V

C821 R821

C822

0V

0V 0V0V

5V 5V 5V

0V

0V

0V

5V

0V

C801

R829

R830

Q821

C824

0V

IC801

C823

R828

R823

R825

D821

R827

R826

0V

0V

0V

I/F 0V

0V

IF transmit
output (SDO)

IF receive
input (SDI)

MICROCOMPUTER

5V

0V

5V

5V

12V

5V 5V

5V

5V5V

5V

C802

R813

L801

R812

Q803

C803

C804

R811

Q802

Q801

R824

3
2

1

R822

R806

R807

R805

R803

R804

5

7

6

IC801

R810

50

49

IF transmit
output (SDO)

HIC

IF receive
input (SDI)

MICROCOMPUTER

11

30

68

29

0V

L801

L802

C801

C809

R802 Q801

5V

0V

R801

R803

0V

0V

0V

0V

0V

0V

0V0V

C808

NF COIL2

C810

C802

C806

C807

C812

C811

Interface
relay

35V

(Communications from outdoor microcomputer to indoor
microcomputer)

(Communications from indoor microcomputer to outdoor
microcomputer)

Fig. 2-1 Indoor/outdoor interface Circuit

– 67 –

Outdoor HIC

29

Pin

30

Pin

Indoor microcomputer

DC 35V line

49

Pin

50

Pin

100ms.
Leader

33ms.
1 frame

0.7V

0V

5V

0V

5V

0V

5V

0V

35V

Indoor microcomputer

4.95ms.
Transmit / receive
switching time

33ms.

1 frame

Outdoor HIC

30

Pin

0V

29

Pin

5V

0V

50

Pin

5V

0V

49

Pin

5V

0V

DC 35V line

35V

Fig. 2-2 Voltages Waveforms of indoor / Outdoor Microcomputers (Outdoor to Indoor Communications)

Fig. 2-3 Voltages Waveforms of indoor / Outdoor Microcomputers (Indoor to Outdoor Communications)

– 68 –

[Serial Communications Format during Normal Communications]

(1) Outdoor microcomputer (HIC) to indoor microcomputer

(2) Indoor microcomputer to outdoor microcomputer (HIC)

(3) Communications waveforms

1 frame = 100ms. + 33.3ms. x 8 + 4.95ms. = 371.35ms.

Outdoor message

Indoor message

[Example] When the outdoor message is all 0s

and indoor message is all 1s:

36 (V)

35 (V)

34 (V)

When reset

(approx. 10ms.)

Transmit/

receive

switching time

(4.95ms.)

Character No.

0

(33.3ms.)

1

(33.3ms.)

2

(33.3ms.)

3

(33.3ms.)

Character No.

0

(33.3ms.)

1

(33.3ms.)

2

(33.3ms.)

3

(33.3ms.)

Bit No = 0

Bit No = 0

07

0707077

07077

Leader

(100ms.)

When reset

(approx. 10ms.)

Leader

(100ms.)

Fig. 2-4

– 69 –

[ Serial Communications Data ]

7

1/0

6

1/0

5

1/0

4

1/0

3

1/0

2

1/0

1

1/0

0

1/0

7

1/0

6

1/0

5

1/0

4

1/0

3

2

1

0

7

6

5

4

3

2

1

0

7

6

5

4

0

3

1/0

2

1/0

1

1/0

0

1/0

Character No.

Bit No.

Data

0 0 0 1/0 1/0 1/0 0 1/0 0 0 1/0 1/0 1/0 1/0 1/0

OVL up

Compressor command speed (0 LSB)

Compressor ON

Reversing valve

2-way valve

Fan (2 MSB)

Fan (1

Fan (0 LSB)

Capacity code (3 MSB)

Capacity code (2)

Capacity code (1)

Capacity code (0 LSB)

Indoor in-operation bit

Operation mode (2 MSB)

Operation mode (0 LSB)

Contents

0

1

2

3

(2) Indoor message

Operation mode (1)

Compressor command speed (1)

Compressor command speed (2)

Compressor command speed (3)

Compressor command speed (4)

Compressor command speed (5)

Compressor command speed (6)

Compressor command speed (7 MSB)

15/20(A)

Compressor minimum rotation speed (4 MSB)

Compressor minimum rotation speed (3)

Compressor minimum rotation speed (2)

Compressor minimum rotation speed (1)

Compressor minimum rotation speed (0 LSB)

7

0

6

0

5

0

4

0

3

0

2

0

1

1

0

0

7

1/0

6

1/0

5

1/0

4

1/0

3

2

1

0

7

6

5

4

3

2

1

0

7

6

5

4

1/0

3

1/0

2

1/0

1

0

0

1/0

Character No.

Bit No.

Data

1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0

Fan-7-step request

Actual compressor rotation speed (5 MSB)

Actual compressor rotation speed (4)

Actual compressor rotation speed (3)

Actual compressor rotation speed (2)

Actual compressor rotation speed (1)

Actual compressor rotation speed (0 LSB)

Compressor during operation

Compressor during operation

Outside temperature (7 MSB)

Outside temperature (6)

Outside temperature (5)

Outside temperature (4)

Outside temperature (3)

Outside temperature (2)

Outside temperature (1

Outside temperature (0 LSB)

Self-diagnosis (3 MSB)

Self-diagnosis (2)

Self-diagnosis (1)

Self-diagnosis (0 LSB)

Defrost request signal

During forced operation

Multi-bit

Contents

0

1

2

3

(1) Outdoor message

– 70 –

3. Power Module Circuit

●

Fig. 3-1 shows the system power module and its peripheral circuit.

The three transistors on the positive e side are called the upper arm, and the three transistors on the negative d side, the lower arm.

+

W

U

V

W

W

–

+

V

V

–

+

U

U

–

A

+

DC

Compressor

motor

U coil

V coil

W coil

System Power module 2

+

–

C501

+

–

C502

+

–

C503

R24

0.35

m

H

Power relay

Coil

R007

R008

Inrush current

protection

relay

C006

R001

Noise filter

coil

L

N

Terminal

board

FUSE (25A)

Fig. 3-1 Power module circuit (U

+

is ON, V

–

is ON)

– 71 –

● DC 260-360V is input to system power module and system power module switches power supply current

according to rotation position of magnet rotor. The switching order is as shown in Fig. 3-2.

E

F

UVVW

Upper arm
transistor

Lower arm
transistor

Time

++T+

+

T

U

–

V

–

W

–

U transistor chopped

U transistor ON

ON

Voltage at

Upper arm transistor

Current at

Chopping period

260V-360V

A

+

-

B

At point E: U+ is ON, V– is ON (circuit in Fig. 3-1)
At point F: U+ is chopped (OFF), V– is ON (circuit in Fig. 3-4)

[]

● Upper arm transistor is controlled to ON/OFF by 3.3kHz chopper signal. Rotation speed of the compress

is proportional to duty ratio (ON time/ ON time + OFF time) of this chopper signal.

● Time T in Fig. 3-2 shows the switching period, and relation with rotation speed (N) of the compressor is

shown by formula below;

Fig. 3-2 Switching order of power module

N = 60/2 X 1/T

● Fig. 3-3 shows voltage waveform at each point shown in Figs. 3-1 and 3-4. First half of upper arm is

chopper, second half is ON, and first half of lower arm is chopper, second half is ON.

