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8.7 Unvented Operation Tube
Termination
Turndown type vent terminal with a screen must be
installed at the exhaust end of the tube. Vent terminal
design shall not incorporate backdraft flap.
FIGURE 23: Tube Termination
8.8 Length Requirements
Minimum vent length allowed is 2 ft (0.6 m). Maximum
vent length allowed is 45 ft (13.7 m). Maximum outside
air supply duct length allowed is 45 ft (13.7 m).
The total vent length, plus outside air duct length,
plus any extensions to minimum heat exchanger
lengths, cannot exceed 65 ft (19.8 m).
Vent length should be limited to less than 20 ft (6
m). If using vent lengths greater than 20 ft (6 m),
condensation will form in the vent pipe. Insulation
and additional sealing measures (high temperature
silicone at all seams) are required. Optional heat
exchanger beyond minimum lengths is considered as
vent length for length determination.
Subtract 15 ft (4.6 m) of maximum allowed vent or
duct length per vent elbow if more than two are used.
8.9 Vent Material Recommendations
Vent recommendations:
1. Heat treated aluminized tubing 4 in. (10 cm) O.D.
Heat treated aluminized tubing 6 in. (15 cm) O.D.
2. Single wall pipe (Type-C) that is corrosion
resistant galvanized steel, minimum 26 ga.
(Supplied by others)
3. Double wall vent (Type-B). For Category l venting
only or used as a continuous section passing
through the outside wall, roof, or outside of the
building.
Note:
4 in. (10 cm) O.D. heat treated aluminized
tubing and 6 in. (15 cm) O.D. heat treated aluminized
tubing are equivalent to single wall corrosion
resistant flue pipe.
Summary of Contents for IRH
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