13
Applicable ASTM Standards for Vent Materials
Materials
Sch. 40
Pipe
SDR
Pipe
Cell
Core
Pipe
Fittings
Primer
Solvent
Cement
ABS
D1527
__
F628
D2468
&
D2661
--- ---
D2235
PVC
D1785
D2241
F891
D2466
&
D2665
F656
D2564
CPVC
F441
F442
--- ---
F438
--- ---
F493
ABS to
PVC
--- ---
--- ---
--- ---
--- ---
--- ---
D3138
NOTE
:
1. In Canada, all pipe, fittings & cements must conform to
applicable CSA standards or to local codes having juris-
diction.
2. Only use solvent cements that are marked for use with the
specific venting material.
3. ABS to PVC transition joints REQUIRE a special solvent
cement that meets the requirements of ASTM D3138.
4. Refer to ASTM D2855 for general procedure to use for
cementing plastic pipe and fittings.
NOTE
: In order to create a seal that allows future removal of
pipe,
RTV sealant MUST be used on the inlet pipe
where it
joins to the furnace.
NOTE
: All vent piping
MUS
T be installed in compliance with
local codes or ordinances, these instructions, good trade practices,
and codes of country having jurisdiction.
1. Determine the best routing and termination for the vent
pipe and air inlet pipe by referring to all of the instructions
and guidelines in this Section.
2. Determine the size required for the vent pipe and air inlet
pipe.
3. Loosely assemble all venting parts without adhesive (pipe
joint cement) for correct fit before final assembly.
4. Furnace shall be installed so as to prevent the accumula-
tion of condensate.
5. Use of vertical piping is preferred because there will be
some moisture in the flue gases that may condense as it
leaves the vent pipe (See
Instructions For Horizontal
Vents
).
6. The vertical vent pipe
MUST
be supported so that no
weight is allowed to rest on the combustion blower.
7. Exhaust vent piping or air inlet piping diameter
MUST
NOT
be reduced.
8. All exhaust vent piping from the furnace to termination
MUST
slope upwards. A minimum of
1
/
4
″
(6 mm) per foot
of run is required to properly return condensate to the fur-
nace drain system.
9. Use DWV type long radius elbows whenever possible, as
they provide for the minimum slope on horizontal runs and
they provide less resistance in the vent system. If DWV
elbows cannot be used, use two, 45
°
elbows when pos-
sible. On horizontal runs the elbows can be slightly mis-
aligned to provide the correct slope.
10. All horizontal pipe runs
MUST
be supported at least every
five feet with galvanized strap or other rust resistant ma-
terial.
NO
sags or dips are permitted.
11. All vertical pipe runs
MUST
be supported every six feet
where accessible.
12. The minimum pipe run length is 2
′
(.6 M).
13. The piping can be run in the same chase or adjacent to
supply or vent pipe for water supply or waste plumbing. It
can also be run in the same chase with a vent from another
90+ furnace.
NOTE
: In
NO
case can the piping be run in a chase where
temperatures can exceed 140
°
F (60
°
C). or where radiated heat
from adjacent surfaces would exceed 140
°
F (60
°
C).
14. The vent outlet
MUST
be installed to terminate in the
same atmospheric pressure zone as the combustion air in-
let.
15. The vent system can be installed in an existing unused
chimney provided that:
S
Both the exhaust vent and air intake run the length of the
chimney.
S
No other gas fired appliance or fireplace (solid fuel) is vented
into the chimney.
S
The top of the chimney
MUST
be sealed flush or crowned up
to seal against rain or melting snow so
ONLY
the piping
protrudes.
S
The termination clearances shown in Fig. 7 and 8 are
maintained.
16. Furnace applications with vertical vents requiring vent dia-
meter increaser fittings
must
have increaser fittings in-
stalled in vertical portion of the vent. Condensate will be
trapped in the vent if the vent diameter is increased prior
to having an elbow turned upward. This could cause nuis-
ance tripping of the pressure switch.
Combustion Air and Vent Piping Insulation
Guidelines
NOTE
: Use closed cell, neoprene insulation or equivalent. If
Fiberglass or equivalent insulation is used it must have a vapor
barrier. Use R values of 7 up to 10
′
, (2.1 -- 3.0 M) R--11 if
exposure exceeds 10
′
. If Fiberglass insulation is used, exterior to
the structure, the pipe
MUST
be boxed in and sealed against
moisture.
1. When the vent or combustion air pipe height above the
roof exceeds 30
″
(762 mm), or if an exterior vertical riser is
used on a horizontal vent to get above snow levels, the ex-
terior portion
MUST
be insulated.
2. When combustion air inlet piping is installed above a sus-
pended ceiling, the pipe
MUST
be insulated with moisture
resistant insulation such as Armaflex or other equivalent
type of insulation.
3. Insulate combustion air inlet piping when run in warm, hu-
mid spaces.
Sizing Combustion Air and Vent Pipe
Consult
Table 3
to select the proper diameter exhaust and
combustion air piping. Exhaust and combustion air piping is sized
for each furnace BTUH size based on total lineal vent length (on
inlet
or
outlet side), and number of 90
°
elbows required. Two 45
°
elbows can be substituted for one 90
°
elbow. The elbow or
elbows used for vent termination outside the structure
ARE
counted, including elbows needed to bring termination above
expected snow levels. The elbow inside the furnace on the
359AAV
IS NOT
included in the count.
359AA
V