Fig. 3-3 Voltage waveform at each point

● When power is supplied U

+

[ U–, because of that U+ is chopped, current flows as shown below;

(1) When U+ transistor is ON: U+ transistor [ U coil [ V coil [ V– transistor [ DC current detection

resistor [ Point (Fig. 3-1)

(2) When U+ transistor is OFF: (by inductance of motor coil) U coil [ V coil [ V– transistor [ Return

diode [ Point (Fig. 3-4)

A

B

B

– 72 –

+

U

U

V

W

—

U

+

V

—

V

+

W

—

W

_

+

System Power Module 2

260V-360V

R24

DC current (Id)
detection resistor

A

U coil

DC compressor
motor

V coil

W coil

B

Fig. 3-5

● Since current flows at point only when U+ transistor is ON, the current waveform at point becomes

intermittent waveform as shown in Fig. 3-3. Since current at point is approximately proportional to the
input current of the air conditioner, input current is controlled by using DC current (Id) detection resistor.

<Reference>

If power module is detective, self diagnosis lamps on the control P.W.B. may indicate as shown below:

● Simplified check of power module (Lighting mode when operated with compressor leads disconnected)

(1) Disconnect connector of 3-pole (WHT, YEL, RED) lead wire connecting to compressor located at the

lower part of electric parts box.

(2) Set to compressor operation state (other than FAN mode) and press Start/stop switch of remote

control.

(3) If normal operation continues for more than 1 minute (LD303 lights), power module is considered

normal.

❈ Refer to other item (troubleshooting on page 94) for independent checking of power module.

Fig. 3-4 Power module circuit (U+ is ON, V– is ON)

Self-diagnosis

Self-diagnosis lamp
and mode

lp (peak current cut)

LD301

Abnormal low speed

rotation

LD301

Switching incomplete

LD301

Blinks 2
times

Blinks 3
times

Blinks 4
times

Table 3-1

B B

B

Self diagnosis lamps
(LD303, 302, 301)

P.W.B (Main)

– 73 –

4. Power Circuit for P.W.B.

● Fig. 4-1 shows the power circuit for P.W.B. and waveform at each point.

22

18

19

+

D908

R917

R915

D909

R918

L903

REG1

C911

20

21

+

D907

C910

R914

C912

16

17

+

C903

C907

+

+

C914

14

13

R916

L902

35V

17V

5V

FM–15V

I/F0V

0V

0V

0V

FM–0V

C913

D910

REG2

Q706

C924

R920

R921

R922

PQ2

1

1

2

4

3

4

3

1

2

2

3

PQ1

VR1

R923

C906

C918

R911

D906

C908

PQ1

12

C

11

D904

R908

R909

D903

D905

D911

R910

R901

C901

R902

R903

R002

Diode stack 2

(RC2)

R904

2 5

3 4

1

+

+

IC901

C011

C010

R011

R010

C905

D902

R906

L901

R907

Switching transformer (T1)

Fig. 4-1 Power circuit for P.W.B.

1

9

+

C919

+

C921

C920

12V

D912

R919

R925

R924 ZD904

C909

15

1 2

JW8

JW8

4 3

● In the power circuit for P.W.B., power supply for microcomputer, peripheral circuits, and system power

module driver circuit and, as well as DC 35V, are produced by switching power circuit.

● Switching power circuit performs voltage conversion effectively by switching transistor IC901 to convert

DC 330V voltage to high frequency of about 20kHz to 200kHz.

● Transistor IC901 operates as follows:

(1) Shifting from OFF to ON

● DC about 330V is applied from smoothing capacitors C010 Œ and C011 œ in the control power circuit.

With this power, current flows to pin of IC901 via R903 and R904 and IC901 starts to tum ON. Since
voltage in the direction of arrow generates at point at the same time, current passing through R910 and
D903 is positive-fed back to IC901.

4

C

– 74 –

(2) During ON

● The drain current at IC901 increases linearly. During this period, the gate voltage and current become

constant because of the saturation characteristics of the transformer.

(3) Shifting from ON to OFF

● This circuit applies a negative feedback signal from the 12V output. When the voltage across C919

reaches the specified value, REG2 turns on and current flows to PQ2 1-2. This turns the secondary
circuits on, sets IC901 pin 1 to “Hi”, and turns IC901 off.

(4) During OFF

● While IC901 is on, the following energy charges the primary windings of the transformer:

Energy=LI2/2. Here, L : Primary inductance

I : Current when IC1 is off

This energy discharges to the secondary windings during power off. That is, C910, C911, C912, C914 is
charged according to the turn ratio of each winding.

● At the start, an overcurrent flows to IC901 because of the charged current at C910, C911, C912, C914.

● The drain current at IC901 generates a voltage across R906. If it exceeds the IC901 base voltage, it sets

the IC901 gate voltage to “HI”.

● R906 limits the gate voltage to prevent excessive collector current from flowing to IC901.

<Reference>

If the power circuit for P.W.B. seems to be faulty:

(1) Make sure that 5V and 12V on the control P.W.B., upper arm U, V and W, and the lower arm power

voltage are the specified values.

(2) When only the 5V output is low:

REG 1 (regulator) faulty, 5V-0V shorted, output is too high, or REG 1 is abnormal.

(3) When 12V and 5V are abnormal:

The following defects can be considered:

1 Fan, operation, power, rush prevention relay (shorting in relay, etc.)
2 Microcomputer is abnormal.
3 REG 1 (regulator is abnormal), etc.

Shorting on primary circuits.
When shorting occurs in the secondary circuits, there is no abnormality in the primary circuits because
of overcurrent protection.
The voltage rises when an opening occurs in the primary circuits, or the feedback system is abnormal.

(4) When 15V and 17V are abnormal:

D908, D909 or drive circuit is abnormal.

(5) When all voltage are abnormal:

IC901, R906, etc. are possibly abnormal.

* If IC901 is abnormal, be aware that other components, such as the power module, REG (regulator), etc.

are possibly defective.

[When the switching power supply seems to be abnormal, the voltage between IC901 pin 4 (to be measured
at the leads of R904 and R903) and IC901 pin 5 (to be measured at R906 lead) may be between 11 and
16V. This is because the protection circuit of IC901 is operating.]

– 75 –

5. Reversing valve control circuit

● Reversing valve control circuit can switch reversing valve ON/OFF according to instruction from indoor

microcomputer depending on the operation condition shows in Table 5-1.

