Mitsubishi Electric PAC-MK54BC Operating manual

May 2020
SPLIT-TYPE, HEAT PUMP AIR CONDITIONERS
TECHNICAL & SERVICE MANUAL
CONTENTS
1. SAFETY PRECAUTION··································· 2
2. OVERVIEW OF UNIT ······································ 5
3. SPECIFICATIONS ·········································· 8
4. OUTLINES AND DIMENSIONS························· 9
5. WIRING DIAGRAM········································10
6 . NECESSARY CONDITIONS FOR SYSTEM CONSTRUCTION ············ 11
7. TROUBLESHOOTING····································15
8. DISASSEMBLY PROCEDURE·························24
BRANCH BOX
HFC
utilized
R410A
Note:
• This service manual
describes technical data of
branch box. As for indoor
units and outdoor unit,
refer to its service manual.
PARTS CATALOG (OCB744)
PAC-MK54BC
No. OCH744
[Service Ref.]
PAC-MK54BC
PAC-MK34BC
[Model Name]
<Branch box>
PAC-MK54BC
PAC-MK34BC

2
OCH744
1SAFETY PRECAUTION
Cautions for units utilizing refrigerant R410A
1-1. CAUTIONS RELATED TO NEW REFRIGERANT
Use new refrigerant pipes.
Avoid using thin pipes.
Use a vacuum pump with a reverse ow check
valve.
Vacuum pump oil may ow back into refrigerant cycle and
that can cause deterioration of refrigerant oil, etc.
Handle tools with care.
If dirt, dust or moisture enters into refrigerant cycle, that
can cause deterioration of refrigerant oil or malfunction of
compressor.
Do not use a charging cylinder.
If a charging cylinder is used, the composition of refrigera-
nt will change and the e󰀩ciency will be lowered.
Use the specied refrigerant only.
Never use any refrigerant other than that specied.
Doing so may cause a burst, an explosion, or re when
the unit is being used, serviced, or disposed of.
Correct refrigerant is specied 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.
Ventilate the room if refrigerant leaks during
operation. If refrigerant comes into contact with
a ame, poisonous gases will be released.
Use the following tools specically designed for
use with R410A refrigerant.
The following tools are necessary to use R410A
refrigerant.
Tools for R410A
Gauge manifold Flare tool
Charge hose Size adjustment gauge
Gas leak detector Vacuum pump adaptor
Torque wrench Electronic refrigerant
charging scale
Make sure that the inside and outside of refrige-
rant piping is clean and it has no contaminants
such as sulfur, oxides, dirt, shaving particles,
etc.,
which are hazard to refrigerant cycle.
In addition, use pipes with specied thickness.
Contamination inside refrigerant piping can cause deterio-
ration of refrigerant oil, etc.
Store the piping indoors, and keep both ends of
the piping sealed until just before brazing.
(Leave elbow joints, etc. in their packaging.)
If dirt, dust or moisture enters into refrigerant cycle, that
can cause deterioration of refrigerant oil or malfunction of
compressor.
The refrigerant oil applied to are and ange
connections must be ester oil, ether oil or
alkylbenzene oil in a small amount.
If large amount of mineral oil enters, that can cause
deterioration of refrigerant oil, etc.
Charge refrigerant from liquid phase of gas
cylinder.
If the refrigerant is charged from gas phase, composition
change may occur in refrigerant and the e󰀩ciency will be
lowered.
Do not use refrigerant other than R410A.
If other refrigerant (R22, etc.) is used, chlorine in refrige-
rant can cause deterioration of refrigerant oil, etc.
Precautions during the repair service
• Do not perform the work involving the electric parts
with wet hands.
• Do not pour water into the electric parts.
• Do not touch the refrigerant.
•
Do not touch the hot or cold areas in the refrigerating cycle.
• When the repair or the inspection of the circuit needs
to be done without turning o󰀨 the power, exercise great
caution not to touch the live parts.
Preparation before the repair service
• Prepare the proper tools.
• Prepare the proper protectors.
• Provide adequate ventilation.
• After stopping the operation of the air conditioner, turn
o󰀨 the power-supply breaker.
• Discharge the condenser before the work involving the
electric parts.

3
OCH744
Electronic weighing scale
Unit
[3] Service tools
(1) Use the below service tools as exclusive tools for R410A refrigerant.
[2] Additional refrigerant charge
When charging directly from cylinder
(1) Check that cylinder for R410A on the market is a syphon type.
(2) Charging should be performed with the cylinder of syphon stood vertically. (Refrigerant is charged from liquid phase.)
[1] Cautions for service
(1) Perform service after recovering the refrigerant left in unit completely.
(2) Do not release refrigerant in the air.
(3) After completing service, charge the cycle with specified amount of refrigerant.
(4) If moisture or foreign matter might have entered the refrigerant piping during service, ensure to remove them.
No. Tool name Specifications
1Gauge manifold
· Only for R410A
· Use the existing fitting specifications. (UNF1/2)
· Use high-tension side pressure of 5.3MPa·G or over.
2Charge hose · Only for R410A
· Use pressure performance of 5.09MPa·G or over.
3Electronic weighing scale
4Gas leak detector · Use the detector for R134a, R407C or R410A.
5Adaptor for reverse flow check · Attach on vacuum pump.
6Refrigerant charge base
7Refrigerant cylinder · Only for R410A · Top of cylinder (Pink)
· Cylinder with syphon
8Refrigerant recovery equipment

