aircon ASKEC4H4R18 User manual

Air Conditioners
Installation Manual
Models
Indoor Unit Outdoor Unit
ASKEC4H4R18 ASKCI4H4R18
ASKEC4H4R24 ASKCI4H4R24
ASKEC4H4R36 ASKCI4H4R36
ASKEC4H4R48 ASKCI4H4R48
DC Inverter U-match Series
Cassette Type Unit
Thank you for choosing these Air Conditioners, please read this owner’s manual carefully
before operation and retain it for future reference.

1 Safety Precautions ..........................................................................................1
2 Outline of the Unit and Main Parts...................................................................3
3 Preparative for Installation...............................................................................4
3.1 Standard Accessory Parts..........................................................................4
3.2 Selection of the Installation Location..........................................................5
3.3 Connection Pipe Requirement ...................................................................7
3.4 Electrical Requirement...............................................................................7
4 Installation of the Unit......................................................................................8
4.1 Installation of the Indoor Unit......................................................................8
4.2 Installation of the Outdoor Unit.................................................................10
4.3 Installation of the Connection Pipe...........................................................11
4.4 Vacuum and Gas Leakage Inspection......................................................15
4.5 Installation of the Drain Hose...................................................................16
4.6 The Panel Installation ..............................................................................20
4.7 Electrical Wiring........................................................................................22
5 Installation of Controllers...............................................................................27
6 Test Running..................................................................................................27
6.1 Trial Operation and Testing.......................................................................27
6.2 Working Temperature Range....................................................................29
7 Troubleshooting and Maintenance ................................................................30
7.1 Troubleshooting........................................................................................30
7.2 Routine Maintenance ...............................................................................31
Contents

DC Inverter U-match Series Cassette Type Unit
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1 Safety Precautions
WARNING! This mark indicates procedures which, if improperly performed, might lead to the
death or serious injury of the user.
CAUTION! This mark indicates procedures which, if improperly performed, might possibly result
in personal harm to the user, or damage to property.
WARNING!
(1). Installation should be left to the dealer or another professional. Improper installation may cause
water leakage, electrical shock, or re.
(2). Install the air conditioner according to the instructions given in this manual. Incomplete installation
may cause water leakage, electrical shock, or re.
(3). Be sure to use the supplied or specied installation parts. Use of other parts may cause the unit to
come to lose, water leakage, electrical shock, or re.
(4). Install the air conditioner on a solid base that can support the weight of the unit. An inadequate base
or incomplete installation may cause injury in the event the unit falls off the base.
(5). Electrical work should be carried out in accordance with the installation manual and the national
electrical wiring rules or code of practice. Insufcient capacity or incomplete electrical work may
cause electrical shock or re.
(6). Be sure to use a dedicated power circuit. Never use a power supply shared by another appliance.
(7). For wiring, use a cable length enough to cover the entire distance with no connection. Do not use
an extension cord. Do not put other loads on the power supply, use a dedicated power circuit.
(Failure to do so may cause abnormal heat, electric shock or re.)
(8). Use the specied types of wires for electrical connections between the indoor and outdoor units.
Firmly clamp the interconnecting wires so their terminals receive no external stresses. Incomplete
connections or clamping may cause terminal overheating or re.
(9). After connecting interconnecting and supply wiring be sure to shape the cables so that they do not
put undue force on the electrical covers or panels. Install covers over the wires. Incomplete cover
installation may cause terminal overheating, electrical shock, or re.
(10). If any refrigerant has leaked out during the installation work, ventilate the room. (The refrigerant
produces a toxic gas if exposed to ames.)
(11). After all installation is complete, check to make sure that no refrigerant is leaking out. (The
refrigerant produces a toxic gas if exposed to ames.)
(12). When installing or relocating the system, be sure to keep the refrigerant circuit free from
substances other than the specied refrigerant (R410A), such as air. (Any presence of air or other
foreign substance in the refrigerant circuit causes an abnormal pressure rise or rupture, resulting in
injury.)
(13). During pump-down, stop the compressor before removing the refrigerant piping. If the compressor
is still running and the stop valve is open during pump-down, air will be sucked in when the
refrigerant piping is removed, causing abnormal pressure in the freezer cycle which will lead to
breakage and even injury.

