8
IV. Vent Pipe (All Models) And
Combustion Air Pipe (GUD Models)
Materials
WARNING
Failure to follow these instructions can
result in bodily injury or death from as-
phyxiation. Therefore, carefully read and
follow all instructions given in this sec-
tion.
In order to achieve high efficiency, the products of
combustion from this furnace are cooled to the point
where condensation takes place. Consequently, the vent-
ing must be done in a different manner and with differ-
ent materials than with a conventional system. Two or
three inch PVC Schedule 40 pipe meeting ASTM D1785,
PVC primer meeting ASTM F656 and PVC solvent
cement meeting ASTM D2564 specifications must be
used. Only DWV type fittings meeting ASTM D2665
and ASTM D3311 can be used. Carefully follow the
manufacturers instructions in cutting, cleaning, and sol-
vent cementing of PVC or ABS pipe.
As an alternate 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 used for the PVC to ABS transition joint
must meet ASTM D3138. Fittings must be DWV type
fittings which meet ASTM D2661 and ASTM D3311
and, if used in Canada, must be CSA listed. Carefully
follow the manufacturers instructions in cutting, clean-
ing, and solvent cementing PVC or ABS pipes.
WARNING
Solvent cements are combustible liquids
and should be kept away from all igni-
tion sources. (i.e. sparks, open flames
and excessive heat). Avoid breathing ce-
ment vapors or contact with skin and
eyes.
5.3.4 Specially Engineered Installations:
The requirements of 5.3.3 shall not necessarily govern
when special engineering, approved by the authority
having jurisdiction, provides an adequate supply of air
for combustion, ventilation, and dilution of flue gases.
5.3.5 Louvers and Grilles:
In calculating free area in 5.3.3, consideration shall be
given to the blocking effect of louvers, grilles or screens
protecting openings. Screens used shall not be smaller
than 1/4 inch mesh. If the area through a design of
louver or grille is known, it should be used in calculating
the size of opening required to provide the free area
specified. If the design and free area is not known, it
may be assumed that wood louvers will have 20-25
percent free area and metal louvers and grilles will have
60-75 percent free area. Louvers and grilles shall be
fixed in the open position or interlocked with the equip-
ment so that they are opened automatically during
equipment operation.
5.3.6 Special Conditions Created by Mechanical Ex-
hausting or Fireplaces:
Operation of exhaust fans, ventilation systems, clothes
dryers, or fireplaces may create conditions requiring
special attention to avoid unsatisfactory operation of
installed gas utilization equipment.
