12. PARTS LIST······················································32
NOTE:
•This manual describes technical data of outdoor units.
•As for indoor units MSC-GA20/GA25/GA35VB -, refer to the service manual OB385.
•As for indoor units MSC-CA20/CA25/CA35VB -, refer to the service manual OB393.
E1
E1
Page 2
1
TECHNICAL CHANGES
MUH-A07YV-➔MUH-GA20VB-
1. Indication of capacity has been changed. (BTU base ➔ kw)
2. Dimension of outdoor unit has been changed. (780W
3. Stop valve cover has been added.
4. Outdoor fan motor has been changed. (RC6V20-AB ➔ RA6V21-AD)
5. Outdoor fan motor capacitor has been changed.
6. Compressor capacitor has been changed.
7. Outdoor heat exchanger has been changed. (L-BEND ➔ FLAT)
MUH-A09YV-➔MUH-GA25VB-
1. Indication of capacity has been changed. (BTU base ➔ kw)
2. Dimension of outdoor unit has been changed. (780Wo540Ho255D ➔ 800Wo 550Ho285D)
3. Stop valve cover has been added.
4. Outdoor fan motor has been changed. (RA6V33-FB ➔ RA6V33-KB)
5. Outdoor fan motor capacitor has been changed.
6. Compressor capacitor has been changed.
7. Outdoor heat exchanger has been changed. (2 Row ➔ 1 Row)
MUH-A12YV-➔MUH-GA35VB-
1. Indication of capacity has been changed. (BTU base ➔ kw)
2. Dimension of outdoor unit has been changed. (780Wo540Ho255D ➔ 800Wo 550Ho285D)
3. Stop valve cover has been added.
4. Outdoor fan motor has been changed. (RA6V33-FB ➔ RA6V33-KB)
5. Outdoor fan motor capacitor has been changed.
6. Compressor capacitor has been changed.
7. Size of stop valve (gas) has been changed.(
8. Outdoor heat exchanger has been changed. (2 Row ➔ 1 Row)
E1E1
o540Ho255D ➔ 800Wo550Ho285D)
E1E1
E1E1
[12.7 ➔ [9.52)
2
Page 3
INFORMATION FOR THE AIR CONDITIONER WITH R410A REFRIGERANT
New SpecificationCurrent Specification
The incompatible refrigeration oil easily separates from
refrigerant and is in the upper layer inside the suction muffler.
Raising position of the oil back hole enables to back the
refrigeration oil of the upper layer to flow back to the
compressor.
Since refrigerant and refrigerating oil are compatible each,
refrigeration oil goes back to the compressor through the
lower position oil back hole.
Compressor
Suction muffler
Oil back hole
Refrigeration oil
Refrigerant
Compressor
Suction muffler
Oil back hole
Refrigeration oil /Refrigerant
Compressor
• This room air conditioner adopts HFC refrigerant (R410A) which never destroys the ozone layer.
• Pay particular attention to the following points, though the basic installation procedure is same as that for R22 conditioners.
1 As R410A has working pressure approximate 1.6 times as high as that of R22, some special tools and piping parts/
materials are required. Refer to the table below.
2 Take sufficient care not to allow water and other contaminations to enter the R410Arefrigerant during storage and
installation, since it is more susceptible to contaminations than R22.
3 For refrigerant piping, use clean, pressure-proof parts/materials specifically designed for R410A. (Refer to 2. Refrigerant
piping.)
4 Composition change may occur in R410A since it is a mixed refrigerant. When charging, charge liquid refrigerant to prevent
composition change.
Refrigerant
Composition (Ratio)
Refrigerant handling
Chlorine
Safety group (ASHRAE)
Molecular weight
Boiling point (:)
Steam pressure [25:](Mpa)
Refrigerant
Saturated steam density [25:](Kg/K)
Combustibility
ODP w1
GWP w2
Refrigerant charge method
Additional charge on leakage
Kind
Color
oil
Smell
Refrigeration
w1:Ozone Destruction Parameter : based on CFC-11
w2 :Global Warmth Parameter : based on CO
2
New refrigerant
R410A
HFC-32: HFC-125 (50%:50%)
Pseudo-azeotropic refrigerant
Not included
A1/A1
72.6
-51.4
1.557
64
Non combustible
0
1730
From liquid phase in cylinder
Possible
Incompatible oil
Non
Non
Previous refrigerant
R22
R22 (100%)
Single refrigerant
Included
A1
86.5
-40.8
0.94
44.4
Non combustible
0.055
1700
Gas phase
Possible
Compatible oil
Light yellow
Non
NOTE : The unit of pressure has been changed to MPa on the international system of units(SI unit system).