OCH744 4
(2) Cautions for refrigerant piping work
New refrigerant R410A is adopted for replacement inverter series. Although the refrigerant piping work for R410A is same
as for R22, exclusive tools are necessary so as not to mix with different kind of refrigerant. Furthermore as the working
pressure of R410A is 1.6 times higher than that of R22, their sizes of flared sections and flare nuts are different.
1 Thickness of pipes
Because the working pressure of R410A is higher compared to R22, be sure to use refrigerant piping with thickness
shown below. (Never use pipes of 0.7 mm or below.)
2Dimensions of flare cutting and flare nut
The component molecules in HFC refrigerant are smaller compared to conventional refrigerants. In addition to that,
R410A is a refrigerant, which has higher risk of leakage because its working pressure higher than that of other refriger-
ants. Therefore, to enhance airtightness and strength, flare cutting dimension of copper pipe for R410A has been speci-
fied separately from the dimensions for other refrigerants as shown below. The dimension B of flare nut for R410A also
has partly been changed to increase strength as shown below. Set copper pipe correctly referring to copper pipe flaring
dimensions for R410A below. For 1/2” and 5/8” inch pipes, the dimension B changes.
Use torque wrench corresponding to each dimension.
3 Tools for R410A (The following table shows whether conventional tools can be used or not.)
1/4
3/8
1/2
5/8
3/4
6.35
9.52
12.70
15.88
19.05
0.8
0.8
0.8
1.0
—
0.8
0.8
0.8
1.0
1.0
Nominal
dimensions (in)
Diagram below: Piping diameter and thickness
Outside
diameter (mm)
Thickness (mm)
R410A R22
1/4
3/8
1/2
5/8
3/4
6.35
9.52
12.70
15.88
19.05
9.1
13.2
16.6
19.7
—
9.0
13.0
16.2
19.4
23.3
Nominal
dimensions (in)
Flare cutting dimensions
Outside
diameter (mm)
Dimension A ( )
+0
-0.4 (mm)
R410A R22
1/4
3/8
1/2
5/8
3/4
6.35
9.52
12.70
15.88
19.05
17.0
22.0
26.0
29.0
—
17.0
22.0
24.0
27.0
36.0
Nominal
dimensions (in)
Flare nut dimensions
Outside
diameter (mm
)
Dimension B (mm)
R410A R22
Gauge manifold
Charge hose
Gas leak detector
Refrigerant recovery equipment
Refrigerant cylinder
Applied oil
Safety charger
Charge valve
Vacuum pump
Flare tool
Bender
Pipe cutter
Welder and nitrogen gas cylinder
Refrigerant charging scale
Vacuum gauge or thermis-
tor vacuum gauge and
vacuum valve
Charging cylinder
Air purge, refrigerant charge
and operation check
Gas leak check
Refrigerant recovery
Refrigerant charge
Apply to flared section
Prevent compressor malfunction
when charging refrigerant by
spraying liquid refrigerant
Prevent gas from blowing out
when detaching charge hose
Vacuum drying and air
purge
Flaring work of piping
Bend the pipes
Cut the pipes
Weld the pipes
Refrigerant charge
Check the degree of vacuum. (Vacuum
valve prevents back flow of oil and refri-
gerant to thermistor vacuum gauge)
Refrigerant charge
Tool exclusive for R410A
Tool exclusive for R410A
Tool for HFC refrigerant
Tool exclusive for R410A
Tool exclusive for R410A
Ester oil and alkylbenzene
oil (minimum amount)
Tool exclusive for R410A
Tool exclusive for R410A
Tools for other refrigerants can
be used if equipped with adop-
ter for reverse flow check
Tools for other refrigerants
can be used by adjusting
flaring dimension
Tools for other refrigerants can be used
Tools for other refrigerants can be used
Tools for other refrigerants can be used
Tools for other refrigerants can be used
Tools for other refrigerants
can be used
Tool exclusive for R410A
Tools and materials Use R410A tools Can R22 tools be used?
(Usable if equipped
with adopter for rever-
se flow)
(Usable by adjusting
flaring dimension)
Can R407C tools be used?
Ester oil:
Alkylbenzene oil: minimum amount
(Usable if equipped
with adopter for rever-
se flow)
(Usable by adjusting
flaring dimension)
: Prepare a new tool. (Use the new tool as the tool exclusive for R410A.)
: Tools for other refrigerants can be used under certain conditions.
: Tools for other refrigerants can be used.
Dimension A
Dimension B

