Return Air Provisions; Air Distribution Systems - Nordyne M2RC-080 Installation Instructions Manual

RETURN AIR PROVISIONS
Upfiow models draw the return air from the
base of the furnace. A stand or return air duct
must be supplied to the furnace to provide the
required return air.
Downflow models draw the return air from the
top of the furnace. The minimum required
clearance to the top of the furnace is detailed
on the furnace rating plate. Additional clear-
ance may be required depending upon filter
accessibility.
For each application, the U.S.A. home manufac-
turer shall comply with all of the following condi-
tions to have acceptable retum air systems for
closet installed forced air heating appliances:
a. Regardless of the location, the return air
opening into the closet shall not be less
than specified in the appliance's listing.
b. Means shall be provided to prevent
inadvertent closure by a flat object placed
over the return air opening when it is
located in the floor of the closet (versus
the vertical front or side wall).
c. The cross-sectional area of the return
duct system leading into the closet shall
not be less than 390 square inches.
d. The total free area of openings in the floor
or ceiling registers serving the return air
duct system must be at least 352 sq. in.
At least one register should be located
where it is not likely to be covered by
For floor return systems, the
manufactured home manufacturer shall
affix a prominent marking on or near the
appliance where it can be easily read
when the closet door is open. The
marking shall read:
CAUTION:
HAZARD OF ASPHYXIATION: Do not
cover or restrict return air opening.
k. Air conditioning systems may require
more duct, register and open louver area
to obtain necessary airflow. Use
NORDYNE's certiduct program to
determine proper duct size for A/C.
AIR DISTRIBUTION SYSTEMS
For proper air distribution, the supply duct
system must be designed so that the static
pressure measured external to the furnace
does not exceed the listed static pressure
rating shown on the furnace rating plate.
Three typical distribution systems are illustrated
in Figure 2. Location, size, and number of
registers should be selected on the basis of
best air distribution and floor plan of the home.
A Single trunk duct []
carpeting, boxes and other objects ............................................................
e. Materials located in the return duct
system must have a flame spread
classification of 200 or less. This includes
a-closetdo0r if theefu-rnac_ is"fna-cios_t._
f. Noncombustible panshaving 1"upturned
flanges are located beneath openings in
a floor duct system.
g. Wiring materials located in the return
duct,system shall conform_to Articles ,-
300-22 of the National Electrical Code
(ANSI CI/NFPA-70).
h. Gas piping is not run in or through the
return duct system.
i. Test the negative pressure in the closet
with the air-circulating fan operating at
high speed and the closet closed. The
negative pressure is to be no more
negative than minus 0.05 inch water
column.
BJ Dual trunk duct _ ]
- _ wlcrossover connector-_- •
J
U U U
Figure 2. Typical Supply Duct System
FLOOR CAVITY
U (depth equal to "X* in F3gure 5 and Table 5)
t JJJJJJJJJJJJJJJJJJJJJ JJ _ J Ji_
x-l--- -----.._ i l ,l
I
I)J
SuPPLYAiR oucT
-- I_! / k h\l
Figure 3. Floor Cavity Cut-Out
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