Installation Guidelines for Ducting and Transition Boxes

When choosing the proper size transitions and duct work for any system, primary consideration should be given to the capacity of that system, along with its required air flow(CFM). Reduced or restricted air flow due to undersized transitions and ducting or imporper installations will result in loss of performance and/or inefficient operation of the system.

Duration boxes for air flow are constructed of insulated aluminium or vacuum formed plastic. A variety of configurations are available for air distribution, including enclosed boxes (which fit directly onto blower assemblies), remote boxes (to distribute air flow from the unit to other areas), and transition boxes (to distribute air into area through grilles and into other boxes).

Unit boxes are to be attached directly to the blower outlet. The mounting plate is attached to the blower flange and the box is attached to the plate. This box should be positioned in such a way as to provide air flow through the duct work with as few bends as possible. On most units, a rotatable blower allows for further flexibilty in proper positions of the box.

Remote boxes are to be secured to any solid shelf or bulkhead. THe duct run from the unit to the box should be as straight as possible . From the remote box, porperly sized ducting is to be installed into each ares based on the air flow (CFM) required.

Transition boxes are to be located as high as possible in any cabin area to provide even air circulation and temperatures. When this location is not possible, transition boxes are to be installed in such a way as to channel air flow up and across any area. Grilles with directional louvers or built-up wedges may be necessary to accomplish proper air circulation, louvers should point upward.

Transition boxes are designed to accept ducting (via transition rings) on either side, end or on the back. Side or end installations should provide pressurization of the box, allowing for a full, event flow of air accross the entire surface of the attached grille. Back installations should provide higher air velocity through the attached grille, with less pressurization or full flow across the entire grille surface.

Proper installations will repvent air leaks. If problems arise due to location or mounting surfaces, strips of adhesive-backed foam can be applied to fill gaps. Caulking or other adhesives are not necessary and should not be used.

A variety of baffles and restrictors can be applied to divert air flow as necessary to ensureadequate CFM to any given area. Consult Marine Air Systems for specific applications.

Flexible ducting is designed to offer optimum routing throughtout vessels. The following guidelines will ensure porper application and performance:

• Route all ducting in smooth, taut and direct manner.Avoid hard bends (90° or more) whenever possible.Cut off any excess length.
• Secure all ducting in place as vessel motion can cause sagging or shifting which may result in reduced or restricted air flow.
• Compress 2 or 3 wraps of the spiral reinforced wire of the ducting on to the ring. Secure the ducting to the ring with 3 or 4 screws above the compressed wire wraps. This method prevents the ducting from slipping of the ring. Note : Hose are not recommended because the ducting can detach from the ring.
• Do not crush or kink any ducting as this restrict air flow.
• Ducting can be reformed to fit odd-shaped spaces, but must be done so carefully in order to prevent restrictions. Ducting can be easily reformed on the ends to fit oval rings
• Insulated ducting should be used when routed in high ambient temperature locations. Make certain the inner liner is routed in a smooth manner to avoid restrictions.