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Marvair ComPac AVHDA I&O Manual 03/2019 Rev.3
2.4 Porting and Duct Work
General Information
Note: The following instructions are for general guidance only. Due to the wide variety of installation
possibilities, specific instructions will not be given. When in doubt, follow standard and accepted
installation practices, or contact Marvair
®
for additional assistance.
Wall Openings
Measure the dimensions of the supply and return ports on the unit.
Cut the openings in the exterior wall for the supply and return.
IMPORTANT:
All units with electric
heat must have 1" (25.4mm) clearance on all four sides of the supply outlet duct flange on the
unit. The 1" (25.4mm) clearance must extend on all sides of the supply duct for the first 3 feet (1
meter) from the unit.
IMPORTANT: Marvair requires a minimum of 1" (25.4mm)
from the surface of any supply ducts
to combustible material for the first 3 feet (1 meter) of the duct.
Ducting
Extensions should be cut flush with the inside wall for applications without duct work.
Applications using duct work should be designed and installed in accordance with
all
applicable safety
codes and standards. Marvair strongly recommends referring to the current edition of the National Fire
Protection Association Standards 90A and 90B
before
designing and installing duct work. The duct
system must be engineered to insure sufficient air flow through the unit to prevent over-heating of the
heater element. This includes proper supply duct sizing, sufficient quantity of supply registers, adequate
return and filter area. Ductwork must be of correct material and must be properly insulated. Duct work
must be constructed of galvanized steel with a minimum thickness of .019 inches for the first 3 feet (1
meter). Ductwork must be firmly attached, secured and sealed to prevent air leakage. Do not use duct
liner on inside of supply duct within 4 feet (122cm) of the unit.
Galvanized metal duct extensions should be used to simplify connections to duct work and grilles. Use
fabric boots to prevent the transmission of vibration through the duct system. The fabric must be U.L.
rated to a minimum of 197°F (92°C).
Minimum Airflow Requirements
The duct system must be engineered to assure sufficient air flow through the unit even under adverse
conditions such as dirty filters, etc.
2.5 Top Flange Installation (See Figure 2)
1. All models have built-in side mounting flanges.
2. Attach the top flange to the top of the air conditioner. The holes in the top of the air condtioner have
been predrilled. Remove the 4 screws in these holes and use these screws to attach the top flange
to the air conditioner.
3. Apply a bead of silicone sealer on the wall side of the bottom support brackets on the unit. Circle
the mounting holes with the silicone bead.
