Vertical Direct Vent System Installation
These installations utilize the heater mounted blower to draw combustion air from outdoors and uses the natural buoyancy of the heated flue products to create a thermal driving head that expels the exhaust gases from the flue. The negative draft must be within the range of
The maximum and minimum venting length for Category I appliance shall be determined per the lat- est edition of the NFGC (U.S.) and B149 Installation Code (Canada).
The connection from the appliance exhaust vent to the stack must be as direct as possible and should be the same as or larger than the vent outlet. The vent must be installed to prevent accumulation of condensate and, where necessary, have means provided for drainage of condensate. The horizontal breaching of a vent must have an upward slope of not less than 1/4 inch per linear foot from the heater to the vent termi- nal. The horizontal portions of the vent shall also be supported for the design and weight of the material employed to maintain clearances and to prevent phys- ical damage or separation of joints.
Vertical Direct Vent Termination
The exhaust vent terminal should be vertical and should terminate outside the building at least two (2) feet above the highest point of the roof within 10 feet. The vent cap should have a minimum clearance of four (4) feet horizontally from and in no case above or below (unless a four (4) foot horizontal distance is maintained) electric meters, gas meters, regulators and relief equipment. The distance of the vent terminal from adjacent public walkways, adjacent buildings, open windows and building openings must be consis- tent with the NFGC, or in Canada, the B149. Installation Code. Gas vents supported only by flash- ing and extended above the roof more than five feet should be securely guyed or braced to withstand snow and wind loads.
The vertical direct vent cap is designed for roof top mounting only. The air inlet opening MUST be installed one (1) foot above the roof line or above normal snow levels that might obstruct combustion air flow. This dimension is critical to the correct operation of the heater and venting system and reduces the chance of
blockage from snow. The vent cap must have a mini- mum 3 foot clearance from the air inlet opening.
Outdoor Installation
Outdoor models are
Care must be taken when locating the outdoor unit because the flue gases discharged from the vent hood can condense as they leave the hood. Improper loca- tion can result in damage to adjacent structures or building finish. For maximum efficiency and safety, the following precautions must be observed:
a)Outdoor models must be installed outdoors and must use the outdoor vent hood supplied by the manufacturer.
b)Periodically check venting system. The heater’s venting areas must never be obstructed in any way and minimum clearances must be observed to prevent restriction of combustion and ventilation air. Keep area clear and free of combustible and flammable materials.
c)Do not locate adjacent to any window, door walk- way, or gravity air intake. The vent must be located a minimum of four (4) feet horizontally, or four (4) feet below, or one (1) foot above such areas.
d)Install above grade level and above normal snow levels.
e)Vent terminal must be at least 3 feet above any forced air inlet located within 10 feet.
f)Adjacent brick or masonry surfaces must be pro- tected with a
g)Multiple Outdoor Vent installations require a four
(4) feet clearance between vent caps.
NOTE: Condensate can freeze on the vent cap. Frozen condensate on the vent cap can result in a blocked flue condition.
The restricted vent cap must be furnished by the heater manufacturer in accordance with its listing.
An outdoor air filter, supplied by the manufacturer is mounted on the heater.
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