66
Venting
MULTIVENTING OF DIRECT-VENT FURNACES
GENERAL VENTING REQUIREMENTS AND
GUIDELINES
Figures 33 & 34: NOTE: WHEN VENTING MULTIPLE FURNACES IN CLOSE PROXIMITY, EACH FURNACE MUST BE
INDIVIDUALLY VENTED – NO COMMON VENTING IS PERMITTED. See Figures 33 & 34 for positioning of the termina-
tions. When more than two furnaces are to be vented, there must be at least 4 feet between the first two furnaces and the
third and etc. Figure 33, (Detail A) below shows the necessary detail for the roof penetration on a standard direct-vent
vertical termination.
FIGURE 33
TWO FURNACE VENTING
FIGURE 34
TWO FURNACE VENTING WITH CONCENTRIC VENTING
3” (8cm) MIN.
12” (32cm) MAX.
COMBUSTION
AIR INTAKE
2” PVC
SEE DETAIL
“A”
A
SEE
8”/20cm
MIN.
12”/31cm MIN. ABOVE
GRADE OR HIGHEST
ANTICIPATED SNOW LEVEL.
CANADA: MUST CONFORM TO
CSA B149.1-10, SECT. 8.14
MINIMUM 12”/31cm IN
U.S. ABOVE AVERAGE
SNOW ACCUMULATION.
MAXIMUM OF 24”/61cm
ABOVE ROOF.*
A
SEE
6’ (1.8m) MINIMUM
10’ (3m) RECOMMENDED
A
SEE
MINIMUM 12”/31cm
ABOVE GRADE IN U.S.*
ST-A1194-18
DETAIL A
ST-A1194-21
ST-A1194-22
DETAIL A
CONCENTRIC VENTING THROUGH ROOF
CONCENTRIC VENTING THROUGH WALL
TWO PIPE VENTING THROUGH ROOF
TWO PIPE VENTING THROUGH WALL
DIRECT VENT VERTICAL TERMINATION DETAIL
*3” (8cm) minimum only if no snow accumulation is anticipated.
ST-A1194-22
2 FURNACES
➀ Terminations must be greater than 8” apart.
➁ Terminations must be less than 24” apart or greater than
➁ 36” apart.
3rd OR MORE FURNACES
Each additional termination must be greater than 48” from
the previous termination.
A
TERMINATIONS MORE
THAN 24” ABOVE ROOF
PENETRATION REQUIRE
ADDITIONAL SUPPORT.
A
*CANADA: Termination must conform to CSA
B149.1-10, Sect. 8.14
NOTE: IF 3 Ø
VENTING IS
USED, BOTH
PIPES (INTAKE
AND EX-
HAUST) MUST
BE REDUCED
TO 2 Ø
BEFORE
PENETRATING
ROOF.
*
12” (31cm) U.S.
CANADA: TERMINATIONS
MUST CONFORM TO
CSA B149.1-10, SECT. 8.14
48” MAX.
(122 cm)
45” MAX.
(114 cm)
36” MAX.
(91 cm)
3” MIN.
(8 cm)
NOTE: IF 3 Ø
VENTING IS USED,
BOTH PIPES (INTAKE
AND EXHAUST) MUST
BE REDUCED TO 2 Ø
BEFORE PENETRATING
ROOF.
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