Voltage at each point in each operation condition is approximately as shown below when measured by
tester. (When collector voltage of Q701 is measured)

3

1

16

24

I/F 0V

0V

Fig. 5 – 1

D702

CN2

Q701

DC voltmeter
or tester

Reversing
valve

R701

R703

R219

Q705

FUSE RESISTOR

MICROCOMPUTER

PQ701

1

23

4

5V

HIC

I/F 35V

R702

V

Operation condition Collector voltage of Q701

Cooling

Heating

Dehumidifying

General operation of Cooling

In normal heating operation

MAX. rotation speed instructed
by indoor microcomputer after
defrost is completed

Defrosting

Sensor dry

About 35V

About 0.8V

About 0.8V

About 35V

About 35V

Table 5-1

– 76 –

6. Rotor magnetic pole position detection circuit

A

B

C

D

E

18

19

20

Outdoor microcomputer

C605

+5V

0V

HIC

0V

+12V

WV U

C608

System power module

DC brushless
motor for compressor

R604

R605

R606

R607

R601

R602

R603

R604

R603

R602

R608

C503

C502

C501

R611

R610

R609

0V

C606

0V

C607

0V

36

33

34

35

47

Fig. 6-1 Rotor magnetic pole position detection circuit and voltage waveform at each point

E

D

C

A

No power
supplied

Upper armONNo power

supplied

No power
supplied

Lower arm

ON

60 120 60 120

Induced voltage

Comparing process

60

Vd 150 ~330

Spike voltage

U phase
terminal voltage

Drive signal

Pole position
detection signal

(B) reference
voltage (1/2Vd)

Detection point

W

+

W

+

U

+

U

+

U

—

V

—

V

—

W

—

V

+

 To detect U phase, voltage at point C is produced by driving motor induced voltage signal (voltage at point A ) and

1/2 voltage of Vd (voltage at point B ), and comparing with comparator.

 For V phase and W phase, voltage at point

D

and voltage at point E are produced in the same way as above. Voltage
at point C is taken into indoor unit microcomputer, switching timing to U+ transistor from W+ transistor is produced by
delaying 30° from rise waveform, ignoring spike voltage. In addition, switching timing to U-transistor from W-transistor is
produced by delaying 30° from fall waveform.

 For V phase and W phase, in the same way as above, drive signals are produced from voltages at point

D

and point

E

. Phases are shifted by 120° and 240°, respectively, comparing with U phase.

– 77 –

7. Drive Circuit

Fig. 7-1 shows the drive circuit.
The circuits for U phase, V phase and W
phase have the same Configuration.

●

In low speed rotation mode (PWM range), as shown in Fig. 7-2, 0-5V chopper signal is ouput from microcomputer for each phase. S

ignal

output from microcomputer is ouput to IC1 and is inverted by active Lo to become 0-15V chopper signal; it is then drive the tra

nsistor

of each phase.

●

In high speed rotation mode (PWM range), as shown in Fig. 7-3, 0-5V drive signal is ouput from microcomputer for each phase (wi

th

no chopper because of full duty). Signal output from microcomputer is input to IC1 and is inverted by active Lo to become 0-15V

drive

signal; it is then drive the transistor of each phase.

Fig.. 7-1

6

5

4

3

2

1

MICROCOMPUTER

A

R512

R521

R511

R510

R509

R508

R507

10

9

4

3

2

1

8

7

6

5

1

13

14

15

16

17

18

1

23

11

8

7

5

4

10

6

3

9

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

19

20

21

2

3

4

5

6

7

8

9

10

12

22

B

B

B

45

44

43

42

41

38

39

40

46

IP CUTTER Id CONTROL CIRCUIT

0V

17V

R501

C404

CN14

17V

0V

PWB (MAIN)

SPM2

0V

17V

U

+

V

+

W

+

U

–

V

–

W

–

IP

Id

IC1

VCC

VCU

PGU

U

VCV

PGV

V

VCW

PGW

W

NGU

NGV

NGW

SVT

SWT

SUB

SVB

SWB

F

OC

CB

A

0

A

–

GL1

GL2

SUT

R502

R503

R504

R505

R506

Q506

R536

R535

R525

Q504

R534

Q503

R524

R533

Q502

Q501

R522

R532

R531

R526

Q505

R523

HIC

P2

N1

HIC

–

+

GRY

R24

U

COMPRESSOR MOTOR

V

W

– 78 –

U

+

V

+

5V
0V

W

+

V

-

W

-

U

-

U

+

V

+

15V

0V

W

+

V

-

W

-

U

-

Drive signal at point B Drive signal at point A

V

+

U

+

W

+

V

+

U

+

V

-

W

-

U

-

V

-

W

-

[Low speed rotation mode]

[High speed rotation mode]

V

+

U

+

W

+

V

+

U

+

U

+

V

+

5V
0V

W

+

V

-

V

-

W

-

U

-

U

+

V

+

15V

0V

W

+

V

-

W

-

U

-

W

-

U

-

V

-

W

-

Drive signal at point

B

Drive signal at point

A

Fig. 7-2

Fig. 7-3

– 79 –

8. HIC and Peripheral Circuits

● Fig. 8-1 shows the micro computer and its peripheral circuits, Table 8-1, the basic operations of each

circuit block, and Fig. 8-2, the system configuration.

Table 8-1

Circuit block

Basic operation

Peak current
cutoff circuit

Set value circuit

Voltage amplifier
circuit

Reset circuit

Trip signal
synthesis circuit

Detects DC current flowing power module and during overcurrent (instantaneous
value) flows, stops upper/lower arm drive circuits and also produces lp signal by
which drive signal output is stopped.

Compares voltage detected, amplified and input to HIC with set voltage value in
microcomputer, and controls overload when set value exceeds input voltage.

Voltage-amplifies DC current level detected by the detection resistor and inputs
this to microcomputer. Internal or external overload is judged in microcomputer.

Produces reset voltage.

Modulates chopper signal to drive signal and stops according to presence/ab­sence of lp signal or reset signal.

59

17

61

48

58

62

+

+

60

Is

D104

L

CT1

N

R005

0V0V

0V

0V

R221

C218

12V

R292

R247

C107

0V

0V

R006

C105

+

+

C217

C009

JW10

R252

R222

R248

IC4

C205

R288

IC5

+

–

2

3

1

+

–

6

5

7

Fig. 8-1 Microcomputer and Peripheral Circuits

RESET

Is

Id

Ip

Vd

CN13CN14

R41

R24

N1

IC1

SPM2 – HIC

DC260-380V

P2

SPM2

MAIN P.W.B

Direct Current

DC Current

Detection Resistor

OC

F

0V0V

HIC

IC1

C2260VR285

R286

D205

D204

R249

R284

0V

C225

C224

0V

0V

C222

0V

0V

C204

0V

C215

R289

0V

0V

5V

5V

R253

R500

R42

R43

C34

37

521

19

20

8

99

10

3938

MICROCOMPUTER

0V

R245

– 80 –

Drive

signal

Chopper

signal

Chopper

signal

DC
Current
level

DC current

Detection

resistor

5V

DC 260V

-360V

Reset circuit

Over-load external

setting circuit

Current amplified

circuit

Drive

Circuit

IP signal

Reset Voltage

Peak current
cut off circuit

Outdoor microcomputer

Trip signal

synthesis circuit

Compressor

motor

Powe r
module

Fig. 8-2

● The following describes the operations of each circuit in detail.

(1) Peak current cut off circuit
Fig.8-3 Peak Current Cut off Circuit and Waveforms at Each Section.

