Maintenance of Modern Stoves, Fireplaces, Inserts, Furnaces and Boilers
It is not always possible to generalize accurately about service and maintenance because of the differences among the categories of wood burning equipment. But, here are some suggestions for keeping your wood burner working the way it was intended to.
Test the seal on the loading door with paper money. Open the door on a cold stove, place the bill across the gasketed area of the door, then close and latch the door. Try to remove the bill by pulling. The bill should not pull out easily. If there is an area where the bill slips out easily the door seal needs attention.
The first thing to try is to adjust the door latch. Some stoves have a mechanism to adjust the door as the gaskets compact through use, and some do not. (That is something to look for when purchasing a new wood heater.)
If you can’t adjust the door, or if after adjustment the bill pulls out easily in one or more places, you will probably have to replace the door gasket(s).
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. While a very few older stoves have carefully fitted ground cast iron surfaces that seal reasonably well without gaskets, virtually all modern wood heaters use gasket material around the loading doors to seal them. Some ash pan doors also have gaskets.
You can purchase gasket cement in a small tube or tub. If you can’t find gasket cement don’t despair. You can use common silicone sealant in a caulking tube. Some have said that silicone hardens the gasket sooner than stove cement, but that’s not a clear consensus, so don’t be afraid to try it. High temperature silicone is not necessary because the temperature rating of household grade seems to work well enough.
To install the gasket, remove the door and place it on cardboard or cloth to prevent scratching of the finish. Pull out the existing gasket; on some stoves you’ll have to disassemble the door to get the gasket out. Clean the gasket groove with an old screwdriver to remove any lumps of old cement.
Clean the groove thoroughly with course steel wool so that it provides a good clean surface for the cement to stick to.
Using the cement or silicone, apply a narrow (usually 1/4″ to 1/2″ wide, depending on gasket size) bead along the entire groove. Lay the gasket in the groove without stretching or bunching it, starting on a long straight part of the groove. Cut the gasket slightly long so that the ends can be tucked into each other forming a good seal. Press the gasket into the cement.
Mount the door and test the seal. Slamming the door lightly, you should hear the muffled sound of the gasket, not metal, hitting the stove body. Test the seal with the bill.
Modern wood heaters use a clear ceramic material instead of the tempered glass that older fireplaces used. This ceramic material is usually called stove glass for simplicity. 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.
Stove glass is very expensive, but should never need to be replaced, although some stove models seem to cause etching of the glass with normal use over time. You may wish to replace it to renew the clear fire viewing.
Regular maintenance and replacing glass will require you to tighten glass fasteners. When so doing ensure that you tighten them lightly, allowing room for the glass to expand when heated.
If you crack your glass, in many cases the stove may be used for a short term while you find a replacement. Replacement glass can be cut to size by a specialty wood heating store or sweep. Alternatively, you can buy replacement glass supplied by the stove manufacturer.
Some EPA certified stoves use specially coated glass. Check your manual. If this is the case, you can buy replacement coated glass from a dealer. Coated glass has a special side facing out. Check it and ensure you are installing the right way out.
Cleaning Door Glass
Most stoves built since the mid-1980s that have ceramic glass panels in their doors also have a air-wash system. The air-wash system supplies most of the primary air to the fire through a narrow slot along the top inside edge of the glass. The objective is to have the combustion air sweep down between the glass and the fire so that soot cannot stick to the glass. Good airwash systems are remarkably effective at keeping the glass clear. When combined with seasoned fuel and good operating technique, these systems can keep the glass door clear for weeks of 24/7 operation. After a period of use, a white or grey haze forms on the glass. The haze is easily removed with a damp paper towel when the stove is cool.
Light brown stains that often form at the lower corners of the glass can be removed with a special wood stove glass cleaner by following the product instructions. Dark stains are difficult to remove and are a sign either that the stove has a poor air-wash system or the fuel is wet or the stove is being turned down too much. Smouldering fires and damp fuel are the most common reasons for dirty glass. You can work at keeping your glass cleaner by following the stove operating suggestions in our tips section. Dark stains can be made easier to remove by burning very hot for a couple of load cycles.
