Mitsubishi Electric Mr. Slim MXZ-2B20NA User manual

Models
SERVICE MANUAL
CONTENTS
1. TECHNICAL CHANGES· ·································· 2
2. PART NAMES AND FUNCTIONS····················· 2
3. SPECIFICATION················································ 3
4. NOISE CRITERIA CURVES······························ 4
5. OUTLINES AND DIMENSIONS ························ 5
6. WIRING DIAGRAM············································ 6
7. REFRIGERANT SYSTEM DIAGRAM··············· 7
8. DATA·································································· 9
9. ACTUATOR CONTROL··································· 17
10. SERVICE FUNCTIONS···································· 17
11. TROUBLESHOOTING····································· 18
12. DISASSEMBLY INSTRUCTIONS···················· 34
INDOOR UNITS COMBINATION SHEETS
No. OBH560
REVISED EDITION-A
The Slim Line.
From Mitsubishi Electric. TM
OUTDOOR UNIT
MXZ-2B20NA
MXZ-2B20NA - 1
MXZ-2B20NA
Indoor unit service manual
MSZ-A·NA Series (OB450)
MSZ-FD·NA Series (OBH497)
MSZ-FE·NA Series (OBH542)
MSZ-GE·NA Series (OBH548)
SEZ-KD·NA.TH Series
SPLIT-TYPE AIR CONDITIONERS
HFC
utilized
R410A
33223
9700058
Revision A:
• MXZ-2B20NA- 1has been added.

TECHNICAL CHANGES
2
1
PART NAMES AND FUNCTIONS
2
MXZ-2B20NA MXZ-2B20NA - 1
Air outlet
Drain outlet
Air inlet
(Back and side)
Revision A:
• MXZ-2B20NA- 1has been added.
MXZ-2B20NA
New model.
MXZ-2B20NA MXZ-2B20NA - 1
1. Outdoor fan motor has been changed.
2. Outdoor electronic control P.C. board has been changed.
3. LEV coil has been changed.

3
SPECIFICATION
3
Item
Outdoor model
Indoor type Wall (09+09) Duct (09+12)
Capacity
Power
consumption
EER
SEER
HSPF IV (V)
COP
External finish
Power supply
Max. fuse size (time delay)
Min. circuit ampacity
Fan motor
Compressor
Refrigerant control
Sound level
Defrost method
Dimensions
Weight
Remote controller
Control voltage (by built-in transformer)
Refrigerant piping
Valve size
Connection method
Refrigerant charge (R410A)
Refrigeration oil (Model)
Model
Winding resistance (at 68°F) Ω
W
D
H
Liquid
Gas
Indoor
Outdoor
Btu/h
Btu/h
Btu/h
W
W
W
V, phase, Hz
A
A
F.L.A
R.L.A
L.R.A
dB(A)
in.
in.
in.
lb.
in.
in.
lb.
oz.
Cooling
Heating 47
Heating 17
Cooling
Heating 47
Heating 17
Cooling
Cooling
Heating
Heating
MXZ-2B20NA MXZ-2B20NA -
Munsell 3.0Y 7.8/1.1
208/230, 1, 60
20
15
0.96
SNB130FQBH1
U-V 0.98 V-W 0.98 W-U 0.98
10.1
15
LEV
49/51
Reverse cycle
33-1/16
13
27-15/16
130
Wireless type
12-24 V DC
Not supplied (optional parts)
1/4
A,B: 3/8
Flared
Flared
5 lb. 15 oz.
23.7 (NEO22)
18,000
22,000
12,500
1,440
1,650
1,350
12.5
18.0
8.9 (7.0)
3.91
20,000
22,000
12,500
2,190
1,780
1,430
9.1
15.5
8.5 (6.9)
3.62
1
Cooling
Heating
Mode
1: "A" Cooling steady state at rated compressor speed
"B-2" Cooling steady state at rated compressor speed
"B-1" Cooling steady state at minimum compressor speed
Low ambient cooling steady state at minimum compressor speed
Intermediate cooling steady state at intermediate compressor speed
1: Standard rating-heating at rated compressor speed
2: Low temperature heating at maximum compressor speed
Maximum temperature heating at minimum compressor speed
High temperature heating at minimum compressor speed
Frost accumulation at rated compressor speed
Frost accumulation at intermediate compressor speed
Test Indoor air condition Outdoor air condition
Dry bulb Wet bulb Dry bulb Wet bulb
80
80
80
80
80
70
70
70
70
70
70
67
67
67
67
67
60
60
60
60
60
60
95
82
82
67
87
47
17
62
47
35
35
(75)
(65)
(65)
(53.5)
(69)
43
15
56.5
43
33
33
Unit: °F
NOTE : Test conditions are based on ARI 210/240.

