Duct Requirements - Nordyne P3RA-030K User's Manual And Installation

location will affect cutting the opening needed
for the box. Floor joists generally are located on
16" centers, leaving 14-3/8" between joists.
After measuring the return air box (approxi-
mately 12-1/4" x 14-1/4"), cut the hole through
the floor so that the box will fit between the floor
joists. Careshould betakenwhen cuttingthrough
carpeting to avoid snags. In most installations
it will be necessary to cut a similar hole in the
fiberboard directly under the hole in the floor.
However, if the floor is more than ten inches
deep, it will only be necessary to cut a hole for
the collar on the return air box orforthe insulated
duct.
Set the box into the opening and fasten with
screws or nails. Put the filter and return air grille
in place.
5. LOCATING AND INSTALLING THE
SUPPLY DAMPER(S)
CAUTION:
When a home is not equipped with a
make-ready kit means must be pro-
vided to prevent simultaneous opera-
tion of the heating and cooling units. A
heat/cool thermostat is available for
this purpose.
When installing this air conditioning
system in conjunction with a furnace,
a damper must be installed in the fur-
nace base assembly to prevent cold
air being discharged around the heat
exchanger. Damage to the heat ex-
changer and asphyxiation may occur
ifa damper is not installed.
Figure 5. Supply Damper
nearest register. The round supply opening in
the slanted side of the damper should face the
side of the home where the air conditioner is
located. To locate the center of the heat duct,
first cut a small hole in the fiberboard below the
duct at the desired location. After locating the
duct center, cut a hole approximately 3/4" larger
than the damper opening in the fiberboard. Cut
a 9-1/8" x 13-1/8" hole in the duct and bend over
all tabs flat on the inside of the heat duct. After
inserting the damper into the duct, bend over all
tabs flat on the inside of the heat duct. Seal the
opening between the fiberboard and damper or
flexible duct.
DUCTINGSYSTEM
DUCT REQUIREMENTS
The supply duct system, including the number
and type of registers, will have much more
effect on the performance of an air conditioning
system than any other factor. The duct must
be sufficiently large to conduct an adequate
amount of air to each register.
THE AIR CONDITIONING OUTPUT OF THE
SYSTEM WILL NOT COOL THE HOME IF
THE AiR IS LOST TO THE OUTSIDE
THROUGH LEAKS IN THE DUCT SYSTEM.
ALSO, DUCTS WHICH ARE COLLAPSED OR
RESTRICTED BY FOREIGN OBJECTS WILL
PREVENT ADEQUATE AIR FLOW.
Check with the furnace manufacturer
for damper requirements. Failure to
install the required furnace damper
may invalidate code agency listing and
limited warranty on the furnace.
When locating the supply damper(s), carefully
check floor joists and frame members that
could interfere with the installation of the damper
or flexible duct. Ideally, the damper should be
located in the bottom of the main duct, forward
of center of the home, at least three feet from the
Note: For highly resistive duct systems it may
be necessary to add an additional return air duct
and or supply to achieve maximum perfor-
mance and prevent coil icing and refrigerant
flood back.
CONNECTING THE RETURN AND SUPPLY
AIR FLEXIBLE DUCTS
a.
The supply duct for all units istwelve inches
in diameter. The return duct may be 12" or
14" diameter depending on unit size. (See
Table on page 4).
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