Mitsubishi Heavy Industries FDT28KXE6A Service Manual page 179

④Installation of indoor unit (continued)
3. Make sure to install the indoor unit horizontally. Confirm the
levelness of the indoor unit with a level gauge or transpar-
ent hose filled with water. Keep the height difference at
both ends of the indoor unit within 3mm.
4. Tighten four upper nuts and fix the unit after height and
levelness adjustment.
Caution
●Do not adjust the height by adjusting upper nuts. It will cause unexpected stress on the indoor
unit and it will lead to deformation of the unit, failure of attaching a panel, and generating noise
from the fan.
●Make sure to install the indoor unit horizontally and set the gap between the unit underside and
the ceiling plane properly. Improper installation may cause air leakage, dew condensation,
water leakage and noise.
⑤Duct work
Air conditioner main unit
Blow outlet
Blowout duct
(optional or marketed item)
Request
①●Calculate air capacity and the outside static pressure to select the
duct's length and shape, and blow outlet.
Caution
●Take care that the outside static pressure does not exceed 30 Pa.
The unit has condensation owing to the decrease in air capacity,
possibly causing the ceiling and household goods to become wet.
②The main body of the air conditioner is not provided with an air filter.
Assemble it into the suction grill for which cleaning is easy.
③Blow duct
●Make the duct the shortest in length.
●Bend a lot less abruptly. (Make the bend radius a lot larger.)
●When connecting the main body to the duct flange of the blow outlet, attach the insulation
material to the fixed portion to protect it from condensation.
●Conduct the duct work before ceiling attachment.
④ Inlet port
●When placing the inlet port to carry out suction from the bottom side, use the following proce-
dure to replace the suction duct joint (prepare on site) and the bottom plate.
●Remove the screws which fasten the
bottom plate and the duct joint (prepare
on site) on the inlet port side of the unit.
●Fit the duct join (prepare on site) with a screw;
fit the bottom plate.
⑤ Make sure to keep the suction duct warm to protect it from condensation.
⑥ Install the blowout hole where air can flow all over the room.
⑦ Make sure to install the inspection opening in the ceiling. It is needed for the maintenance of
electrical parts, the motor and other parts.
Indoor unit
hose
Ceiling suriace
Suction duct
Suction hole
(marketed item)
(marketed item)
(with air filter)
Inspection hole
●Replace the removed bottom plate
and duct joint (prepare on site).
⑤Duct work (continued)
Example of bad duct work
Bad example of duct work
①If the suction duct is made in the ceiling without using the suction side duct, the temperature
inside the ceiling will be high owing to the ventilating fan's performance, the strength of any
wind blowing against the outdoor air louver, weather (on a rainy day) and other factors.
●The outside plate of the unit may have condensation, causing water to drip on the ceiling.
Also, in the case of a new house of a concrete structure, the temperature may be high
without a duct inside the ceiling. In such a case, keep the whole unit warm using glass wool
(25mm). (Cover the glass wool with wire netting or the like.)
●The unit may be beyond its operation limit, causing overloading of the compressor, and other
trouble.
●Because the blowing capacity of the unit increases, owing to the ventilating fan's perfor-
mance and any wind blowing against the outdoor air louver, up to its use limit, draining liquid
from the heat exchanger does not flow into the drain pan, possibly flowing to the outside and
causing water leaks (in which drained liquid drips on the ceiling).
⑥Refrigerant pipe
Caution
●Use the new refrigerant pipe.
When re-using the existing pipe system for R22 or R407C, pay attention to the following items.
・Change the flare nuts with the attached ones (JIS category 2), and reprocess the flare parts.
・Do not use thin-walled pipes.
●Use phosphorus deoxidized copper alloy seamless pipe (C1220T specified in JIS H3300) for
refrigeration pipe installation.
In addition, make sure there is no damage both inside and outside of the pipe, and no harmful
substances such as sulfur, oxide, dust or a contaminant stuck on the pipes.
●Do not use any refrigerant other than R410A.
Using other refrigerant except R410A (R22 etc.) may degrade inside refrigeration oil. And air
getting into refrigeration circuit may cause over-pressure and resultant it may result in bursting,
etc.
●Store the copper pipes indoors and seal the both end of them until they are brazed in order to
avoid any dust, dirt or water getting into pipe. Otherwise it will cause degradation of refrigeration
oil and compressor breakdown, etc.
●Use special tools for R410 refrigerant.
Work procedure
1. Remove the flare nut and blind flanges on the pipe of the indoor unit.
※ Make sure to loosen the flare nut with holding the nut on pipe side with a spanner and giving
torque to the nut with another spanner in order to avoid unexpected stress to the copper pipe, and
then remove them.
(Gas may come out at this time, but it is not abnormal.)
● Pay attention whether the flare nut pops out. (as the indoor unit is sometimes pressured.)
2. Make a flare on liquid pipe and gas pipe, and connect the refrigeration pipes on the indoor unit.
※Bend the pipe with as big radius as possible and do not bend the pipe repeatedly. In
addition, do not twist and crush the pipes.
※Do a flare connection as follows:
● Make sure to loosen the flare nut with holding the nut on pipe side with a spanner and giving
torque to the nut with another spanner in order to avoid unexpected stress to the copper
pipe, and then remove them.
● When fastening the flare nut, align the refrigeration pipe with the center of flare nut, screw
the nut for 3-4 times by hand and then tighten it by spanner with the specified torque
mentioned in the table below. Make sure to hold the pipe on the indoor unit securely by a
spanner when tightening the nut in order to avoid unexpected stress on the copper pipe.
3. Cover the flare connection part of the indoor unit with attached insulation material after a gas
leakage inspection, and tighten both ends with attached straps.
●Make sure to insulate both gas pipes and liquid pipes completely.
※ Incomplete insulation may cause dew condensation or water dropping.
4. Refrigerant is charged in the outdoor unit.
As for the additional refrigerant charge for the indoor unit and piping, refer to the installation
manual attached to the outdoor unit.
Pipe diameter Tightening torque N·m
φ 6.35
φ 9.52
φ 12.7
φ 15.88
φ 19.05 100 to 120
176
- -
Louver to
outdoor air
For ventilation
Strap (Accessory) Pipe cover (Accessory)
14 to 18
34 to 42
49 to 61
68 to 82
The thickness of insulation should be 20mm or more.
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