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