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INDOOR UNIT
TECHNICAL &
SERVICE MANUAL
Models
MLZ-KX09NL
MLZ-KX12NL
MLZ-KX18NL
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U1
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U1
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U1
CONTENTS
1. TECHNICAL CHANGES· ·····························2
2. SAFETY PRECAUTION ·······························3
3. PART NAMES AND FUNCTIONS ··················8
4. SPECIFICATION ········································9
5. OUTLINES AND DIMENSIONS ··················· 12
6. WIRING DIAGRAM· ·································· 13
7. REFRIGERANT SYSTEM DIAGRAM ··········· 14
8. SERVICE FUNCTIONS ······························ 15
9. MICROPROCESSOR CONTROL ················· 20
10. TROUBLESHOOTING ······························· 29
11. DISASSEMBLY INSTRUCTIONS ················· 48
13. NOISE CRITERION CURVES ························· 55
DISTRIBUTIONS ······································ 56
No. OBD957
Outdoor unit service manual
MXZ-D•NL Series (OBD949)
MXZ-SM•NL Series
MXZ-SM•NLHZ Series
SUZ-AA•NL Series
SUZ-AA•NLHZ Series
Outdoor unit service manual
MXZ-D•NL Series (OBH949)
MXZ-SM•NL Series
MXZ-SM•NLHZ Series
SUZ-AA•NL Series
SUZ-AA•NLHZ Series
Indoor unit service manual
MLZ-KX•NL Series (OBH957)
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Table of Contents
Troubleshooting
Related Manuals for Mitsubishi Electric MLZ-KX09NL-U1
Summary of Contents for Mitsubishi Electric MLZ-KX09NL-U1
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Page 1: Table Of Contents
INDOOR UNIT No. OBD957 TECHNICAL & SERVICE MANUAL Models MLZ-KX09NL Outdoor unit service manual MXZ-D•NL Series (OBD949) MLZ-KX12NL MXZ-SM•NL Series MXZ-SM•NLHZ Series MLZ-KX18NL SUZ-AA•NL Series SUZ-AA•NLHZ Series Outdoor unit service manual MXZ-D•NL Series (OBH949) MXZ-SM•NL Series MXZ-SM•NLHZ Series SUZ-AA•NL Series SUZ-AA•NLHZ Series Indoor unit service manual MLZ-KX•NL Series (OBH957) -
Page 2: Technical Changes
Use the specified refrigerant only Never use any refrigerant other than that specified. Doing so may cause a burst, an explosion, or fire when the unit is being used, serviced, or disposed of. Correct refrigerant is specified in the manuals and on the spec labels provided with our products. We will not be held responsible for mechanical failure, system malfunction, unit breakdown or accidents caused by failure to follow the instructions. -
Page 3: Safety Precaution
SAFETY PRECAUTION MEANINGS OF SYMBOLS DISPLAYED ON THE UNIT Refrigerant This unit uses a flammable refrigerant. WARNING Safety Group If the refrigerant leaks and comes in contact with fire or a heating part, it will create a harmful gas and there (Risk of fire) is a risk of fire. - Page 4 [1] Warning for service (1) Do not alter the unit. (2) For installation and relocation work, follow the instructions in the Installation Manual and use tools and pipe components specifically made for use with refrigerant specified in the outdoor unit installation manual. (3) Ask a dealer or an authorized technician to install, relocate and repair the unit.
- Page 5 [4] Cautions for unit using R454B refrigerant Basic work procedures are the same as those for conventional units using refrigerant R410A. However, pay careful attention to the following points. (1) Information on servicing (1-1) Checks to the area Prior to beginning work on systems containing FLAMMABLE REFRIGERANTS, safety checks are necessary to ensure that the risk of ignition is minimized.
- Page 6 (3) Repair to intrinsically safe components Intrinsically safe components must be replaced. (4) Cabling Check that cabling will not be subject to wear, corrosion, excessive pressure, vibration, sharp edges or any other adverse environmental effects. The check shall also take into account the effects of aging or continual vibration from sources such as compressors or fans.
