Every season, we receive several calls from concerned stove-owners, worried that their stoves are malfunctioning and/or dangerous. The good news is that many of these problems are not actually problems at all, and merely things your stove will do from time to time. Let’s address some of the issues you may encounter in your wood stove or insert, as well as some troubleshooting steps you can take before scheduling a service call:
Some change in the color of your stove can be normal. If you have a stove with porcelain enamel cladding, the enamel may darken as it heats up, then return to its original color as it cools (the bordeaux enamel from Vermont Castings, for example, darkens to a particularly vibrant deep red when the stove is going).
Some wood-burning appliances have a stainless steel firebox, rather than the traditional firebrick or refractory cement. Although this lighter, thinner firebox will transmit heat to your room faster, the lighter constructions means it’s also subject to a certain amount of warping and discoloration (which looks like rust, but doesn’t damage the material of your firebox). During a chimney sweep and inspection, we will inspect any warping or discoloration in the firebox, and assess whether or not it’s severe enough to cause a problem.
Sometimes, problems with draft can cause the smoke from your wood stove to come back into the room, rather than going up the flue as it’s supposed to. While a blockage in the flue or the cap may be responsible, there are some steps you can take before scheduling a chimney cleaning.
The most frequent cause of cool, smoky fires is wet wood, so the very first thing to check is your firewood supply. Firewood that has been properly seasoned (cut, split, stacked to allow free air circulation, and left in the sun and air for at least 9 months) has a moisture content between 15-20%. Dry wood will have cracking and splitting at the ends, as shown in the picture next to this paragraph. Also, if you hit two pieces of firewood against each other, wet wood will make a dull “thud,” whereas dry wood will make a hollow, resonant “thunk.” While this isn’t as scientific or precise as a moisture meter, it will give you a reasonably good idea of how dry your firewood is. Another way to check the quality of your firewood is to look at the smoke coming out of your chimney. At the start of a good fire, the smoke coming out of the chimney will be white; after the fire is fully established, you shouldn’t see very much smoke at all, only a slight distortion from the heat radiating out of the top of the chimney, and a little bit of translucent steam.
Sometimes, the weather outside can be the problem. Damp, heavy air provides more resistance to draft, and it will be harder for your chimney to get a good draw at these times. And a good draft requires a difference of temperature between the indoor and outdoor air, as the warm air inside your stove is drawn up the flue towards the colder air outside. If the temperature outside is above 55°F, this temperature difference will not be high enough, and it’ll be hard to get a good draft going. You can help your chimney out by pre-heating the flue (holding a burning rolled-up newspaper as near to the flue opening as you can get, for example), but some weather conditions will always interfere with wood stove performance.
Depending on where in your house your stove is installed, some problems with draft may be unavoidable. All homes have a neutral pressure plane, above which air is trying to leave the house, and below which air is trying to get into the house. Many basement fireplaces, unfortunately, are in negative pressure planes, which means they can sometimes experience backdraft from the flue connected to an upstairs appliance. There are steps we can take to reduce this backdraft, like extending one flue so that the smoke isn’t as readily pulled back into the house, but it’s an unfortunate reality that your wood stove may not perform equally well in all parts of your home.
Uncommon Stove Problems: Contact a Professional
While many stove issues are comparatively minor, there are some situations that require the immediate attention of a certified wood service professional. If the wall in front of your chimney, or surrounding the thimble where your stove plugs into the wall, becomes hot to the touch (some warmth is ok, but the wall shouldn’t be too hot to touch), or begins to discolor, stop using your stove immediately, and call your local certified stove technician. If the wall is hot or discolored (turning brown around the thimble, for example), this indicates that pyrolysis is occurring, and often that you have had (or are having) a chimney fire. We inspected just such an installation last year; the flue liner showed evidence of multiple chimney fires, and the wood studs in the wall were beginning to char around the edges. We removed the damaged parts and relined the chimney, but this could easily have started a house fire if left unresolved.
The bottom line is that your wood stove is a complex system, and it’s important to pay attention to how it’s working. If you notice something unusual, don’t panic! There will always be variations in the way each stove performs in different environments, and most of these variations aren’t cause for concern. But as always, if you’re unsure, feel free to call your friendly neighborhood Wooden Sun technicians, and we can discuss your stove problems with you.
Have a safe, warm, and happy fireplace and stove season!