Marine Air Systems vector compact - Supply & Return Air Grilles; Ducting

SUPPLY & RETURN AIR GRILLES
Install the supply air grille as high as possible in a location that will provide uniform air distribution
throughout the cabin, grille louvers should be directed upward. The return air grille should be installed
as low and close to the a/c unit as possible to insure direct uninterrupted airflow to the evaporator. The
return air grille should have a minimum four inches (4") or clearance in front of it, free from any
furniture or other obstructions. In no instance should a supply air discharge be directed towards a
return air grille, as this will cause the system to short cycle. Allow for adequate clearance behind the
supply air grille(s) for the transition box and ducting connection. The following table shows minimum
grille sizes. See the MAINTENANCE section of this manual for return air filter cleaning instructions.
DUCTING
Good air flow is critical for the performance of the entire system. It is highly dependent on the quality
of the ducting installation. The ducting should be run as straight, smooth and taut as possible
minimizing the number of 90 degree bends (two tight 90 degree bends can reduce airflow by 25%).
The following table shows minimum duct diameters and their corresponding supply and return air
grille minimum areas in square inches. If a transition box is used, the total area of supply air ducts
going out of the box should equal the area of the supply duct feeding the box. To calculate the square
inch area of a round duct, multiply the radius by itself (r2) and multiply that number by 3.1416 (tt).
MODEL
DUCT DIA
DUCT AREA
R/A GRILLE
S/A GRILLE
7K
5" dia
19.6 sq in
88 sq in
40 sq in
10K
5" dia
19.6 sq in
98 sq in
50 sq in
12K
6" dia
28.3 sq in
140 sq in
70 sq in
16K
7" dia
38.5 sq in
168 sqin
84 sq in
24K
8" dia
50.3 sq in
280 sq in
140 sqin
The following is a summary of proper ducting connections:
1. Pull back the fiberglass insulation exposing the inner mylar duct hose.
2. Slide the mylar duct hose around the mount ring until it bottoms out.
3. Screw 3 or 4 stainless steel sheet metal screws through the duct hose into the transition ring.
Make sure to catch the wire in the duct hose with the heads of the screws. Do not use band
clamps, as the hose will slide off.
4. Wrap the duct tape around the ducting and ring joint to prevent any air leaks.
5. Pull the insulation back up over the mylar to the ring and tape this joint.
6. Remove excess ducting and use the same connection method at the s/a grille.
All ducting should:
• Be appropriately sized for each application.
• Run as smoothly and taut as possible.
• Have as few bends or loops as possible.
• Be securely fastened to prevent sagging during boat operation.
• Have all excess ducting lengths trimmed off.
• Not be flattened or kinked.
• Insulated when located in high heat load areas (hull side, mechanical compartments, etc.).
• Be properly protected against potential damage when routed through open areas.