These approved “Category IV” vented appliances offer flexible installations via direct vent (sealed
combustion) or indoor combustion air.
When planning a boiler's installation, consider the appropriate vent materials, travel and termination.
3.7.1 Venting code
All venting must be installed in accordance with the requirements of the jurisdiction having authority:
in Canada, Part 8, Venting Systems of the B149.1-10 Code and any other local building codes are to
be followed. In the USA, the National Fuel Gas Code, ANSI 223.1, latest edition, prevails. Where
there is a discrepancy between the installation instructions provided, and the code requirements,
apply the more stringent.
3.7.2 Venting options
These appliances are approved with alternative venting options: either 2-pipe direct vent or vent pipe
with indoor air. With direct vent, combustion air is piped directly to the boiler’s air intake from
outdoors. Using the indoor air alternative, air for combustion is drawn from the indoor air surrounding
the boiler.
Provided the maximum overall vent length limit is not exceeded, the boiler may be vented through
the wall, directly through the roof, or upward using an existing, but otherwise unused, chimney as a
vent raceway.
3.7.3 Exhaust vent material
Warnings
Condensate can cause corrosion of metal roofing components and other roofing
materials. Check with the builder or roofing contractor to ensure that materials are
resistant to acidic condensate. pH levels can be as low as 3.0.
Covering non-metallic vent pipe and fittings with thermal insulation is prohibited.
Exhaust vent material – Canada
Use PVC, CPVC, Polypropylene (PPs), or Stainless Steel (SS) vent component systems approved
under ULC-S636 Standard for Type BH Gas Venting Systems, or stainless steel Type BH venting
systems*. ULC-S636 components are certified as systems including pipe, fittings and
cement/primer for PVC/CPVC and must be installed in strict accordance with manufacturers
instructions. The vent temperature is limited by the boiler controller with the use of a flue
temperature sensor to ensure the maximum temperature of the PVC venting material is not
exceeded.
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