DC current Id

Voltage at point

1.05V (1.35V for RAC-50NH4)

21A (27A, for RAC-50NH4)

Voltage at point

A

B

A

–

Fig.8-3

Detection

resistor

Negative
Terminal

DC
current

0V

0V

R43

0V

R41

QC

R42

SPM2

SPM2 – HIC

Main P.W.B

HIC

IC1

CN14

IP
Outdoor
microcomputer

F

R43

9 9

8

20 9 2 39 17

B

● The Ip cut off circuit detects an instantaneous excessive current and stops inverter to protect parts such

as SPM2, etc.

● As shown in diagram, if current exceeding 21A (27A for RAC-50NH4) flows, voltage at point recognized

by detecting resistor is input to pin of SPM2 – HIC, and voltage divided by R41 and R43 is input to pin

of IC1. Since threshold of IC1 is exceeded in this case, Lo signal is input from pin (Voltage at point
. When Lo signal is input to pin of microcomputer, microcomputer stops drive output.

● When drive output from microcomputer is stopped, all drive output goes Hi, and microcomputer is initialized

to enter drive signal standby mode. 3 minutes later, microcomputer outputs drive signal again, to start
operation.

10

8

9

B

A

17

– 81 –

(2) Overload control circuit (OVL control circuit)

● Overload control is to decrease the speed of the compressor and reduce the load when the load on the

air conditioner increases to an overload state, in order to protect the compressor, electronic components
and power breaker.

● Overloads are judged by comparing the DC current level and set value.

● Fig. 8-4 shows the overload control system configuration and Fig. 8-5 is a characteristic diagram of

overload judgement values. There are two judgement methods-external judgement which compares the
externally set value with the DC current value regardless of the rotation speed and internal judgement
which compares the set value that varies according to the rotation speed programmed in the microcomputer
software with the DC current value.

To power module
negative terminal

(R24)

DC current

Voltage amp

circuit

(Internal judgement)

DC voltage

Judgement value according to the rotation speed

(internal judgement value)

OVL judgement
with respect to
externally set
value

A/D

converter

A/D

converter

Judgement OVL
according to the rotation
speed

Selects data according
to the rotation speed and
DC voltage

OVL start current data

Rotation speed data

Motor control
process

Microcomputer

Detection

resistor

Fig. 8-4 Overload Control System Configuration

Fig. 8-5

DC current

Rotation speed

1. Overload external judgement circuit

● Fig. 8-1. The filter consisting of R245 and C217 removes high harmonic components from the voltage

generated by the current flowing to Detection resistor; R245 and C217 average the voltage. This voltage
is then input to IC4 pin is then amplified and supplied to microcomputer pin . The microcomputer
compares this input with the internally set value, and if the input exceeds the set value, it enters overload
control status.

● Fig. 8-7 shows the rotation speed control. When the voltage at pin of the microcomputer exceeds the

set value, the microcomputer decreases the rotation speed of the compressor and reduces the load
regardless of the rotation speed commanded by the indoor microcomputer.

5

60

60

– 82 –

60

Fig. 8-6

Fig. 8-7

Voltage at microcomputer pin

Rotation speed of compressor

Deceleration DecelerationAcceleration Acceleration

Commanded rotation speed

Actual rotation speed

59

61

58

+

60

Is

D104

L

CT1

N

R005

0V0V

0V

0V

0V0V

R247

R006

C105

+

C217

C009

R222

C218

R221

R248IC4

+

–

6

5

7

Is

Id

Vd

CN13

CN14

R24

N1

DC 260-380V

SPM2

MAIN P.W.B.

P2

Direct Current

DC Current

Detection Resistor

HIC

IC1

Microcomputer

D205

D204

C224

0V

C222

0V0V

5V

5V

R253

R249

R500

+

C205

0V

5

1

373938

R245

10

1

2. Voltage amp. circuit

● The voltage amp. circuit amplifies the DC current level detected by the detection resistor after being

converted to a voltage and supplies it to the microcomputer. Receiving this, the microcomputer converts
it to a digital signal and compares it with the internal data to judge whether or not overload control is
required.

< During overload control >

● The filter consisting of R245 and C217 removes high harmonic components from the voltage generated

from the DC current flowing to the detection resistor, and supplies it to IC4 pin 5 IC4 forms a non-inverting
voltage amp. circuit together with the peripheral elements.

● The microcomputer stores the set values which vary according to the rotation speed. When the DC current

level exceeds the set value, the microcomputer enters the overload control state.

● The set Value is determined by the amplification of the voltage amp. circuit.

● Amplification : high [ DC current : low

● Amplification : low [ DC current: high

{

– 83 –

● R500, R253, detect the DC voltage at the power circuit. The microcomputer receives a DC voltage (260-

380V) via HIC U and applies correction to the overload set value so the DC current is low (high) when
the DC voltage is high (low).

(Since the load level is indicated by the DC voltage multiplied by DC current, R247, R248, R249 are
provided to perform the same overload judgement even when the voltage varies.)

< During start current control >

● It is required to maintain the start current (DC current) constant to smooth the start of the DC motor for

the compressor.

● RAC-25NH4, RAC-35NH4, RAC-50NH4 uses software to control the start current.

● The start current varies when the supply voltage varies. This control method copes with variations in the

voltages as follows.

(1) Turns on the power module's U+ and V– transistors so the current flows to the motor windings as
shown in Fig8-9.

(2) Varies the turn-ON time of the W+ transistor according to the DC voltage level and the start is
controlled so the start current is approx. 10A as shown in Fig. 8-10.

Fig. 8-8

DC current

G

0

0

Rotation speed

Amplification : low
DC voltage : low
DC current : high

Amplification : high
DC voltage : high
DC current : low

Amplification : 8.5 times
DC voltage : 260V

U

+

U

—

V

+

V

—

W

+

W

—

U
V

W

Compressor motor

DC current

Power module

DC 260-360V

Detection

resistor

Fig. 8-9

Fig. 8-10

20

15

10

5

0

DC current (A)

W transistor

ON-time

Start

DC voltage (start current)

Set value

Time

Chopper duty: high

DC voltage: low
DC voltage: 280V
DC voltage: high

– 84 –

9. Temperature Detection Circuit

● The Over heat thermistor circuit detects the temperature at the surface of the compressor head, the

Defrost. thermistor circuit detects the defrosting operation temperature.

● A thermistor is a negative resistor element which has the characteristics that the higher (lower) the

temperature, the lower (higher) the resistance.

● When the compressor is heated, the resistance of the Over heat thermistor becomes low and voltage at

pin 62 of microcomputer is increased.

● Microcomputer compares the voltage present at pin

62

with the internal set value, if it is exceeded the

set value microcomputer judges that the compressor is overheated and stops operation.

● When frost forms on the outdoor heat exchanger, the temperature at the exchanger drops abruptly.

Therefore the resistance of the Defrost. thermistor becomes high and the voltage at pin

63

of microcomputer
drops.
If this voltage becomes lower than the set value stored inside, the microcomputer starts defrosting control.

● During defrosting operation the microcomputer transfers the defrosting condition command to the indoor

microcomputer via the circuit interface.