4
90
80
70
60
50
40
30
20
10
63 125 250 500 1000 2000 4000 8000
APPROXIMATE
THRESHOLD OF
HEARING FOR
CONTINUOUS
NOISE
NC-60
NC-50
NC-40
NC-30
NC-20
NC-70
OCTAVE BAND SOUND PRESSURE LEVEL, 0dB = 0.0002 MICRO BAR
BAND CENTER FREQUENCIES, Hz
CoolingHigh
FUNCTION
FAN SPEED
HeatingHigh
49
SPL(dB(A))
51
LINE
NOISE CRITERIA CURVE
4
MXZ-2B20NA
MXZ-2B20NA - 1

5
OUTLINES AND DIMENSIONS
5
MXZ-2B20NA MXZ-2B20NA - 1Unit: inch
LIQ 1/4"FLARE
GAS 3/8"FLARE
Unit B
Unit A
LIQ
GAS
GAS
LIQ
1-3/16" 1/2"13"
2-5/8"
7-7/8"
9-7/16"
14-3/16"
11-3/4"
27-15/16"
1-3/16"33-1/16"
(Bolt Pitch)
3- (1-5/16") Drain Hole
4-(13/32"×13/16") Oval Hole
(Foundation Bolt M10)
Air
Discharge
Side Air Intake
Rear Air
Intake
1-7/32"
6-21/32"19-11/16"6-9/16"
17/32" 13/16"
9-3/16" 11-11/32"
21/32"
14-3/16"
2-1/2"
15-19/32"
11/16"11/16"
3- 7/8" Punched holes
(Connecting wire hole)
2-3/8"
1-3/16"
14-1/4"
5-5/16"
3-5/16"
1-25/32"
29/32"
1-5/32"
More than 3-15/16"
More than 19-11/16"
More than 7-7/8"
More than13-25/32"
More than 3-15/16"
More than 19-11/16"
More than 13-25/32"
More than 13-25/32"
More than 3-15/16"
SERVICE SPACE
More than 3-15/16"
More than 19-11/16"
Note : Leave front and both sides
clearance fully.
Note : Leave front and overhead
clearance fully.
Note : Leave rear, overhead and
both sides clearance fully.
1.Installation space
2.Service space
Lock nut Connector
Grounding terminal
Conduit
cover

6
WIRING DIAGRAM
6
MXZ-2B20NA
MXZ-2B20NA - 1

7
Stop valve with
service port
Stop valve
Strainer
#100
Power
receiver
LEV A
LEV B
Oil separator
Compressor
Defrost
thermistor
RT61
Distributor
Muffler
4-way valve
LEV E
Indoor unit
B
Indoor unit
A
Indoor unit
A
Indoor unit
B
Capillary tube
O.D.0.14 x I.D.0.09 x 19.68
Capillary tube
O.D.0.10 x I.D.0.02 x 39.37
Capillary tube
O.D.0.16 x I.D.0.11 x 3.93
Capillary tube
O.D.0.16 x I.D.0.11 x 3.93
Discharge
temperature
thermistor RT62
Strainer
#100
Strainer
#100
R.V. coil
OFF
ON
Refrigerant flow in cooling
Refrigerant flow in heating
Ambient
temperature
thermistor
RT65
Outdoor heat
exchanger
temperature
thermistor
RT68
FAN-OUT
HEX-OUT
Service
port
Service
port
Strainer
#100
REFRIGERANT SYSTEM DIAGRAM
7
Unit: mm
MXZ-2B20NA MXZ-2B20NA - 1

