Panasonic Cu 3ks19nbucu 4ksxxnbu Technical Service Manual

							15
2-6.Diagram of Outdoor Unit Installation
Never install only a single indoor unit.
Be sure to connect indoor and outdoor units only in
combinations that are listed in the catalog or in the
combination table that was provided with the outdoor unit. 
(Use caution. Connecting any other model may result in
operation failure and malfunction.) 
The dimensions indicated by    in the figure below are  
spaces that are required in order to maintain
performance. Install in a location where the dimensions
indicated by    are ensured, and where 2 or more faces  
of the unit are unobstructed. In principle, the top direction
should be unobstructed. Indoor unit D   Wall-mounted types Ceiling-mounted
cassette types
Indoor unit C  
Indoor unit B  
Indoor unit A  Indoor unit D  
Indoor unit C  
Indoor unit B  
Indoor unit A  
Service space 
Power breaker 
Ground
wire
(not
provided) Ensure 6"(15cm)
of space if a 
drain hose is to 
be used.
Base (not provided) 
(concrete or similar material) 
Fasten with anchor bolts
(not provided)
(3/8" or M10, 4 locations)
A B
C
D
Access panel  C 
Over 10"(25cm)
Over 8"(20cm)
Over 4"(10cm)
Over 1'8"(50cm)
Fig. 7 
						

							16
3.  Installation Process
3-1.Embedding the Tubing and Wiring

Do not connect tubes to locations that are embedded.

Be sure to bind refrigerant tubing and inter-unit cables
together with vinyl tape.

The power cable must be obtained on-site. 
(#12: Less than 85 ft.) 
# ... AWG (American Wire Gauge)

Be sure to apply the provided labels to both ends of
the inter-unit cables to prevent miswiring.

Securely seal the end of embedded tubing with vinyl
tape in order to prevent dirt or moisture entry.

In order to prevent insulation breakdown and ground
faults, do not allow the wire ends to come in contact
with rainwater, or be subject to dew condensation.
Deburring
BeforeAfter
Fig. 8
3-2.  Use of the Flaring Method
Many of the conventional split system air conditioners
employ the flaring method to connect refrigerant tubes
which run between indoor and outdoor units. In this
method, the copper tubes are flared at each end and
connected with flare nuts.
3-3.  Flaring Procedure with a Flare Tool
(1) Cut the copper tube to the required length with a
tube cutter. It is recommended to cut approx. 12 to
20 (30 to 50 cm) longer than the tubing length you
estimate.
(2) Remove burrs at the end of the copper tube with a
tube reamer or file. This process is important and
should be done carefully to make a good flare. 
(Fig. 8) 
						

							17
When reaming, hold the tube end downward and be sure that
no copper scraps fall into the tube. (Fig. 9)
(3) Remove the flare nut from the unit and be sure to mount
it on the copper tube.
(4) Make a flare at the end of copper tube with a flare tool.*
(Figs. 10 and 11) 
(*Use “RIDGID” or equivalent.)
A good flare should have the following characteristics:

inside surface is glossy and smooth.

edge is smooth.