The conversion factor is: 1(MPa [Gauge]) =10.2(kgf/
ff
[Gauge])
3
Page 4
Wall
thickness
Outside diameter
Pipe
mm
For liquid
For gas
6.35
9.52
0.8 mm
0.8 mm
Heat resisting foam plastic
Specific gravity 0.045 Thickness 8 mm
Insulation material
-30 -20 -10010 20
30
40 5060
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
(MPa [Gauge])
R410A
R22
Conversion chart of refrigerant temperature and pressure
Saturated liquid pressure
(:)
NOTE : The unit of pressure has been changed to MPa on the
R410A toolsCan R22 tools be used?
Gas leak detector
R410A has high pressures beyond the measurement range of existing
gauges. Port diameters have been changed to prevent any other refrigerant
from being charged into the unit.
Hose material and cap size have been changed to improve the pressure
resistance.
Dedicated for HFC refrigerant.
6.35 mm and 9.52 mm
Description
Clamp bar hole has been enlarged to reinforce the spring strength in the tool.
Provided for flaring work (to be used with R22 flare tool).
Provided to prevent the back flow of oil. This adapter enables you to use
vacuum pumps.
It is difficult to measure R410A with a charging cylinder because the
refrigerant bubbles due to high pressure and high-speed vaporization
No
No
No
Yes
Yes
New
New
New
Gauge manifold
Charge hose
Torque wrench
Flare tool
Flare gauge
Vacuum pump
adapter
Electronic scale for
refrigerant charging
No : Not Substitutable for R410A Yes : Substitutable for R410A
international system of units(SI unit system).
The conversion factor is: 1(MPa [Gauge]) =10.2(kgf/ff[Gauge])
1.Tools dedicated for the air conditioner with R410A refrigerant
The following tools are required for R410A refrigerant. Some R22 tools can be substituted for R410A tools.
The diameter of the service port on the stop valve in outdoor unit has been changed to prevent any other refrigerant being
charged into the unit. Cap size has been changed from 7/16 UNF with 20 threads to 1/2 UNF with 20 threads.
2.Refrigerant piping
1 Specifications
Use the refrigerant pipes that meet the following specifications.
• Use a copper pipe or a copper-alloy seamless pipe with a thickness of 0.8 mm. Never use any pipe with a thickness less
than 0.8mm, as the pressure resistance is insufficient.
4
Page 5
2 Flaring work and flare nut
Electronic scale for refrigerant charging
Outdoor unit
Refrigerant gas
cylinder
operating valve
Refrigerant gas cylinder
for R410A with siphon
Refrigerant (liquid)
Service port
Gauge manifold
valve (for R410A)
Union
Liquid pipe
Gas pipe
Stop valve
Indoor unit
Charge hose (for R410A)
Flaring work for R410A pipe differs from that for R22 pipe.
For details of flaring work, refer to Installation manual “FLARING WORK”.
Pipe diameter
mm
6.35
9.52
Dimension of flare nut
R410A
17
22
R22
17
22
3.Refrigeration oil
Apply the special refrigeration oil (accessories: packed with indoor unit) to the flare and the union seat surfaces.
4.Air purge
• Do not discharge the refrigerant into the atmosphere.
Take care not to discharge refrigerant into the atmosphere during installation, reinstallation, or repairs to the refrigerant
circuit.
• Use the vacuum pump for air purging for the purpose of environmental protection.
5.Additional charge
For additional charging, charge the refrigerant from liquid phase of the gas cylinder.
If the refrigerant is charged from the gas phase, composition change may occur in the refrigerant inside the cylinder and the
outdoor unit. In this case, ability of the refrigeration cycle decreases or normal operation can be impossible. However,
charging the liquid refrigerant all at once may cause the compressor to be locked. Thus, charge the refrigerant slowly.