8
Refrigerant pipe diameter is different according to indoor unit to be connected. When using extension pipes, refer to the
tables below.
When diameter of refrigerant pipe is different from that of outdoor unit union, use optional Different-diameter pipe.
For further information on Different-diameter pipe. Unit: inch
It does not matter which unit is higher.
MAX. REFRIGERANT PIPING LENGTH & PIPE SIZE SELECTION
MXZ-2B20NA MXZ-2B20NA - 1
Operating Range MXZ-2B20NA MXZ-2B20NA - 1
Cooling
Heating
Maximum
Minimum
Maximum
Minimum
Indoor intake air temperature
95°FDB, 71°FWB
67°FDB, 57°FWB
80°FDB, 67°FWB
70°FDB, 60°FWB
Outdoor intake air temperature
115°FDB
14°FDB
75°FDB, 65°FWB
6°FDB, 5°FWB
a
b
Outdoor
unit
Indoor
units
49 ft.
33 ft.
49 ft.
Max. height difference
Indoor unit class Extension pipe diameter
09 or less Liquid 1/4
Gas 3/8
12 Liquid 1/4
Gas 3/8
15 Liquid 1/4
Gas 1/2
Outdoor unit union diameter
For
Indoor unit A Liquid 1/4
Gas 3/8
Indoor unit B Liquid 1/4
Gas 3/8
Piping length each indoor unit (a, b) 82 ft. MAX.
Total piping length (a+b) 164 ft. MAX.
Bending point for each unit 25 MAX.
Total bending point 60 MAX.

9
DATA
8
Model MXZ-2B20NA MXZ-2B20NA - 1
Indoor type Wall (09+09) Duct (09+12)
Item Unit Cooling Heating Cooling Heating
Total Capacity But/h 18,000 22,000 20,000 22,000
SHF – – – – –
Input kW 1.44 1.65 2.19 1.78
Electrical
circuit Power supply (V,phase,Hz) 208/230, 1, 60
Input kW 1.396 1.604 2.06 1.69
Comp. current (208/230V) A 6.08/5.87 7.25/6.80 9.81/8.87 7.98/7.22
Fan motor current A 0.43/0.39 0.43/0.39 0.43/0.39 0.43/0.39
Refrigerant
circuit Condensing pressure PSIG 411 319 417 350
Suction pressure PSIG 141 102 130 101
Discharge temperature ºF 169 154 174 172
Condensing temperature ºF 114 100 120 104
Suction temperature ºF 71 46 65 46
Comp. shell bottom temp. ºF 163 149 185 167
Ref. pipe length
[Total pipe length for multi-system] ft 82 [164]
Refrigerant charge (R410A) – 5 lb. 15 oz.
Outdoor
unit Intake air temperature DB ºF 95 47 95 47
WB ºF – 43 – 43
Fan speed rpm 650 700 650 700
Airflow CFM 1485 1640 1485 1640
8-1. OPERATING RANGE
(1) POWER SUPPLY
Outdoor unit
Rating
208/230 V 60 Hz 1
Guaranteed Voltage
Model
Min. 198 V Max. 253 V
208 V 230 V
MXZ-2B20NA
MXZ-2B20NA-
1

10
(2) OPERATION
Function
Cooling
Heating
"A" Cooling steady state
at rated compressor speed
"B-2" Cooling steady state
at rated compressor speed
"B-1" Cooling steady state
at minimum compressor speed
Low ambient cooling steady state
at minimum compressor speed
Intermediate cooling steady state
at intermediate compressor speed
Standard rating-heating
at rated compressor speed
Low temperature heating
at rated compressor speed
Max. temperature heating
at minimum compressor speed
High temperature heating
at minimum compressor speed
Frost accumulation
at rated compressor speed
Frost accumulation
at intermediate compressor speed
DB (°F)
80
80
80
80
80
70
70
70
70
70
70
WB (°F)
67
67
67
67
67
60
60
60
60
60
60
Indoor
DB (°F)
95
82
82
67
87
47
17
62
47
35
35
WB (°F)
(75)
(65)
(65)
(53.5)
(69)
43
15
56.5
43
33
33
Outdoor
Condition
Intake air
temperature