tapered sides are of uniform length.
3-4.  Caution before Connecting Tubes Tightly
a) Be sure to apply a sealing cap or water-proof tape to
prevent dust or water from getting into the tubes before
they are used.
b) Be sure to apply refrigerant lubricant to the matching 
surfaces of the flare and union before connecting them
together. This is effective for reducing gas leaks. 
(Fig. 12)
c) For proper connection, align the union tube and flare
tube straight with each other, then screw in the flare nut
lightly at first to obtain a smooth match. (Fig. 13)
3-5.  Tubing Connections
a) Temporary connection:
Screw in 3 – 5 turns by hand. (Fig.14)
b) To fasten the flare nuts, apply specified torque as:
Table 4
NOTE
NOTE
Reamer Copper
tubing
Fig. 9
Flare toolFlare nut
Copper
tubing
Fig. 11
Fig. 10
Apply refrigerant 
lubricant here and here
Fig. 12
Flare nut
Union
Fig. 13
0 to 0.0196"
(0 to 0.5 mm) If the special R410A 
flare tool is used:
0.0472" (1.2 mm) If the previous flare tool 
(clutch-type) is used:
Adjust so that the amount of tube 
protrusion is as shown in the figure.
Apply the provided labels 
to the indoor and outdoor 
unit tubing connectors to 
prevent errors in 
connections.
Service valve on 
narrow tube side
Service valve on 
wide tube side
A B C
D
Fig. 14
Tube Dia. Nut Tightening Torque
1/4 (6.35 mm) 21/32 (17 mm) Approx. 120 – 160 lbs· in (140 – 180 kgf· cm)
3/8 (9.52 mm) 7/8 (22 mm) Approx. 300 – 360 lbs· in (340 – 420 kgf· cm)
1/2 (12.70 mm) 1-1/32 (26 mm) Approx. 430 – 480 lbs· in (490 – 550 kgf· cm)
5/8 (15.88 mm) 1-5/32 (29 mm) Approx. 590 – 710 lbs· in (680 – 820 kgf· cm) 
						

							18
3-6.  Insulation of Refrigerant Tubing
To prevent heat loss and wet floors due to dripping of con-
densation,both tubes must be well insulated with a
proper insulation material.
The thickness of the insulation should be a minimum 5/16
(8 mm). (Fig. 16)
For wall-mounted units
After connecting the refrigerant tubing to the outdoor unit
and performing a leak test on the connecting part, insulate it
with the tubing insulation. (Fig 17a)
For ceiling-mounted cassette units
Wind the insulation tape around the flare nuts at the tube
connections. Secondly cover up the tubing connections
with the flare insulation (1/8 (T3, supplied)). Then wind the
other flare insulation (3/16 (T5, supplied)). Finally, fasten
the insulation at both ends with the supplied vinyl ties. 
(Fig. 17b)
Insulation material
The material used for insulation must have good insulation
characteristics, be easy to use, be age resistant, and must
not easily absorb moisture.
IMPORTANT
Indoor unit
Outdoor unitSpanner Torque wrench
Fig. 15
Insulation
Min. 
5/16
(8 mm)
Thickness:
min. 5/16
(8 mm)
Fig. 16
Insulation
Fig. 17a
CAUTIONBe sure to match refrigerant
tubing and electric wiring
between indoor and outdoor
units.
Fig. 17b
Fig. 17c
Never grasp the drain or refrigerant connecting out-
lets when moving the unit.
Insulation tape (supplied) Flare insulation (3/16(T5, supplied) )
Flare insulation (1/8(T3, supplied) )
Tube insulation 
(not supplied) 
Vinyl tie (supplied)  Flare nut
The procedure used for installing 
the insulation for both wide and 
narrow tubes are the same. 
Flare
insulation (supplied)Vinyl tie (supplied)Insulation tape (supplied)Refrigerant tubing 
and insulation 
(not supplied)  Drain pipe and insulation 
(not supplied)  Drain hose insulation 
and vinyl tie 
(supplied)
Drain hose 
and hose band 
(supplied) 
						

							19
4.  Air Purging
Air and moisture remaining in the refrigerant system have
undesirable effects as indicated below. Therefore, they
must be purged completely.

pressure in the system rises

operating current rises

cooling efficiency drops

moisture in the air may freeze and block capillary tubing

water may lead to corrosion of parts in the refrigerant
system

Air Purging with a Vacuum Pump 
(for Test Run)