- Page 7 (8) Decommissioning Before carrying out this procedure, it is essential that the technician is completely familiar with the equipment and all its detail. It is recommended good practice that all refrigerants are recovered safely. Prior to the task being carried out, an oil and refrigerant sample shall be taken in case analysis is required prior to re-use of recovered refrigerant.
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Page 8: Part Names And Functions
PART NAMES AND FUNCTIONS INDOOR UNIT MLZ-KX09NL MLZ-KX12NL MLZ-KX18NL Horizontal vane Vertical vane Air inlet Intake grille Air outlet Air filter (Air purifying filter) Air cleaning filter (Anti-Allergy Enzyme filter, option) Display section Spec name plate Safety strings Open the display cover Remote control receiving section Emergency operation switch Operation indicator lamp... -
Page 9: Specification
SPECIFICATION 1. Single connection Indoor model MLZ-KX09NL Power supply V, phase, Hz 208/230, 1, 60 Max. fuse size (time delay)/Disconnect switch COOL Dry (Wet) CFM 311 - 282 - 254 - 201 Airflow High - Med. - Low - SLow HEAT Dry 325 - 290 - 247 - 212 Cooling... - Page 10 2. Multi connection Indoor model MLZ-KX09NL Power supply V, phase, Hz 208/230, 1, 60 Max. fuse size (time delay)/Disconnect switch COOL Dry (Wet) CFM 311 - 282 - 254 - 212 Airflow High - Med. - Low - SLow HEAT Dry 325 - 290 - 247 - 212 Cooling dB (A)
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Page 11: Operation
4-1. OPERATING RANGE (1) POWER SUPPLY Rated voltage Guaranteed voltage (V) 208/230 V Min. 187 Max. 253 Indoor unit 1 phase 60 Hz (2) OPERATION *The operating range of the outdoor unit depends on the connected outdoor unit. Intake air temperature (°F) Mode Condition Indoor... -
Page 12: Outlines And Dimensions
OUTLINES AND DIMENSIONS MLZ-KX09NL MLZ-KX12NL MLZ-KX18NL Unit: inch INDOOR UNIT OBD957... -
Page 13: Wiring Diagram
WIRING DIAGRAM INDOOR UNIT MLZ-KX09NL MLZ-KX12NL MLZ-KX18NL OBD957... -
Page 14: Refrigerant System Diagram
REFRIGERANT SYSTEM DIAGRAM Unit: inch(mm) INDOOR UNIT MLZ-KX09NL MLZ-KX12NL Refrigerant pipe ø3/8(ø9.52) (with heat insulator) Indoor coil Indoor thermistor heat RT12 (main) exchanger Flared connection Indoor coil thermistor RT13 (sub) Room temperature thermistor RT11 Flared connection Refrigerant pipe ø1/4(ø6.35) (with heat insulator) Refrigerant flow in cooling Refrigerant flow in heating MLZ-KX18NL... -
Page 15: Service Functions
SERVICE FUNCTIONS MLZ-KX09NL MLZ-KX12NL MLZ-KX18NL 8-1. TIMER SHORT MODE • For service, the following set time can be shortened by bridging the timer short mode point on the electronic control P.C. board. (Refer to 10-7.) • The set time for the ON/OFF timer can be reduced to 1 second for each minute. •... -
Page 16: Auto Restart Function
8-3. AUTO RESTART FUNCTION When the indoor unit is controlled with the remote controller, the operation mode, the set temperature, and the fan speed are memorized by the indoor electronic control P.C. board. “AUTO RESTART FUNCTION” automatically starts operation in the same mode just before the shutoff of the main power. - Page 17 8-4. P.C. BOARD MODIFICATION FOR CHANGING AIRFLOW VOLUME Change Slide switch SW3 setting according to the height of ceiling. Slide switch SW3 Normal Increase airflow volume Ceiling height 8.0 ft. (2.4 m) or below above 8.0 ft. (2.4 m) and 9.0 ft. (2.7 m) or below NOTE: When the ceiling is above 9.0 ft.