● The microcomputer always reads the outdoor temperature via a thermistor (microcomputer pin

64

), and
transfers it to the indoor unit, thus controlling the compressor rotation speed according to the value set
at the EEPROM in the indoor unit, and switching the operation status (outdoor fan on/off, etc.) in the dry
mode.

The following shows the typical values of outdoor temperature in relation to the voltage:

<Reference>

When the thermistor is open, in open status, or is disconnected, microcomputer pins 62 – 64 are approx. 0V;
when the thermistor is shorted, they are approx. 5 V, and LD301 blinks seven times.

However, an error is detected only when the OH thermistor is shorted; in such a case, the blinking mode is
entered 12 minutes after the compressor starts operation.

Table 9-1

Outdoor temperature (°C)

Microcomputer pin 5 voltage (V)

-10

1.1901.69102.23

20

3.22403.62

627

0V

+5V

O.H. thermistor

O.H.

Normal 2.7V or less
Over heat 2.7V or more
Reset 2.3V or less

CN8

636

0V

+5V

DEF. thermistor

DEF.

Normal 2.4V or more
Over heat 2.4V or less
Reset 2.9V or more

CN9

645

0V

+5V

Outdoor temperature
thermistor

Outdoor
temperature

Refer to the table 10-1

CN10

Microcomputer

HIC

Fig. 9-1

2.75

30

– 85 –

10. Reset Circuit

● The reset circuit initializes the microcomputer program when Power is “ON” or “OFF”.

● Low voltage at pin

48

resets the microcomputer, and HI activates the microcomputer.

● Fig. 10-1 shows the reset circuit and Fig. 10-2 shows waveform at each point when power is turned on

and off.

● When power is turned on, 12V line and 5V line voltages rise and 12V line voltage reaches 10.9V and

reset voltage input to pin 48 of microcomputer is set to Hi.

● Reset voltage will be hold “Hi” until the 12V line voltage drops to 9.90V even though the power shuts down.

Microcomputer

R252

R289

0V0V

R288

0V

5V

12V

HIC

R284

JW10

IC5 (1/2)

C204

48

RESET

Main

P. W . B

Fig. 10-1

C215

R286

C225

C107

C226

R285

0V

1

3

2

62

8

–

+

+

0V

0V

R292

12V line

12V line

5V line

5V line

Fig. 10-2

Reset voltage

Reset voltage

12

6

0

Power is ON

Voltage (V)

12

6

0

Power is OFF

Voltage (V)

Time

Time

– 86 –

R297

R298

C208

R108

R107

C101

VSD

RC Filter

Motor coil

System power module

Power supply for DC fan motor from smoothing
capacitor in system power module

Smoothing Capacitor

U

V

W

BOARD

DC Fan motor with control board

ONE CHIP DRIVER IC

R242

HIC

0V

0V

0V

0V

R283

R246

Q201

5V

PQ102

5V

5V

t

33.3KHz

Ap 7V

T/2

14

23

T

0V

0V

Vcc

PWM control voltage

FG Pulse

CN6

FM-0V

FM-15V

D101

Q101

R101

R102

Main P.W.B

CN12

FM-15V

FM-0V

12V

0V

0V

IC4

R244

Microcomputer

R243

D105

R104

R105

R103

R106

C104

C219

R114

C209

FM–60˚ el
FG Pulse
input

Fig. 11-1

1

3

60

61

59

2

8

15

75

65

–

+

+

C106

C103

ZD101

+

R115

7

6

5

4

3

2

1

321

123 4 5321

+++

2A-FUSE

11. Outdoor DC Fan Motor control circuit.

● This model uses DC Fan Motor which has a controller circuit in the Motor.

● This DC Fan Motor will rotate by control voltage apply to Vsp input. (Voltage range: 1.7 to 7V DC)

Vsp high : Faster ; Vsp low : slower ; Vsp lower than 1.7V : stop

● Motor will output FG pulse by following this motor revolution.

● Outdoor Microprocessor will output PWM control signal from FMCHOP terminal by following the instruction

from indoor Microprocessor.

● This PWM control signal will convert to Vsp voltage by smoothing circuit (Q101 & RC filter)

● Fan motor will start to rotate when Vsp was proceeding over than 1.7V, and generate FG pulse by rotation

speed.

● FG pulse will feed back to Outdoor Microprocessor through PQ102.

● PQ102 is the isolator between Microprocessor circuit and DC Fan Motor circuit, which has to match the Fan

Motor revolution with instructed revolution. Such as...

FG feedback: Faster – Instruction: Slower ... Decrease pulse width
FG feedback: Slower – Instruction: Faster ... Increase pulse width

● FG pulse is also used for Fan Motor failure detection

● Microprocessor will monitor FG pulse 30 seconds after start the fan motor. If there is no signal detected, it

will consider that the Fan Motor was malfunction and stop the operation. In this case, LD302 on control PWB
will blink 12 times. (Fan Motor lock detected)

● R107 and IC4 are used for Fan Motor over current

– 87 –

< Reference >

● When operation stop with LD301 blinks 12 times, it may be caused by faulty DC fan motor.

● In this case, please check CN6 and CN12 connection first. It makes Fan Motor Lock also if those

connectors are in misconnection.

● DC Fan Motor has broken when 2A Fuse was burned. Please replace both DC Fan Motor and 2A Fuse

together.

● It will makes “Fan Lock Stop”when something has disturb the Fan rotation by inserting materials into

propeller fan or ice has growing inside of outdoor unit by snowing.

● It may make “Fan Lock Stop” by strong wind (ex. 17m/sec or above) against the Fan rotation. In this case,

unit will be restart again after a while.

● In case of “Fan Lock Stop” even though the DC Fan Motor is rotating correctly, the possible casue is

Fan Motor problem or PQ102 on board or control board problem. Stop after the Fan motor runs 2 minutes,
Fan Motor may be broken.

< Caution >

● Please take care for the electrical shock by high voltage of DC Fan Motor power source which is common

with compressor when you are servicing this unit.

● You can not confirm the coil and wiring of Motor due to the built in control circuit in Fan Motor.

– 88 –

Power factor is controlled to almost 100%. (Effective use of power)

With IC in ACT module, control is performed so that input current waveform will be similar to waveform of input
voltage

12. Power Factor Control Circuit

* Assuming the same current capacity (20A), power can be used about 10% effective, comparing with curent use
(power factor of 90%), and maximum capacity is thereby improved.

I (input current)

V (input voltage)

Invalid power area

(Even if voltage is applied. current does not flow)

Effective

voltage

area

input voltage

input current

Effective

voltage area

– 89 –

SERVICE CALL Q & A

Model RAD-25NH4

RAD-40NH4

COOLING MODE

The compressor has
stopped suddenly during
cooling operation.

Sound of running water is heard from
indoor unit during dehumidifying.

Compressor occasionally does not
operate during dehumidifying.

The circulation stops
occasionally during
Heating mode.

When the fan speed is set
at HIGH or MED, the flow
is actually Weak.

Heating operation stops
while the temperature is
preset at "30".

Check if the indoor heat
exchanger is frosted.
Wait for 3-4 minutes
until it is defrosted.

If the air conditioner operates
in cooling mode when it is
cold, the evaporator may get
frosted.