5
OCH744
2OVERVIEW OF UNIT
Indoor unit (Ceiling concealed type)
Indoor unit
(Wall mounted type)
Outdoor unit Branch box
2-1. SYSTEM OUTLINE
The additional connection of the branch box together with employment of the compact trunk-looking outdoor unit can
successfully realize a long distance piping for big houses. Equipped with a microprocessor, the branch box can translate
the transmission signal of indoor units to achieve the optimum control.
2-1-1. System example
2-1-2. Method for identifying
Branch box (Controller)
Number of branches
5: 5 branches
3: 3 branches
Model type
Model type
P A C – MK 5 4 BC
(Indispensable)
Optional parts
Development No. : A, B, ···,etc.
Power supply
Single phase 220/230/240 V, 50 Hz
Multi type heat pump
inverter outdoor unit
Indicates equivalent to rated cooling capacity.
(kBTU/h)
Number of connectable indoor units (MAX.)
Control and refrigerant
A : New A control and R410A
M X Y-
100 4 C V A
■ Branch box

6
OCH744
2-2. INSTALLATION
Space required for Installation and servicing for branch box for PAC-MK54/34BC
(1) Front View (Fig. 2-1)
A Branch box
B On the side of piping
(2) Side View (Fig. 2-2, Fig. 2-3, Fig. 2-4)
C For indoor installations
D Ceiling board
E Maintenance hole
F Reactor box (Optional parts)
*1: A minimum 350 mm is required for 90° bends in refrigerant piping.
*2: Ais “Min 200 mm”.
In the case of less than 200 mm (for example A is 100 mm), the exchange work of branch box from a maintenance hole
becomes difficult (Only exchange work of a PCB, linear expansion valve coils and sensors is possible).
To install the optional reactor box, set A to Min 270 mm <recommendation>. (Fig. 2-4)
*3: Bis “□ 600 mm”.
In the case of “□450 mm”, prepare a maintenance hole at a PCB side (as it is shown in Fig. 2-3, Fig. 2-4), and “Min 300
mm” is needed as distance A.
In the case of less than 300 mm (for example A is 100 mm), the exchange work of Branch box, linear expansion
valve coils and sensors from a maintenance hole becomes difficult. Only exchange work of a PCB is possible.
(3) Top View (Fig. 2-5)
NOTE 1: The branch box is only for indoor use.
NOTE 2: Please attach the special optional cover (PAC-AK350CVR-E) to install branch box outdoors.
Fig. 2-5
Fig. 2-3
Fig. 2-2Fig. 2-1
Unit: mm
(3)
Min 250
(1) (2)
50 450
� 450
250 250 250
170 30
278
180-200
A
C
B
D E
*1
*3
*2
E D
450
E D
F
Fig. 2-4

7
OCH744
Branch box
■ In the case of using 1-branch box
Flare connection employed
2 branches pipe (joint)
: optional parts
Branch box #1
Branch box #2
■ In the case of using 2-branch boxes
■ Installation procedure (2 branch pipe (joint))
Refer to the installation manuals of MSDD-50AR-E and MSDD-50BR-E.
2-3. SIMPLIFIED PIPING SYSTEM
The piping connection size differs according to the type and capacity of outdoor/indoor units.
Match the piping connection size of branch box with outdoor/indoor unit.
If the piping connection size of branch box does not match the piping connection size of outdoor/indoor unit,
use optional different-diameter (deformed) joints to the branch box side.
(Connect deformed joint directly to the branch box side.)

8
OCH744
3 SPECIFICATIONS
Model Name PAC-MK54BC PAC-MK34BC
Connectable number of indoor units Maximum 5 Maximum 3
Power supply (from outdoor unit) ~/N, 220/230/240 V, 50 Hz, ~/N, 220/230 V, 60 Hz
Input kW 0.003
Running current A 0.05 (Max. 6)
External nish Galvanized sheets
Dimensions Width mm 450
Depth mm 280
Height mm 170
Weight kg 7.4 6.7
Piping
connection
(Flare)
Branch (indoor side)* Liquid mm ø6.35 × 5 {A,B,C,D,E} ø6.35 × 3 {A,B,C}
Gas mm ø9.52 × 4 {A,B,C,D}, ø12.7 × 1{E} ø9.52 × 3 {A,B,C}
Main (outdoor side) Liquid mm ø9.52
Gas mm ø15.88
*
The piping connection size differs according to the type and capacity of outdoor/indoor units.
Match the piping connection size of branch box with outdoor/indoor unit. If the piping connection size of branch box does not
match the piping connection size of outdoor/indoor unit, use optional different-diameter (deformed) joints to the branch box side.
(Connect deformed joint directly to the branch box side.)