11
MXZ-2B20NA MXZ-2B20NA - 1
The standard 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 pro-
vided to clarify the operating characteristics of the air conditioner under the conditions indicated by the performance curve.
(1) GUARANTEED VOLTAGE
198 ~ 253 V 60 Hz
(2) AIR FLOW
Air flow should be set at MAX.
(3) MAIN READINGS
(1) Indoor intake air wet-bulb temperature : °FWB
(2) Indoor outlet air wet-bulb temperature : °FWB
(3) Outdoor intake air dry-bulb temperature : °FDB
(4) Total input: W
(5) Indoor intake air dry-bulb temperature : °FDB
(6) Outdoor intake air wet-bulb temperature : °FWB
(7) Total input : W
Indoor air wet/dry-bulb temperature difference on the left side of the following chart 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
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. Compressor starts running at 33 Hz (COOL) or 45 Hz (HEAT). The frequency at each operation mode is fixed.
7. When system stabilizes after more than 15 minutes, measure temperature and take an average temperature.
8. 10 minutes later, measure temperature again and check that the temperature does not change.
INDOOR UNIT OUTDOOR UNIT
Wet-and dry-bulb
thermometers
Wet-and dry-bulb
thermometers

12
09 class
(47Hz)
12 class
(59Hz)
15 class
(78Hz)
Indoor unit class (Inverter output frequency)
Indoor air DB temperature
difference (degree)
22.1
20.5
18.7
17.1
15.3
13.7
11.9
10.3
8.5
6.8
32.9
30.4
27.9
25.4
22.9
20.3
17.8
15.3
12.8
10.1
40.9
37.6
34.6
31.3
28.3
25.0
22.0
18.9
15.7
12.6
06 class
(31Hz)
47.3
43.7
40.1
36.5
32.3
29.2
25.6
22.0
18.2
14.6
Outdoor intake air Wet-bulb temperature (°F)
5 142332415059
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
Heating capacity ( at Rated frequency)
Capacity correction factor
59
68
79
Outdoor intake air Wet-bulb temperature (°F)
5142332415059
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
Total input (Heating : at Rated frequency )
Input correction factor
59
68
79
Indoor intake air Dry-bulb temperature (°F)
Indoor intake air Dry-bulb temperature (°F)
NOTE: The above broken lines are for the heating operation without any frost and defrost operation.
0.8
0.9
1.0
1.1
1.2
1.3
14 23 32 41 50 59 68 77 86 95 104 113
Outdoor intake air Dry-bulb temperature (°F)
Input correction factors
79
75 72
68
64
Indoor intake air Wet-bulb
temperature( F)
Total input (Cooling : at Rated frequency )
09 class
(35Hz)
15 class
(69Hz)
12 class
(50Hz)
Indoor unit class (Inverter output frequency)
Indoor air WB temperature
difference (degree)
7.2
6.7
6.1
5.6
5.0
4.7
4.1
11.2
10.3
9.5
8.6
7.9
7.0
6.3
15.5
14.2
13.1
11.9
10.8
9.7
8.6
06 class
(25Hz)
14.2
13.1
12.1
11.2
10.1
9.0
8.1
Cooling capacity ( at Rated frequency)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
14 23 32 41 50 59 68 77 86 95 104 113
Outdoor intake air Dry-bulb temperature(°F)
Capacity correction factors
79
75
68
64
72
Indoor intake air Wet-bulb
temperature(°F)
8-2. CAPACITY AND THE INPUT CURVES
MXZ-2B20NA MXZ-2B20NA - 1