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Page 18: Wireless Lan Control
8-6. WIRELESS LAN CONTROL 1. Radio wave usage precautions 2. Wireless LAN module introduction This Wireless LAN module, communicates the status information and Contains FCC ID:NKR-MB43 Contains IC:4441A-MB43 controls the commands from the kumo cloud by connecting to an ® indoor unit. -
Page 19: Specifications
Wi-Fi service. in order to change the settings to a different network, the user can follow the • This Wireless LAN module should not be connected to any Mitsubishi Electric instructions below to place the system back into network configuration mode. -
Page 20: Microprocessor Control
MICROPROCESSOR CONTROL MLZ-KX09NL MLZ-KX12NL MLZ-KX18NL WIRELESS REMOTE CONTROLLER Signal transmitting section Operate the remote controller Distance of signal: About 20 ft. (6 m)* in the area where signal is received, Beep(s) is (are) heard from the indoor and beep is heard. unit when the signal is received. - Page 21 9-1. COOL ( ) OPERATION (1) Press OFF/ON(stop/operate) button. OPERATION INDICATOR lamp of the indoor unit turns on with a beep tone. (2) Select COOL mode with Operation select button. (3) Press Temperature buttons TEMP button to select the desired temperature. The setting range is 61 - 88°F (16 - 31°C).
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Page 22: Operation Indicator
NOTE 2 FOR MULTI SYSTEM AIR CONDITIONER OUTDOOR UNIT: MXZ series Multi system air conditioner can connect 2 or more indoor units with one outdoor unit. • When you try to operate 2 or more indoor units with one outdoor unit simultaneously, one for the cooling and the others for heating, the operation mode of the indoor unit that operates first is selected. -
Page 23: Drain Pump/Float Sensor Control
(6) SWING ( ) mode By selecting SWING mode with VANE control button, the horizontal vanes swing vertically. When COOL, DRY or FAN mode is selected, only the upper vane swings. (7) Cold air prevention in HEAT operation The horizontal vane position is set to Upward. (8) ECONO COOL ( ) operation (ECONOmical operation) When ECONO COOL button is pressed in COOL mode, set temperature is automatically set 4°F(2°C) higher by micro- processor. -
Page 24: Timer Operation
9-8. TIMER OPERATION 1. How to set the time (1) Check that the current time is set correctly. NOTE: Timer operation will not work without setting the current time. Initially “0:00” blinks at the current time display of TIME MONITOR, so set the current time correctly with CLOCK button. How to set the current time (a) Press the CLOCK button. -
Page 25: Weekly Timer Operation
9-9. WEEKLY TIMER OPERATION • A maximum of 4 ON or OFF timers can be set for individual days of the week. • A maximum of 28 ON or OFF timers can be set for a week. E.g. : Runs at 75°F (24°C) from waking up to leaving home, and runs at 81°F (27°C) from getting home to going to bed on weekdays. - Page 26 (4) Press button to complete and transmit the weekly timer setting. which was blinking goes out, and the current time will be displayed. NOTE: • Press button to transmit the setting information of weekly timer to the indoor unit. Point the remote controller toward the indoor unit for 3 seconds.
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Page 27: Sleep Operation
9-11. SLEEP ( ) OPERATION 1. How to set SLEEP operation (1) Press STOP/OPERATE (OFF/ON) button. (2) Select COOL, DRY, HEAT or FAN mode. (3) Press SLEEP ( ) button. (4) PRESS Temperature buttons [ (Increase) and (Decrease) ] to set the temperature of SLEEP operation. -
Page 28: Emergency/Test Operation
9-13. EMERGENCY/TEST OPERATION In the case of test run operation or emergency operation, use the emergency operation switch on the right side of the indoor unit. Emergency operation is available when the remote controller is missing or has failed, or the batteries in the remote con- troller are running out. -
Page 29: Troubleshooting
TROUBLESHOOTING MLZ-KX09NL MLZ-KX12NL MLZ-KX18NL 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 miswiring. 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 confirming the horizontal vane is closed, turn off the breaker and/or disconnect the power plug. - Page 30 10-2. FAILURE MODE RECALL FUNCTION AND ERROR CODE DISPLAY MODE Outline of the function This air conditioner can memorize the failure which has occurred last time. Even though LED indication listed on the troubleshooting check table (10-4.) disappears, the memorized failure can be recalled.