9
OCH744
4OUTLINES AND DIMENSIONS
Unit: mm
PAC-MK54BC
PAC-MK34BC
{6.35
{9.52
SUSPENSION BOLT : W3/8(M10)
GAS PIPE
REFRIGERANT PIPE FLARED CONNECTION
{6.35 {9.52
{9.52 {15.88
TO OUTDOOR UNIT
LIQUID PIPE
A B C
{9.52
{6.35
DE
{6.35 {6.35
{9.52 {12.7
SUSPENSION BOLT PITCH
SUSPENSION BOLT PITCH
320
12
402
E D C B A
E D C B A
TO INDOOR UNIT
70 70
90450
67 72
7070
2525
252525
65 47
170
5-ELECTRIC WIRE INLET
BUSH
CONTROL COVER
SERVICE PANEL
(for LEV,THERMISTOR)
TO OUTDOOR UNIT
40280
83
96
112
7087
TERMINAL BLOCK
TO M-NET UNIT
TERMINAL BLOCK
TO INDOOR UNIT
TERMINAL BLOCK
TO OUTDOOR UNIT
TB2B
TB5
TB3ETB3CTB3A
TB3DTB3B
24
CAP
CAP
C B
CBA
A
TO INDOOR UNIT
450
70
70
25
65 47
170
209
2525
90
72
5-ELECTRIC WIRE INLET
BUSH
CONTROL COVER
TO OUTDOOR UNIT
SERVICE PANEL
(for LEV.THERMISTOR)
83
96 40 280
87 70
112
TB3A TB3C
TB3B
TB5 TB2B
TERMINAL BLOCK
TO OUTDOOR UNIT
TERMINAL BLOCK
TO INDOOR UNIT
TERMINAL BLOCK
TO M-NET UNIT
SUSPENSION BOLT PITCH
SUSPENSION BOLT PITCH
12
402
320
24
{6.35
{9.52
SUSPENSION BOLT : W3/8(M10)
GAS PIPE
REFRIGERANT PIPE FLARED CONNECTION
{ 6.35 { 9.52
{9.52 {15.88
TO OUTDOOR UNIT
LIQUID PIPE
A B C
{9.52
{6.35

10
OCH744
5WIRING DIAGRAM
PAC-MK54BC PAC-MK34BC
<Note>
1. At servicing for outdoor unit,
always follow the wiring diagram
of outdoor unit.
2. When work to supply power
separately to Branch box and outdoor
units are applied, refer to Fig. 1.
However, when the Branch box is
connected to MXZ-6C/8C∙NAM1/XAM,
power must not be supplied separately.
3. For the connection method, please
refer to the installation manual of
Branch box for details.
<Combination of indoor units>
Enter the location of combined indoor units with model name in each
blank below because it is necessary for service and maintenance.
SYMBOL
B.C.
LEV-A~E
TH-A~E
TB2B
TB5
REACTOR BOX
F1
F2~F4
SW1
SW4
SW5
CNM
LED1,2
TB3A~E
SW11
SW12
TB2C
TB2D
Branch box controller board
Fuse <T6.3AL 250V>
Fuse <T10AL 250V> *1
Switch for indoor unit connection *2
Switch for function selection *3
Switch for function selection *4
Connector <Connection for service>
Light emitting diode *5
Terminal block <To Indoor unit-A~E> *6
Address Setting ones digit
Address Setting tens digit
Linear expansion valve *6
Thermistor <Gas pipe> *6
Terminal block <To Power Supply>
Transmission line
Optional parts
Terminal block <To Power Supply>
Terminal block <To Branch box (TB2B)>
NAME
Indoor unit-A Indoor unit-B Indoor unit-C Indoor unit-D Indoor unit-E
<Symbols used in wiring diagram>
: Terminal block, : Connector
: Dip switch (■ (black square)
indicates a switch position)
After each indoor unit is connected to the outdoor unit, turn on
the switch corresponding to each indoor unit. For example,
when the indoor units are connected to INDOOR UNIT-A
and C, turn SW1-1 and SW1-3 to on.
*3
SW 4 setting
When the outdoor unit is cooling only system, turn
SW4-5 to on.
*4 Refer to the installation manual of Branch box for details.
*5 LED on Branch box controller board for service
*6 D and E for PAC-MK54BC only
• start-up
Mark
LED 1
LED 2
Main power supply
Meaning
Main power supply (220/230/240V)
Power on →Lamps are lit
Function
Mark
LED 2 Total number of
indoor units
Meaning
Blink depend on the total number
<example> The total number is 2
1 Blink
2 times.
2 Turn off for 3 sec.
3 Repeat
1 to 2 .
LED 1 Main power supply Lamp is lit
Function
• normal operating
PAC-MK
54BC
only
BU BU
BK
WH
RD
BU
BK
WH
TO OUTDOOR UNIT
LEV-E
LEV-D
LEV-C
LEV-B
LEV-A
TH-E
tº
TH-D
tº
TH-C
tº
TH-B
tº
TH-A
tº
1 2 3 4 5 6
SW5
ON
OFF
10s
DIGIT
1s
DIGIT
TO
INDOOR
UNIT-E
TO
INDOOR
UNIT-D
TO
INDOOR
UNIT-C
TO
INDOOR
UNIT-B
TO
INDOOR
UNIT-A
L
N
S3
S2
S1
S3
S2
S1
S3
S2
S1
S3
S2
S1
S3
S2
S1
M1
M2
S
TO OUTDOOR UNIT
DC24-30V
TB3E
TB3C
TB3A
TB3D
TB3B
TB1
F4
F3
F2
TB2B
L
N
L
N
TB5
(SHIELD)
(SHIELD)
CND
(BK)
F1
+–
3
1
5
LEV-E
(GN)
1
5
LEV-D
(BK)
1
5
LEV-C
(BU)
1
5
LEV-B
(RD)
1
5
LEV-A
(WH)
1
2 TH-E
1 (GN)
2 TH-D
1 (BK)
2 TH-C
1 (BU)
2 TH-B
1 (RD)
2 TH-A
1 (WH)
M
M
M
M
M
(PAC-MK54BC only)
(PAC-MK54BC only)
0
1
2
3
4
5
6
7
8
9
SW12
0
1
2
3
4
5
6
7
8
9
SW11
ON
OFF
1 2 3 4 5 6 7 8 9 10
SW4
*
3
1 2 3 4 5 6
SW1
*
2
ON
OFF
LED1
LED2 CNM
(WH)
114
INDOOR UNIT-A
INDOOR UNIT-B
INDOOR UNIT-C
INDOOR UNIT-D
INDOOR UNIT-E
NO USE
SW1-1
SW1-2
SW1-3
SW1-4
SW1-5
SW1-6
NOT CONNECT
NOT CONNECT
NOT CONNECT
NOT CONNECT
NOT CONNECT
CONNECT
CONNECT
CONNECT
CONNECT
CONNECT
*
1 F4 for PAC-MK54BC only
*
2 SW1 setting
OFF ON
Cooling & Heating system
SW4-5 Cooling only system
OFF ON
B.C.
BU
BU
(PAC-MK54BC only)
TO ANOTHER
BRANCH BOX
TO ANOTHER BRANCH BOX or
M-NET CONTROL INDOOR UNIT
POWER SUPPLY
220/230/240V 50Hz
220/230V 60Hz
L
N
TB2B
TO ANOTHER
BRANCH BOX,
REACTOR BOX
(optional parts)
*
7
or M-NET
CONTROL
INDOOR UNIT
CIRCUIT
BREAKER
Fig. 1
PULL
BOX
M-NET
CN3M
(BU)
1
3
PULL
BOX
REACTOR BOX (optional parts)*7
L
N
L
N
*
7 Depending on which
indoor unit is combined
with which outdoor unit,
reactor box should be
installed.
Refer to the installation
manual of Branch box or
that of outdoor unit for
details.
REACTOR BOX
(optional parts)*7
TB2D TB2C
TB2D TB2C