5
Page 6
2
( )
Air inlet
Air outlet
Drain outlet
Piping
Drain hose
back : MUH-GA20VB
back and side : MUH-GA25VB
MUH-GA35VB
Capacity
Dehumidification
Outdoor air flow
Power outlet
Running current
Power input
Auxiliary heater
Power factor
Starting current
Compressor motor current
Fan motor current
Model
Output
Winding
resistance (at 20:)
Model
Winding
resistance (at 20:)
Dimensions WOHOD
Weight
Sound level
Fan speed
Fan speed regulator
Refrigerant filling
capacity (R410A)
Refrigeration oil (Model)
Thermistor RT61 (at 0:)
Refrigerant flow in cooling
Refrigerant flow in heating
10
Page 11
MAX. REFRIGERANT PIPING LENGTH
Refrigerant piping
Model
Max. length : m
A
Piping size O.D : mmLength of connecting pipe : m
Gas
Liquid
Indoor unit
Outdoor unit
MUH-GA20VB - E1
MUH-GA25VB - E1
MUH-GA35VB - E1
20
9.52
25
MAX. HEIGHT DIFFERENCE
Indoor
unit
Height difference should be within
10m regardless of which unit,
indoor or outdoor position is high.
w Max. Height
difference 10m
ADDITIONAL REFRIGERANT CHARGE(R410A : g)
Model
MUH-GA20VB - E1
Outdoor unit precharged
650
7m
Gas 0.43
6.35
Liquid 0.5
Refrigerant Piping
Max.length
A
Refrigerant piping length (one way)
10m
15m
20m
Gas 0
Liquid 0
Outdoor unit
25m
MUH-GA25VB - E1
MUH-GA35VB - E1
8
PERFORMANCE CURVES
800
0
MUH-GA20VB -MUH-GA25VB -MUH-GA35VB -
The standard data contained in these specifications apply only to the operation of the air conditioner under normal conditions,
since operating conditions vary according to the areas where these units are installed. The following information has been provided to clarify the operating characteristics of the air conditioner under the conditions indicated by the performance curve.
60
160
Calculation : Xg = 20g/m x (A-7)m
E1E1E1
260
360
(1) GUARANTEED VOLTAGE
198~264V
(2) AIR FLOW
Air flow should be set at MAX.
(3) MAIN READINGS
(1) Indoor intake air wet-bulb temperature :°CWB
(2) Indoor outlet air wet-bulb temperature :°CWB
(3) Outdoor intake air dry-bulb temperature :°CDB
(4) Total input:W
(5) Indoor intake air dry-bulb temperature :°CDB
(6) Outdoor intake air wet-bulb temperature :°CWB
(7) Total input :W
Indoor air wet/dry-bulb temperature difference on the left side of the chart on page 10 shows the difference between the
indoor intake air wet/dry-bulb temperature and the indoor outlet air wet/dry-bulb temperature for your reference at service.
Cooling
}
Heating
}
11
Page 12
MSC-GA20VB - E1
MUH-GA20VB - E1
MUH-GA35VB - E1
MSC-GA35VB - E1
MUH-GA25VB - E1
MSC-GA25VB - E1
8.5
7.8
7.1
6.4
5.8
5.1
10.0
9.2
8.3
7.5
6.8
6.0
11.0
10.0
9.1
8.2
7.4
6.5
20.0
18.5
16.9
15.4
13.9
12.3
10.8
9.2
19.2
17.8
16.3
14.8
13.3
11.8
10.4
8.9
MSC-GA20VB - E1
MUH-GA20VB - E1
MUH-GA25VB - E1
MSC-GA25VB - E1
MUH-GA35VB - E1
MSC-GA35VB - E1
24.0
22.1
20.3
18.4
16.6
14.7
12.9
11.1
How to measure the indoor air wet-bulb/dry-bulb temperature difference
1. Attach at least 2 sets of wet-and dry-bulb thermometers to the indoor air intake as shown in the figure, and at least 2 sets
of wet-and dry-bulb thermometers to the indoor air outlet. The thermometers must be attached to the position where air
speed is high.
2. Attach at least 2 sets of wet-and dry-bulb thermometers to the outdoor air intake.
Cover the thermometers to prevent direct rays of the sun.
3. Check that the air filter is cleaned.
4. Open windows and doors of room.
5. Press the EMERGENCY OPERATION switch once(twice) to start the EMERGENCY COOL
(HEAT) MODE.
6. When system stabilizes after more than 15 minutes, measure temperature and take an average temperature.
7. 10 minutes later, measure temperature again and check that the temperature does not change.
INDOOR UNIT
Wet-and dry-bulb
thermometers
8-1.CAPACITY AND THE INPUT CURVES
OUTDOOR UNIT
Wet-and dry-bulb
thermometers
NOTE:The above curves are for the heating operation without any frost.