DC Inverter U-match Series Cassette Type Unit
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(14). During installation, attach the refrigerant piping securely before running the compressor. If the
compressor is not attached and the stop valve is open during pump-down, air will be sucked in
when the compressor is run, causing abnormal pressure in the freezer cycle which will lead to
breakage and even injury.
(15). Be sure to establish an earth. Do not earth the unit to a utility pipe, arrester, or telephone earth.
Incomplete earth may cause electrical shock, or re. A high surge current from lightning or other
sources may cause damage to the air conditioner.
(16). Be sure to install an earth leakage breaker. Failure to install an earth leakage breaker may result in
electric shocks, or re.
(17). This appliance is not intended for use by persons (including children) with reduced physical,
sensory or mental capabilities, or lack of experience and knowledge, unless they have been given
supervision or instruction concerning use of the appliance by a person responsible for their safety.
(18). Children should be supervised to ensure that they do not play with the appliance.
(19). If the supply cord is damaged, it must be replaced by the manufacturer, its service agent or
similarly qualied persons in order to avoid a hazard.
CAUTION!
(1). Do not install the air conditioner in a place where there is danger of exposure to inammable gas
leakage. If the gas leaks and builds up around the unit, it may catch re.
(2). Establish drain piping according to the instructions of this manual. Inadequate piping may cause
ooding.
(3). Tighten the are nut according to the specied method such as with a torque wrench. If the are
nut is tightened too hard, the are nut may crack after a long time and cause refrigerant leakage.

DC Inverter U-match Series Cassette Type Unit
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2 Outline of the Unit and Main Parts
1. Drainage device
2. Drainage pipe
3. Air ow ap
4. Connection pipe
5. Wired Controller
6. Wireless Controller
7. Big handle
8. Liquid Pipe
9. Gas pipe
10. Drainage pipe
11. Front Board
Indoor
Outdoor
2
3
4
7
5 6
1
8
9
10
11
Air inlet
Air outlet
Fig.1

DC Inverter U-match Series Cassette Type Unit
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3 Preparative for Installation
3.1 Standard Accessory Parts
The standard accessory parts listed below are furnished and should be used as required.
Table 3.1
Indoor Unit Accessories
No. Name Appearance Q'ty Usage
1 Drain Hose 1To connect with the hard PVC drain
pipe
2 Nut with Washer 4To x the hook on the cabinet of the
unit.
3 Washer 10 To be used together with the
hanger bolt for installing the unit.
4 installation paperboard 1 used for ceiling drilling
5 Gasket mounting board 4Used to prevent gasket from falling
off
6Wireless Controller
+Battery 1+2 To control the indoor unit
7 sealing plaster 1
8 Fastener 4 To fasten the sponge
9 Insulation 1 To insulate the gas pipe
10 Insulation 1 To insulate the liquid pipe
11 Sponge 4 To insulate the drain pipe
12 Nut 1 To connect gas pipe
13 Nut 1 To connect liquid pipe
14 Enswathement 2
Table 3.2
Outdoor Unit Accessories
No. Name Appearance Q'ty Usage
1 Drain Plug 2 or 3 To plug the unused drain hole.
2 Drainage Connecter or 1To connect with the hard PVC drain
pipe

DC Inverter U-match Series Cassette Type Unit
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3.2 Selection of the Installation Location
WARNING!
The unit must be installed where strong enough to withstand the weight of the unit and xed securely,
otherwise the unit would topple or fall off.
CAUTION!
① .
Do not install where there is the danger of combustible gas leakage.
② .
Do not install the unit near heat source of heat, steam, or ammable gas.
③ .
Children under 10 years old must be supervised not to operate the unit.
Decide the installation location with the customer as follows:
3.2.1 Indoor Unit
Select an installation site where the following conditions are fulfilled and that meets your
customer’s approval.
(1). Obstruct should be put away from the intake or outlet vent of the indoor unit so that the
airow can be blown through all the room.
(2). Make sure that the installation meets the requirement of the schematic diagram of
installation spaces.
(3). Select the place where can stand 4 times of the weight of the indoor unit and would not
increase the operating noise and vibration.
(4). The horizontality of the installation place should be guaranteed.
(5). Select the place where is easy to drain out the condensate water, and connect with outdoor
unit.
(6). Make sure that there are enough space for care and maintenance, and the height fall
between the indoor unit and ground is above 1800mm.
(7). When installing the suspension bolt, check if the installation place can stand 4 times of the
weight of the unit. If not, reinforce it before installation.
Note: There will be large amount of greasy dirt accumulated on the fan, heat exchanger and water
pump located in the dinning room and kitchen, which would reduce the capacity of the heater
exchanger, lead to leakage and abnormal operation of the water pump.
Models H(mm)
ASKEC4H4R18 255
ASKEC4H4R24 260
ASKEC4H4R36 340
ASKEC4H4R48 320
Table 3.3
Fig.3.1

