12
The use of Schedule 40 PVC cellular core DWV meeting ASTM F891-1 or ABS cellular core (Foam Core) plastic pipe is also
acceptable as a flue/vent and intake pipe material. PVC primer meeting ASTM F656 and PVC solvent cement meeting ASTM
D2564 specifications must be used. Fittings must be DWV type fittings meeting ASTM D2665 and ASTM D3311. Carefully
follow the manufactures instructions for cutting, cleaning and solvent cementing of PVC.
For Canadian installations; all PVC pipe, fittings and joining materials must be UL S636 listed.
As an alternative to PVC pipe, primer, solvent cement, and fittings, ABS materials which are in compliance with the following
specifications may be used. Two-or-three-inch ABS Schedule 40 pipe must meet ASTM D1527 and, if used in Canada, must be CSA
listed. Solvent cement for ABS to ABS joints must meet ASTM D2235 and, if used in Canada, must be CSA listed. The solvent cement
for the PVC to ABS transition joint must meet ASTM D3138. Fittings must be DWV type fittings meeting ASTM D2661 and ASTM D3311
and, if used in Canada, must be CSA listed. Carefully follow the manufacturers’ instructions for cutting, cleaning, and solvent
cementing PVC and/or ABS.
All 90° elbows must be medium radius (1/4 bend DWV) or long radius (Long sweep 1/4 bend DWV) types conforming to ASTM D3311.
A medium radius (1/4 bend DWV) elbow measures 3 1/16” minimum from the plane of one opening to the center line of the other
opening for 2” diameter pipe, and 4 9/16” minimum for 3” pipe.
P
ROPER
V
ENT
/F
LUE
AND
C
OMBUSTION
A
IR
P
IPING
P
RACTICES
Adhere to these instructions to ensure safe and proper furnace performance. The length, diameter, and number of elbows of the
vent/flue pipe and combustion air pipe (when applicable) affects the performance of the furnace and must be carefully sized. All
piping must be installed in accordance with local codes and these instructions.
Some models require the use of 3” pipe. Do not transition from a 2” to 3” pipe in a horizontal section of pipe as this may
create a water trap.
PREFERRED
TRANSITION NO LESS
THAN 45 DEGREES TO
HORIZONTAL PLANE TO
AVOID CREATING A WATER
TRAP IN VENT PIPING.
ACCEPTABLE
NO TRANSITION ON
HORIZONTAL PLANE,
THIS CREATES A
WATER TRAP AND
RESTRICTS FLUE
GASES
Figure 4
Figure 5
Figure 6
Piping must be adequately secured and supported to prohibit sagging, joint separation, and/or detachment from the furnace.
Horizontal runs of vent/flue piping must be supported every three to five feet and must maintain a 1/4 inch per foot downward slope,
back towards the furnace, to properly return condensate to the furnace’s drain system. Allowances should be made for minor
expansion and contraction due to temperature variations. For this reason, particular care must be taken to secure piping when a long
run is followed by a short offset of less than 40 inches.
Precautions should be taken to prevent condensate from freezing inside the vent/flue pipe and/or at the vent/flue pipe termination.
All vent/flue piping exposed to freezing temperatures below 35°F for extended periods of time must be insulated with 1/2” thick
closed cell foam. Also all vent/flue piping exposed outdoors in excess of the terminations shown in this manual (or in unheated areas)
must be insulated with 1/2” thick closed cell foam. Inspect piping for leaks prior to installing insulation.
T
ERMINATION
L
OCATIONS
NOTE:
Refer to
Location Requirements and Considerations
for combustion air contaminant restrictions.
The following bullets and diagram describe the restrictions concerning the appropriate location of vent/flue pipe and combustion air
intake pipe (when applicable) terminations. Refer to
Non-Direct Vent (Single Pipe) Piping
and
Direct Vent (Dual Pipe) Piping
located
in this section for specific details on termination construction.
•
All terminations (flue and/or intake) must be located at least 12 inches above ground level or the anticipated snow level.
•
Vent terminations (non-direct and direct vent) must terminate at least 3 feet above any forced air inlet located within 10
feet.
NOTE:
This provision does not apply to the combustion air intake termination of a direct vent application.
