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Draft is not a function of the appliance. Draft is purely a function of the chimney. Modern stoves and furnaces are much more airtight and efficient than those of the past, and, therefore, require greater draft. A minimum of .05" measured in water column (gauges to measure chimney draft are readily available at stove shops and are economical to purchase or rent) is required for proper drafting to prevent back-puffing, smoke spillage, and to maximize performance. Chimneysperformtwofunctions -oneofwhich is apparent: The chimney provides a means for exhausting smoke and flue gases resulting from combustion of the fuel. Secondarily, though, the chimney provides "Draft" which allows oxygen to be continuously introduced intotheappliance,sothatpropercombustionis possible. As of April 1, 1987, all wood heaters and furnaces manufactured by United States Stove Company should be installed using a factory-builtchimneythatmeetsthe "TypeHT" requirement of UL 103 (when a factory-built chimney is used). A chimney connector shall not pass through an attic, roof space, closet, floor, ceiling, or similar concealed space. Where passage through a wall or partition of combustible construction is desired, the installation must conform with NFPA 211. 7 VENTING INTO A fIREPLACE Many people may wish to convert an existing fireplace to heater use. Usually, safe connection of stovepipe to a masonry chimney requires more effortthanconnectionto a prefabricated chimney. The fireplace must be tightly closed and sealed at the damper in the flue. Good sealants are high-temperature caulking, ceramic wool, and furnace cement. Always remember to inspect themasonrychimneyandfireplace. Ifnecessary, clean the flue and smoke shelf before beginning your installation. Install the heater into the fireplace so that the system can be dismantled for cleaning and inspection. Before deciding to convert your fireplace, keep in mind that some fireplaces and existing chimneys are unsafe. They must be structurally sound, and the flue liner must be in good condition. Do not use a chimney if it is unlined (should have a fire clay tile liner to protect brickwork). Have it relined professionally. Clearances to combustibles are explained in the previous section on masonry chimneys. If you have any questions regarding the condition of the chimney, consult a qualified engineer, competent mason, or knowledgeable inspector. Many prefabricated fireplaces fall into the "zeroclearance fireplace" category. This is a factory- built metal fireplace with multi-layered construction. It is designed to provide enough insulation and/or air cooling so that the base, back and sides can be safely placed in direct contact with combustible floors and walls. Although many prefabricated fireplaces have been tested by nationally recognized organizations for use as fireplaces, they have not been tested to accept heaters. In fact, their use as such may void the manufacturer's warranty. Steel-lined fireplaces, on the other hand, can be used with heaters. These units use a 1/4-inch fireboxliner andanairchamberinconnectionwith 8inchesofmasonrytomeetcode. Theycontainall the essential parts of a fireplace, firebox, damper, throat, smoke shelf, and smoke chamber. Many of them look exactly like a masonry fireplace and must be checked closely for above requirements before installing a wood heater into them. Another method frequently used by some people is to vent the heater directly into the fireplace. This does not meet code since the heater is being vented into another appliance - the fireplace. This method should not be attempted because combustion products will deposit and build up in the firebox or fireplace. Be certain not to install a hazard in your house. You will void your warranty with this installation. CAUTION: NOT ALL FIREPLACES ARE SUITABLE FOR INSTALLATION OF A WOOD HEATER. 8 VENTING INTO A MASONRY CHIMNEY When considering a masonry chimney, round tiles are preferable to square or rectangular, as round tiles have much better airflow characteristics and are far easier to clean. Unfortunately, most North American chimneys use square or rectangular tile liners that are really designed for open fireplaces, not stoves or furnaces. Of mostimportance,second onlytooverallchimney height, is the diameter of the flue liner itself. In most instances, it should be sized to the appliance; i.e., 6" flue outlet on the appliance requires a 6" chimney. The inner diameter should never be less than the flue-outlet diameter and should never be greater than 50% larger than the appliance flue outlet. For example, do not expect a wood or coal burning stove or furnace to function properly if installed into a chimney with a flue greater than 50% more than the appliance outlet - - such as a 6" flue outlet requires a 6" diameter for optimum drafting, but can function well with an 8", but becomes borderline beyond an 8" diameter. Masonry chimneys built of concrete blocks with or without flue liners do not meet...