13
0 50 100
0.5
1.0
1.5
2.0
0 50 100
0.5
1.0
1.5
2.0
050100
0.5
1.0
1.5
2.0
050100
0.5
1.0
1.5
2.0
050100
0.5
1.0
1.5
2.0
050100
0.5
1.0
1.5
2.0
050100
0.5
1.0
1.5
2.0
0 50 100
0.5
1.0
1.5
2.0
050100
0.5
1.0
1.5
2.0
0 50 100
0.5
1.0
1.5
2.0
050100
0.5
1.0
1.5
2.0
050100
0.5
1.0
1.5
2.0
<COOL>Capacity
Frequency
Hz
Frequency
<COOL>Total input
Hz
<HEAT>Capacity
Frequency
Hz
Frequency
<HEAT>Total input
Hz
<COOL>Capacity
Frequency
Hz
Frequency
<COOL>Total input
Hz
<HEAT>Capacity
Frequency
Hz
Frequency
<HEAT>Total input
Hz
<COOL>Capacity
Frequency
Hz
Frequency
<COOL>Total input
Hz
<HEAT>Capacity
Frequency
Hz
Frequency
<HEAT>Total input
Hz
2. 09-class unit in single operation
3. 12-class unit in single operation
4. 15-class unit in single operation
0 50 100
0.5
1.0
1.5
2.0
0 50 100
0.5
1.0
1.5
2.0
050100
0 50 100
1.0
1.5
2.0
2.5
<COOL>Capacity
Frequency
Hz
Frequency
<COOL>Total input
Hz
<HEAT>Capacity
Frequency
Hz
Frequency
<HEAT>Total input
Hz
1. 06-class unit in single operation
0.5
1.0
1.5
2.0
2.5
0.5
8-3. CAPACITY AND INPUT CORRECTION BY MEANS OF INVERTER OUTPUT FREQUENCY
(OUTDOOR UNIT: MXZ-2B20NA MXZ-2B20NA - 1)

14
8-4. OUTDOOR LOW PRESSURE AND OUTDOOR UNIT CURRENT
1. 09-class unit in single operation (OUTDOOR UNIT: MXZ-2B20NA MXZ-2B20NA - 1)
(1) COOL operation
Data is based on the condition of indoor humidity
50%
Air flow speed: High
Inverter output frequency: 33 Hz
(2) HEAT operation
65 70 75 80 85 90 95 100 105 110 115
120
130
140
150
160
170
Ambient temperature (°F)
(°F)
86
80
75
70
Indoor DB temperature (°F)
65 70 75 80 85 90 95 100 105 110 115
0.0
1.0
2.0
3.0
4.0
5.0
6.0
Ambient temperature (°F)
(°F)
(°F)
15 20 25 30 35 40 45 50 55 60 65 70 75
2.0
3.0
4.0
5.0
6.0
7.0
Ambient temperature (°F)
Outdoor low pressure
Outdoor unit current (A)
Outdoor unit current (A)
45 Hz
(PSIG)
33 Hz
33 Hz
65
75
70
86
80
75
70
Indoor DB temperature (°F)
Indoor DB temperature (°F)
<How to work fixed-frequency operation>
1. Set emergency switch to COOL or HEAT. The switch is located
on indoor unit.
2. Press emergency run ON/OFF button.
3. Compressor starts running at 33 Hz (COOL) or 45 Hz (HEAT).
4. Indoor fan runs at High speed and continues for 30 minutes.
5. To cancel this operation, press emergency run ON/OFF button
or any button on remote controller.
Data is based on the condition of indoor humidity
75%
Set air flow to High speed.
Inverter output frequency is 45 Hz.