In order to protect the earth’s environment, be sure to use
a vacuum pump to perform the air purge.
(Never perform an air purge by using the refrigerant gas
cylinder or other external gas, or by using the gas inside
the outdoor unit.)
Fig. 20
CAUTION
In order to prevent charging errors
with the air conditioner that uses
R410A, the screw diameter at the
service valve charging port has
been changed. When recharging or
performing other servicing, use the
special charging hose and manifold
gauge.
Service
valve on 
wide tube 
side Service
valve on 
narrow
tube side
A B C D
Vacuum 
pump
Vacuum pump 
adapter
(for preventing 
reverse flow)
(special for 
R410A) High-pressure valve Manifold gauge 
(special for R410A)
Low-pressure
valve
Leave the 
valve open.
Open
Charging hose
(special for R410A) Hex wrench 
With push-pin
Hi Lo
3-7.  Taping the Tubes
(1) At this time, the 2 refrigerant tubes (and electrical wire 
if local codes permit) should be taped together with
armoring tape. The drain hose may also be included 
and taped together as 1 bundle with the tubing.
(2) Wrap the armoring tape from the bottom of the outdoor
unit to the top of the tubing where it enters the wall. As
you wrap the tubing, overlap half of each previous tape
turn. (Fig. 18)
(3) Clamp the tubing bundle to wall, using 1 clamp approx.
every 47 (120 cm).
Do not wind the armoring tape too tightly, since this will
decrease the heat insulation effect. Also, be sure the con-
densation drain hose splits away from the bundle and drips
clear of the unit and the tubing.
3-8.  Finishing the Installation
After finishing insulating and taping over the tubing, use
sealing putty to seal off the hole in the wall to prevent rain
and draft from entering. (Fig. 19)
NOTE
Fig. 18
Clamp
Insulated tubes
Apply putty here
Tubing
Fig. 19
CAUTION
After a tube has been insulated,
never try to bend it into a narrow
curve, as this may cause the tube
to break or crack. 
						

							20
Cap tightening torque:
170 – 215 lbs·in
(200 – 250 kgf·cm)
(Tighten by hand, then 
use a wrench to turn 
 approximately 
      45°.) Stopper
Spindle
Service port
Screw diameter: 1/2
UNF 20 threads
Valve core
Cap nut tightening torque:
60 – 95 lbs·in
(70 – 110 kgf·cm)
(Tighten by hand, then use a 
wrench to turn approximately 30 .)

External diameter of service port
R410A: 5/16
NOTE
Fig. 21

When using a hex wrench to open the spindle, an
extremely small amount of refrigerant may leak. 
This does not indicate a problem.

Use a hex wrench of a type to which force can be
easily applied. 
(4) With the “Lo” knob of the manifold valve open and high-pressure valve (“Hi”) closed completely, run the vacuum pump.
Run the pump until the pressure is –101 kPa (–76 cmHg). The operation time for the vacuum pump varies with tubing
length and the capacity of the pump. The following table shows the amount of time required for evacuation:
Table 5
(5) With the vacuum pump still running, close the “Lo” knob of the manifold valve. Then stop the vacuum pump. Fully
close the low-pressure valve and stop the vacuum pump. (Wait 1 – 2 minutes and check that the manifold gauge
pointer does not return. If it does return, find and repair the leak, then apply the vacuum again.)
(6) With a hex wrench, turn the valve stem on the narrow tube service valve counter-clockwise by 90 degrees (1/4 turn)
for 10 seconds, and then turn the stem clockwise to close it again.
(7) With a standard screwdriver, turn the wide tube service valve stem counterclockwise to fully open the valve.
(8) Turn the narrow tube service valve stem counter-clockwise to fully open the valve.
(9) Loosen the vacuum hose connected to the wide tube service port slightly to release the pressure. Then, remove
the hose.
(10) Leak test all joints at the tubing (both indoor and outdoors) with liquid soap. Bubbles indicate a leak. Be sure to wipe
off the soap with a clean cloth.
CAUTIONBe sure to completely insert the hex
wrench before attempting to turn the
valve.
Required time for evacuation when capacity
of 100 liter/h vacuum pump is used
20 min. or moreThe required time in Table 5 is calculated based on the
assumption that the ideal (or target) vacuum condition is
around 10 mmHg abs.
NOTE
CAUTIONIf a CFC gas detector is used, use a
special detector for HFC refrigerant
(such as R410A and R134a).
Perform the air purge for tubes A, B, C, and D. Use the same
procedures for all tubes.
(1) Check that each tube (both narrow and wide tubes)
between the indoor and outdoor units have been proper-
ly connected and all wiring for the test run has been
completed. Note that both narrow and wide tube service
valves on the outdoor unit are kept closed at this stage.
(2) Using an adjustable wrench or box wrench, remove the
valve caps from the service valve on both narrow and
wide tubes.
(3) Connect a vacuum pump and a manifold valve (with
pressure gauges) to the service port on the wide tube
service valve. (Fig. 20).
CAUTIONBe sure to use a manifold valve for
air purging. If it is not available, use
a stop valve for this purpose. The
“Hi” knob of the manifold valve
must always be kept closed.
CAUTIONBefore using the vacuum pump
adapter, read the vacuum pump
adapter manual, and use the
adapter correctly. 
						

