Proper Maintenance

Proper maintenance is crucial to ensure that your wood heating appliances continue to function safely and efficiently. Here, we are once again focusing on wood stoves, since they are the equipment most easily maintained by homeowners. Boilers and pellet stoves must be regularly maintained, as well, but it is usually best to set up a maintenance schedule with a professional service person, such as your local retailer. This may be true in the case of your wood stove, but here we provide basic information on some simple maintenance most homeowners can do themselves, as well as some of the main areas to look for wear or damage before every heating season in order to keep your wood stove working the way it was intended to.

Keep in mind that it is not always possible to generalize accurately about service and maintenance because of the differences among wood stoves. If you have any questions on specific procedures, contact your stove's manufacturer or your local retailer.

In order to work at maximum efficiency, wood stoves need to retain their air tightness. Some models dating before around 1991, when the EPA Phase II certifications went into effect, had the problem of being too airtight. This allowed their operators to damp them down too far, thus suffocating the fire and creating an inefficient burn that could not only accumulate creosote (incompletely combusted oils from the wood) in the pipe but also lead to high levels of particulate emissions (smoke). EPA Phase II-certified wood stoves have various features that draw in air for a more complete combustion of the gases created as the wood is heated up. If not properly maintained, however, these stoves can form leaks and other problems that can drop their efficiency considerably.

Gaskets

All air-controlled appliances have a method of reducing random leaks into the firebox so that air only enters the stove through the air control. Virtually all modern wood heaters use gasket material around the loading doors to seal them. Some ash pan doors also have gaskets, as do viewing windows.

Look for obvious wear or areas where the gaskets have come loose. Conduct the following test to check the tightness of the seal on the loading door, even when there is no obvious wear: When the stove is cold, open the door and place a dollar bill across the gasketed area of the door, then close and latch the door. The bill should not pull out easily. If there is an area where the bill slips out easily, the door seal needs attention.

Some stoves have a mechanism to adjust the door, so try this first. If the door is not adjustable, or if after adjustment the bill pulls out easily in one or more places, you will probably have to replace the door gasket(s).

Most gaskets are 3/8" to 1" thick and may be cut to length from a large reel or packaged by the manufacturer in a kit specifically for your stove. Cement to hold the gasket in place is often included in kits, or it can be purchased in a small tube or tub.

If your wood stove has a viewing window, it must also be sealed tightly to the door to prevent air leaks. This is usually done with a flat woven gasket with adhesive on one side. These gaskets tend to not require replacement as often as door seals, but if you see brown streaks on the glass coming in from the door frame, it's time to replace the gasket.

Glass

Modern wood stoves use a clear ceramic material instead of the tempered glass that older fireplaces used. It will not break with heat generated by wood burners, but it can break if the fasteners are over-tightened or if it is struck hard with a poker or piece of wood. If the viewing window is cracked, it needs to be replaced. Contact your stove's manufacturer or local retailer for a replacement window.

Firebrick and Baffles

Firebrick is used in many wood stoves to protect steel or cast iron while increasing firebox temperatures for better combustion. Firebrick can become cracked over time. When replacing firebrick, be sure to use the same brick type to maintain your stove's efficiency. Again, contact your stove's manufacturer or local retailer to ensure you use the correct kind of brick.

Baffles reflect heat toward the fire, increase the length of the flame path, and create a chamber for secondary combustion, all of which are essential for clean burning and high efficiency. They may be steel, cast iron, firebrick, ceramic fiber board, or a combination of these materials. Since they are exposed to flame on both sides, baffles get very hot and may fail over time.

Removal and replacement is usually detailed in the owner's manual. Some horizontal baffles include a ceramic fiber blanket, which usually lies on top of the baffle. During maintenance and cleaning, this blanket must be pressed down flat so that it doesn't block the area above the baffle where the exhaust flows. Ceramic fibers should be treated like asbestos; take care not to inhale airborne particles.

Some stoves use special refractory material, which is usually made of firebrick or ceramic fiber. When handling this material, do so gently and avoid breathing any dust. Replace when necessary with factory-supplied components.

Air tubes

Stainless steel air tubes are used at the top of the fire below the horizontal baffle in many EPA-certified stoves. The intense heat in this location can cause them to sag or disintegrate over time. The tubes are removable by undoing the fastener or turning to unlock the keyed ends. Replace with factory parts and new fasteners.

Catalysts

Catalytic elements generally last 12,000 hours or about six years, provided they are cared for properly. Your owner's manual gives directions on cleaning, inspecting, and replacing them.

Inspect the catalyst after a few years of use, or if you see a change in stove performance. This can usually be done without removing it from the stove. If the catalytic element isn't chipped, cracked or crumbling, is all about the same beige color, and has no pieces missing, it is probably still functioning and suitable for continued use.

You can also gauge the condition of the catalyst by watching the smoke at the top of the chimney. There may be a little smoke as the stove heats up but it should disappear completely when the catalyst is engaged.

Cleaning the catalyst involves removal from the stove and gentle vacuuming and/or sweeping with a soft brush. If a catalytic element has pieces missing or if the coating shows signs of flaking, replacement is the only option.

Warped steel parts

Interior steel stove parts may warp over time. In many cases, warping allows exhaust to bypass the combustion system, producing a drop in efficiency.  Warped parts should be replaced with components supplied by your stove's manufacturer.

Structural welded steel plates, such as sides, back, and top, can also warp. These parts are not replaceable so if they crack or badly distort it means the body is not suitable for continued use and should be recycled.

Cracked castings

Cast iron may warp or crack over time, but it's usually a sign of severe stress caused by overfiring, often due to leaks in joints between castings. Interior parts may be replaced with manufacturer-supplied parts. Exterior parts can be replaced during a complete teardown and rebuilding.

Paint and Enamel

Spray cans of stove paint can be used to touch up your installed stove to make it look like new without taking it to a shop. Be sure to use only high-temperature paint made specifically for wood stoves, and always let the stove cool down before painting it. Some stoves are factory-enameled. Enamel is very tough, even under heat stress, but can be damaged by chipping. Touch-up and enamel filler kits are available from stove dealers. 

Heating with Wood resources developed by Guillermo Metz, Renewable Energy & Green Building Program Coordinator at CCE-Tompkins 

Last updated August 20, 2020