12
Page 13
8-2.OUTDOOR LOW PRESSURE AND OUTDOOR UNIT CURRENT
1832
7
8
9
10
11
12
13
230V
1520
50
25
6030 70(%)
35(:)
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1520
50
25
60
30
70(%)
35(:)
1
2
4
3
1832
230V
1832
230V
1520
50
25
6030 70(%)
35(:)
0.7
0.8
0.9
1.0
1.1
1.2
1.3
7
8
9
10
11
12
13
1520
50
25
60
30
70(%)
35(:)
1
2
4
3
1832
230V
1832
230V
1520
50
25
60
30
70(%)
35(:)
0.7
0.8
0.9
1.0
1.1
1.2
1.3
7
8
9
10
11
12
13
1520
50
25
6030 70(%)
35(:)
3
4
5
6
1832
230V
COOL operation
① Both indoor and outdoor unit are under the same temperature/humidity condition.
Dry-bulb temperature
20
25
Relative humidity(%)
50
60
3070
➁ Air flow should be set at MAX.
③ The unit of pressure has been changed to MPa on the international system of units(SI unit system).
The conversion factor is : 1(MPa[Gauge]) =10.2(kgf/ff[Gauge] )
NOTEQ :Total capacity (kW)SHF :Sensible heat factorDB :Dry-bulb temperature
SHC :Sensible heat capacity (kW)INPUT :Total power input (W)WB :Wet-bulb temperature
20
Page 21
PERFORMANCE DATA
HEAT operation (230V)
MSC-GA20VB -: MUH-GA20VB -
CAPACITY : 2.5(kW)
INDOOR
DB(:)
15
21
26
QINPUTQINPUTQINPUTQINPUTQINPUTQINPUTQINPUT
1.58
1.50
1.35
INPUT : 690(W)
-10-505101520
2.23
538
1.90
449
2.13
573
1.80
483
1.98
607
1.68
518
E1E1
OUTDOOR WB(:)
607
635
669
2.55
2.43
2.30
656
683
718
2.88
2.75
2.63
697
718
752
3.18
3.05
2.93
718
738
773
3.50
3.36
3.25
731
766
794
MSC-GA25VB -: MUH-GA25VB -
CAPACITY : 3.0(kW)
INDOOR
DB(:)
15
21
26
-10-505101520
QINPUTQINPUTQINPUTQINPUTQINPUTQINPUTQINPUT
1.89
1.80
1.62
INPUT : 820(W)
2.28
533
2.16
574
2.01
615
640
681
722
2.67
2.55
2.37
MSC-GA35VB -: MUH-GA35VB -
CAPACITY : 3.7(kW)
INDOOR
DB(:)
15
21
26
NOTEQ:Total capacity (kW) INPUT:Total power input (W) DB:Dry-bulb temperature WB:Wet-bulb temperature
QINPUTQINPUTQINPUTQINPUTQINPUTQINPUTQINPUT
2.33
2.22
2.00
INPUT : 1020(W)
-10-505101520
3.29
796
2.81
663
3.15
847
2.66
714
2.92
898
2.48
765
E1E1
OUTDOOR WB(:)
3.06
722
2.91
754
2.76
795
E1E1
OUTDOOR WB(:)
3.77
898
3.59
938
3.40
989
779
812
853
969
1010
1061
3.45
3.30
3.15
4.26
4.07
3.89
828
853
894
1030
1061
1112
3.81
3.66
3.51
4.70
4.51
4.33
853
877
918
1061
1091
1142
4.20
4.04
3.90
5.18
4.98
4.81
869
910
943
1081
1132
1173
21
Page 22
Lead wiring
Housing point
9
Jumper wire
JRF
JRG
MODELChange point
Defrost interval time changes from 40 minutes to 15 minutes.
Deforst start temperature changes from -3: to 0:.
MUH-GA20VB MUH-GA25VB MUH-GA35VB -
E1
E1
E1
SERVICE FUNCTIONS
MUH-GA20VB MUH-GA25VB MUH-GA35VB -
E1
E1
E1
9-1. COMPULSORY DEFROSTING MODE FOR SERVICE
By short circuit of the connector JPDS and JPSG on the outdoor deicer P.C. board, defrosting mode can be accomplished regardless of the defrost interval restriction. (Refer to 10-5.)
Defrost thermistor RT61 must read below -3°C.