15
2. 12-class unit in single operation (OUTDOOR UNIT: MXZ-2B20NA MXZ-2B20NA - 1)
(1) COOL operation
65 70 75 80 85 90 95 100 105 110 115
120
140
150
160
170
130
Ambient temperature (˚F)
(˚F)
86
80
75
70
86
80
75
70
15 20 25 30 35 40 45 50 55 60 65 70 75
2.0
3.0
4.0
5.0
6.0
7.0
Ambient temperature (˚F)
65 70 75 80 85 90 95 100 105 110 115
0.0
1.0
2.0
3.0
4.0
5.0
6.0
Ambient temperature (˚F)
(˚F)
(˚F)
(PSIG)
Outdoor low pressure
Outdoor unit current (A)
Outdoor unit current (A)
45 Hz
33 Hz
33 Hz
65
70
75
Indoor DB temperature (˚F)
Indoor DB temperature (˚F)
Indoor DB temperature (˚F)
Data is based on the condition of indoor humidity
50%
Air flow speed: High
Inverter output frequency: 33 Hz
<How to work fixed-frequency operation>
1. Set emergency switch to COOL or HEAT. The switch is located
on indoor unit.
2. Press emergency run ON/OFF button.
3. Compressor starts running at 33 Hz (COOL) or 45 Hz (HEAT).
4. Indoor fan runs at High speed and continues for 30 minutes.
5. To cancel this operation, press emergency run ON/OFF button
or any button on remote controller.
(2) HEAT operation
Data is based on the condition of indoor humidity
75%
Set air flow to High speed.
Inverter output frequency is 45 Hz.

16
3. 15-class unit in single operation (OUTDOOR UNIT: MXZ-2B20NA MXZ-2B20NA - 1)
(1) COOL operation
65 70 75 80 85 90 95 100 105 110 115
120
130
140
150
160
170
Ambient temperature (˚F)
(˚F)
86
80
75
70
86
80
75
70
15 20 25 30 35 40 45 50 55 60 65 70 75
2.0
3.0
4.0
5.0
6.0
7.0
Ambient temperature (˚F)
65 70 75 80 85 90 95 100 105 110 115
0.0
1.0
2.0
3.0
4.0
5.0
6.0
Ambient temperature (˚F)
(˚F)
(˚F)
(PSIG)
Outdoor low pressure
Outdoor unit current (A)
Outdoor unit current (A)
45 Hz
33 Hz
33 Hz
65
70
75
Indoor DB temperature (˚F)
Indoor DB temperature (˚F)
Indoor DB temperature (˚F)
Data is based on the condition of indoor humidity
50%
Air flow speed: High
Inverter output frequency: 33 Hz
<How to work fixed-frequency operation>
1. Set emergency switch to COOL or HEAT. The switch is located
on indoor unit.
2. Press emergency run ON/OFF button.
3. Compressor starts running at 33 Hz (COOL) or 45 Hz (HEAT).
4. Indoor fan runs at High speed and continues for 30 minutes.
5. To cancel this operation, press emergency run ON/OFF button
or any button on remote controller.
(2) HEAT operation
Data is based on the condition of indoor humidity
75%
Set air flow to High speed.
Inverter output frequency is 45 Hz.

17
SERVICE FUNCTIONS
10
ACTUATOR CONTROL
9
Relation between main sensor and actuator
MXZ-2B20NA MXZ-2B20NA - 1
Discharge temperature thermistor
Indoor coil thermistor
Defrost thermistor
Fin temperature thermistor
Ambient temperature thermistor
Outdoor heat exchanger temperature
Capacity code
Purpose
Protection
Defrosting Protection
Defrosting
Protection
Control
Protection
Control
Compressor LEV Outdoor
fan motor
4-way
valve
Sensor
Actuator
10-1. PRE-HEAT CONTROL
If moisture gets into the refrigerant cycle, or when refrigerant is liquefied and collected in the compressor, it may interfere
the start-up of the compressor.
To improve start-up condition, the compressor is energized even while it is not operating.
This is to generate heat at the winding.
The compressor uses about 50 W when pre-heat control is turned ON.
Pre-heat control is ON at initial setting.
[How to deactivate pre-heat control]
Turn OFF the power supply for the air conditioner before making the setting.
Set the 4th Dip Switch of SW1 on the outdoor electronic control P.C. board to ON to deactivate pre-heat control func-
tion.
ON
SW1
1234
ON
1234
SW1
MXZ-2B20NA
MXZ-2B20NA-
1
Turn ON the power supply for the air conditioner.
NOTE: Pre-heat control will be turned OFF when the breaker is turned OFF.