Normal sound when refrigerant flows in pipe.

Compressor may not operate when room
temperature is 10°C or less. It also stops
when the humidity is preset humidity or less.

It occurs during defrost­ing. Wait for 5-10
minutes until the
condenser is defrosted.

At the beginning of heating,
the fan speed remains
LOW for 30 seconds. If
HIGH is selected, it
switches to LOW and again
to MED after additional 30
seconds.

If temperature is high in
the outdoor, heating
operation may stop to
protect internal devices.

DEHUMIDIFYING MODE

HEATING MODE

Q1

A1

Q2

A2

Q3

A3

Q4

A4

Q5

A5

Q6

A6

– 90 –

AUTO FRESH DEFROSTING

AUTO OPERATION

NICE TEMPERATURE RESERVATION

INFRARED REMOTE CONTROL

After the ON/OFF button is pressed
to stop heating, the outdoor unit is
still working with the OPERATION
lamp lighting.

Fan speed does not change when
fan speed selector is changed
during auto operation.

When on-timer has been
programmed, operation starts before
the preset time has been reached.

Does “Nice temperature reservation”
function operate during dehumidifying?

Even if the same time is preset,
the operation start time varies.

Timer cannot be set.

The current time display
disappears soon.

The timer has been programmed,
but the preset time disappears.

Auto Fresh Defrosting is carried out : the
system checks the outdoor heat exchanger
and defrosts it as necessary before stopping
operation.

At this point fan speed is automatic.

This is because “Nice temperature reservation”
function is operating. This function starts
operation earlier so the preset temperature is
reached at the preset time. Operation may start
maximum 60 minutes before the preset time.

It does not work. It works only during cooling
and heating.

This is because “Nice temperature reservation”
function is operating. The start time varies
according to the load of room. Since load varies
greatly during heating, the operation start time is
corrected, so it will vary each day.

Has the clock been set? Timer cannot be set
unless the clock has been set.

The current time disappears
in approx. 10 seconds. The
time set display has priority.

Is the current time past the preset time?
When the preset time reaches the current
time, it disappears.

When the current time is
set the display flashes for
approx 3 minutes.

Q7

A7

Q8

A8

Q9

A9

Q10

A10

A11

Q12

A12

Q13

A13

Q14

A14

Q11

– 91 –

OTHERS

Q15

A15

Q16

A16

Q17

A17

Q18

A18

Q19

A19

The indoor fan varies among
high air flow, low air flow and
breeze in the auto fan speed
mode. (Heating operation)

This is because the cool
wind prevention function
is operating, and does
not indicate a fault.

The heat exchanger temperature
is sensed in the auto speed mode.
When the temperature is low, the
fan speed varies among high air
flow, low air flow and breeze.

Loud noise from the outdoor unit is
heard when operation is started.

When operation is started, the compressor
rotation speed goes to maximum to increase the
heating or cooling capability, so noise becomes
slightly louder. This does not indicate a fault.

Noise from the outdoor unit
occasionally changes.

The compressor rotation speed changes according to
the difference between the thermostat set temperature
and room temperature. This does not indicate a fault.

There is a difference between the set
temperature and room temperature.

There may be a difference between the set
temperature and room temperature because of
construction of room, air current, etc. Set the
temperature at a comfortable for the space.

Air does not flow immediately
after operation is started.

Preliminary operation is performed for one
minute when the power switch on and heating
or dehumidifying is set. The operation lamp
blinks during this time for heating. This does
not indicate a fault.

– 92 –

TROUBLE SHOOTING

Model RAC-25NH4

RAC-50NH4

PRECAUTIONS FOR CHECKING

Power source

+

~

+

–

~

ACT Module

+–+

–

N

C

D

L

Compressor motor

System power module 2

Indoor unit
electric parts

Control
P. W . B .

DC35V

0V

(0V)

MAIN P.W.B.

Power module

a

b

M

1. Remember that the
0V line is biased to
155-170V in
reference to the
ground level.

2. Also note that it takes
about 10 minutes
until the voltage fall
after the power switch
is turned off.

DANGER

Across a – b (0V line)....................

Across a – ground..........................

Across b (0V line)– ground............

approx 260-360V

approx 155-170V

approx 155-170V

When using an
oscilloscope, never
ground it. Don't forget
that high voltages as
noted above may
apply to the
oscilloscope.

DANGER

Always keep your hands
and metallic things away
from the enclosure of the
oscilloscope.

DANGER!

Don’t install

the ground

line.

Oscilloscope

Outdoor unit P.W.B.

– 93 –

1. Turn OFF the Power supply to the outdoor unit.

2. After power is turned off, wait for 10 minutes or more. Then, remove electrical parts cover and apply soldering
iron of 30 to 75W for 15 seconds or more to P2 and N1 terminals on system power module, in order to
discharge voltage in smoothing capacitor.

3. Remove receptable of red/gray lead wire connected to system power module from diode stack before
performing operation chech of each circuit.

Caution

●

Voltage of about 300-330V is charged between both ends of smoothing capacitors

●

During continuity check for each part of circuit in indoor unit electrical parts, disconnect red/gray
lead wire connected from diode stack to system power module (SPM2) to prevent secondary
trouble. (Be sure to discharge smoothing capacitor)

Do not use a soldering iron with
transformer: If one is used, thermal fuse
inside transformer will be blown

DISCHARGE PROCEDURE AND POWER SHUT OFF METHOD FOR POWER CIRCUIT

WARNING

As shown above, apply soldering iron to metal
parts (receptable) inside the sleeve
corresponding to P1 and N1 terminals of
system power module: Do this with smoothing
capacitors kept connected. By removing red/
gray lead wire from diode stack, power supply
can be shut off. (corresponding to + and –
terminals of system power module)

N1

P1

Soldering
iron

System power module

SPM2

Smoothing capacitors

SPM2

Smoothing capacitors

RAC-25NH4

RAC-50NH4

– 94 –

CHECKING THE INDOOR/OUTDOOR UNIT ELECTRICAL PARTS AND REFRIGERATING CYCLE

Model RAC-25NH4

RAC-50NH4

Does the timer lamp on the indoor unit blink?

Is the compressor in the outdoor unit operating?

Does the operation lamp on the indoor unit
start to light or blink?

Remove the outdoor unit cover and
electrical parts cover, and check
self-diagnosis lamp LD301

Does LD301 blink one time ?
* Repeats 0.25-second on and
2-second off.

Blinking other than
one time

One-time blinking

Yes

Yes

Yes

Yes No

No

No

Normal

No

No

Timer
lamp

Press the service switch for 1 sec.
Does the compressor operate?
(After checking, be sure to press
the service switch to stop the
operation).

Check the refrigerating cycle.

Check the outdoor electrical parts.

Check the indoor electrical parts.

Check to see whether the F­cable is connected incorrectly
or disconnected

See Out door unit self-diagnosis lamp
lighting mode .

See Troubleshooting when the timer lamp
blinks .

Is approx. DC 33 to 37V being generated? Is the
polarity correct?