							21
Pump Down

When relocating or disposing of the air conditioner, request this
service from the dealer where the unit was purchased, or from an
appropriate agent. Perform pump-down as described below.
What is pump-down?

Pump-down refers to recovering the refrigerant gas from the refrig-
erant cycle at the outdoor unit. This work must be performed dur-
ing cooling operation. The refrigerant gas cannot be recovered 
during heating operation.

During winter, or if the temperature sensor prevents cooling opera-
tion, perform “forced cooling operation.”
Pump-down procedure
(1) Fully close the spindles at the valves on the narrow tube side of
tubes A, B, C and D. (Refer to Fig. 22.)
(2) Connect the manifold gauge to the charging port at the valve on
the wide tube side of tube D. Purge the air from the charging hose.
(Refer to Fig. 23.)
(3) Perform cooling operation or forced cooling operation.
When the pressure at the low-pressure side is 0.05 – 0.1 MPaG
(0.5 – 1 kg/cm
2G), fully close the spindles at the valves on the
wide tube side of tubes A, B, C, and D, and  immediately stop
operation. (Refer to Fig. 23.)
In the winter, the outdoor unit may stop after 5 - 10 minutes of
operation. This is in order to protect the indoor unit heat
exchanger from freezing and does not indicate a problem.
(4) Disconnect the manifold gauge and the inter-unit tubes, and
attach the caps and flare nuts. At this point, pump-down is com-
pleted. (If the caps and flare nuts are not reattached, there is the
danger of gas leakage.) (Refer to Fig. 24.)
If pump-down is not possible
If the air conditioner cannot be operated because of a malfunction or
other cause, use a refrigerant recovery device to recover the refrigerant.
In order to protect the earth’s environment, be sure to perform pump-down to recover refrigerant
gas without releasing it into the atmosphere.
Fig. 22
(11) Replace the flare nut on the wide tube service port and fasten the flare nut securely with an adjustable wrench or
box wrench. Next, mount the valve cap and tighten it with a torque wrench (the cap needs to be tightened with the
torque of 180 lbs·in (200 kgf·cm)). This process is very important to prevent gas from leaking from the system.
(12) Test run the air conditioner. (See page 26.)
(13) While the air conditioner is running, apply liquid soap to check for any gas leaks around the service valves or caps.
(14) If there is no leakage, stop the air conditioner.
(15) Wipe off the soap on the tubing.
This completes air purging with a vacuum pump and the air conditioner is ready for actual operation.
Fig. 23
C D
B
A
Manifold gauge Wide tube side 
Charging hose
Cap
Cap
Cap
CapAfter disconnecting 
the inter-unit tubes, 
attach the flare nuts 
with flare bonnets.
Fig. 24
D
C
B
A
Charging port Narrow tube sideClose
Close
Close
Close 
						