11
OCH744
6 NECESSARY CONDITIONS FOR SYSTEM CONSTRUCTION
6-1. TRANSMISSION SYSTEM SETUP
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
2
Branch box
001
Branch box
006
A-control
Indoor unit
A
(001)
A-control
Indoor unit
B
(002)
C
(003)
A-control
Indoor unit
A
(006)
B
(007)
C
(008)
D
(004)
E
(005)
M-NET cable
①M-NET cable shielding wire must
be connected to each refrigerant
system (outdoor and branch box).
②Set addresses:
Outdoor unit ............051–100 Branch box ............... 001–046
③Outdoor unit has no 100s digit switch.
The address automatically become "100" if it is set as "01–50".
Piping
Signal line
④Make sure that the wiring between the
branch box and indoor unit is properly done, matching with the piping connection.
A B C D E A B C
MA remote
controller
MA remote
controller
MA remote
controller
MA remote
controller
WL-RC WL-RC
WL-RC
WL-RC
For centralized
management
051
Outdoor unit Piping
For Branch box/CITY MULTI indoor unit
1
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Address SW
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Address SW
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Address SW
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Address SW
SW1
ON
123456
SW1
ON
123456
CITY MULTI
Indoor unit
009
CITY MULTI
Indoor unit
010
MA remote
controller
CITY MULTI ............. 001–050
For centralized management
061
Outdoor unit
For Branch box/CITY MULTI indoor unit
0
1
2
3
4
5
6
7
8
9
Address SW CITY MULTI
Indoor unit
011
CITY MULTI
Indoor unit
012
CITY MULTI
Indoor unit
013
CITY MULTI
Indoor unit
014
CITY MULTI
Indoor unit
015
114 164
MA remote
controller
M-NET
remote
controller
M-NET
remote
controller
0
1
2
3
4
5
6
7
8
9
Address SW
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Address SW
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Address SW
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Address SW
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Address SW
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Address SW
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Address SW
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
⑤M-NET remote controller cannot be connected with a refrigerant system which includes branch box.
5
A-control
Indoor unit
A-control
Indoor unit A-control
Indoor unit
A-control
Indoor unit A-control
Indoor unit
⑥The refrigerant system which includes branch box cannot be operated as a group by M-NET remote controller or system controller.
CITY MULTI

12
OCH744
Capillary
tube
Capillary
tube
E
D
C
B
A
Strainer
#100
Strainer
#100
Thermistor (TH-A–E)
(Gas pipe temperature)
LEV A–E
(Linear expansion valve)
C
B
A
Strainer
#100
Strainer
#100
Thermistor (TH-A–C)
(Gas pipe temperature)
LEV A–C
(Linear expansion valve)
PAC-MK54BC
PAC-MK34BC
Branch box
Capillary tube behind LEV
(in cooling mode)
(ø4 oø3.0 oL130) o5
(ø4 oø3.0 oL130) o3
Unit: mm
■PAC-MK54BC ■PAC-MK34BC
6-2. REFRIGERANT SYSTEM DIAGRAM

