Vermont Casting 2477CE manual Creosote, Backpuffing, Draft Testing, Negative Pressure, Conclusion

Creosote

Creosote is a by-product of low-temperature stove operation, weak draft, or both. It is a tar that results when unburned gases condense inside the flue sys- tem at temperatures below 143° C (290˚ F). Creosote is volatile and can generate a chimney fire. All of the installation characteristics that adversely affect chimney draft also promote creosote condensation. Conse- quently, you can minimize creosote accumulation with an effective chimney design and the use of operational techniques that encourage good draft and complete combustion.

Inspect your chimney frequently and clean it whenever accumulation exceeds 1/4”.

Backpuffing

Backpuffing is a condition that results when the draft is too weak to pull flue gases out of the chimney system as fast as the fire generates them. Volatile gases build up within the firebox until reaching a density and tem- perature at which they ignite. With this ignition, you may hear a muffled popping sound and see a bit of smoke forced out of the stove.

This condition is most likely to occur in the Spring or Fall when moderate outdoor temperatures and low intensity fires produce weak draft. If your stove back- puffs, open the damper to let the smoke rise to the flue more quickly. Also, open the air inlets to induce a livelier fire and speed airflow through the stove. Avoid large loads of firewood at one time. You should always see lively, dancing flames in the firebox; a lazy, smoky fire is inefficient and will promote draft problems.

Draft Testing

An easy way to determine whether your chimney draft is strong enough is to close the stove damper, wait a few minutes to let the airflow stabilize, and then test whether you can vary the strength of the fire by swing- ing the air control open and closed. Results here are not 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 is no change, the draft is not yet strong enough to let you close the damper. You will need to open it for a while longer and manage the fire with the air inlet until the draft strengthens.

Keep a record of your operating habits and relate them to their effects on the stove’s function. You’ll be reward- ed with safe and efficient performance.

Dutchwest Non-Catalytic Convection Heater

Negative Pressure

Good draft also depends on a sufficient supply of air to the stove. The chimney can’t pull in more air than is available to it. Sluggish draft can be caused by a house that is tight enough to prevent the ready flow of air to the stove, or by competition between the stove and other appliances that vent indoor air to the outside; i.e., exhaust fans for range hoods, clothes dryers, bathroom fans, etc.

If the chimney draws well when all such equipment is turned off (or sealed, in the case of fireplaces and/or other stoves), you need to be attentive in timing the use of the other appliances. If you need to crack a nearby window or door to enable the chimney to pull well, you should install an outside-air intake to bring combustion air into the room.

In many cases, local or national codes require the installion 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

Woodburning is more an art than a science. Art includes technique; and since installations, homes, and fuel vary, the stove operator must also vary technique, (mostly timing), to achieve satisfying results. Over time, you will become familiar with the features of your particular installation; you will be able to identify cause and effect in a variety of seasonal circumstances, and adapt your operating habits to changing conditions.

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