1
ComPac 6/09-18
2.4 p
orTinG
anD
D
uCT
W
ork
(aVp24-72)
General Information
Note: The following instructions are for general guidance only. Due to the wide variety of installa-
tion 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 one inch clearance on all four sides of the supply outlet duct flange on the unit.
The one inch clearance must extend on all sides of the supply duct for the first three feet from
the unit.
IMPORTANT: Marvair
®
requires a minimum of one inch
from the surface of any supply ducts to
combustible material for the first three feet 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 three feet. 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 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.
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. Use
Table 6
below and
Table 1
,
CFM at External Static Pressure
(Wet Coil)
in section 1.4.
WARNING
FIRE HAZARD
Improper adjustment, alteration, service, maintenance or installation could cause serious
injury, death and/or property damage.
Installation or repairs made by unqualified persons could result in hazards to you and
others. Installation MUST conform with local codes or, in the absence of local codes, with
codes of all governmental authorities have jurisdiction.
The information contained in this manual is intended for use by a qualified service
agency that is experienced in such work, is familiar with all precautions and safety
procedures required in such work, and is equipped with the proper tools and test
instruments.