Do not use abrasives on door glass. Some people recommend using a razor blade to remove black stains from ceramic glass, but this will almost certainly scratch the material because it is much softer than regular window glass.
Stoves have been painted with high temperature paint since the 1970s. Good stove paint is widely available and will withstand high stove temperatures. Spray cans of stove paint can be used to touch up your installed stove to make it look like new without removing it to a shop. Let the stove cool down first. Mask those parts not to be painted and protect everything around the stove from over spray. Most stove paint dries to the touch in about fifteen minutes.
Colors are widely available too, so you can experiment by changing from traditional black to a more decorative color. How about a two-tone paint job?
Some stoves are factory enameled, finish that cannot be added later. 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.
Cast Iron Stove Rebuilding
Cast iron stoves are usually built using “tongue in groove” construction, which, while durable, may require maintenance.
The owner’s manual usually suggests breaking the stove in over time with a few fires. These increasingly hot fires melt the stove cement in the channels allowing the cement to fill every crevasse, thus ensuring air tightness.
If a cast stove is moved from its original location cracks in the cement can develop, meaning that the stove will leak air and be harder to control. If a cast stove leaks too much air, and the gaskets are in good shape, it should be torn down and rebuilt with new stove cement in the grooves.
Firebrick is used in many wood stoves to protect steel or cast iron while increasing firebox temperatures for better combustion. Modern EPA certified wood heaters often use a lighter, lower density brick for higher performance. When replacing such brick it’s important to replace with the same brick type to maintain your stove’s efficiency.
Cracked firebricks, which remain in position, do not have to be replaced immediately. The bricks in most stoves and furnaces are a standard size, which is half the size of a normal house brick. They measure about 4 1/2″ x 9″ x 1 1/4″ inches, and are referred to as firebrick ‘splits’. Standard splits can be purchased at some building supply stores, but the special low density bricks found in some EPA certified stoves must be purchased from a wood stove dealer.
Baffles in wood heaters reflect heat towards 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. Replacement parts can be ordered from stove retailers or directly from the manufacturer.
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; airborne particles should not be inhaled.
The term refractory means a material that can tolerate high temperatures and is usually in the form of firebrick or ceramic fiber. Some stoves use custom-cast refractory components for a secondary combustion chamber. These are usually white or off-white material and may be very soft board like material or a hard masonry material. In either case they should be handled gently. Avoid breathing any dust created by handling. Repair may be possible in cases of breaking in some cases. Replace when necessary with factory-supplied components.
Stainless steel air tubes are used at the top of the fire below the horizontal baffle in many modern EPA certified stoves. The intense heat in this location can cause them to sag or disintegrate in time. The tubes are removable by undoing the fastener or turning to unlock the keyed ends. Replace with factory parts and new fasteners.
Catalytic elements deteriorate over time, generally lasting 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. EPA standards dictate a six year prorated warranty, which you should be read to understand how to care for the combustor.
After a few years of use, or if you see a change in stove performance, it is a good idea to inspect the catalyst. This can usually be done without removing it from the stove. If the catalytic element looks good, is all about the same beige color and has no pieces missing, it is probably still functioning and suitable for continued use.
You can check the condition of the catalyst by watching the smoke at the top of the chimney. There will be smoke as the stove heats up but it should decrease dramatically or 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 parts in a stove may warp over time. In some cases this distortion is acceptable because it does not affect performance. In other cases, warping may allow exhaust to bypass the combustion system, producing a drop in efficiency. Warped parts should be replaced with components supplied by the appliance manufacturer.
Structural welded steel plates, such as sides, back and top, that warp may be unsightly, but provided that there’s no leakage, the appliance can continue to be used. These parts of welded steel stoves are not replaceable so if they crack or badly distort it means the body is not suitable for continued use and should be recycled.
Cast iron may warp or crack through 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.