9-2. CHANGE IN DEFROST SETTING
<JRF> When the JRF wire of the deicer P.C. board is cut, the defrost interval time will be changed.
<JRG> When the JRG wire of the deicer P.C. board is cut, the defrost temperature will be changed.(Refer to 10-5.)
10
TROUBLESHOOTING
MUH-GA20VB MUH-GA25VB MUH-GA35VB -
E1
E1
E1
10-1. Cautions on troubleshooting
1. Before troubleshooting, check the following:
1) Check the power supply voltage.
2) Check the indoor/outdoor connecting wire for mis-wiring.
2. Take care the following during servicing.
1) Before servicing the air conditioner, be sure to turn off the main unit first with the remote controller, and then after confirming the horizontal vane is closed, turn off the breaker and/or disconnect the power plug.
2) Be sure to turn OFF the power supply before removing the front panel, the cabinet, the top panel, and the electronic
control P.C. board.
3) When removing the electronic control P.C. board, hold the edge of the board with care NOT to apply stress on the
components.
4) When connecting or disconnecting the connectors, hold the housing of the connector. DO NOT pull the lead wires.
3. Troubleshooting procedure
1) First, check if the OPERATION INDICATOR lamp on the indoor unit is flashing on and off to indicate an abnormality.
To make sure, check how many times the abnormality indication is flashing on and off before starting service work.
2) If the electronic control P.C. board is supposed to be defective, check the copper foil pattern for disconnection and the
components for bursting and discoloration.
3) When troubleshooting, refer to 10-2. “Instruction of troubleshooting”.
22
Page 23
10-2. Instruction of troubleshooting
Start
Indoor unit
operates.
Outdoor unit
doesn't
operate.
Indoor unit
doesn't receive
the signal from
remote controller.
Indoor unit
operates.
Outdoor unit
doesn't operate
normally.
OPERATION
INDICATOR
lamp on the
indoor unit is
flashing on
and off.
Outdoor unit
operates in
only Test Run
operation.
Outdoor unit
doesn't
operate
even in
Test Run
operation.
Indoor unit
operates,
when the
EMERGENCY
OPERATION
switch is
pressed.
Indoor unit
doesn't operate,
when the
EMERGENCY
OPERATION
switch is
pressed.
Check room
temperature
thermistor.
Refer to 10-5
"Test point
diagram and
voltage".
Refer to 10-4.
A "Check of
outdoor unit".
Refer to
"Check of
remote
controller
and receiver
P.C. board".
Cause:
Indoor/Outdoor unit
• Mis-wiring or
trouble of serial
signal
2-time flash
Cause:
Indoor unit
• Trouble of
room temp erature/
indoor coil
thermistor
3-time flash
Cause:
Indoor unit
• Trouble of
indoor fan
motor
6-time flash
Cause:
Outdoor unit
• Trouble of
thermistor
in outdoor
unit
7-time flash
Cause:
Outdoor unit
• Trouble of
outdoor
control
system
Check room
temperature
thermistor
and indoor
coil thermistor.
Refer to 10-5
"Test point
diagram and
voltage".
Refer to
"Check of
indoor fan
motor".
Refer to 10-4.
E"Check of
outdoor
thermistor".
Replace the
deicer
P.C. board.
Refer to 10-4. D
"How to check
mis-wiring and
serial signal
error (When
outdoor unit
doesn't work)".
W1
1. Check indoor /
outdoor
connecting wire.
2. Refer to
"Check of indoor
electronic control
P.C. board".
Outdoor unit
doesn't
stop even
if indoor unit
stops.
Unit doesn't
operate
normal
operation in
COOL or
HEAT mode.
Refer to 10-4.
B "Check of
outdoor unit".
Refer to 10-4.
C "Check of
R.V. coil".
W1.<The case of the trouble of the serial signal>
When the power is turned off and then turned on again, the indication shows “the trouble of mis-wiring”.
As for indoor unit
MSC type,
refer to service
manual OB385
or OB393.
Flash on and off at
0.5-second intervals
4-time flash
Cause:
Indoor unit
• Trouble of
indoor unit
control
system
Replace the
indoor
electronic
control
P.C. board.
MUH-GA20VB MUH-GA25VB MUH-GA35VB -
E1
E1
E1
23
Page 24
Yes
Compressor
doesn't operate.
Yes
Yes
Is there 230V AC between 3 on the
compressor contactor (52C) and N
on the outdoor terminal block (TB1)?
