Table des Matières
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VENTING
4. For Category I vent systems limit length of horizontal runs to
75% of vertical height. Install with a minimum upward slope
from unit of 1/4 inch per foot and suspend securely from
overhead structure at points no greater than 3 feet apart.
For best venting, put vertical vent as close to the unit as
possible. For Model Digit 3=P units, a minimum of 12"
straight pipe is recommended from the power exhauster
outlet before turns in the vent system. Fasten individual
lengths of vent together with at least three corrosion-resistant
sheet-metal screws.
5. It is recommended that vent pipes be fitted with a tee with a
drip leg and a clean out cap to prevent any moisture in the
vent pipe from entering the unit. The drip leg should be inspected
and cleaned out periodically during the heating season.
6. The National Fuel Gas Code requires a minimum clearance
of 6 inches from combustible materials for single wall vent
pipe. The minimum distance from combustible materials is
based on the combustible material surface not exceeding
160°F. Clearance from the vent pipe (or the top of the unit)
may be required to be greater than 6 inches if heat damage
other than fire (such as material distortion or discoloration)
could result.
7. Avoid venting through unheated space. When venting does
pass through an unheated space, insulate runs greater than
5 feet to minimize condensation. Inspect for leakage prior to
insulating and use insulation that is noncombustible with a
rating of not less than 350°F. Install a tee fitting at the low
point of the vent system and provide a drip leg with a clean
out cap as shown in Figure 6.1.
8. When the vent passes through a combustible wall or floor, a
metal thimble 4 inches greater than the vent diameter is
necessary. If there is 6 feet or more of vent pipe in the open
space between the appliance and where the vent pipe
passes through the wall or floor, the thimble need only be 2
inches greater than the diameter of the vent pipe. If a thimble
is not used, all combustible material must be cut
provide 6 inches of clearance. Any material used
to close the opening must be noncombustible.
9. Do NOT use dampers or other devices in the vent pipes.
10. Precautions must be taken to prevent degradation of
building materials by flue products.
11. For category I vent systems the outlet of the vent should
extend as shown in Figure 6.1 and Tables 6.1 and 6.2.
12. Use a listed vent terminal to reduce downdrafts and moisture
in vent. For Model Digit 3=G, a vent terminal that is very
open will avoid spillage at unit's diverter relief opening and
tripping of the blocked vent safety switch.
13. For instructions on common venting refer to the National
Fuel Gas Code.
14. The vent must terminate no less than 5' above the vent
connector for Category I vent systems.
15. A unit located within an unoccupied attic or concealed space
shall not be vented with single wall vent pipe.
16. Single wall vent pipe must not pass through any attic, inside
wall, concealed space, or floor.
17. Do NOT vent Model Digit 3=P units into a masonry chimney.
Model Digit 3=G units can be vented into a masonry
chimney if the following requirements are met:
a. Do not vent a Category l unit into a common vent with
mechanical draft systems operating under positive
pressure (Category lll or lV units.)
b. When connecting a vent to an existing chimney, do not
push the vent pipe beyond internal surface of chimney.
c. When venting into a common vent, the area of the
common vent should be equal to or greater than the
area of the largest vent plus 50 percent of the area of all
additional vents.
d. When venting into a common vent, the individual vents
should enter at different levels.
6
Figure 6.1 - Vertical Category I Vent System
away to
Table 6.1 - Minimum Height from Roof to Lowest
Discharge Opening
Roof Rise
"X" (in)
0-10
10-12
12-14
14-16
16-18
18-21
Increase "H" as required to accommodate snow depth.
j
Table 6.2 - Minimum Height Above Adjacent Wall
Less than 10 Feet Away
"D"
10 Feet or Less
Greater than 10 Feet
5-564.4
10 FEET OR LESS
TO ROOF PEAK
2 FEET MINIMUM
"H" FEET MINIMUM
X
12"
ROOF PITCH IS:
X / 12
USE LISTED
THIMBLE
THROUGH
ROOF
MAINTAIN MINIMUM
CLEARANCE TO
COMBUSTIBLES
12" MINIMUM
(SLOPE PIPE UP
1/4" PER FOOT
TOWARD DRIP LEG)
DISTANCE "D" TO
WALL OR ADJOINING
BUILDING
"H" FEET MINMUM
ABOVE WALL OR
ADJOINING
BUILDING PER
TABLE 6.2
3 FEET
MINIMUM*
* SIZE ACCORNING
TO EXPECTED
SNOW DEPTH.
MAINTAIN MINIMUM
CLEARANCE TO
COMBUSTIBLES
12" MINIMUM
(SLOPE PIPE UP
1/4" PER FOOT
TOWARD DRIP LEG)
Equivalent
Roof Pitch
Flat to 10/12
10/12 to 12/12
12/12 to 14/12
14/12 to 16/12
16/12 to 18/12
18/12 to 21/12
2 Feet Minimum
No Additional Height Required
LISTED
TERMINAL
PER TABLE 6.1
ROOF
FLASHING
USE LISTED
THIMBLE
THROUGH
CEILING
TEE WITH DRIP LEG
AND CLEANOUT CAP
LISTED
TERMINAL
ROOF
FLASHING
USE LISTED
THIMBLE
THROUGH
CEILING
TEE WITH DRIP LEG
AND CLEANOUT CAP
Minimum Height
"H" (ft) j
3.00
4.00
5.00
6.00
7.00
8.00
"H"
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