This wood stove installation guide provides the information you need to safely install a wood stove in your home. (Please refer to the wood stove diagram in the image library.)
In the eyes of the soul, the tongue of flame from a clean pine tree evokes more than just temperature. What followed was romance, economy, family, independence, and a simpler life—or at least the image of toasted marshmallows. In many ways, burning wood is a symbol of many things that we value in our rural lifestyle. However, just like all the fun brought by our participation in livelihoods, wood heating also bears its responsibilities and responsibilities.
Woodstove installation is not a trivial task. Without a group of self-sacrificing friends and/or stove lifts, lifting a 500-pound piece of metal and masonry is likely to win you a season pass for a chiropractor. Without the necessary sheet metal processing tools, it is easier to wrap your fingers with bandages than custom-made stovepipe tubes. Without proper precautions, the lives of you and your family will be at risk of fire.
You can expect to pay at least $50 plus materials for a professional chimney sweep or wood stove shop to install the wood stove for you. Considering the expertise and labor involved, this may be a good deal. Of course, you may want to do this work yourself. Maybe you like the challenge and self-satisfaction of your own installation. Maybe your local wood stove dealer became the fleeting victim of these oil gluts. Or, you may just move the stove from one room to another.
Whether you intend to observe or participate, there are many things to know. Because no two wood stove installations may be the same, no one can provide a blueprint to guide you.
Rare installation can be as simple as putting down the stove and adding a section of prefabricated stovepipe. However, more often, it is necessary to have insulation to protect walls and floors, custom-length stovepipes, factory-built chimneys, or perhaps even perforations in masonry chimneys to connect stovepipes. In addition to these themes, there are also the complex issues of zero-clearance fireplaces and the construction or reconstruction of masonry chimneys. We will take you to the last boundary of the underworld, but not further. Even a six-page journey is fair, so let's move on.
Asking the paper pusher wants to know
When adding a wood stove to your home or office, there may be three officials who want to learn about and participate. Your construction officer may need to obtain a permit to install a stove, especially if you are installing a factory-made chimney through a wall or floor. Different regions have different building codes, so you need to know what your officials do and what they are not allowed to do. Don't repeat the mistake of a Californian we know. He installed a chimney on the second floor and roof of his new home-just to allow the inspector to ask it to go through a wall and climb up from the outside of the house. As a general rule, any installation details provided with the furnace and approved by Underwriters Laboratories (UL) take precedence over building codes; if there is no UL guideline, please follow the National Fire Protection Association (NFPA) recommendations and current codes.
In some areas, the fire chief may have the authority to inspect and approve all wood stove installations. Call your local fire department to learn about any relevant regulations. (In any case, firefighters are almost always willing to come out to inspect your wood stove and inform you of any dangerous situations.)
Finally; contact the agent who handles your homeowner's insurance. Many policies now have special regulations on wood-burning appliances. The wording is sometimes very particular about the type of chimney covered, and often mentions the presence of a UL plaque on the heater. Many insurance companies require the fire chief’s approval before they can underwrite a home equipped with a wood stove. Failure to notify the company and comply with the terms of the policy may invalidate your coverage.
The smallest steel and cast iron wood stove may weigh only 200 pounds-a burden that two people can bear without hernias. But most of the larger wood burners available today are much heavier. The correct tool for moving heavy wood stoves is the stove lift (Figure 1). It is similar to a trolley, but heavier, with deeper blades and a hydraulic lift, so you can lower the heater from the truck to the ground or raise it to the height of the fireplace. You can’t find a stove lift at your local tool rental store, but you may be able to persuade a wood stove dealer to rent a stove lift from you.
In addition, borrow or rent a heavy-duty trolley weighing at least 500 pounds. Then take out everything that can be taken out of the stove.
A stove lift or trolley will only bring the heater closer to where you want it. The last few feet will have to be handled with brute force or skill. If the latter sounds more attractive, prepare six 3/4-inch to 1 1/2-inch water pipes to roll the stove (Figure 2). (The PVC is strong enough to not damage the surface.) Use pipes, just like the Egyptians used logs to move huge pyramid blocks: lift up one edge of the stove and roll the pipe underneath. Put the stove on one tube so you can put another underneath. Then roll the device to move the tube from back to front when the tube pops out.
A well-designed and well-maintained chimney is a prerequisite for any safe wood stove installation. The flue must be made of suitable heat-resistant materials, must be separated from combustibles by an appropriate prescribed distance, must be leak-proof, and must have the correct diameter and height. Based on the inspection of these factors, you must decide whether to use the existing chimney as is, repair it, or abandon and install a new chimney.
Is it the right size? Measure the size of the top chimney and calculate its cross-sectional area. The regulations prohibit the connection of wood stoves to chimneys with a cross-sectional area less than or greater than three times the furnace outlet. Forewarning: Masonry chimneys designed for fireplaces may cause problems for wood stoves. The cross-sectional area increases rapidly as the size increases—the area of an 8-inch diameter flue is almost twice that of a 6-inch diameter flue—and fireplaces usually have larger chimneys. The attached chart summarizes the maximum chimney size for common exits.
Remember, these are the maximum values. In the guide, bigger is not better. Because excess chimney capacity slows down the smoke and cools it down, a chimney that is too large will reduce ventilation and increase the accumulation of creosote. Most experts recommend that the cross-sectional area of the chimney should not exceed twice the cross-sectional area of the outlet, and they think that it is ideal to be equal or only slightly larger.
