11
VI. Combustion Air And Vent Piping
(GUD - Two Pipe)
General Information And Safety
Precautions
WARNING
Failure to follow these instructions can
result in bodily injury or death from as-
phyxiation. Therefore, carefully read and
follow all instructions given in this sec-
tion.
CAUTION
Terminate the combustion air intake as
far as is practical from the air condition-
ing unit or heat pump, swimming pools,
swimming pool pumping units, and dryer
vents.
All combustion air and exhaust piping must be installed
in accordance with local codes and these instructions.
When the furnace is installed in a confined space where
the minimum clearances to combustible surfaces (see
Specification Sheet) are applied, such as in a closet or a
utility room, two ventilation openings are required with a
total minimum free area of 0.25 square inches per
1,000 BTUH of the furnace input rating. One opening
must be within 12 inches of the top and one must be
within 12 inches of the bottom of the confined space. In
typical construction, the clearance between the door
and door frame will usually be adequate to satisfy this
ventilation requirement.
When the GUD furnace is installed in the same space
with other gas appliances, such as a water heater, make
sure there is an adequate supply of combustion and
ventilation air for the other appliances. See the latest
edition of the National Fuel Gas Code (ANSI 7793.1) for
determining the combustion air requirements for the
appliances.
The GUD furnaces are supplied with a 3 inch air intake
terminal screen. This screen is shipped in the same
plastic sack that held this manual. For both vertical and
horizontal installations, insert the screen into the air
intake terminal until it is firmly secured at the hub of the
terminal elbow.
If the vent (flue) pipe is exposed to extremely cold
temperatures and/or long runs through unheated spaces
or outdoors, insulation may be required on the outside
of the vent pipe to prevent condensate from freezing.
Canadian installers must take note of the Additional
Canadian Venting Requirements in this section. Where
required, use 1/2 inch thick closed cell foam insulation
such as Armaflex or Insultube.
NOTE:
Inspect the flue for leaks before installing any
insulation.
If the combustion air pipe is to be installed above a
suspended ceiling or other area where dripping of con-
densation will be objectionable, insulation of the com-
bustion air pipe may be required. Where required, use
1/2 inch thick closed cell foam insulation such as
Armaflex or Insultube.
Location of Exhaust And Intake
Terminations
All Installations
This furnace can be installed with either a vertical or
horizontal direct vent. In either case, the exhaust vent
and the combustion air intake pipe must be located on
the same side of the structure and separated by no less
than 3 inches and no more than 24 inches.
This ensures enough distance to prevent flue gas recir-
culation and limits the distance to ensure the vent outlet
and air inlet terminals are in the same atmospheric
pressure zone.
The following points must also be considered when
installing the vent pipe in either a horizontal or vertical
application:
1. The vent termination must be at least 3 feet above
any forced air inlet located within 10 feet.
Exception:
This provision shall not apply to the
combustion air intake of a direct vent furnace.
2. The vent termination must be at least 12 inches
from any door, window, or gravity air inlet into any
building.
3. The vent must terminate at least 2 feet above
ground level or roof level. If heavy snow accumula-
tion is expected, this distance will need to be in-
creased.
4. The vent shall not terminate over public walkways
or over an area where condensate or vapor could
create a nuisance or hazard or could be detrimental
to the operation of regulators, relief valves, or other
equipment.
5. In addition, the combustion air intake should not be
terminated in areas that are frequently very dusty or
dirty.