Remove the terminal cover and check the voltage
between terminal (C) and terminal (D)

Service switch

P. W. B
Self diagnosis lamps
(LD303, 302, 301)

CN17

IC3

022527

– 95 –

TROUBLESHOOTING WHEN TIMER LAMP BLINKS.
Model RAD-25NH4, RAD-40NH4
Perform troubleshooting according to the number of times the indoor timer lamp and outdoor LD301 blink.

SELF-DIAGNOSIS LIGHTING MODE
Model: RAD-25NH4, RAD-40NH4

No. Timer indicator flashing mode Reason for display Section of estimated fault

Four-way valve faulty

The room heat exchange
temperature is low during heating,
or it is high during cooling.

Outdoor unit forced operation

The outdoor unit is in forced
operation or undergoing balancing
after forced operation.

Indoor/outdoor interface faulty

The interface signal from the
outdoor unit has been interrupted.

Outdoor electrical assembly
defective.

Abnormal water level detection

All stop when the float switch has
been activated.

Drain pump forced operation.

When the knob of drain pump test
switch at Indoor P.W.B main slide to
‘test’ position.

Room thermistor or heat
exchanger thermistor is faulty

When room thermistor or heat
exchanger thermistor is opened
circuit or short circuit.

DC fan motor overcurrent detection

Overcurrent in indoor DC fan motor
has been detected.

IC401 data reading fault

There was error in the data read
from IC401

(1) Four-way valve faulty.
(2) Disconnection in heat exchange

thermistor (only during heating)

Service SW in outdoor electrical
parts turned ON.

(1) Indoor interface circuit
(2) Outdoor interface circuit

Please check at the outdoor
electrical led lamp blinking (LD301)
and refer to self diagnosis lighting
mode for outdoor unit.

(1) Drain stopped up
(2) Drain pump
(3) Float switch

(1) Indoor P.W.B. Main.

(1) Room thermistor
(2) Heat exchanger thermistor

(1) Indoor fan locked
(2) Indoor fan motor
(3) Indoor P.W.B. Main

IC401 faulty

<Cautions>

(1) If the interface circuit is faulty when power is supplied, the self-diagnosis display will not be displayed.

(2) If the indoor unit does not operate at all, check to see if the F-cable is connected or disconnected.

(3) To check operation again when the timer lamp is blinking, you can use the remote control for operation

(except for mode mark 1).

1

2

3

4

5

6

7

8

9

( –– Lights for 0.35 sec. at interval of 0.35 sec..)

5

–– 7 times

– ––––– 3 times

– ––––––– Once

– –––––– Twice

–– 9 times

5 sec.

5 sec.

5 sec.

5 sec.

5 sec.

1

–– 6 times

5 sec.

–– 4 times

5 sec.

–– 10 times

5 sec.

–– 13 times

5 sec.

– 96 –

SELF-DIAGNOSIS LIGHTING MODE

MODEL: RAC-25NH4, RAC-50NH4

– 97 –

1. Power does not come on (no operation)

Is AC 220-240V AC being generated
between terminals L and N on the
outdoor unit terminal board?

Is DC 35V being generated between
terminals C and D on the outdoor
unit terminal board?

Check the indoor/outdoor unit
connection cable, and correct any
defective section (wrong connection,
incomplete insertion reversed).

Check AC outlet and breaker, and
repair any defective part.

Check the outdoor unit power circuit,
and repair the defective section.

Is DC 35V being generated between
terminals C and D on the terminal
board?

Are control voltages (12V, 5V)
being generated normally?

Check according to the proper method
for checking the power circuit.

No No

No

No

Yes

Yes

Do the air deflectors perform initial
operation when the power supply is
turned on and off?

Check the indication P.W.B.
connection cord and light receiving
unit.

No

No

Is the microcomputer reset input
(pin 7 ) Hi ?

Replace the P.W.B Main

Perform final operation check.

Check the reset circuit, and repair
any defective section.

Yes

No

Is the microcomputer clock signal
10MHz at pin

10 11

being

generated normally?

Replace the microcomputer and
oscillator.

Yes

Yes

Yes

CHECKING INDOOR UNIT ELECTRICAL PARTS

– 98 –

2. Outdoor unit does not operate (but receives remote infrared signal)

– 99 –

3. Only indoor fan does not operate (other is normal)

Is approx 20 V DC generated
between pins 2 (blue) and 4 (red)
of CN 10 when operated at high fan
speed during cooling?

Are pulses of approx. 33 Vp-p
generated at the collectors of Q901
in the fan operation mode? Are
collectors of Q903 approx.
O V?

Are microcomputer fan PWM
outputs (micro computer pins r)“Hi”
or are pulses output
in the fan operation mode?

Has the fan been stopped by
remote control?

Are microcomputer fan PWM
outputs micro computer pins F “Hi”?

Is 5 V DC generated between pins

2

(blue) and 1 (yellow) of CN10?

Is there 1 or less between L901
and L902?

Replace indoor fan motor.

Check disconnection, etc of lead
wires.

Replace Q901.

Replace L901.

Replace Q903.

Replace micro computer.

Perform final operation check.

Replace micro computer.

Replace Q903.

Replace Q901.

Replace micro computer.

Replace micro computer.

Replace the air deflector motor.Replace IC111.

Perform final operation check.

Perform final operation check.

Is there a voltage higher than 15V
across C114 (12 V line)?

Is pulse signal output to micro
computer pins %~* with air
deflector set to auto during cooling?

No

Yes

No

No

Are the collectors of Q903 approx
OV?

No

No

Yes

No

Yes

No

No

Yes Yes

No

Yes

Yes

Yes

4. Indoor fan speed does not change (other is normal)

5. Air deflector does not move (other is normal)

No

Yes

Yes

– 100 –

6. All systems stop from several seconds to several minutes after operation is started
(all indicators are also off)

Set to the "Hi" fan mode.

The operation lamp lights once and goes out in
5-10 seconds.

Disconnect, CN10 and set to the fan mode again.

The operation lamp lights once and goes out in
5-10 seconds.

Check to see if shorting, etc.
has occurred in the P.W.B.
pattern.

Can the indoor fan be lightly turned by hand?
(Set the power switch to "off" to check.)

Replace the indoor fan motor.

Yes

Yes

Check to see if the indoor fan is
touching the chassis, etc.
If it does, repair.

No

Yes

No

– 101 –

CHECKING THE REMOTE CONTROLLER

– 102 –

MODEL RAC-25NH4, RAC-50NH4

[No operation or abnormal operation]

Is AC220-240V being

supplied to terminal L and N?

Is the 25A fuse normal?

If the 25A fuse has blown, be aware

that other parts may also be

defective (mainly, varistor 2, diode

stack, smoothing capacitors, system

power module, etc.).

No

Ye s

CHECKING THE OUTDOOR UNIT ELECTRICAL PARTS

Replace any defective parts.

Is the power circuit normal?

See the description on

power circuit for details.

Is 5V being generated

between Pin 4 (0V) and pin

3 (5V) at CN 18 (test pin)?

Operate the outdoor unit

according to the instruction

“How to operate the outdoor

unit independently

”.

How did the self-diagnosis

lamp (LD301) light?

Is the switching power circuit OK?

Has the 3A fuse blown?