- Page 31 A (From previous page) Press OFF/ON (stop/operate) button of the remote controller with the remote controller headed towards the indoor unit. *1. The indoor unit is normal, but the outdoor unit might be abnormal. Does the left OPERATION INDICATOR lamp on the There are some abnormalities that cannot be recalled with this way.
- Page 32 2. Flow chart of error code display mode This explains how customers can check the error code on their own. This is included in OPERATING INSTRUCTIONS. Operational procedure The remote controller is powered OFF. Get close to the front of the indoor unit. Point the remote controller at the receiving section of the indoor unit, and keep pressing CHECK with a fine- tipped object.
- Page 33 3. Table of indoor unit failure mode recall function Left OPERATION Error Abnormal point Condition Remedy INDICATOR lamp code (Failure mode) Not blink Normal — — The room temperature thermistor short or 1-time blink every Room temperature Refer to the characteristics of the room open circuit is detected every 8 seconds 0.5-second thermistor...
- Page 34 10-3. INSTRUCTION OF TROUBLESHOOTING 1. Check of the unit Start Indoor unit operates. Indoor unit operates. Indoor unit does not OPERATION INDICATOR Outdoor unit does not Outdoor unit does not receive the signal lamp on the indoor unit is operate. operate normally.
- Page 35 2. Check of Wireless LAN module Follow the procedure below if the air conditioner cannot be monitored or controlled with a device such as a smartphone. Did the right lamp of the operation indicator lamp There is a problem in a communication between the air blink 10 times after you selected the setting of the conditioner and the wireless LAN module.
- Page 36 10-4. TROUBLESHOOTING CHECK TABLE • Blinking of OPERATION INDICATOR lamp (left-hand side lamp) indicates abnormalities. OPERATION INDICATOR Blinking Not lit NOTE: Before taking measures, make sure that the symptom reappears for accurate troubleshooting. Self check table Abnormal Operation indicator lamp Symptom Condition Remedy...
- Page 37 Abnormal Operation indicator lamp Symptom Condition Remedy point • The buzzer 1. Refrigerant leaks from the piping or the heat • Press and hold the emergency Left lamp blinks 3 times, then sounds. exchanger in the indoor unit. operation button to turn off the right lamp lights on.
- Page 38 FL: Refrigerant leakage Abnormal points and detection methods Causes and checkpoints Refrigerant is leaking from the air conditioner. • Refrigerant leak from air conditioner The refrigerant sensor has detected refrigerant leak. • Refrigerant leak from piping Refrigerant is leaking in the room where the alarm is beeping. •...
- Page 39 FH: Refrigerant sensor error Abnormal points and detection methods Causes and checkpoints A refrigerant sensor has failed. • A refrigerant sensor connected to an M-IC has failed. • A Sensor and Alarm Kit connected to a branch box has failed. Diagnosis of failure Check the display of the remote controller or the 7-segment LED on the outdoor controller board...
- Page 40 10-5. TROUBLESHOOTING CRITERION OF MAIN PARTS MLZ-KX09NL MLZ-KX12NL MLZ-KX18NL Part name Check method and criteria Figure Room temperature Measure the resistance with a multimeter. thermistor (RT11) [Part temperature 50°F – 86°F (10°C – 30°C)] Indoor coil thermistor Normal (RT12,RT14,RT15 (MAIN), 8 kΩ...
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Page 41: Troubleshooting Flow
10-6. TROUBLESHOOTING FLOW When the left lamp of OPERATION INDICATOR lamp blinks 3 times and the right lamp of OPERATION INDICATOR lamp is not lighted, indoor fan does not operate. Check of indoor fan motor The indoor fan motor error has occurred, and the indoor fan does not operate. Turn OFF the power supply. - Page 42 Indoor unit operates by pressing the emergency operation switch, but does not operate with the remote controller. Check of remote controller, receiver P.C. board and indoor electronic control P.C. board * Check if the remote controller is exclusive for this air conditioner. Press STOP/OPERATE (OFF/ON) button on the remote controller.