							22
5.  Wiring Instructions
5-1.  General Precautions on Wiring
(1) Before wiring, confirm the rated voltage of the unit as
shown on its nameplate, then carry out the wiring 
closely following the wiring diagram.
(2) Provide a power outlet to be used exclusively for each
unit, with a power supply disconnect and circuit break-
er for overcurrent protection provided in the exclusive
line.
(3) To prevent possible hazard due to insulation failure, 
the unit must be grounded.
(4) Each wiring connection must be done tightly and in
accordance with the wiring system diagram. Wrong
wiring may cause the unit to misoperate or become 
damaged.
(5) Do not allow wiring to touch the refrigerant tubing, 
compressor, or any moving parts of the fan.
(6) Unauthorized changes in the internal wiring can be 
very dangerous. The manufacturer will accept no
responsibility for any damage or misoperation that
occurs as a result of such unauthorized changes.
5-2.  Recommended Wire Length and Diameter
Regulations on wiring diameter differ from locality to locality.
For field wiring requirements, please refer to your local elec-
trical codes. Carefully observe these regulations when car-
rying out the installation.
Table 6 shows maximum wire lengths for control line and
power line and fuse or circuit capacity.
Refer to the wiring system diagram (Fig. 25a or 25b) for the
meaning of (A), (B), and (C) in Table 6.
Refer to your local codes or in the absence of local codes
see the National Electric Code: ANSI/NFPA70.
NOTE
Table 6
AWG Max. Power Line Length (ft.) 
(A)Max. Control Line Length (ft.) 
(B) (C) Fuse
or
Circuit Capacity  Model
(#12) (#14) 
CU-3KS19NBU 85 (Max.)  82 (Max.)  15 A
CU-4KS24NBU 85 (Max.)  82 (Max.)  20 A 
CU-4KS31NBU 85 (Max.)  100 (Max.)  20 A 
# ... AWG (American Wire Gau
ge) 
						

							23
WARNING

Be sure to comply with local codes on running the
wire from the indoor unit to the outdoor unit (size
of wire and wiring method, etc.).

Each wire must be firmly connected.

No wire should be allowed to touch refrigerant
tubing, the compressor, or any moving part.

Be sure to connect power wires correctly match-
ing up numbers on terminals of the outdoor unit
and respective indoor units A – D.
CAUTION

Be sure to connect the power supply line to the
outdoor unit as shown in the wiring diagram. The
indoor unit draws its power from the outdoor unit.

Do not run wiring for antenna, signal, or power
lines of television, radio, stereo, telephone, secu-
rity system, or intercom any closer than 34 (1 m)
from the power cable and wires between the
indoor and outdoor units. Electrical noise may
affect the operation.

To avoid the risk of electric shock, each air conditioner
unit must be grounded.

For the installation of a grounding device, please
observe local electrical codes.

Grounding is necessary, especially for units using
inverter circuits, in order to release charged electricity
and electrical noise caused by high tension. 
Otherwise, electrical shock may occur.

