Air conditioning

Capacity

• Calculated in BTU or kW.
• See the Webasto website for a BTU calculator or their catalogue.

Grills

• Minimum air grille sections. To obtain acceptable noise levels at maximal blower speed minimum requirements for grille and ducts sections should be observed. The size of the transition box behind the supply air-grille is also important.
• 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. Many fancoil blowers 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 airducts.
• Air speed at supply grill to be 2-2.5 m/s
• Area of return air grill should be about twice the area of the supply grill
• Calculating grill area:
  • net grill area (cm2) is the air flow of the air handler (fancoil) (m3/h) divided by 3.6 divided by the desired air speed at grill (2 or 2.5)

References

• Cruisair
• Frigomar
• Mar-ix
• Webasto Marine Offers complete range of installation materials too, including an extensive range of ducting items.