10
EXAMPLE
A space with a water heater rated at 45,000 Btuh input
WARNING:
this section and provide air for combustion and ventilation
according to on page 7, page 8, page 9, page 10.
The length of vent and combustion air piping for either
type of installation are shown in in 10)
slightly acidic and can cause severe corrosion of ordinary
affected by restrictive vent and combustion air piping.
Alternate Method of Providing Air from
Outside:
combustion air. One opening must be within 12 inches of
the ceiling, and the other must be within 12 inches of the
floor. However, an alternative method recently adopted by
of the space. This method may be used if it is acceptable
to the local codes.
THE FOLLOWING CONDITIONS MUST BE MET:
structure and connect with the out of doors through
vertical or horizontal ducts or be ducted to a crawl or
attic space that connects with the out of doors.
2. The opening must have a minimum free area of 1 in2.
per 3,000 Btu per hour of the total input rating of all
3. The free area must not be less than the sum of all the
areas of the vent connectors in the enclosure.
Spaces
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.
combustion and venting, even though the furnace is located
above.
Table 1
Vent Pipe Lengths
FURNACE
MODELS
(BTU)
FURNACE
INSTALLATION
WITH 1 LONG RADIUS ELBOW*
WITH 1 LONG RADIUS ELBOW ON EACH PIPE*
OUTLET
2” DIAMETER
OUTLET
3” DIAMETER
INLET/OUTLET
2” DIAMETER
INLET/OUTLET
3” DIAMETER
60,000
Upflow 50 80 50 80
Horizontal 40 80 40 80
80,000
Upflow 60 90 60 90
Horizontal 50 90 50 90
100,000
Upflow 50 90 50 90
Horizontal
40 90 40 90
120,000
Upflow
90 90
Horizontal 70 70
*NOTES:
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