Operate the unit in COOL or HEAT mode by pressing the EMERGENCY OPERATION switch.
3-minute time delay works.
Test run operation operates for 30 minutes.
Outdoor fan motor
doesn't operate.
No
Rectify the indoor and
outdoor connecting wire.
Rectify the connecting wire.
Check the compressor and compressor
capacitor, and rectify the connecting wire.
Start
Yes
Is there 230V AC between 4 on the
compressor contactor (52C) and
TAB20 on the deicer P.C. board?
Is there 230V AC between L–N
on the outdoor terminal block (TB1)?
Replace the
deicer P.C. board.
Replace the
deicer P.C.
board.
No
No
Yes
Yes
No
Check the outdoor fan motor
and rectify the connecting
wire.
Is there 230V AC between 4 on the
compressor contactor (52C) and
TAB 20 on the deicer P.C. board?
Replace the
deicer P.C. board.
No
Yes
Rectify the indoor and
outdoor connecting wire.
Rectify the connecting wire.
Is there 230V AC between L–N on
the outdoor terminal block (TB1)?
No
No
Is the switch SW2-2 on the
indoor electronic control
P.C. board set to MUH type?
No
Change the switch SW-2-2
on the indoor electronic control
P.C. board to MUH type.
Yes
+
–
Is there 5V DC between J205 –J101 on
the deicer P.C. board?
+
–
Is there 5V DC between J205 –J101 on
the deicer P.C. board?
P
R
C
S
RED
BLK
WHT
MAINAUX.
WHTRED
BLK
MAIN
AUX.
FUSE
10-3. Trouble criterion of main parts
MUH-GA20VB -MUH-GA25VB -MUH-GA35VB -
Part name
Defrost
thermistor
(RT63)
Measure the resistance with a tester.
(Part temperature –10°C ~ 40°C)
Normal
5kΩ ~ 60kΩ
Check method and criterion
Abnormal
Open or short-circuit
E1E1E1
Figure
Compressor
(MC)
INNER
PROTECTOR
MUH-GA20/GA25VB
150i 5°C OPEN
90i10°C CLOSE
MUH-GA35VB
155i 5°C OPEN
90i10°C CLOSE
Outdoor fan
motor
(MF)
INNER FUSE
145i 2°C
CUT OFF
Measure the resistance between the terminals with a tester.
(Coil wiring temperature –10°C ~ 40°C)
Normal
MUH-GA35VB
2.46~3.01Ω
2.96~3.63Ω
C-R
C-S
MUH-GA20VB
3.41~4.18Ω
5.41~6.63Ω
MUH-GA25VB
2.99~3.67Ω
4.02~4.92Ω
Measure the resistance between the terminals with a tester.
(Coil wiring temperature –10°C ~ 40°C)
Color of
lead wire
WHT-BLK
BLK-RED
MUH-GA20VB
323 ~ 396 Ω
241 ~ 296 Ω
Normal
MUH-GA25/GA35VB
10-4. Troubleshooting flow
Compressor and/or outdoor fan motor doesn’t operate.
189 ~ 233 Ω
270 ~ 332 Ω
Abnormal
Open or short-circuit
Abnormal
Open or short-circuit
P INNER PROTECTOR
AA
Check of outdoor unit
24
Page 25
Compressor and/or outdoor fan motor doesn’t stop.
After 3 minutes, does the unit
operate in HEAT mode?
Ok
No
Is there 230V AC between
CN7211 – 2 on the deicer
P.C. board?
Replace the
deicer P.C. board.
Yes
Yes
Yes
No
Replace the R.V. coil.
Turn ON the power supply and operate
the indoor unit in COOL mode by pressing
the EMERGENCY OPERATION switch.
BB
Check of outdoor unit
Start
Turn OFF the power supply.
After 1 minute, turn ON
power supply again.
Is there 230V AC between 3 on the
Does compressor stop?
Yes
OK
No
compressor contactor (52C) and N on the
outdoor terminal block (TB1)?
Yes
Replace the
deicer P.C. board.
No
Rectify the connecting wire.
Does outdoor fan motor stop?
Yes
OK
No
Replace the
deicer P.C. board.
Unit operates COOL mode even if it is set to HEAT mode.
w First, measure the resistance of R.V. coil to confirm it is disconnected or is not short-circuit.
CC
Check of R.V. coil
Turn ON the power supply and operate
the indoor unit in HEAT mode by pressing
the EMERGENCY OPERATION switch.