Place a dedicated ground more than 7 (2 m) away from
other grounds and do not have it shared with other
electric appliances.
WARNING
Fig. 25a
Fig. 25b
4 indoor units with CU-4KS24NBU, CU-4KS31NBU
1
2
3Terminal INDOOR  UNIT
1
2
3
INDOOR  UNIT
1
2
3
1
UNIT  B
2
3
4
UNIT  C
5
6
7
8
9
1
2
Terminal Terminal
L1
L2
INDOOR  UNIT
UNIT  A
(A)
(B)
(C)
Terminal
(2P) Terminal(
9P) OUTDOOR  UNIT
Disconnect
switch*
*
*
230/208V
230/208V
230/208V
230/208V
230/208V
230/208V
230/208V
230/208V
230/208V
Grounding
line Grounding
line
Disconnect
switchField  supply
Disconnect
switch
Field  supply Field  supply
Power  supply
Single-phase  230/208VAC  60HZ
Grounding
line
Grounding  line
(A) (B)
(B)
(B)(B)
(B)
(B) (C)
(C)
(C)
1
2
3Terminal1
UNIT  B
2
3
4
UNIT  C
5
6
7
UNIT  D
8
9
10
11
12
1
2
L1
L2
INDOOR  UNIT
UNIT  A
(A)
1
2
3Terminal INDOOR  UNIT
(B)
Terminal
(
2P)
Terminal(
12P) OUTDOOR  UNIT
Disconnect
switch
230/208V
230/208V
230/208V
230/208V
230/208V
230/208V
Grounding  line
Grounding  line
Field  supply
230/208V
230/208V
230/208V
230/208V1
2
3Terminal INDOOR  UNIT
(C)
1
2
3Terminal INDOOR  UNIT
(D)(Inter-unit)
power line230/208V
230/208V
Power  supply
Single-phase  230/208VAC  60HZ
Grounding  line
Grounding
line
Grounding
line
Disconnect  switch
Field  supply Disconnect
switch
Field  supply
Disconnect  switch
Field  supply
(A) (B)
(B)
(B) (B) (B)
(B)
(B)
(B) (C)
(C)
(C)
(C)
*
*
*
*
3 indoor units with CU-3KS19NBU
5-3.  Wiring System Diagram
*
Disconnect switch may be required by
national or local codes.
Always comply with national and local code
requirements.
CAUTION
NOTE 
						

							24
When connecting each power wire to the corresponding
terminal, follow the instructions “How to connect wiring
to the terminal” and fasten the wire securely tight with
the fixing screw of the terminal plate.
How to connect wiring to the terminal
a) For Indoor Unit
(1) Cut the wire end with a cutting pliers, then strip the
insulation to expose the wire about 9/32 (7 mm).
See the label (Fig. 26) near the terminal plate.
(2) Using a screwdriver, loosen the terminal screw on
the terminal plate.
(3) Insert the wire and tighten the terminal screw com-
pletely using a screwdriver.
b) For Outdoor Unit
For solid core wiring (or F-cable)
(1) Cut the wire end with a cutting pliers, then strip the
insulation to expose the solid wire about 15/16 (25
mm). (Fig. 27)
(2) Using a screwdriver, remove the terminal screw(s)
on the terminal plate.
(3) Using the pliers, bend the solid wire to form a loop
suitable for the terminal screw.
(4) Shape the loop wire properly, place it on the termi-
nal plate and fix it securely with the removed termi-
nal screw using a screwdriver.
For stranded wiring
(1) Cut the wire end with a cutting pliers, then strip the
insulation to expose the stranded wiring about 3/8
(10 mm) and tightly twist the wire ends. (Figs. 28
and 29)
(2) Using a screwdriver, remove the terminal screw(s)
on the terminal plate.
(3) Using a ring connector fastener or pliers, securely
clamp each stripped wire end with a ring connector.
(Fig. 28)
(4) Place the ring connector wire, and replace and
tighten the removed terminal screw using a screw-
driver. (Fig. 30)
Solid wire
Loop
Insulation
Strip 15/16 (25 mm)
Fig. 27
STRIP
SIZE9/32"
(7 mm)
(ACTUAL 
SIZE)
Fig. 26
Stranded wire
Ring
connector
Strip 3/8 (10 mm)
Fig. 28
Screw
Ring connector
Terminal plate
WireSpecial
washer
Fig. 30
Screw and
special washer
Ring
connector
Wire
WARNINGLoose wiring may cause the
terminal to overheat or result
in unit malfunction. A fire
hazard may also exist. There-
fore, be sure all wiring is
tightly connected.
Twist wire ends
Fig. 29
5-4.  How to Connect Wiring to the Terminal