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13
Return Air
The return air ductwork may be connected to any
or all of the following: left side return, right side
return, or bottom return. Tables 1 and 2 show
the airfl ow data for each furnace model. Where
maximum airfl ow is 1800 CFM or more two
openings must be used.
VENTING AND COMBUSTION AIR
REQUIREMENTS
NORDYNE condensing furnaces may be installed
with outdoor combustion air piped directly to the
furnace, or without such special piping. Codes
refer to the former as “direct vent” or “two pipe”
installation. Installation with air taken from around
the furnace is sometimes referred to as “one
pipe” installation where only the vent (exhaust)
pipe is provided.
Provisions must be made for adequate sup-
ply of air for combustion and ventilation. For
United States installations, the adequacy of air
provisions can be determined by consulting the
current version of the National Fuel Gas Code
(ANSI Z223.1/NPFA-54). For Canadian installa-
tions, requirements are specifi ed in the National
Standard of Canada (CAN/CGA B149.1 & .2).
Consult local codes for special requirements.
An important consideration in selecting one or
two pipe installation is the quality of the combus-
tion air. Indoor air is sometimes contaminated
with various household chemicals which can
cause severe corrosion in the furnace combus-
tion system.
NOTE: If the furnace is operated without ade-
quate air for combustion and ventilation, it may not
perform properly. Furnace components may be
strained by high temperature and could fail .
!
WARNING:
Furnace installation using methods
other than those described in the fol-
lowing sections must comply with the
National Fuel Gas Code and all appli-
cable local codes to provide suffi cient
combustion air for the furnace.
Figure 5. Opening for Concrete Slab
Concrete
Floor
Furnace
Sheet
Metal
Plenum
Figure 6. Furnace on a Concrete Slab
Figure 7. Opening in Wood Floor
MODEL A B
*RL 040/060 13.25” 19.25”
*RL 080/100 18.75” 19.25”
*RL 120 21.50” 19.25”
MODEL A B
*RL 040/060 13.25” 19.63”
*RL 080/100 18.75” 19.63”
*RL 120 21.50” 19.63”
B
A
B
A