Vermont Casting 1610CE Single Venting, Creosote, Fuel, Back-puffing, Draft Testing, Conclusion

Defiant 1610CE Non-Catalytic Woodburning Stove

they must turn, it leaves some pipe in the room for heat transfer, and it gives you long-term flexibility for install- ing a different stove without relocating the thimble.

There should be no more than eight feet of single-wall stove pipe between the stove and a chimney; longer runs can cool the exhaust enough to cause draft and creosote problems. With prefabricated chimney, bring it down to six to eight feet from the stove. With a masonry chimney, arrange the pipe so that it turns into the chim- ney within eight feet of the stove.

Single Venting

Each ‘airtight’ stove requires its own flue. If an airtight stove is vented to a flue that also serves an open fire- place, or a leakier stove, it’s easier for the chimney draft to pull air in through those channels and performance of the stove suffers. Imagine a vacuum cleaner with a hole in the hose to understand the effect here. In some cases the other appliance can even cause a negative draft through the stove, and result in a dangerous draft reversal.

Creosote

Creosote is a by-product of slow wood-burning. It’s an organic tar that can condense in the flue if it is present in the exhaust, slow-moving, and cools to less than 290°F (130°C). Condensed creosote is volatile, and can gener- ate chimney fires if it gets hot enough. All the features that affect chimney draft also affect creosote condensation

-so use whatever combination of installation features and operational steps that will encourage good draft and mini- mize creosote production.

Because letting the exhaust cool off and slow down is one of the keys to creosote accumulation, it makes sense to line a chimney to match the stove’s outlet size, for safety reasons as well as performance. Consult a qualified installer and check local and national codes for recom- mended chimney sizing.

Fuel

Even the best stove installation will not perform well with poor fuel. The best fuel is hardwood that has air-dried 12- 18 months. Softwood burns, but not as long as hardwood. ‘Green’ wood has a lot of moisture in it; it will burn, but some of the heat potential is used to boil the extra mois- ture from the wood. This reduces the amount of heat that reaches your home and can contribute to a creosote prob- lem. There are moisture meters available for firewood; you can also judge your wood by its appearance and weight. If you get it green, lift a piece and get a sense of its weight; it can lose a third or more of its weight as it dries. Also look at the ends of a log; as it dries it shrinks and often cracks. The more weathered and cracked a piece is, the drier it is.

Dry wood burns readily with a good chimney draft. But with modern stoves, wood can be too dry and too vola- tile. Smoke and combustible gases can ‘gas out’ from the wood quickly and densely enough to overload the combus- tion system. If you hear a rumbling or roaring noise (like a

propane torch) from the stove, that is a sign that the stove is overfiring.

Back-puffing

Back-puffing results when the fire produces volatile gases faster than the chimney draft pulls them out of the firebox. The gases back up in the firebox until they are concen- trated enough and hot enough to ignite. If your stove back- puffs, the stove needs to cool down. You should open the damper to let the smoke rise to the flue more quickly, allow more air into the firebox, avoid big loads of firewood and check that the wood moisture is not too low.

Draft Testing

An easy way to test your chimney draft is to close the stove’s damper, wait a few minutes to let the airflow stabi- lize, then see whether you can vary the strength of the fire by swinging the air control open and closed. Results are not always instant; you may need to wait a few minutes for a change in the air control setting to have an effect on the fire. If there’s no change, then the draft isn’t strong enough yet to let you close the damper, and you’ll need to open it for awhile longer and manage the fire with the air inlet until the draft strengthens. If you keep track of your burning habits and relate them to their effects on the stove’s opera- tion, you’ll be rewarded with good performance and a safe system.

Negative Pressure

Good draft also depends on a supply of air to the stove; a chimney can’t pull in more air than is available to it. Sluggish draft results when a house is tight enough to prevent the ready flow of air to the stove, or by competition between the stove and other equipment that sends indoor air outside - especially power-driven equipment like range hoods, clothes dryers, etc. If the chimney draws well with all other equipment turned off (or sealed, in the case of fireplaces and/or other stoves), then you simply need to be careful with timing the use of the other air consuming equipment. If you need to crack a nearby window or door to enable the chimney to flow well, it may be a good idea to install an outside-air intake to bring combustion air di- rectly to the stove. An outside air kit is available to connect the stove directly to a source of outdoor combustion air.

In many cases, local or national codes require the installa- tion of permanently open air vents, particularly with larger appliances (i.e. above 5 kW). Refer to these codes to determine specific requirements for your installation.

Conclusion

Wood-burning is an art rather than a science. Once the stove and chimney system are in place, you can only vary your technique, mostly your timing, to achieve good results. If you keep track of your burning habits and relate them to their effects on the stove’s operation, you’ll be rewarded with good performance and year of reliable heat- ing.

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