- Page 43 The unit cannot be operated with the remote controller. Also, OPERATION INDICATOR lamp does not light up by pressing the emergency operation switch. Check of indoor electronic control P.C. board and indoor fan motor Turn OFF the power supply. Remove indoor fan motor connector CN211 and vane Turn OFF the power supply.
- Page 44 When the left lamp of OPERATION INDICATOR lamp blinks ON and OFF in every 0.5-second, outdoor unit does not operate. How to check miswiring and serial signal error Turn OFF the power supply. Is there rated voltage of Check the power 208/230 V AC in the power supply.
- Page 45 When the left lamp of OPERATION INDICATOR lamp blinks 9-time, indoor unit and outdoor unit do not operate. Check of float sensor Turn OFF the power supply and check connectors CN145 and CN1N2 visually. Are there abnormality in Are the lead wires Replace the indoor the soldering part of Connect the lead wire.
- Page 46 Electromagnetic noise enters into TV sets or radios Is the unit grounded? Ground the unit. Is the distance between the antennas Extend the distance between the antennas and and the indoor unit within 9.91 ft. (3m), or the indoor unit, and/or the antennas and the out- is the distance between the antennas door unit.
- Page 47 10-7. TEST POINT DIAGRAM AND VOLTAGE MLZ-KX09NL MLZ-KX12NL MLZ-KX18NL CN145 Indoor electronic control P.C. board CN202 NR11 F11 FUSE CN201 Connector to Serial signal Varistor T6.3AL250V Power supply input R111 float sensor 208/230 V AC To disable “Auto restart function”, cut the Jumper wire to JR77.
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Page 48: Disassembly Instructions
DISASSEMBLY INSTRUCTIONS <Detaching method of the terminal with locking mechanism> The terminal which has the locking mechanism can be detached as shown below. There are 2 types 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. - Page 49 OPERATING PROCEDURE PHOTOS/FIGURES 2. Removing the grille Figure 5 (1) Remove the intake grille. (2) Remove the fixing screws for side panels (2 screws) on the left and right sides (Figure 5). Attach to the (3) Open the side panels on the left and right sides. hook of grille.
- Page 50 OPERATING PROCEDURE PHOTOS/FIGURES (7) Install the screw cap. Figure 9 (8) After attaching the safety strings for the left and right side panels to the grille, install the side panels (Figure 9). NOTE: Make sure that the tabs of the side panels securely fit into place (Figure 9).
- Page 51 OPERATING PROCEDURE PHOTOS/FIGURES 3. Removing the indoor electric control P.C. board, Photo 2 the receiver P.C. board and the display P.C. Fixing screw of the electrical box Drain pan board (1) Remove the intake grille. (2) Remove the side panel (L). (3) Remove the electrical cover (4 fixing screws) (Photo 2).
- Page 52 OPERATING PROCEDURE PHOTOS/FIGURES 6. Removing the drain pump and float sensor Photo 5 Connector of Connector of the drain pump the float sensor (1) Remove the grille. (2) Remove the drain pan. Screws Screws (3) Disconnect the connector of the drain pump (Photo 5). securing the securing the drain pump...
- Page 53 OPERATING PROCEDURE PHOTOS/FIGURES 8. Removing the refrigerant sensor Photo 7 (1) Remove the panel. (Refer to section 1.) (2) Loosen the screw of the refrigerant sensor plate, and take the refrigerant sensor plate. (3) Remove the screw of the V.A. clamp cover and remove the V.A.