See the self-diagnosis lamp

lighting mode.

Check to see whether the

connected C and D cable

correctly? If reversed, correct the

cable connection.

Replace any defective parts.

If the 3A fuse has blown, the

switching transformer (T1),

R906, etc. may also be

defective.

()

No

Ye s

Ye s

No

Ye s

– 103 –

LD301 blinks 9 time.

Communication error.

Is DC 35V being output at

terminals C and D? (Normally,

DC 33-38.5V is output.)

Ye s

Interface relay

Coil terminal

Contact terminal

Is DC 35V being output across R914?

Is DC 12V being supplied across

the control side (coil terminal) of

interface relay?

Is a voltage (at least 10V) being

generated between the contact

terminals of interface relay?

Check the interface curcuit.

Ye s

Ye s

No

No

Ye s

D907 and C910 may be defective.

There is a defective section between the

12V output of switching power supply on

the main P.W.B. and interface relay (also,

check for contact with solder, etc.).

Repalce the interface relay.

No

– 104 –

Ye s N o

No

Ye s

Ye s

Ye s

No

No

No

LD301 blinks 8 time.

Acceleration defect.

LD301 blinks 7 time.

Thermistor abnormal.

Is the power module normal?

Is the drive circuit normal?

Is the thermistor connector

disconnected?

❈ The problem may be

“forgetting

to connect after servicing

”.

Is the continuity of thermistor normal?

Is the thermistor circuit normal?

Replace the power module.

Replace any defective parts.

Connect the thermistor.

Replace the thermistor.

Replace parts in the

thermistor circuit.

Check continuity of pattern and

lead wires according to the

P.W.B. and schematic diagrams.

Check continuity of pattern and

lead wires according to the

P.W.B. and schematic diagrams.

– 105 –

LD301 blinks 6 time.

The temperature at the

OH thermistor rises.

LD301 blinks 5 time.

Overload lower limit cut.

LD301 blinks 4 time.

Failure of switching.

LD301 blinks 3 time.

Abnormal low speed.

Replace parts in the

thermistor circuit.

No

No

No

Check continuity of new parts.

Check continuity of pattern and

lead wires according to the

P.W.B. and schematic diagrams.

Ye s

Ye s

Replace system power

module or defective parts.

Replace the system power

module.

Replace any defective

parts.

Is the thermistor circuit normal?

Are R503, R541, R542, R549

and peripheral circuits of

system power module normal?

Replace the main P.W.B.

Is the system power module

normal?

Is the drive circuit normal?

– 106 –

– 107 –

POWER CIRCUIT

Phenomenon 1 <Rotation speed does not increase>

Is the DC voltage at least 350V?

Is the OVL lamp lit?
If the lamp is lit, it does not
indicate fault, but the unit
is overload status.

Recheck cord, etc. of the
system power module. If
they are disconnected,
connect them securely.

If abnormality continues,
replace the system
power module.

Overvoltage defect: system power
module faulty (15-times blinking)

Ye s

No

– 108 –

CHECKING THE REFRIGERATING CYCLE

1. Troubleshooting procedure (No operation, No heating, No cooling)

Connect U,V,W phase leads to the
power module again and operate the
air conditioner.

Gas leaks.
Repair and seal refrigerant.

Is the self-diagnosis lamp mode as
shown on the right?

YES

Gas leaking
(less than 4kg/cm

2

G)

(less than 0.39 MPaG)

Normal
(0.39-0.98 MPaG)
(4-10 kg/cm

2

G)

Perform a final check of operation.

When the
self-diagnosis lamp
lights in the same
condition as above.

The compressor is defective. Replace it
and seal refrigerant.

If the compressor checker for an
inverter type air conditioner is
available, re-check using it.

( )

(JUDGING BETWEEN GAS LEAKAGE AND
COMPRESSOR DEFECTIVE)

Blinking off

Time until the

lamp lights

Approx. 10 seconds

Approx.
10
seconds

Approx.
10
seconds

Within
Approx.
30
seconds

Compressor

Compressor

Gas
leakage

Possible

malfunctioning

part

LD301

Self­diagnosis lamp

Lighting mode

Blinks

2 times

Blinks

3 times

Blinks

4 times

Blinks

5 times

Blinks

6 times

Blinks

8times

Stop to operate and check the gas
pressure in balancing mode.

Checking the system power module

– 109 –

HOW TO CHECK SYSTEM POWER MODULE

+

+

+–

– +

+

–

P1 P2 U

WV

N1

L2 L1

+

–

+

–

– +

–

–

P1 P2 U

WV

N1

L2 L1

Checking system power module using tester

Set tester to resistance range (X 100)
If indicator does not swing in the following conductivity check, the system power module is normal.
(In case of digital tester, since built-in battery is set in reverse direction, + and – terminals are reversed.)

CAUTION

If inner circuit of system power module is disconnected (open), the indicator of tester will not swing and this may
assumed as normal. In this case, if indicator swings when + and – terminals are connected in reverse of diagram
below, it is normal. Furthermore, compare how indicator swings at U, V and W phases. If indicator swings the same way
at each point, it is normal.

– 110 –

HOW TO OPERATE USING THE SERVICE SWITCH THE OUTDOOR UNIT

MODEL RAC-25NH4, RAC-50NH4

1. Turn off the power supply to outdoor unit and then turn on again.

2. Remove the electrical box cover.

LD303 (red) will light and the unit will operate in the forced cooling mode at this time.

Never operate the unit for
more than 5 minutes.

(Cautions)
(1) If interface signal (DC 35V) terminals C and D are not connected when the outdoor unit is in forced cool mode, the outdoor

unit defect indicator (LD301) will blink 9 times during operation to indicate communication error.

(2) If checking is done with the compressor connector disconnected, the unit will continue normal operation when the

electrical parts are normal, or it will repeat operating for approx. one minute and stop due to overload power limit cut,
or it will operate in the overload status.

Be sure to push the service switch again to stop the forced cool operation.

HOW TO OPERATE THE OUTDOOR UNIT INDEPENDENTLY

The operation method is the same as “How to operate using the connector to servicing the outdoor unit”.

1 The charging amount of 300g is equivalent to the load in normal operation.

Charge refrigerant of 300g
after vacuuming (

1 )

Do not operate for more than 5
minutes

Parts to be prepared

(1) Reducing union

2/8” (6.35mm)

1/2” (12.7mm)
(2) Copper pipe (2/8” and 1/2”)
(3) Shorting leads

2 leads approx. 10 cm long

with alligator clip or IC clip

1. Connect the large dia. pipe side and small dia. pipe side service valves using a pipe.

Large dia. service valve

Reducing union
(2/8” and 3/8”)

Copper pipe
(2/8”)

Small diameter
service valve

Reversing
valve

Compressor

Outdoor unit

Connect the small diameter
service value and the large
diameter service valve using the
reducing union and copper pipe
as shown on the right.

Electrical Box Cover

Electrical Box Cover

RAC-25NH4

RAC-50NH4

Self diagnosis lamps
(LD303, 302, 301)

Service switch

(forced-cooling mode is set by
pressing for 1 second or more,
and stopped by pressing again.)