Chimney Connectors and Chimneys
Draft
Draft is widely misunderstood. It is important that you, the stove operator, realize that draft is a variable ef-
fect, not a given quantity. Stoves and chimneys do not have draft, yet draft is the key to your stove’s performance.
Draft is a force, produced by an operating stove and the chimney to which it is attached. It is created by hot gases rising up the chimney, creating a pressure dif- ference between the inside of your home and the outside air. It continually moves fresh combustion air into the stove, and hot exhaust gases out of the stove; without this con- stant flow, the fire will go out.
Other factors, such as barometric pressure, winds, the air tightness of the home, the total inside chim- ney volume, chimney height and the presence of vent- ing devices such as exhaust fans also play a role in maintaining an adequate draft. Low barometric pres- sures, super insulated homes and exhaust fans can reduce draft; winds can play havoc with draft; and too large or too small a chimney volume can cause reduced draft due to the excessive cooling or not enough room to vent exha ust gas es quic kly. Introducing outside air directly to the stove may help remedy a low draft prblem. Some signs of inadequate draft are smoking, odor, difficulty in maintaining the fire, and low heat output. Overdraft can be caused by a very tall chimney even if it is the recommended size, and can cause overfiring of your stove. Signs of an overdraft include rapid fuel consumption, inabil- ity to slow the fire, and parts of the stove or chimney connector glowing red. It is important that you fol- low the chimney guidelines in this manual, including size, type, and height to avoid draft problems.
Other causes of poor ventilation or draft are icing, exhaust fans, a blocked outside air inlet, and room air starvation. If your stove is sluggish and you get occa- sional odor, check these possibilities and increase the air flow in your home.
When installed and operated according to this manual, the Exception will produce enough hot gases to keep the chimney warm so that adequate draft is maintained throughout the burn cycle.
Chimney Connectors
In general, following these guidelines will en- sure compliance with all national and provincial codes; prior to beginning your installation, check with your lo- cal building code official to check on additional local regulations which may influence the design and place- ment of your venting system.
The Harman Exception may be installed with a minimum of (150 mm) 24 gauge chimney connector pipe. Size of the connector should correspond to the size of the flue collar opening. Do not use makeshift compromises. No part of the chimney connector may pass through an attic or roof space, closet or other concealed space, or through a floor or ceiling. Whenever possible, avoid passing the connector through a combustible wall; if you must, use an approved wall pass-through, described later in this section.
Assemble the connector beginning at the flue col- lar, with the crimped ends pointing towards the stove (to
keep debris and creosote flakes inside the system). Each joint, including the one to the stove’s flue collar and the
one to the chimney itself should be secured with at least three sheet metal screws. Screws may be a maximum of 3 inches apart. A 1-1/4" (30 mm) overlap is required at each joint, including the flue collar attachment. No more than two 90 degree elbows should be used, and the total length of connector should not exceed 10 feet (3 m). All horizontal runs of connector must have a minimum up- ward slope of 1/4"(6 mm) per foot (20 mm per meter).
Wall Pass-throughs
Occasionally it is necessary to pass the chimney connector through a combustible wall to reach the chim- ney. Depending on your local building codes, and the per- tinentprovincial ornational codes, there are several choices for accomplishing this safely. Before beginning your in- stallation, contact local officials, and also the chimney con- nector and chimney manufacturer forspecific requirements.
Canada. Three methods are approved by the Cana- dianStandards Association. The diagram shows one method requiring an 18"(450 mm) air space between the connector and the wall. It allows use of one or two covers as described in the diagram. The two other methods are described in detail in the current issue of CAN/CSA B365, the national standard.
United States In the U.S., the national code is NFPA
211.While many localities adopt this standard, be sure to check with local authorities before beginning your installa- tion.
The NFPA (National Fire ProtectionAssociation) per- mits four methods for passing through a combustible wall. A commonly used method to pass through a wall directly to a masonry chimney is to clear a minimum 12"(300 mm) around the entire chimney connector, and fill it with brick masonry which is at least 3.5"(90 mm) thick. A fireclay liner, mini- mum 3/8" (9 mm) wall thickness must run through the brick wall to the chimney liner (but not beyond the inner surface of the liner). It must be cemented in place with refractory ce- ment. This method is illustrated. For details on the other three options, refer to the most recent edition of the NFPA
