Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 627

(3) Duct work
2 Silencer chamber (blowout)
Canvas coupling 3 A
3
7 Insulation
Air conditioner main unit.
5 Blow
outlet
6 Insulation hole
(600 )
3 In order not to transmit vibration from the main unit of air conditioner to the ceiling or slab, it is necessary to provide means to prevent
vibration, for example, a canvas coupling on the duct or rubber cushion on the main unit of air conditioner.
4 A damper to control air volume should be installed on the joint of OA duct to facilitate control of air capacity after the installation.
5 Location and from of blow outlet should be selected so that air from the outlet will be distributed all over the room, and equipped with
a device to control air volume.
6 Make sure to provide an inspection hole on the ceiling. It is indispensable to service electric equipment, motor, functional components
and cleaning of heat exchanger.
7 Make sure to insulate the duct to prevent dewing on it.
Thickness of insulating material is 65 mm minimum.
Bad example of duct work
2
For ventilation
In such occasion, it is necessary to insulate the entire unit with glass wool (25 mm).
(Use a wire net or equivalent to hold the glass wool in place.)
b) It may run out the allowable limit of unit operation (Example: When outdoor air temperature is 35°CDB, suction air temperature is
27°CWB) and it could result in such troubles as compressor overload, etc.
c) There is a possibility that the blow air volume may exceed the allowable range of operation due to the capacity of ventilation fan or
strength of wind blowing against external air louver so that drainage from the heat exchanger may fail to reach the drain pan but leak
outside (e.g. drip onto the ceiling) with consequential water leakage in the room.
2 Unless vibration isolation is provided between the unit and duct and between the unit and the slab, vibration will be transmitted to the
duct so that vibration noise may generate from between the ceiling and blow outlet or vibration may be transmitted to the slab. Make
sure to provide an effective vibration prevention means.
<Simplified method for determination of duct dimensions>
In the following method, it is assumed that the friction resistance per unit length of duct is
1 Pa/m (0.1 mm Aq/m) and a side of duct is 250 mm.
Air volume rating is assumed to be FDU508HES-SA, 60 Hz.
Air conditioner
A
main unit
2400 m /h
2
B
Supply
B
600 m 2 /h
(blowout)
600 m 2 /h
chamber
Air Duct
(mm × mm)
volume
2400m /h
2
250 × 560
Section A
(40m 2 min)
600m /h
2
250 × 190
Section B
(10m 2 min)
(4) Drain Piping
(a) Drain piping should always be in a downhill grade (1/50~1/100) and avoid riding across an elevation or
making traps.
Good piping
Suspension
1.5m ~ 2m
bolts
Heat A downhill grade
insulation of 1/100 or more
(b) When connecting the drain pipe to unit, pay sufficient attention not to apply excess force to the
piping on the unit side. Also, fix the piping at a point as close as possible to the unit.
(c) For drain pipe, use hard PVC general purpose pipe VP-25(I.D.1˝) which can be
purchased locally.
3 Silencer chamber (intake)
Detail of section A
(Vibration prevention of hanger)
3 Canvas coupling
4 Wind capacity
control damper
OA
Ceiling surface
Suction hole
(With air filter)
1
1
Louver to
outdoor air
With air filter
A 2400 m /h Calculation of duct resistance
2
(Use following simplified calculations.)
Linear pipe Calculate based on 1 Pa (0.1 mm Aq)
section per 1 m in length 1 Pa/m (0.1 mmAq/m).
Curved pipe Take a curved section as equivalent to 3
section ~4 m in straight line.
Blowout
Calculate based on 25 Pa (2.5 mmAq).
section
Calculate by taking 1 pc. as 50Pa
Chamber
(5 mmAq).
Suction grill Calculate by taking 1 pc. as 40Pa
(with filter) (4 mmAq).
Improper piping
Air vent
1 Air filter is not installed in the main unit of air condi-
tioner. Air filter should be installed in the suction grill
which allows an ample access for cleaning.
2 Silencer chamber(s) may be necessary depending on the
noise level allowed in the room where the air conditioner
is installed.
Additional silencer may be necessary where a particu-
larly low noise is required.
(Provision of silencer is a must at offices and a meeting
room.)
1 If a duct is not provided at the suction side but it is substituted with the
space over the ceiling, humidity in the space will increase by the influ-
ence of capacity of ventilation fan, strength of wind blowing against the
outdoor air louver, weather (rainy day) and others.
a) Moisture in air is likely to condense over the external plates of the
unit and to drip on the ceiling.
Unit should be operated under the conditions as listed in the above
table and within the limitation of wind volume.
When the building is a concrete structure, especially immediately
after the construction, humidity tends to rise even if the space over
the ceiling is not substituted in place of a duct.
Section B
Section A
Avoid riding across an elevation
Keep free from traps
Do not pipe under water
A downhill grade of
1/100 or more
FDU-H
<Table of simplified selection
of duct dimensions>
Duct form
Square duct
Air
Item
Dimensions
volume
×
m 3 /h(m 3 /min) (mm mm)
×
100 250 60
×
200 250 90
×
300 250 120
×
400 250 140
×
500 250 170
×
600(10) 250 190
×
800 250 230
×
1,000 250 270
×
1,200(20) 250 310
×
1,400 250 350
×
1,600 250 390
×
1,800(30) 250 430
×
2,000 250 470
×
2,400 250 560
×
3,000(50) 250 650
×
3,500 250 740
×
4,000 250 830
×
4,500 250 920
×
5,000 250 1000
×
5,500 250 1090
×
6,000(100) 250 1180
Secure the elevation as high as possible
(approx. 100 mm)
V.P.30
625