13
OCH744
6-3. TYPICAL CONTROL SYSTEM
TB7
TB3
(51)
L5
L1
OC
TB7
(53)
OC
24 VDC
L6
L7
M1 M2
S
M1 M2
S
S
M1 M2
S
TB3
M1 M2
S
M1 M2
S
M1 M2
TB3A
A-IC
(01)
A-IC
(02)
A-IC
(03)
A-IC
(04)
A-IC
MA-RC
MA-RC
MA-RC
MA-RC
WL-RC
WL-RC
WL-RC
WL-RC
(05)
A-IC
(06)
A-IC
(07)
A-IC
(08)
S1
S2
S3
TB
S1
S2
TB5/TB15
1
2
A
B
A
B
A
B
A
B
TB5/TB15
1
2
TB5/TB15
1
2
TB5/TB15
1
2
S3
TB
S1
S2
S3
TB
S1
S2
S3
TB
S1
S2
S3
TB
S1
S2
S3
TB
S1
S2
S3
TB
S1
S2
S3
TB
S1
S2
S3
TB3B
S1
S2
S3
TB3C
S1
S2
S3
TB3D
S1
S2
S3
TB3E
S1
S2
S3
TB3A
S1
S2
S3
TB3B
S1
S2
S3
TB3C
S1
S2
S3
M1
M2
S
TB5
M1
M2
S
TB5
L2
A
A
A
M-IC
(09)
M-IC
(10)
MA-RC
MA-RC
TB5
M1
M2
TB15
1
2
A
B
A
B
TB15
1
2
S
TB5
M1
M2
S
L3
L4
Power
Supply
Unit
System
controller
Branch Box
Branch Box
A: Shielded wire
( ): Address example
Note: M-NET remote controller cannot be connected with a refrigerant system which includes branch box.
(1) Di󰀨erence between display and operation
1 When operating the system using the system controller, details of those operations will not appear on the display of the
wireless remote controller.
2 The set temperature range is di󰀨erent in the wireless remote controller that comes with room air conditioner and the system
controller. The room air conditioner has a wider range. If the target temperature is set to below 17°C or less, or 30°C or
more by the wireless remote controller that comes with room air conditioner, the temperature displayed on the system
controller may be converted to their maximum/minimum set temperature. For instance, when HEAT operation at 16°C is set
at the room air conditioner, the system controller may display 17°C.
3 When DRY mode is set with the wireless remote controller, the room air conditioner automatically set the optimum target
temperature. The system controller will display the target temperature as a set temperature.
4 When DRY mode is set with the system controller, the room air conditioner performs DRY mode control operation according
to the temperature set with the system controller.
(2) Timer operation
1 Timer operation should be set using only 1 controller from the remote controller that comes with the room air conditioner,
the system controller or the MA remote controller. If more than 1 controller is used to set the timer at the same time, the
timer will not function properly.
2 When the timer is set with the wireless remote controller; the system controller will not show the timer display.
3 The timer set with the system controller will not be cancelled with the wireless remote controller.
(3) Manual operation prohibition
1 When the manual operation (ON/OFF, set temperature, or operation mode) is prohibited with the system controller, the
command to perform the prohibited operation will not be accepted from the wireless remote controller that comes with the
room air conditioner. The operation partially enabled by the system controller can be operated with the wireless remote
controller. Regardless of whether the operation is disabled or enabled, 3 short beeps will sound when the signal is sent
from the wireless remote controller.
(4) Trouble
1 If the MA remote controller or the system controller shows the abnormal indication, clear it by stopping the operation with
one of the following: the MA remote controller, the system controller, or the wireless remote controller.
(Abnormal indication of the air conditioner could be recovered automatically, but that of the MA remote controller or the
system controller cannot be recovered unless the operation is stopped.)
IMPORTANT:
Make sure that the current leakage breaker is one compatible with higher
harmonics.
Always use a current leakage breaker that is compatible with higher
harmonics as this unit is equipped with an inverter.
The use of an inadequate breaker can cause the incorrect operation of
inverter.
Longest length via outdoor units:
L1+ L2+ L3+ L4+ L5 +L6 + L7 500 m (1640 ft) (1.25 mm² or more)
Longest transmission cable length
L1+ L2+ L3+ L4, L5 + L6, L7200 m (656 ft) (1.25 mm² or more)
OC: Outdoor unit
M-IC: M-NET Control indoor unit (CITY MULTI indoor unit)
A-IC: A-control indoor unit
MA-RC: MA Remote controller
WL-RC: Wireless Remote controller

14
OCH744
(5) Group setting
1MA group or M-NET group setting cannot be set.
(6) Restricted functions
The following functions of system controller cannot be used.
• DIDO controller (Interlock with the air conditioner)
• Fan control of energy saving control or peak cut control function
• Air conditioning charge [TG-2000A]
• Set temperature range limiting function
• Operation mode changeover limit (season changing) [PAC-SF44SRA]
• Dual set point function
• Cylinder unit or hydrobox cannot be operated from system controller.

