Vermont Casting 2479 Single Venting, Fuel, Creosote, Backpuffing, Draft Testing, Negative Pressure

Dutchwest Non-Catalytic Convection Heater

for installing a different appliance 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 smoke enough to cause draft and creosote problems. Use double-wall stove pipe for longer runs.

Single Venting

Your stove requires a dedicated flue. Do not connect the stove to a flue used by any other appliance. Chim- ney draft is a natural form of energy and follows the path of least resistance. If the stove is vented to a flue that also serves an open fireplace or another appliance, the draft will also pull air in through those avenues.

The additional air flow will lower flue temperatures, reduce draft strength and promote creosote develop- ment; overall stove performance will suffer. The effect is similar to that of a vacuum cleaner with a hole in the hose. In some extreme instances, the other appliance can even impose a negative draft and result in a dan- gerous draft reversal.

Fuel

Even the best stove installation will not perform well with poor fuel. If available, always use hardwood that has been air-dried (“seasoned”) 12-18 months. Soft- wood burns more rapidly than hardwood and has a high pitch content that can result in creosote. Decayed wood of any type has little heat value and should not be used.

Unseasoned (‘green’) wood has a high moisture con- tent. Much of its heat value will be used to evaporate moisture before the wood can burn. This significantly reduces the amount of energy available to warm your home, as well as the intensity of the fire and tempera- ture of the exhaust gas. Incomplete combustion and cool flue temperatures promote creosote formation and weak draft.

You can judge the moisture content of wood by its ap- pearance and weight or use a commercially available moisture meter for an exact measurement. Unsea- soned wood will be a third heavier than dry wood. Also, look for cracks (“checking”) in the ends of the log that result from contraction as the wood dries. The longer and wider the cracks are, the dryer the wood is.

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 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. Consequently, you can

minimize creosote accumulation with an effective chim- ney 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.

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

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