Carrier service manual R410a DC Inverter 60Hz
Installation 141
5. Duct Engineering
5.1 Fabrication of Duct
1. The material, specification, performance and thickness of metal duct should be in accordance with the
relevant regulations of present National Products Standard. The thickness of steel sheet or galvanized
steel sheet should not be less than the regulation in table below:
Thickness of steel sheet duct (mm)
Diameter(D) or edge length (b) of duct Circular duct
Rectangle duct
Middle/low pressure system High pressure system
D(b)≤320 0.5 0.5 0.75
320＜D(b)≤450
0.6 0.6 0.75
450＜D(b)≤630
0.75 0.6 0.75
630＜D(b)≤1000
0.75 0.75 1
1000＜D(b)≤1250
1 1 1
2. The material, specification, performance and thickness of non-metal duct should be in compliance
with design and regulations of present National Products Standard.
3. The body, frame, fixing material and sealed cushion of fire-proof air duct should be made of
non-combustible materials. Its fire resistance rating should be in accordance with the design
requirement.
4. The sheathing of composite duct should be made of non-combustible materials. Inner insulation
material should be no burning or burning retardant with rating B1, and no harm to people’s body.
5. The permitting deviation to outer diameter or long edge of duct: when no more than 300mm, it is 2mm;
when more than 300mm, it is 3mm. The permitting deviation of pipe end flatness is 2mm.
Discrepancy between two diagonal lines of rectangle duct shall not be more than 3mm. Discrepancy
between two diameters of any cross-cut circular flange shall not be more than 2mm.
5.2 Connection of Duct
1. Connection of metal duct
1) The seam of duct board splice should be stagger and cross-seam is not allowed.
2) Specification of metal duct flange shall not be less than the data as shown in table below.
Specification to flange and bolt of circular metal duct (mm)
Diameter of duct(D)
Specification of flange
Specification of bolt
Flat steel Angle steel
D≤140 20×4 -
M6
140＜D≤280
25×4 -
280＜D≤630 - 25×3
630＜D≤1250 - 30×4
M8
1250＜D≤2000
- 40×4
Specification to flange and bolt of rectangle metal duct (mm)
Dimension of long edge of duct(b) Specification of flange(angle steel) Specification of bolt
b≤630 25×3 M6
630＜b≤1500
30×3
M8
1500＜b≤2500
40×4
2500＜b≤4000
50×5 M10
3) Diameter of bolt and rivet to duct flange for middle/low pressure system should be no more than
150mm.
As for duct of high pressure system, it should be no more than 100mm.
4) Four angles of rectangle duct flange should be designed with screw hole.
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