Proper venting of gas appliances is important for both safety and efficiency. For a vent to operate properly, it must be the correct size and type for the appliance, and it must be installed as specified in the manufacturer's instructions.
All venting must conform to local building codes. In the absence of local codes, it should comply with the latest edition of the CGA B149 (National Standard of Canada). This standard lists the minimum requirements for safe venting performance, and specifies requirements for adequate drafting.
When designing a venting system, consult the equipment manufacturer's instructions, your propane supplier and/or your local building codes. The ability of an appliance to vent satisfactorily is determined through certification tests in accordance with ANSI standards. Appliance designs bearing the Canadian Gas Association (CGA) or Underwriters Laboratories of Canada (ULC) seals have met these standards.
VENTING OPTIONS
The following residential appliances must be vented in accordance with national codes:
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Steam and hot water boilers |
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Warm air floor and wall furnaces |
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Unit heaters and duct furnaces |
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Incinerators |
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Water heaters with input ratings over 5,000 BTUs |
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Built-in domestic cooking units identified only as vented units |
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Room heaters listed only for vented use |
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Appliances with conversion burners |
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All other appliances that have a draft hood supplied by the manufacturer |
These appliances do not have to be vented, according to CGA B149 |
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Listed ranges |
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Built-in domestic cooking ranges as listed and identified for optional venting |
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Listed hot plates |
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Counter appliances |
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Room heaters listed for non-vented use (in specified jurisdictions only) |
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Other equipment listed for non-vented use and not provided with flue collars |
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Specialized equipment of limited input, such as gas lights |
Appliance manufacturers generally offer detailed information on proper venting of gas appliances. These instructions must be closely followed as specified in the appliance installation manual, operating instructions and the buyer's guide.
The Importance of Proper Venting
All aspects of venting and ventilation systems must comply with CGA B149. A properly designed and installed appliance venting system serves these purposes:
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Directs combustion gases to the outside atmosphere |
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Protects the building structure from fire hazards due to overheating walls or other surfaces |
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Prevents damage to walls and furnishings due to the escape and condensation of combustion gases. |
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Provides for good air circulation and adequate oxygen supply for the appliance and home occupants. |
INSULATION
Appropriate insulation is as important as proper venting. Some manufacturers specify double wall pipe (UL listed type "B" and "L") to ensure adequate insulation. Built-in air space between outer and inner pipes helps keep outer pipes relatively cool. Internal spacing heads between the pipes to ensure a uniform insulating space between pipe walls. This minimizes the possibility of condensation in the pipe, or the overheating of nearby enclosed piping surfaces. Various other approaches to insulating are available. In all instances, insulation must meet the requirements of CGA B149 and Local Building Codes.
AIR SUPPLY
For proper combustion, rooms or spaces with propane-burning equipment must have a constant air supply at adequate pressure levels. Outside air is needed to replace all air that enters the chimney system through draft hoods and barometric draft regulators. Outside air is also needed to replace any other air that may be vented to the outside. Therefore, any combustion air vented to the outside must always be replaced with more outside air.
Whatever the design, combustion air supply systems must conform with the local building codes, or in the absence of local codes, with the provisions of CGA B149.
VENTING PRODUCTS
Today's mid and high-efficiency furnaces create the potential for harmful corrosives to form on the heating equipment, especially when they are horizontally vented. In order to combat this problem, manufactures now produce venting products made from non-metallic materials that are temperature tested to 480 degrees Fahrenheit, and can withstand pH levels from one to nine. One such product has earned the highest rating for flame resistance under UL Bulletin 94. Also produced are amber-coloured, transparent interior fittings made of polyethylene which allow the installer to see if the piping seals are properly fastened. This type of piping is corrosion resistant.
Type "B" bird-proof louvered vent caps are also available. They come in diameters from 3-12 inches and will also keep out rain, snow and down drafts.
All venting products should meet or exceed building codes for flame combustion resistance. When choosing this type of equipment, make sure that it is in full compliance with the terms of UL listings.
