13
Horizontal Venting
WARNING:
Horizontal vent systems must be sealed with
a high temperature sealant that can withstand
temperatures of 450° F. Recommended sealants:
Dow Corning Sealant 736 RTV; GE 106 RTV;
High Tech Ind., High TEMP RED.
This furnace is not approved for horizontal venting
without the use of an add-on power venter. Power venters
establish negative pressure in the vent piping and the
furnace operates as if connected to a Category I vertical
vent. The power venter is only for use when exhausting
through an exterior wall.
The power venter must be installed according to the
instructions provided by the power venter manufacturer
and applicable requirements of local codes. For Canadian
installations please refer to the Canadian Installation Code
(CAN/CGA-B149.1 or 2) and/or local codes.
The outlet of the vent must be at least 12 inches above
the highest expected snow accumulation.
Flexible Vent Systems
Flexible venting systems are approved for use providing
they are listed for the application and meet all local Code
requirements. These systems are primarily used to line
existing masonry chimneys. They must be sized to the
application according to the sizing tables in the National
Fuel Gas Code, including the required 20% reduction in
maximum capacity.
Flexible venting systems are permitted to be used as the
vent connector. However, great care must be taken to
ensure that there are no sags in the venting system which
could accumulate condensate. The fl exible vent system
must be supported at no more than 5 foot intervals and
maintain a minimum slope of ¼ inch per foot of horizontal
run.
CIRCULATING AIR REQUIREMENTS
WARNING:
Do not allow combustion products to enter the
circulating air supply. Failure to prevent the
circulation of combustion products into the
living space can create potentially hazardous
conditions including carbon monoxide
poisoning that could result in personal injury
or death.
All return ductwork must be secured to
the furnace with sheet metal screws. For
installations in confi ned spaces, all return
ductwork must be adequately sealed. When
return air is provided through the bottom of the
furnace, the joint between the furnace and the
return air plenum must be air tight.
The surface that the furnace is mounted on must
provide sound physical support of the furnace
with no gaps, cracks or sagging between the
furnace and the fl oor or platform.
Return air and circulating air ductwork must
not be connected to any other heat producing
device such as a fi replace insert, stove, etc.
This may result in fi re, explosion, carbon
monoxide poisoning, personal injury, or
property damage.
Plenums and Air Ducts
• Plenums and air ducts must be installed in accordance
with the Standard for the Installation of Air Conditioning
and Ventilating Systems (NFPA No. 90A) or the
Standard for the Installation of Warm Air Heating and
Air Conditioning Systems (NFPA No. 90B). Additional
reference information for US and Canadian installations
can be found in the Duct Systems section (page 4).
• Table 2 and Table 3 (pages 26-28) contain the airfl ow and
temperature rise data. If the maximum airfl ow is 1,600
CFM or more, it is recommended that two openings be
used for return air on upfl ow furnaces. Downfl ow furnaces
can only use one return opening.
• It is recommended that the outlet duct contain a removable
access panel. The opening should be accessible when
the furnace is installed in service and shall be of a size
that smoke or refl ected light may be observed inside
the casing to indicate the presence of leaks in the heat
exchanger. The cover for the opening shall be attached
in such a manner as to prevent leaks.
• If outside air is used as return air to the furnace for
ventilation or to improve indoor air quality, the system
must be designed so that the return air is not less than
60° F (15° C) during operation. If a combination of indoor
and outdoor air is used, the ducts and damper system
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