by Nick Gromicko, CMI® and Kenton Shepard
Pellet stoves are sophisticated combustion appliances used for home heating. Unlike wood stoves and fireplaces, pellet stoves burn small, dried, compressed pellets made from biomass products, such as sawdust, wood shavings, corn, and cherry pits. These fuels produce less ash than traditional wood logs and are more efficient sources of heat.
Requirements for pellet stoves vary by their models and can be found in their instruction manuals. Unfortunately, inspectors may not have access to the instruction manuals. These stoves must also conform to local fire and building code restrictions.
InterNACHI Inspectors may want to learn the following facts, which are generally true of pellet stoves:
- Pellet stoves are engineered so that heat is concentrated in the front, meaning that their surfaces (with several exceptions) will not get as hot as those on standard wood-burning stoves. For this reason, pellet stoves are permitted to be closer to walls and other combustibles than wood-burning stoves. Dell-Point’s “Europa 75” model, for instance, is permitted to be as close as 3 inches from side walls, and 4 inches from rear walls. Some models require as little as 1 inch of clearance from rear walls. Larger models, such as Enviro’s “Maxx,” require more clearance. Many pellet stoves are equipped with a sticker on the rear that details specific clearance requirements.
- Pellet stoves are equipped with narrower flues than wood-burning stoves. Three-inch diameter pipes made from approved materials are standard.
- Pellet stoves may vent horizontally or vertically. Vertical ventilation, while generally more expensive and conspicuous than horizontal ventilation, is less likely to result in back-drafting of smoke into the house, in the event of a power outage or component failure.
- Some manufacturers, such as Enviro, prohibit venting into flues that serve other appliances.
- High-altitude locations (above 2,500 feet) may require special venting options to provide enough combustion air.
- A pellet stove must rest on a noncombustible, stable surface (such as porcelain or stone) that is at least 3/8-inch thick.
In summary, inspectors should know that while pellet stoves appear similar to woodstoves, they are quite different.