15
OCH744
7 TROUBLESHOOTING
7-1. HOW TO CHECK THE PARTS
BRANCH BOX: PAC-MK54BC PAC-MK34BC
Parts name Checkpoint
Thermistor (TH-A–E)
<Gas pipe>
Disconnect the connector then measure the resistance with a tester.
(At the ambient temperature 10 to 30°C)
Thermistor R0=15k" ± 3%
Fixed number of B=3480 ± 2%
Rt=15exp { 3480 ( ) }
10°C 9.7 k"
15°C 7.9 k"
20°C 6.4 k"
25°C 5.3 k"
30°C 4.4 k"
< Thermistor for lower temperature >
Temperature (°C)
Resistance (k")
10 15 20 25 30
0
2
4
6
8
10
12
Linear expansion valve
( LEV-A–E )
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
1
2
3
4
5
M
Blue
Yellow
Orange
Red
White
Disconnect the connector then measure the resistance with a tester.
(Winding temperature 20°C)
Normal Abnormal
Red - White Red - Orange Red - Yellow Red - Blue Open or short
46 ± 4Ω
1
273+t
1
273

16
OCH744
<Output pulse signal and the valve operation>
(2) Linear expansion valve operation
A
B
Open
Extra tightening (about 32 pulse)
Pulse number
500 pulse
Opening a valve
all the way
Close
Valve position (capacity)
Close
Open
The output pulse shifts in the following order.
Opening a valve: 8 → 7 → 6 → 5 → 4 → 3 → 2 → 1 → 8
Closing a valve: 1 → 2 → 3 → 4 → 5 → 6 → 7 → 8 → 1
• When linear expansion valve operation stops, all output phases
become OFF.
• When the power is turned on, 700 pulse closing valve signal will be
sent till it goes to Apoint in order to define the valve position.
(The pulse signal is being sent for about 20 seconds.)
• When the valve moves smoothly, there is no sound or vibration
occurring from the linear expansion valve: however, when the pulse
number moves from Bto A or when the valve is locked, sound can
be heard.
No sound is heard when the pulse number moves from Bto Ain
case coil is burnt out or motor is locked by open-phase.
• Sound can be detected by placing the ear against the screw driver
handle while putting the screw driver to the linear expansion valve.
Linear expansion valve
(1) Operation summary of the linear expansion valve
• Linear expansion valve opens/closes through stepping motor after receiving the pulse signal from the branch box controller
board.
• Valve position can be changed in proportion to the number of pulse signal.
<Connection between the branch box controller board and the linear expansion valve>
1
ON
OFF
OFF
OFF
ON
ON
OFF
OFF
OFF
ON
OFF
OFF
OFF
ON
ON
OFF
ø1
Output
(Phase)
Output
ø2
ø3
ø4
2 3 4 5 6 7 8
OFF
OFF
ON
OFF
OFF
OFF
ON
ON
OFF
OFF
OFF
ON
ON
OFF
OFF
ON
(LEV) in Branch box
LEV
M
1
5
ø4 ø
4
ø 3
ø 2
ø 1
1
Red
Blue
Orange
Yellow
White
2
3
4
5
Connector LEV-A
LEV-B
LEV-C
LEV-D
LEV-E
12 VDC
branch box controller board
Drive circuit
ø3
ø2
ø1
2
1
4
3

17
OCH744
Main body
Lead wire Stopper
Coil
(3) How to attach and detach the coil of linear expansion valve
<Composition>
Linear expansion valve is separable into the main body and the coil as shown in the diagram below.
A
<How to detach the coil>
Hold the lower part of the main body (shown as A) firmly so that
the main body does not move and detach the coil by pulling it
upward.
Be sure to detach the coil holding main body firmly. Otherwise
pipes can bend due to stress.
Be sure to attach the
stopper to pipe B.
BA
<How to attach the coil>
Hold the lower part of the main body (shown as A) firmly so that
the main body does not move and attach the coil by inserting it
downward into the main body. Then securely attach the coil stop-
per to pipe B. (At this time, be careful that stress is not added to
lead wire and main body is not wound by lead wire.) If the stopper
is not firmly attached to pipe B, coil may be detached from the
main body and that can cause defective operation of linear expan-
sion valve.
To prevent piping stress, be sure to attach the coil holding the
main body of linear expansion valve firmly. Otherwise pipe may
break.