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Page 54: Position Of The Center Of Gravity
POSITION OF THE CENTER OF GRAVITY Ceiling-cassette type Unit: inch (mm) Model name MLZ-KX09NL 21-7/16 4-1/8 MLZ-KX12NL (545) (152) (105) MLZ-KX18NL OBD957... -
Page 55: Noise Criterion Curves
NOISE CRITERION CURVES MLZ-KX09NL MLZ-KX12NL FAN SPEED FUNCTION SPL(dB(A)) LINE FAN SPEED FUNCTION SPL(dB(A)) LINE COOLING COOLING High High HEATING HEATING NC-70 NC-70 NC-60 NC-60 NC-50 NC-50 NC-40 NC-40 NC-30 NC-30 APPROXIMATE APPROXIMATE THRESHOLD OF THRESHOLD OF HEARING FOR HEARING FOR NC-20 NC-20 CONTINUOUS... -
Page 56: Temperature And Air Flow Distributions
TEMPERATURE AND AIR FLOW DISTRIBUTIONS MLZ-KX09NL Temperature distribution <Cooling mode> Air volume: high Air direction: auto (upward air flow) [°C(F)] [°C(F)] 23(73) 23(73) 21(70) 21(70) 25(77) 25(77) 27(81) 27(81) 3000 2000 1000 (118.11) (78.74) (39.37) Floor distance [ mm (inch) ] <Heating mode>... - Page 57 MLZ-KX09NL Airflow distribution <Cooling mode> Air volume: high Air direction: auto (upward air flow) [m/s(ft/s)] [m/s(ft/s)] 0.9(3.0) 0.9(3.0) 2.7(8.9) 2.7(8.9) 2.1(6.9) 2.1(6.9) 1.5(4.9) 1.5(4.9) 0.9(3.0) 0.9(3.0) 0.3(1.0) 0.3(1.0) 0.3(1.0) 0.3(1.0) 3000 2000 1000 (118.11) (78.74) (39.37) Floor distance [ mm (inch) ] <Heating mode>...
- Page 58 MLZ-KX12NL Temperature distribution <Cooling mode> Air volume: high Air direction: auto (upward air flow) [°C(F)] [°C(F)] 21(70) 21(70) 25(77) 25(77) 23(73) 23(73) 25(77) 25(77) 27(81) 27(81) 4000 3000 2000 1000 (157.48) (118.11) (78.74) (39.37) Floor distance [ mm (inch) ] <Heating mode>...
- Page 59 MLZ-KX12NL Airflow distribution <Cooling mode> Air volume: high Air direction: auto (upward air flow) [m/s(ft/s)] [m/s(ft/s)] 2.7(8.9) 2.7(8.9) 2.1(6.9) 2.1(6.9) 1.5(4.9) 1.5(4.9) 0.9(3.0) 0.9(3.0) 0.9(3.0) 0.9(3.0) 0.3(1.0) 0.3(1.0) 4000 3000 2000 1000 (157.48) (118.11) (78.74) (39.37) Floor distance [ mm (inch) ] <Heating mode>...
- Page 60 MLZ-KX18NL Temperature distribution <Cooling mode> Air volume: high Air direction: auto (upward air flow) [°C(F)] [°C(F)] 21(70) 21(70) 23(73) 23(73) 27(81) 27(81) 25(77) 25(77) 6000 5000 4000 3000 2000 1000 (236.22) (196.85) (157.48) (118.11) (78.74) (39.37) Floor distance [ mm (inch) ] <Heating mode>...
- Page 61 MLZ-KX18NL Airflow distribution <Cooling mode> Air volume: high Air direction: auto (upward air flow) [m/s(ft/s)] [m/s(ft/s)] 3.3(10.8) 3.3(10.8) 2.7(8.9) 2.7(8.9) 2.1(6.9) 2.1(6.9) 1.5(4.9) 1.5(4.9) 0.9(3.0) 0.9(3.0) 0.3(1.0) 0.3(1.0) 6000 5000 4000 3000 2000 1000 (236.22) (196.85) (157.48) (118.11) (78.74) (39.37) Floor distance [ mm (inch) ] <Heating mode>...
- Page 62 HEAD OFFICE: TOKYO BUILDING, 2-7-3, MARUNOUCHI, CHIYODA-KU, TOKYO 100-8310, JAPAN © Copyright 2025 MITSUBISHI ELECTRIC CORPORATION Published: Jan. 2025. No. OBD957 Made in Japan Specifications are subject to change without notice.
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