6
RETURN AIR IS VERY IMPORTANT
When installing a Furnace, return air MUST BE incorpo-
rated into the system. Return air can be provided by in-
stalling a separate duct system or by tying into the cold air
return of an existing gas or oil furnace. The cold air return
duct can be connected to the furnace with either a factory
manufactured U. S. Stove
fi
lter box, model UFB908 or an
equivalent fabricated from sheet metal.
When installing a cold air return, the minimum size shall
be a 16” x 20” or equivalent (320 sq. in.) in order to insure
proper furnace performance. Failure to provide return air
ducts of the speci
fi
ed size will void your warranty.
A
fi
lter should be installed in the cold air return. Furnace
fi
lters should be checked and cleaned/replaced regularly.
If return air is not provided, the warm air distributed into
your home will be restricted and the ef
fi
ciency of the fur-
nace is decreased. Without a return air system, warm air
will be drawn into your basement, unnecessarily heating
unused areas of the home. In extreme cases, if your base-
ment or utility room is fairly airtight, the blowers on the
furnace could depressurize the room and pull toxic
fl
ue
gases from the furnace, a gas water heater, or gas fur-
nace. The fumes could then be distributed throughout the
house.
COMBUSTION AIR
All
fi
res need air (speci
fi
cally oxygen) to burn. Furnaces,
fi
replaces, and wood burning furnaces need enough oxy-
gen for complete combustion of their fuels. The incomplete
combustion that takes place when a furnace is “air starved”
causes carbon monoxide (CO) to be formed in quantities
that can be dangerous inside a well sealed house. Hav-
ing a source of combustion air from outside the home will
prevent “air starvation” of the furnace. A simple positive air
supply can be constructed using dryer vent and a modi
fi
ed
termination.
NEGATIVE
PRESSURE IN
BASEMENT
THE PLENUM OPENINGS DIFFER
BETWEEN THE 1602 AND 1802
MODEL 1602 -
13” x 18” Rectangular
MODEL 1802 -
18” x 18” Rectangular
PLENUM OPENING