18
OCH744
Troubleshooting
Problem Checkpoint Corrective measure
If the linear expansion valve becomes locked and the motor is still operating,
the motor will emit a clicking noise and will not function. This clicking noise
indicates an abnormality.
Use an all-purpose electrical meter to measure the resistance between the
different coils (red-white, red-orange, brown-yellow, brown-blue). Normal
resistance is within a range of 46"± 4%.
In order to check the linear expansion valve, operate 1 indoor unit in the
fan mode and another in the cooling mode. Then, use the outdoor multi
controller board to operate the monitor and check the pipe temperature of
the indoor unit. The linear expansion valve should be fully closed when the
fan is operating. The temperature measured by the temperature sensor
will drop if there is any leakage.
If the measured temperature is significantly lower than that on the remote
controller, this indicates that the valve is not closed. It is not necessary to
replace the linear expansion valve if the leak of refrigerant is small and does
not cause a malfunction.
1Check improperly connected connector terminals and the wire colors.
2Remove the connector on the controller board side and check electrical
conductance.
Locked expansion
valve
Short circuit or broken
circuit in expansion
valve motor coil
Valve does not close
completely.
Incorrect connection
or connection failure
Replace the linear
expansion valve.
Replace the linear
expansion valve.
Replace the linear
expansion valve if there
is a major leak of
refrigerant.
Continuity check of
wrong part

19
OCH744
7-2. TEST POINT DIAGRAM
Branch box controller board
PAC-MK54BC PAC-MK34BC
LEV-A to E
Connect to LEV-A to E
LEV-D and E for PAC-MK54BC only
CND
Power supply for
Branch box
Controller board
1–3 220/230/240 VAC
F1
Fuse 6.3 A 250 V
F2,F3,F4
Fuse 10 A 250 V
F4 for PAC-MK54BC
only
CN3M
Connected to the terminal
block (TB5)
(M-NET transmission con-
necting wire)
24–30 VDC (non polar)
TB3A to E
Connect to indoor unit TB3D and TB3E for PAC-MK54BC only
1–3: Power supply 3
–5: Transmission
2–4 220/230/240 VAC 4
–6 0–24 VDC
LED1,LED2
·Startup
Main power supply
(220/230/240 VAC)
·Normal operating
LED1: Main power supply
LED2: Blink depend on the
total number of indoor
units.
<Example>
The total number is 2,
1Blink 2 times
2Turn OFF for 3 seconds
3Repeat 1–2
TH-A to E
Connect to thermistor-A to E
TH-D and E for PAC-MK54BC only
SW4
Mode selection
SW11
Address setting ones DIGIT
SW12
Address setting tens DIGIT
SW5
Service setting
SW1
Indoor unit connection

20
OCH744
Switch
Step
Function Operation in Each Switch Setting
<Initial switch setting>
Additional Information
ON OFF When to Set
SW11 Ones digit
address setting SW12 Tens digit address setting
Rotary switch
How to set addresses Example: if address is "3", remain SW12 (for over 10) at "0", and match SW11 (for 1 to 9) with "3".
Before turning the power ON
Switch setting example. Branch box: 001 (setting No. =x)
indoor-A: 001 (=x) indoor-B: 002 (=x+1) indoor-C: 003 (=x+2) indoor-D: 004 (=x+3) indoor-E: 005 (=x+4)
SW1 Indoor unit connection
1–6
Before turning the power ON
After each indoor unit is connected to the outdoor unit, turn ON the switch corresponding to each indoor unit. For example, when the indoor units are connected to INDOOR UNIT-A and C, turn SW1-1 and SW1-3 to ON.
SW4 Mode selection
1Change temperature indication Fahrenheit
temperature
Celsius temperature
Before turning the power ON
—
2Power-supply voltage setting 220 or 230 V 240 V Set at factory only 3Change operation if M-NET
communication error occurs. Stop operation Continued
operation
Before turning the power ON
4Automatic restoration when the
power comes back ON.*2Inactive Active
5System type Cooling only
system
Cooling & heating system
When the outdoor unit is cooling only system, turn SW4-5 to ON.
6–7
Model setting
Refer to "Initial switch setting".
—
8–10
— — —
SW5 Service setting
1–3
Change INDOOR UNIT No. for monitoring
Refer to "7-4. BRANCH BOX UNIT OPERATION MONITOR FUNCTION".
Can be activated at any time —
4–6
When the cylinder unit or hydrobox is used in a house, connect the indoor unit for bed room to A
–
C port of the branch box, then
set the switches as follows:
Before turning the power ON
Port A to C are available for setting for up to a maximum of 3 rooms.
Ports available for setting
Port A Port B Port C Port D Port E
Ports available for setting
Port A Port B Port C Port D Port E
1
ON
OFF
2 3 4 5 6
Tens digit
0
1
2
3
4
5
6
7
8
9
SW12
Ones digit
0
1
2
3
4
5
6
7
8
9
SW11
OFF ON
SW1
1Indoor unit A Not connected Connected
2Indoor unit B Not connected Connected
3Indoor unit C Not connected Connected
4*1Indoor unit D Not connected Connected
5*1Indoor unit E Not connected Connected 6Not used
1
ON
OFF
2 3 4 5 6 7 8 9 10
1
ON
OFF
2 3 4 5 6
The black square (■) indicates a switch position.
*1 PAC-MK54BC only *2 Note that the automatic restoration starts after the unit has stopped once.
7-3. INTERNAL SWITCH FUNCTION TABLE
OFF ON
SW5
4
Port A
Other Bedroom
5
Port B
Other Bedroom
6
Port C
Other Bedroom