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Vent Connections
⚠ DANGER ⚠
• All Category III vent joints MUST BE secured using #8 × 3/8 sheet metal screws and MUST BE
sealed using high-temperature (≥550°F (≥288°C)) silicone sealant.
• For all Category III venting, the installer MUST perform a leak test on the complete venting system.
A soap and water solution is recommended.
The heater is a Category I or III vented appliance. Refer to the rating plate for the vent category.
Venting General Requirements
• The heater must be vented in accordance with this manual and with the National Fuel Gas Code (NFPA 54/ANSI
Z223.1, latest revision) in the US, with the Natural Gas and Propane Installation Code (CSA B149.1, latest revision)
in Canada, and with any state, provincial, or local codes that may apply. Any portion of vent pipe passing through
a combustible wall must have an approved thimble to conform with these codes.
• Maintain a 6-inch (15-cm) minimum clearance around all single-wall flue pipe.
• Vent pipe must be sloped downward away from the heater 1/2 inch (1 cm) for every 20 feet (6 meters).
• The heater may be individually vented or common vented. When venting vertically, a maximum of four heaters can
be commonly vented. When venting horizontally, a maximum of two heaters can be commonly vented.
Vent Material Recommendations
• For Category l venting: field-supplied Type B double wall vent—only or used as a continuous section passing
through the outside wall or roof or outside of the building.
• For Category I and lII venting: 4-inch OD porcelain-coated tubing or 4- or 6-inch OD heat-treated aluminized
tubing or field-supplied Type C single wall corrosion-resistant galvanized steel (minimum 26-gauge) pipe.
Vent/Combustion Air Duct Length Requirements
⚠ CAUTION ⚠
Recommended vent length is <20 feet (<6 meters). If vent length is >20 feet (>6 meters), condensation
will form in vent pipe and insulation and additional sealing measures (high-temperature silicone
at all seams) are required.
Table 11. Vent/Combustion Air Duct Length Requirements
Vent Length
Maximum Combustion Air
Duct Length*
Minimum
Maximum*
Feet (Meters)
2 (0.6) 45 (13.7) 45 (13.7)
*The total vent length + outside air duct length + any extensions to minimum heat exchanger lengths cannot exceed 65 feet (19.8 meters).
Subtract 15 feet (4.6 meters) of maximum allowed vent or duct length per vent elbow if more than two elbows are used.
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