DC Inverter U-match Series Cassette Type Unit
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3.2.2 Outdoor Unit
WARNING!
① .
Install the unit where it will not be tilted by more than 5°.
② .
During installation, if the outdoor unit has to be exposed to strong wind, it must be xed securely.
If possible, do not install the unit where it will be exposed to direct sunlight. (If necessary, install
a blind that does not interfere with the air ow.)
(1). Install the outdoor unit in a place where it will be free from being dirty or getting wet by rain
as much as possible.
(2). Install the outdoor unit where it is convenient to connect with the indoor unit.
(3). Install the outdoor unit where the condensate water can be drained out freely during
heating operation.
(4). Do not place animals and plants in the path of the warm air.
(5). Take the air conditioner weight into account and select a place where noise and vibration
are small.
(6). Install the outdoor unit where is capable of withstanding the weight of the unit and
generates as less noise and vibration as possible.
(7). Provide the space shown in Fig.3.2, so that the air ow is not blocked. Also for efcient
operation, leave three of four directions of peripheral constructions open. Units: mm
＞500
＞500 ＞500 ＞500
＞2000
＞2000
＞1000
Fig. 3.2

DC Inverter U-match Series Cassette Type Unit
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3.3 Connection Pipe Requirement
CAUTION!
The maximum length of the connection pipe is listed in the table below. Do not place the units between
which the distance exceeds the maximum length of the connection pipe.
Table 4
Item
Model
Size of Fitting
Pipe(Inch) Max.
Pipe
Length
(m)
Max. Height
Difference between
Indoor Unit and
Outdoor Unit (m)
Drainage
pipe(Outer
Diameter × wall
thickness) (mm)
Liquid Gas
1/4 1/2 20 15
φ25×1.5
3/8 5/8
30 15
30 15
50 30
The connection pipe should be insulated with proper water-proof insulating material.
The pipe wall thickness shall be 0.5-1.0mm and the pipe wall shall be able to withstand the
pressure of 6.0 MPa. The longer the connecting pipe, the lower the cooling and heating effect
performs.
3.4 Electrical Requirement
Electric Wire Size and Fuse Capacity. Table 5
Indoor Units Power Supply Fuse Capacity Breaker Capacity Min. Power Supply Cord
V/Ph/Hz A A mm2
18K~48K 220-240V~ 60Hz 5 6 1.0
Table 6
Model Power
Supply Capability of Air Switch(A)
Minimum Sectional Area of
Power Cable and Earth line
(mm2)
220-240V~ 60Hz
16 1.5
20 2.5
25 2.5
40 6.0
Notes:
① .
The fuse is located on the main board.
② .
Install the disconnect device with a contact gap of at least 3mm in all poles nearby the units
(Both indoor unit and outdoor unit).The appliance must be positioned so that the plug is
accessible.
ASKCI4H4R18 ASKEC4H4R18
ASKCI4H4R24 ASKEC4H4R24
ASKCI4H4R36 ASKEC4H4R36
ASKCI4H4R48 ASKEC4H4R48
ASKCI4H4R18
ASKCI4C4R24
ASKCI4H4R36
ASKCI4H4R48

DC Inverter U-match Series Cassette Type Unit
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③ .
The specications of the breaker and power cable listed in the table above are determined
based on the maximum power (maximum amps) of the unit.
④ .
The specications of the power cable listed in the table above are applied to the conduit-
guarded multi-wire copper cable (like, YJV copper cable, consisting of PE insulated wires and
a PVC cable jacket) used at 40°С and resistible to 90°С(see IEC 60364-5-52). If the working
condition changes, they should be modied according to the related national standard.
⑤ .
The specifications of the breaker listed in the table above are applied to the breaker with
the working temperature at 40°С. If the working condition changes, they should be modied
according to the related national standard.
⑥ .
Take 2 pieces of power cord of 0.75mm2as the communication lines between indoor and
outdoor unit, with their longest lengths of 50m. Please select the appropriate line length as
per the actual installation conditions. The communication lines can not be twisted together.
For the unit (≤30K), it’s recommended to use 8m long communication line.
⑦ .
Take 2 pieces of power cord of 0.75mm2as the communication lines between the wired
controller and the indoor unit, with their longest lengths of 30m. Please select the appropriate
line length as per the actual installation conditions. The communication lines can not be
twisted together. It’s recommended to use 8m long communication line.
⑧ .
The wire size of the communication line should be no less than 0.75mm2. It’s recommended
to take 0.75mm2power cords as the communication line.
4 Installation of the Unit
4.1 Installation of the Indoor Unit
4.1.1 Indoor unit dimension
Fig.4.1