18
11
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 seems to be defective, check the copper foil pattern for disconnection and the com-
ponents for bursting and discoloration.
3) When troubleshooting, refer to 11-2, 11-3 and 11-4.
Lead wiring Housing point
11-1. 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 of the following during servicing.
1) Before servicing the air conditioner, be sure to turn off the unit first with the remote controller, and then after confirm-
ing 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 electrical parts, be careful of the residual voltage of smoothing capacitor.
4) When removing the electronic control P.C. board, hold the edge of the board with care NOT to apply stress on the
components.
5) When connecting or disconnecting the connectors, hold the housing of the connector. DO NOT pull the lead wires.
MXZ-2B20NA MXZ-2B20NA - 1
11-2. FAILURE MODE RECALL FUNCTION
This air conditioner can memorize the abnormal condition which has occurred once.
Even though LED indication listed on the troubleshooting check table (11-4.) disappears, the memorized failure details
can be recalled.
This mode is very useful when the unit needs to be repaired for the abnormality which does not recur.
1. Type of failure mode recall function
There are 2 types in failure mode recall function as shown below.
Indoor and outdoor unit failure mode recall function
With this function, failure mode of indoor unit and a part of failure mode of outdoor unit can be recalled.
The details of outdoor unit failure mode recall function
With this function, more detailed failure mode of outdoor unit can be recalled.
Refer to the service manual of indoor unit for how to recall the failure mode and the details of indoor unit failure mode.
The outdoor unit failure mode is indicated by the operation indicator lamp on the indoor unit and the LED of outdoor unit.
See "11-2.2. Outdoor unit failure mode table".
TROUBLESHOOTING

19
The left lamp of
OPERATION INDICATOR
lamp (Indoor unit)
OFF
2-time flash
3-time flash
4-time flash
5-time flash
6-time flash
7-time flash
8-time flash
Lighting Lighting
Lighting Lighting
Lighting Once
Lighting Once
Lighting Twice
Lighting 3 times
Lighting 4 times
Lighting 9 times
Once
Goes out
Lighting Lighting
Lighting Lighting
3 times Goes
out
4 times Goes
out
Lighting Lighting
Lighting Lighting
Lighting 5 times
9-time flash
10-time flash
• Replace the outdoor
electronic control
P.C. board.
• Replace the outdoor
electronic control
P.C. board.
•Check refrigerant circuit
and refrigerant amount.
• Refer to 11-6. "Check
of LEV".
• Reconnect compressor
connector.
• Refer to 11-6. "How to
check inverter/
compressor".
• Check the stop valve.
•Check refrigerant circuit
and refrigerant amount.
• Check the stop valve.
• Refer to 11-6. "Check
of outdoor fan motor".
•Check refrigerant circuit
and refrigerant amount.
• Refer to 11-6. "Check
of LEV".
• Check around outdoor
unit.
• Check outdoor unit air
passage.
• Refer to 11-6. "Check
of outdoor fan motor".
• Check the connection
of the compressor
connecting wire.
• Refer to 11-6.
"How to check
inverter/compressor".
• Check the stop valve.
• Refer to 11-6. "Check
of outdoor thermistors".
• Refer to 11-6. "Check
of outdoor thermistors".
When overcurrent protection stop is
continuously performed three times
within 1 minute after the compressor
gets started, or when converter
protection stop or bus-bar voltage
protection stop is continuously
performed three times within 3
minutes after start-up.
When thermistor shorts or opens
during compressor running.
When 28A current flows into intelligent
power module.
When discharge temperature exceeds
240.8°F during operation.
Compressor can restart if discharge
temperature thermistor reads 212°F or
less 3 minutes later.
When the outdoor heat exchanger
temperature exceeds 158°F
during cooling or the indoor gas
pipe temperature exceeds 158°F
during heating.
When the fin temperature exceeds
188.6°F during operation.
When the P.C. board temperature
exceeds 158°F during operation.
When failure occurs continuously
three times within 30 seconds after
the fan gets started.
When nonvolatile memory data
cannot be read properly.
When the frequency of the
compressor is kept 80Hz or
more and the discharge
temperature is kept under 102.2°F
for more than 20 minutes.
Outdoor power system
Discharge temperature
thermistor
Defrost thermistor
Ambient temperature thermistor
Fin temperature thermistor
P.C. board temperature
thermistor
Outdoor heat exchanger
temperature thermistor
Overcurrent
Discharge temperature
High pressure
Fin temperature
P.C. board temperature
Outdoor fan motor
Nonvolatile memory data
Discharge temperature
None (Normal)
Abnormal point
(Failure mode/protection) Condition Remedy
Indoor/outdoor
unit failure mode
recall function
LED indication
(Outdoor P.C. board)
LED 1 LED 2
2. Outdoor unit failure mode table
NOTE: Blinking patterns of this mode differ from the ones of Troubleshooting check table (11-4.).

