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Installation In An Unconfi ned Space
An unconfi ned space is an area including all rooms not
separated by doors with a volume greater than 50 cubic
feet per 1,000 Btuh of the combined input rates of all
appliances which draw combustion air from that space.
In general, a furnace installed in an unconfi ned space will
not require outside air for combustion. However, in homes
built for energy effi ciency (low air change rates), it may
be necessary to provide outside air to ensure adequate
combustion and venting, even though the furnace is
located in an unconfi ned space. See example.
A space with a water heater rated at 45,000 Btuh
input and a furnace rated at 75,000 Btuh requires a
volume of 6,000 cubic feet [50 x (45 + 75) = 6,000] to
be considered unconfi ned. If the space has an 8 foot
ceiling, the fl oor area of the space must be 750 square
feet (6,000 / 8 = 750).
VENTING REQUIREMENTS
Upon completion of the furnace installation,
carefully inspect the entire fl ue system both
inside and outside the furnace to assure it is
properly sealed. Leaks in the fl ue system can
result in serious personal injury or death due
to exposure of fl ue products, including carbon
monoxide.
This furnace must be vented in compliance with the
current revision of the International Fuel Gas Code and
the instructions provided below. Consult local codes for
special requirements.
Category I Venting
This furnace is listed as a Category I vented appliance.
Category I furnaces generally operate with a slight negative
pressure (draft) and must be vented vertically or near
vertically. Additionally it is important to guard against
excessive condensation.
IMPORTANT NOTE: This furnace must never be vented
to a chimney or fl ue that services a fi replace or other
appliance designed to burn solid fuel. If the furnace
vent is to be connected to a chimney serving a fi replace,
the fi replace must be sealed off from the chimney.
• Category I furnace installations must be connected
to a factory built vent complying with a recognized
standard, or a masonry or concrete chimney lined with
a lining material acceptable to the authority having
jurisdiction.
8
Example:
WARNING:
WARNING:
Venting into an unlined masonry chimney or
concrete chimney is prohibited. This may result
in improper draft and excess condensation
forming in the chimney.
• This furnace may be vented with a dedicated venting
system or common vented with other Category I
appliances. The vent system dimensions and material
must conform to local Codes.
• The venting system should be designed to have the
minimum number of elbows or turns. All horizontal runs
shall slope upwards from the furnace at ¼ inch per
running foot of vent. Supports for the vent pipe must
be installed a minimum of every fi ve feet along the
vent run to ensure no displacement after installation.
IMPORTANT NOTE: Under no circumstances shall
any portion of the vent system extend into or pass
through any return air duct, supply air duct, or
plenum.
• Single wall vent connectors may be used under the
limited capacity ranges found in the vent sizing tables.
It is recommended that Type "B" double wall vent
be used for the connector whenever possible. An
existing masonry chimney should be inspected and
relined if necessary.
• Single wall metal vertical vents shall not be used for
Category I venting. The furnace vent, if metal, may be
insulated if local codes allow. Any part of the vent system,
metal vent only, not exposed to weather, but which are
exposed to temperatures below 35° F (1° C) must be
insulated to prevent condensation. All vent insulation
shall be foil backed fi berglass of one inch minimum
thickness.
• Sheet metal fasteners should be used to secure the vent
pipe to the furnace fl ue.
• When an existing furnace is removed from a vent system
serving other appliances, the existing vent system
may no longer be sized to properly vent the remaining
appliances. An improperly sized venting system can result
in the formation of condensate, leakage, or spillage. The
existing vent system should also be checked to make
sure it is in compliance with local codes. If it isn't, the
vent system must be brought into compliance before
installing the furnace.
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