DC Inverter U-match Series Cassette Type Unit
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Table 4.1
Item
Model A B C D E F
ASKEC4H4R18
670 596 592 571 145 240
ASKEC4H4R24
950 840 780 680 160 240
ASKEC4H4R36 950 840 780 680 160 320
ASKEC4H4R48 1040 910 842 788 170 290
4.1.2 Installing the Main Body Unit
Fig. 4.2
(1). Install the hoisting stand on the hoisting screw by using nuts and gaskets at both the upper
and lower sides of the hoisting stand. To prevent the gasket from breaking off, a gasket
anchor board can be helpful.
(2). Install the paper template on the unit, and x the drain pipe at the outlet vent.
(3). Adjust the unit to the best position.
(4). Check if the unit is installed horizontally at four directions. If not, the water pump and the
oat switch would function improperly and even lead to water leakage.
(5). Remove the gasket anchor board and tighten the nut remained.
(6). Remove the paper template.
4.1.3 Installing the Suspension Bolts
(1). Using the installation template, drill holes for bolts (four holes). (Fig. 4.3)
(2). Install the bolts to the ceiling at a place strong enough to hang the unit. Mark the bolt
positions from the installation template. With a concrete drill, drill for 12.7mm (1/2”)
diameter holes. (Fig. 4.4)
(3). Insert the anchor bolts into the drilled holes, and drive the pins completely into the anchor
bolts with a hammer. (Fig. 4.5)

DC Inverter U-match Series Cassette Type Unit
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Fig. 4.3 Fig. 4.4 Fig. 4.5
4.1.4 Leveling
The water level test must be done after installing the indoor unit to make the unit is horizontal,
as shown below.
Horizontal tester
Fig.4.6
4.2 Installation of the Outdoor Unit
WARNING!
① .
Install the unit where it will not be tilted by more than 5°.
② .
During installation, if the outdoor unit has to be exposed to strong wind, it must be xed securely.
4.2.1 Outdoor unit dimension
D
A
B
C
E
Fig.4.7

DC Inverter U-match Series Cassette Type Unit
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Table 4.2 Unit: mm
Item
Model A B C D E
955 396 700 560 360
980 427 790 610 395
1107 440 1100 631 400
958 412 1349 572 376
4.2.2 Condensate Drainage of the Outdoor Unit(Only for the heat pump unit) (Fig.
4.8)
(1). It is required to install a drain pipe for the outdoor unit to drain out the condensate water
during heating operation. (only for the heat pump unit)
(2). When installing the drain pipe, apart from the drain pipe mounting hole, all other holes
should be plugged so as to avoid water leakage. (only for the heat pump unit)
(3). Installation Method: Insert the pipe joint into the hole φ25 located at the base plate of the
unit and then connect the drain pipe to the pipe joint.
Bottom Drain cap
Drain pipe
mounting hole Fig. 4.8
4.3 Installation of the Connection Pipe
4.3.1 Flare Processing
(1). Cut the connection pipe with the pipe cutter and remove the burrs.
(2). Hold the pipe downward to prevent cuttings from entering the pipe.
(3). Remove the are nuts at the stop valve of the outdoor unit and inside the accessory bag of
the indoor unit, then insert them to the connection pipe, after that, are the connection pipe
with a aring tool.
(4). Check if the are part is spread evenly and there are no cracks (see Fig. 4.9).
Fig. 4.9
ASKCI4H4R18
ASKCI4H4R24
ASKCI4H4R36
ASKCI4H4R48