20
Operation start
Check the outdoor unit
LED indicator.
Refer to 11-6.
"Check of power supply".
• Indoor unit
serial signal
error
Refer to 11-6.
"How to
check
mis-wiring and
serial signal
error".
• COOL or
HEAT
operation only
Refer to 11-6.
"Check of
R.V. coil".
• When cooling,
room is not
cool.
Refer to 11-6.
"How to check
inverter/
compressor".
• When cooling, heat
exchanger of
non-operating indoor
unit frosts.
•When heating, non-
operating indoor unit
gets warm.
Refer to 11-6.
"Check of LEV".
• When heating,
room does not get
warm.
Refer to 11-6.
"How to check
inverter/compressor".
Check mis-piping,
shortage of capacity.
• When cooling
dew drops in the
non-operating
indoor unit.
Check of
miss-piping.
Refer to 11-4.
"Troubleshooting check table".
Both LED1 and
LED2 are OFF.
Both LED 1 and
LED 2 are lighting.
LED 1 or LED 2
has blinked.
11-3. INSTRUCTION OF TROUBLESHOOTING
• Check the indoor unit with referring to the indoor unit service manual, and confirm that there is any problem in the indoor
unit.
Then, check the outdoor unit with referring to this page.
11-time flash
15-time flash
• Check the connecting
wire between outdoor
electronic control
P.C. board and power
board.
• Replace the power
board.
• Check the connecting
wire among electronic
control P.C. board,
noise filter P.C. board
and power board.
• Check the voltage of power
supply.
• Replace the power board.
• Check the voltage of power
supply.
• Replace the outdoor
electronic control P.C. board.
• Refer to 11-6. "Check
of LEV".
• Check the drain pump of
the indoor unit.
When the communication between
boards protection stop is
continuously performed twice.
Communication error occurs
between the electronic control P.C.
board and power board for more
than 10 seconds.
Current sensor protection stop is
continuously performed twice.
When a short or open circuit is
detected in the current sensor
during compressor operating.
The protection stop of the zero
cross detecting circuit is
continuously performed 10 times.
When zero cross signal cannot be
detected while the compressor is
operating.
When a failure is detected in the
operation of the converter during
operation.
When the bus-bar voltage exceeds
400V or falls to 200V or below
during compressor operating.
When the bus-bar voltage exceeds
400V or falls to 50V or below during
compressor operating.
Communication error
between P.C. boards
Current sensor
Zero cross detecting circuit
Converter
Bus-bar voltage
(1)
Bus-bar voltage
(2)
Even if this protection stop is
performed continuously three
times, it does not mean the
abnormality in outdoor power
system.
LEV for drain
Lighting 6 times
Lighting 7 times
5 times Goes
out
5 times Goes
out
5 times
6 times
Goes
out
Goes
out
When the indoor unit detects any
abnormal in the LEV for drain.
Lighting Lighting
Abnormal point
(Failure mode/protection) Condition Remedy
Indoor/outdoor
unit failure mode
recall function
LED indication
(Outdoor P.C. board)
LED 1 LED 2
The left lamp of
OPERATION INDICATOR
lamp(Indoor unit)
NOTE: Blinking patterns of this mode differ from the ones of Troubleshooting check table (11-4.).