Air System Functioning Principals
Minimum air grille sections To obtain acceptable noise levels at maximal blower speed levels the requirements for grille and ducts sections should be observed. The size of the transition box behind the supply air-grille is also important.
Capacity BlueCool A/C component
Duct size S-Series (mm)
Duct size A-Series (mm)
Supply air grill (cm 2 )
Recommended supply air grill (“)
Return air grill (cm 2 )
Recommended return air grill (“)
4,000 BTU/ h
–
100
150
8 x 4
325
12 x 5
6,000 BTU/ h
–
125
190
10 x 4
490
11 x 8
8,000 – 10,000 BTU/ h
100 – 125
125
235
12 x 4
490
11 x 8
12,000 – 13,000 BTU/ h
125 – 150
150
250
10 x 5
550
14 x 7
16,000 – 20,000 BTU/ h
125 – 150
150
390
12 x 6
800
14 x 10
24,000 BTU/ h
–
2 x 150
2 x 250
2 x 10 x 5
1,000
14 x 12
27,000 BTU/ h
2 x 150
–
650
2 x 12 x 6
1,600
2 x 14 x 10
36,000 BTU/ h
–
2 x 150
2 x 380
2 x 12 x 6
1,600
2 x 14 x 10
Blower outlets 90° turns with flexible ducts directly from blower outlets should be avoided at all costs as they introduce severe restrictions in the air-flow. All WB blowers (except on 24,000 BTU/ h models) can be rotated through 45° steps to obtain a straight-line outlet from the blower. This facility should be used whenever possible. Return grille offset It should be avoided to place a return air grille directly opposite the finned coil surface of an air handler, because this will allow propagation of direct blower- motor noise through the grille. The grille should be offsetted to chicane the return air to the coil inlet. Direct noise propagation will be reduced in a significant manner. Duct type To avoid accidental crushing, flexible air-ducts should be of high quality with sufficiently strong steel spiral
reinforcement. Spiral type ducts should be extended to their maximum length for the best interior smoothness. For very long duct sections smooth bore ducts (in PVC for example) should be preferred. This offers better smoothness than flexible spiral type ducting and hence reduces internal friction. For very short lengths non-insulated ducts can be used. For greater lengths it is advisable to use insulated type ducts to avoid condensation on the outside of the air-ducts. Big luxury yacht In general requirements for megayachts and big luxury vessels are even more stringent than the table here above. These special requirements can be obtained from Webasto on request.
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