DC Inverter U-match Series Cassette Type Unit
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4.3.2 Bending Pipes
(1). The pipes are shaped by your hands. Be careful not to collapse them.
Fig.4.10
(2). Do not bend the pipes in an angle more than 90°.
(3). When pipes are repeatedly bent or stretched, the
material will harden, making it difficult to bend or
stretch them any more. Do not bend or stretch the
pipes more than three times.
(4). When bending the pipe, do not bend it as is. The pipe
will be collapsed. In this case, cut the heat insulating
pipe with a sharp cutter as shown in Fig.4.11, and
bend it after exposing the pipe. After bending the pipe as you want, be sure to put the heat
insulating pipe back on the pipe, and secure it with tape.
Fig.4.11
Pipe
Cutter
Cutt line
Heat insulating
pipe
CAUTION!
① .
To prevent breaking of the pipe, avoid sharp bends. Bend the pipe with a radius of curvature of 150
mm or over.
② .
If the pipe is bent repeatedly at the same place, it will break.
4.3.3 Connecting the Pipe at the Indoor Unit Side
Detach the caps and plugs from the pipes.
CAUTION!
① .
Be sure to apply the pipe against the port on the indoor unit correctly. If the centering is improper,
the flare nut cannot be tightened smoothly. If the flare nut is forced to turn, the threads will be
damaged.
② .
Do not remove the are nut until the connection pipe is to be connected so as to prevent dust and
impurities from coming into the pipe system.
When connecting the pipe to the unit or removing it from the unit, please do use both the
spanner and the torque wrench.(Fig.4.12)
When connecting, smear both inside and outside of the are nut with refrigeration oil, screw it
hand tight and then tighten it with the spanner.
Refer to Table 4.3 to check if the wrench has been tightened properly (too tight would mangle
the nut and lead to leakage).
Examine the connection pipe to see if it leaks, then take the treatment of heat insulation, as
shown in the Fig.4.12.

DC Inverter U-match Series Cassette Type Unit
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Use the medium-sized sponge to insulate the coupler of the gas pipe.
Fig.4.12
Table 4.3 Flare nut tightening torque
Pipe Diameter Tightening Torque
1/4˝(Inch) 15-30 (N·m)
3/8˝(Inch) 35-40 (N·m)
5/8˝(Inch) 60-65 (N·m)
1/2˝(Inch) 45-50 (N·m)
3/4˝(Inch) 70-75 (N·m)
7/8˝(Inch) 80-85 (N·m)
CAUTION!
Be sure to connect the gas pipe after connecting the liquid pipe completely.
4.3.4 Connecting the Pipe at the Outdoor Side Unit
Tighten the are nut of the connection pipe at the outdoor unit
valve connector. The tightening method is the same as that as at
the indoor side.
4.3.5 Checking the Pipe Connections for Gas Leaking
For both indoor and outdoor unit side, check the joints for gas
leaking by the use of a gas leakage detector without fail when the
pipes are connected. Fig.4.13

DC Inverter U-match Series Cassette Type Unit
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4.3.6 Heat Insulation on the Pipe Joints (Indoor Side Only)
Stick coupler heat insulation (large and small) to the place where connecting pipes.
Fig.4.14
4.3.7 Liquid Pipe and Drain Pipe
Sealed
Drain
pipe
Saddle
Fig.4.15
Fig.4.16
Trap
If the outdoor unit is installed lower than
the indoor unit (See Fig.4.15)
(1). A drain pipe should be above ground
and the end of the pipe does not
dip into water. All pipes must be
restrained to the wall by saddles.
(2). Taping pipes must be done from
bottom to top.
(3). All pipes are bound together by tape
and restrained to wall by saddles.
If the outdoor unit is installed higher than
the indoor unit (See Fig.4.16)
(1). Taping should be done from lower to
the upper part.
(2). All pipes are bound and taped
together and also should be trapped
to prevent water from returning to the
room.
(3). Restraint all pipes to the wall with
saddles.

