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Two Stage Unitary Range
DU/DUH-LT210_10152019al
VENTING AND COMBUSTION AIR DUCTING
General Requirements
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Refer to the National Fuel Gas Code, ANSI Z223.1 (NFPA 54) in the US and CSA B149.1 and B149.2 Installation
Codes in Canada, as well as all local requirements for general venting guidance.
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DU/DUH Infrared Heaters may be installed vented or un-vented.
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DU/DUH Infrared Heaters may be vented horizontally or vertically using conventional venting materials.
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This series of heaters are considered a Category I appliance for vertical venting and a Category III appliance
for horizontal venting.
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If heater is to be vented horizontally, the vent from building must:
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Be not less than 7' above grade when located adjacent to public walkways.
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Terminate at least 3' above any forced air inlet located within 10'.
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Terminate at least 4' below, 4' horizontally from or 1' above any door, window, or gravity inlet into any
building.
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Be located at least 12" (30cm) from any opening through which vent gases could enter a building.
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Extend beyond any combustible overhang.
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Be installed at a height sufficient to prevent blockage by snow.
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Optional outside air supply may be directed to the heater horizontally or vertically.
Un-Vented Operation
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Requirements for combustion air supply and dilution air vary by jurisdiction, building type and specific
installation details. See local codes for guidance. In general, fresh air ventilation must be provided to the
building space at 4 cfm per 1000 BTU/hr in the US (3 cfm per 1000 BTU/hr in Canada).
•
Optional outside air supply is not recommended for un-vented heaters due to possible pressure imbalances
in the building space.
Ensure that minimum combustible clearances are maintained for un-vented heaters. Refer to Table 2, for required
clearance dimensions.
IMPORTANT
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Maximum total vent length allowed for any model heater is 30' (9m).
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Maximum total fresh air inlet duct length allowed for any model heater is 30' (9m).
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Total of vent length plus outside air supply duct length cannot exceed 50' (15m). for any heater
with minimum heat exchanger length.
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If condensation in the vent pipe or outside air supply duct is a problem, shorten or adequately
insulate the section.
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Install a minimum 18" (30 cm) straight length of duct for air intake or vent before any Tee or
elbow.
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Do not install any elbow or 45° fitting to bring vent lower than the horizontal tube system
Note: The above stated requirements assume a maximum of 2 elbows in the total
combination of vent and air supply duct. Subtract 5' of allowable length for each elbow if 3
or more elbows are used.
Summary of Contents for DU-100
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