The airflow behind the shield is critical for its success. Not to mention pellet pipe is very toxic when heated to wood stove temperatures. Connect pellet pipe to a wood stove, and the manufacturer's rated clearances are no longer adequate. Pellet pipe is rated for much lower temperatures that wood stoves produce, so the clearances are calculated assuming those lower temperatures. For instance, if you use pellet pipe instead of proper Class A chimney pipe to penetrate your roof, and you follow the manufacturer's suggested clearance to combustibles, you'll create a dangerous clearance violation. You could use your wood stove with no problems for months or years until one day, your wall catches fire from the inside without warning.Ĭheating clearances can also be caused by using improper materials. Sometimes pyrolysis is visible as discoloration or charring on the surface of combustibles, but sometimes the pyrolysis can occur inside a wall. But you won't always be able to see it.Ĭlearance violations are an especially dangerous problem because they often don't cause a fire immediately. If you observe potentially combustible materials around a stove discoloring, that can be an indication that pyrolysis is occurring. To be safe, exposed combustible materials around the stove should never exceed 117 degrees F over ambient temperature, and unexposed areas (under the hearth, for example) should never exceed 90 degrees F over ambient. After months or years of repeated heating, a surface that "hadn't had a problem yet" can spontaneously burst into flames. As material is repeatedly heated, it deteriorates on a molecular level and its autoignition temperature begins to drop in a process is called pyrolysis. In most cases, clearance violations will not cause a fire immediately. A spark is not required to start a fire, just heat, fuel, and oxygen. Combustible materials that are too close to the stove can heat up past their autoignition temperature, and catch fire. Read about building a masonry heat shieldĬlearances are important because wood stoves get very hot while in operation.Read about building an insulated heat shieldĭistance to Combustibles with a Masonry Heat Shield (1/3 reduction).Read about building an attached heat shieldĭistances to Combustibles with an Insulated Heat Shield (1/2 reduction).Read about building an air-cooled heat shieldĭistances to Combustibles with an Air-Cooled Heat Shield Attached to Stove(1/2 reduction).18" from the top of the stove to the ceiling.36" from the top of the stove to the ceilingĭistances to Combustibles With an Air-Cooled Heat Shield on the wall or pipe (2/3 reduction).The rules in NFPA-302 are less detailed than NFPA-211, so we suggest following NFPA-211 standards unless you're installing on a boat.) Dwarf Stove Clearance Requirements Distances to Combustibles Without Shielding (Note: NFPA-302 is the standard for boats, which is a bit different from the rules outlined in NFPA-211 and this article. NFPA-211, the industry standard for wood stove installations, describes three different types of heat shields. It's critical that heat shields are designed properly, and that rated clearance reductions for the type of shield are followed. Wood stove clearances cannot be eliminated entirely, but they can be reduced significantly by using a properly constructed heat shield. But cheating on clearances can create a very dangerous situation. A properly installed and maintained wood stove can be one of the safest appliances in your home. In addition to using proper materials, adequate clearances are one of the most important safety features of any wood stove installation.
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