DC Inverter U-match Series Cassette Type Unit
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4.4 Vacuum and Gas Leakage Inspection
CAUTION!
Do not purge the air with refrigerants but use a vacuum pump to vacuum the installation! There is no
extra refrigerant in the outdoor unit for air purging!
4.4.1 Vacuum
(1). Remove the caps of the liquid valve, gas valve and also the service port.
(2). Connect the hose at the low pressure side of the manifold valve assembly to the service
port of the unit’s gas valve, and meanwhile the gas and liquid valves should be kept closed
in case of refrigerant leak.
(3). Connect the hose used for evacuation to the vacuum pump.
(4). Open the switch at the lower pressure side of the manifold valve assembly and start the
vacuum pump. Meanwhile, the switch at the high pressure side of the manifold valve
assembly should be kept closed, otherwise evacuation would fail.
(5). The evacuation duration depends on the unit’s capacity, generally, 20 minutes for the
18K units, 30 minutes for the 24/36K units, 45 minutes for the 48K units. And verify if the
pressure gauge at the low pressure side of the manifold valve assembly reads -1.0Mp
(-75cmHg), if not, it indicates there is leak somewhere. Then, close the switch fully and
then stop the vacuum pump.
(6). Wait for some time to see if the system pressure can remain unchanged, 5 minutes for the
18/24K units, 10 minutes for the units 36/48K. During this time, the reading of the pressure
gauge at the low pressure side can not be larger than 0.005Mp (0.38cmHg).
(7). Slightly open the liquid valve and let some refrigerant go to the connection pipe to balance
the pressure inside and outside of the connection pipe, so that air will not come into the
connection pipe when removing the hose. Note that the gas and liquid valve can be opened
fully only after the manifold valve assembly is removed.
(8). Place back the caps of the liquid valve, gas valve and also the service port.
Hose with the valve pin
gauge manifold
pipe
pipe
VAC valve
Vacuum pump
Service port
Low pressure gauge
High pressure gauge
Gauge manifold kit
Fig.20
Note: For the large-sized unit, it has the service port for both the gas valve and the liquid valve.
During evacuation, it is available to connect two hoses of the manifold valve assembly to two

DC Inverter U-match Series Cassette Type Unit
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service ports to quicken the evacuating speed.
4.4.2 Additional Charge
18K~36K：Refrigerant suitable for a piping length of 5m is charged in the outdoor unit at the
factory.When the piping is longer than 7m, additional charging is necessary.
48K：Refrigerant suitable for a piping length of 7.5m is charged in the outdoor unit at the
factory.When the piping is longer than 10 m, additional charging is necessary.
For the additional amount, see Table 10. Table 10
Model
Item Additional Refrigerant Amount for Extra Pipe
18K 30 g/m
24~48K 60 g/m
When the height difference between the indoor unit and outdoor unit is larger than 10 meters,
an oil bend should be employed for every 6 meters.
Oil bend
Oil bend
Indoor
Outdoor
6m
Fig.4.18
4.5 Installation of the Drain Hose
4.5.1 Installationof Drain Piping
(1). Keep piping as short as possible and slope it downwards at a gradient of at least 1/100 so
that air may not remain trapped inside the pipe.
(2). Keep pipe size equal to or greater than that of the connecting pipe.
(3). Install the drain piping as shown and take measures against condensation. Improperly
rigged piping could lead to leaks and eventually wet furniture and belongings.
Extension drain piping
(commercially available)
Insulating tube
(commercially
available)
Indoor unit
drain hose
Insulating tape
(accessory)
Fig.4.19

DC Inverter U-match Series Cassette Type Unit
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4.5.2 Installing the Drain Pipes
(1). Insert the drain pipe to the drain outlet of the unit and then tighten the clamp securely with
tape.
(2). Connect the extension drain pipe to the drain pipe and then tighten the clamp with tape.
1
2
≤ 4mm
1 2
3
Tighten the clamp until the screw head is less
then 4mm from the hose.
Metal clamp
Drain hose (accessory)
Grey tape (accessory)
Insulate the pipe clamp and the drain hose using heat
insulation sponge.
Metal clamp (accessory)
Insulation sponge (accessory)
(3). When unifying multiple drain pipes, install the pipes as Fig. 4.20. Select converging drain
pipes whose gauge is suitable for the operating capacity of the unit.(take the cassette type
unit for example)
100 mm
T-joint converging drain pipes
0~675 mm
T-joint converging drain pipes
0~1000mm
Fig.4.20
(4). When the drain hose cannot keep a sufcient gradient, it is necessary to t a riser pipe
(eld supplied) to it.
(5). If the air ow of indoor unit is high, this might cause negative pressure and result in return
suction of outdoor air. Therefore, U-type water trap shall be designed on the drainage side
of each indoor unit.(Fig. 4.21)
(6). Install one water trap for each unit.
(7). Installation of water trap shall consider easy cleaning in the future.