After 3 minutes, does the unit
operate in COOL mode?
Yes
Is there 230V AC between
CN7211 – 2 on the deicer P.C.
board?
Yes
Replace the R.V. coil.
No
OK
No
Replace the
deicer P.C. board
Unit operates HEAT mode even if it is set to COOL mode.
w First, measure the resistance of R.V. coil to confirm it is disconnected or is not short-circuit.
CC
Check of R.V. coil
25
Page 26
When OPERATION INDICATOR lamp flashes 0.5-second intervals or 1-time.
Outdoor unit does not operate.
DD
How to check mis-wiring and serial signal error
w 1 Set the switch(SW2-2) on indoor electronic control P.C. board to
MU or MUX type, when the outdoor unit is MU or MUX type.
Start
Turn OFF the power supply(indoor/outdoor unit).
If the setting is MUH or MXZ type, the unit does not work.
w 2 Short circuit of JPG and JPS on the indoor electronic control
P.C. board enables self-check to be displayed in 3 seconds.
Is the outdoor unit "MUH" type?
Yes
•Turn ON the power supply(indoor/outdoor unit).
•Press once EMERGENCY OPERATION switch.
•3 min. later, check the self-check result
displayed on OPERATION INDICATOR
lamp on indoor unit.
w 2
Serial signal error is indicated.
No
Set the switch(SW2-2) on the indoor electronic
control P.C. board to MU or MUX type.
Does the unit operate?
Refer to the
"Instruction of
troubleshooting."
(0.5-sec. ON, 0.5-sec. OFF)
Make them sure.
Yes
Is this mis-wiring, poor contact,
or disconnection of wire?
No
1. Turn OFF the power supply(indoor/outdoor unit) and disconnect indoor and outdoor connecting wire on indoor side.
2. Short-circuit between indoor terminal block N and 3.
3. Turn ON the power supply(indoor unit) and press once EMERGENCY OPERATION switch.
Is there 20V DC between both ends of
R132 on indoor electronic control P.C.
board ?
( By tester, the stylus is between 0 ~ 20V. )
Yes
•Turn OFF the power supply(indoor unit).
•Connect ON indoor and outdoor connecting wire.
Turn ON the power supply(outdoor unit).
No
Replace the indoor electronic
control P.C. board.
No
Yes
w1
OK
Is there 230V AC between outdoor terminal
block L-N (TB1)?
Yes
Is there 5V DC between J205 + –J101 - on the deicer P.C. board?
Yes
Turn ON the power supply(indoor unit).
During EMERGENCY OPERATION,
is there 10V DC between both ends
of R601?
(By tester, the stylus is between 5 ~10V)
Yes
Replace the deicer P.C. board.
No
No
As for indoor unit MSC type, refer to service manual OB385 or OB393.
26
Check the outdoor power supply,
power supply cord and
connection.
No
Replace the deicer P.C. board.
Make the wiring between CN730
on the deicer P.C. board and
outdoor terminal block correct.
Page 27
When OPERATION INDICATOR lamp flashes 6-time.
Thermistors in the outdoor unit are abnormal.
EE
Check of outdoor thermistor
Start
Turn OFF the
power supply.
Defrost thermistor (RT61)
Measure
resistance
between CN 661
1 and 2.
Is the resistance of
thermistor normal?
No
Replace the
thermistor.
Reconnect CN661.
Turn ON the power
Yes
supply and press
the EMERGENCY
OPERATION
switch.
Replace the deicer P.C.
board.
No
Does the unit operate
10 minutes or more?
Yes
OK ❈
❈ Defective contact of the connector is considered.
27
Page 28
10-5. Test point diagram and voltage
MUH-GA20VB MUH-GA25VB MUH-GA35VB -
E1
E1
E1
Outdoor deicer P.C. board
CN711
Outdoor fan motor
230V AC
}
CN721
R.V. coil
230V AC
}
5V DC
J205
J101
Power supply input
230V AC
}
NR61
Varistor
F61
Fuse
2A/250V
R601
+
5~10VDC
}
--
Defrost interval time
short pin
(JPDS, JPSG)
(Refer to 9-1.)
Jumper wire for
change in
}
}
CN661 1-2
Defrost thermistor RT61
+
--
defrost setting
(JRF,JRG)
(Refer to 9-2.)
12V DC
J204
+
J101
--
28
Page 29
11
(1) Slide the sleeve and check if there is a locking lever or not.(2) The terminal with this connector has the locking
mechanism.
