986TC: Installation, Start-up, Operating, Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
32
Direct Vent / 2-Pipe System
In a direct-vent (2-pipe) system, all air for combustion is taken directly
from outdoor atmosphere, and all flue products are discharged to outdoor
atmosphere. Combustion-air and vent pipes must terminate together in
the same atmospheric pressure zone, either through the roof (preferred)
or a sidewall. See Fig. 46 for references to clearances required by
National code authorities.
Ventilated Combustion Air Systems
In a ventilated combustion air option, the vent terminates and discharges
the flue products directly to the outdoors similar to a direct vent system.
See Fig. 47 for references to clearances required by National code
authorities.
All air for combustion is piped directly to the furnace from a space that is
well ventilated with outdoor air (such as an attic or crawl space) and the
space is well isolated from the living space or garage. Combustion air
requirements for this option are the same as the requirements for
providing outside air for combustion for a single pipe vent system. Refer
to the “Air For Combustion and Ventilation” Section.
Non-Direct Vent (1-pipe) System
In a non direct-vent (1-pipe) system, all air for combustion is taken from
the area adjacent to furnace, and all flue products are discharged to
outdoor atmosphere. Air for combustion must be supplied as described
in the Air For Combustion and Ventilation Section. Do not use an
abandoned chimney to supply outside air to the furnace. See Fig. 47 for
references to vent clearances required by National code authorities.
A combustion air pipe to the outdoors is not required for a single-pipe
vent system. A 12-in. (304 mm) long pipe with a 2-in. (51 mm) tight
radius 90 degree elbow is required to be attached to the combustion air
pipe adapter on the furnace. See Fig. 49. This short inlet air pipe helps to
ensure stable combustion, as well as allow for sound attenuation. To aid
sound attenuation, point the inlet air pipe away from occupants. An extra
elbow and/or five feet of pipe may be used to accomplish the sound
attenuation function.
NOTICE
!
RECOMMENDED SUPPORT FOR VENT
TERMINATION
It is recommended that sidewall vent terminations of over 24 inches
(0.6 M) in length or rooftop vent terminations of over 36 inches (1 M)
in length be supported by EITHER the factory accessory vent
termination kit or field-supplied brackets or supports attached to the
structure. A factory accessory vent termination kit may be used for
direct vent terminations. Termination kits are available for 2-in. or 3-in.
pipe. See Table 11 for available options.
NOTICE
!
OPTIONAL CONFIGURATION FOR COMBUSTION
AIR INLET PIPE
In applications where there is a risk of excessive moisture entering the
combustion air inlet pipe, a moisture trap may be added to the inlet pipe
to help prevent moisture from entering the furnace from the combustion
air inlet pipe. See Fig. 51.
When sizing venting systems, the equivalent length of the optional inlet
pipe moisture trap must be taken into account.
NOTICE
!
OPTIONAL VENTING BELOW THE FURNACE
The venting system may be positioned below the furnace ONLY IF the
factory accessory External Vent Trap Kit is used. The External Vent
Trap Kit is only approved for PVC/ABS DWV venting systems.
CAREFULLY FOLLOW THE INSTRUCTIONS PROVIDED
WITH THE EXTERNAL VENT TRAP KIT FOR LAYING OUT
THE VENTING SYSTEM AND THE DRAIN SYSTEM. The
instructions included with this furnace DO NOT APPLY to vent
systems that are located below the furnace.
WARNING
!
CARBON MONOXIDE POISONING HAZARD
Failure to follow the instructions outlined below for each appliance
being placed into operation could result in carbon monoxide poisoning
or death.
The instructions included with this furnace DO NOT APPLY to vent
systems that are located below the furnace. CAREFULLY FOLLOW
THE INSTRUCTIONS PROVIDED WITH THE EXTERNAL
VENT TRAP KIT FOR LAYING OUT THE VENTING SYSTEM
AND THE DRAIN SYSTEM when all or part of the venting system is
placed below the furnace.
Proper configuration of the venting and drain system is critical when
placing all or part of the venting system below the level of the furnace.
VENT GASSES COULD BE RELEASED FROM THE
DRAINAGE SYSTEM if the instructions provided with the External
Vent Trap Kit are not followed.
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