1Slide the sleeve.
2Pull the terminal while
pushing the locking
lever.
1Hold the sleeve, and
pull out the terminal
slowly.
The terminal which has the locking mechanism can be detached as shown below.
There are two types ( Refer to (1) and (2)) of the terminal with locking mechanism.
The terminal without locking mechanism can be detached by pulling it out.
Check the shape of the terminal before detaching.
<"Terminal with locking mechanism" Detaching points>
Connector
Sleeve
Locking lever
DISASSEMBLY INSTRUCTIONS
MUH-GA20VB -MUH-GA25VB -MUH-GA35VB -
OUTDOOR UNIT
OPERATING PROCEDUREPHOTOS
1. Removing the cabinet
(1) Remove the screws of the top panel.
(2) Remove the screw of the service panel.
(3) Remove the screws of the cabinet.
(4) Remove the screws of the front panel and motor support.
(5) Remove the service panel, and remove the screw from
the insides.
(6) Remove the top panel.
(7) Remove the cabinet.
Photo 3
Screws of the
top panel
Photo 1
Photo 2
E1E1E1
Screw of the front panel and motor support
Screws of the cabinet
Screw of the
Service panel
Screw of the cabinet
29
Screws of the
cabinet
(W) This photo shows MUH-GA20VB.
Screws of the
top panel
Page 30
OPERATING PROCEDUREPHOTOS
2. Removing the deicer P.C. board
(1) Remove the service panel and the cabinet.
(2) Disconnect all the connectors and the terminals on the
deicer P.C. board.
(3) Remove the deicer P.C. board.
3. Removing the propeller and the outdoor fan motor
(1) Remove the cabinet. (Refer to 1.)
(2) Remove the propeller nut.
(3) Remove the propeller.
NOTE : Loose the propeller in the rotating direction for
removal.
When attaching the propeller, align the mark on the
propeller and the motor shaft cut section.
Set the propeller in position by using the cut on the
shaft and the mark on the propeller.
(4) Disconnect the outdoor fan motor connector.
(5) Remove screws fixing the fan motor.
(6) Remove the outdoor fan motor.
Photo 4
Screw of the
relay panel
Photo 5
Propeller
Deicer
P.C. board
Terminal
cover
Screw of the
outdoor fan motor
Relay panel
Terminal
block
Surge absorber
Screws of
the relay
panel
30
Propeller
nut
(W) This photo shows MUH-GA20VB.
Sound proof felt
R.V. coil
Page 31
OPERATING PROCEDUREPHOTOS
4. Removing the compressor
(1) Remove the cabinet. (Refer to 1.)
(2) Remove the relay panel.
(3) Remove the soundproof felt.
(4) Remove the terminal cover on the compressor.
(5) Disconnect lead wires from the glass terminal of the com-
pressor.
(6) Recover gas from the refrigerant circuit.
NOTE : Recover gas from the pipes until the pressure gauge
shows 0 kg/cm
(7) Disconnect the welded part of the discharge pipe.
(8) Disconnect the welded part of the suction pipe.
(9) Remove nuts fixing the compressor.
OUTDOOR HEAT EXCHANGER
OUTDOOR HEAT EXCHANGER
OUTDOOR HEAT EXCHANGER
OUTDOOR FAN MOTOR
OUTDOOR FAN MOTOR
CABINET
CABINET
GRILLE
PROPELLER
BASE
BASE
COMPRESSSOR RUBBER SET
COMPRESSOR
COMPRESSOR
COMPRESSOR
STOP VALVE (GAS)
STOP VALVE (LIQUID)
BACK PANEL
BACK PANEL
SERVICE PANEL
DRAIN SOCKET
TERMINAL BLOCK
TERMINAL BLOCK
4-WAY VALVE
4-WAY VALVE
COMPRESSOR CAPACITOR
COMPRESSOR CAPACITOR
COMPRESSOR CAPACITOR
SURGE ABSORBER
DEICER P.C. BOARD
DEICER P.C. BOARD
DEFROST THERMISTOR
CONDENSER NET
CONDENSER NET
TOP PANEL
SEPARATOR
MOTOR SUPPORT
R. V. COIL
R. V. COIL
FUSE
VARISTOR
CHECK VALVE
CAPILLARY TUBE
CAPILLARY TUBE
CAPILLARY TUBE
CAPILLARY TUBE
CAPILLARY TUBE