The chimney must also be high enough. A tall chimney is more attractive than a short chimney, and 12 feet from the chimney connector to the top is a practical minimum. In addition, the top of the chimney must be at least 3 feet higher than the roof and at least 2 feet higher than any part within 10 feet of the building (Figure 3).
Existing masonry chimney. Any masonry chimney used for ventilation of wood stoves must be lined-usually clay flue bricks, refractory cement mortar should be used at the joints, and a 1/2 inch air space should be separated from the stone, brick or block (image 3). If there is a lining, please check if it is in good condition. There should be no signs of chipping on the inner surface. Likewise, the external masonry and joints should be intact.
Some further regulations regarding masonry chimneys used for wood stoves: The walls of the structural chimney must be at least 4 inches thick (if made of brick) and at least 12 inches thick (if made of stone). Solid 4-inch cement blocks are allowed, but hollow blocks are not accepted. The internal chimney must be at least 2 inches away from any combustible materials, and there must be 1 inch of space between the external chimney and the house. In both cases, the air space must have fireproof panels of non-combustible material (such as at least No. 26 metal) no more than 1/2 inch thick (Figure 3). Only one device can be connected to the flue, all other openings must be sealed. Ideally, the only other penetration of the lining would be a low-confinance clean door.
Well, let's be honest. It is unlikely to find an existing chimney that meets all these criteria. There are approximately 20 million chimneys in the United States serving wood-burning appliances, and experts estimate that at least half of them are unsafe. How come you behave so badly? The fireplace chimney is not designed to cope with the pressure of a strong chimney fire caused by the large amount of creosote deposited in a controlled burning wood stove. Therefore, with the increasing understanding of the problems caused by wood stoves, the chimney construction guidelines have also changed. For example, the 1-inch airspace requirement for external chimneys is a new NFPA change.
Change the lining. What would you do if your chimney is not suitable for use as a wood stove? If the chimney is defective because it is too large, lacks a lining, or is poorly repaired, you can choose to replace the lining. There are two basic methods, each with many variations. These are not do-it-yourself systems, so you can only use those products provided by professionals in your area. The most common type is a stainless steel tube—usually a special spiral-wound corrugated tube—surrounded by insulating material (Figure 4). Masonry linings, in which hot concrete is poured around the removable formwork or lowered in the prefabricated part, are becoming more and more popular because they increase the strength of the aging chimney and resist thermal shock well (Figure 5). Both methods have a good durability record, although masonry linings are better established and have been used in Europe for more than 30 years. So far, the cost of stainless steel systems has generally been lower. In any case, expect to pay between $25 and $50 per foot, depending on the details of the job. For this price, you will get a safe chimney with a good draft and very little creosote accumulation.
Insulated metal chimney. If you encounter a defective masonry chimney, another option is to abandon it. You can install a factory-made insulated metal chimney, which costs about the cost of relining. These are durable stainless steel systems with prefabricated wall, floor and roof "passages". They can usually pass combustibles within 2 inches, so depending on the layout of your home, it may not be difficult to install one between the wall column or ceiling joist and the rafters.
There are three basic types of factory chimneys: triple wall, air insulation; double wall, solid insulation; and double wall, solid insulation, air-cooled (Figure 6). Any of these three will work, but most installers now prefer the last two because they are more compact. Solid-insulated double-walled chimneys have been around for more than a decade and are widely available from various manufacturers. The double-walled, solid-insulated, air-cooled chimney-a recent development by Simpson Dura-Vent-attempts to answer concerns about the warping of the double-walled chimney at the high temperatures of the chimney fire. The design allows the liner to bend outwards and up and down when heated, and it contains air holes to cool the outer metal walls and the exterior of the ceramic insulation material during a chimney fire. All factory-made chimneys used to control wood burning appliances (even fireplaces in New York City) must now use UL 103 HT (high temperature, 2,100°F) stainless steel pipes to solve warpage problems encountered at lower rated temperatures. .
Radiant heat from wood stoves or chimney connectors can cause problems with combustible materials at surprisingly low temperatures. Continuous exposure to temperatures as low as 150°F is enough to cause wood deterioration. Any new wood stove will list the minimum clearances for combustible materials; such information is a necessary condition for UL approval. If you are installing an old heater without a UL plaque or other instructions, please follow the minimum clearance recommended by NFPA (Figure 7).
Floor protection. There are two problems with protecting combustible floors-radiant heat from the stove and embers spilled during refueling or cleaning-so there must always be some floor protection. The degree of protection depends on the height of the furnace body from the ground. For heaters without legs, such as fireplace inserts, the floor must be completely non-combustible, ie concrete slabs. For wood stoves 2 inches to 6 inches above the floor, there must be a hollow concrete block of at least 4 inches thick on top of a 24 gauge or thicker metal plate. For wood stoves more than 6 inches above the floor, you can use bricks, rocks, or blocks that are at least 2 inches thick on a 24 gauge or thicker metal plate. In all cases, the protector should extend at least 18 inches in all directions or walls.
Reduce the gap. Once you begin to figure out where you can place the stove so that it is at least 36 inches away from any combustible material, you will quickly become interested in ways to reduce the required clearance. Effective insulation can reduce the gap on unlisted furnaces to 12 inches, which provides greater flexibility for installation and configuration.
All methods of reducing gaps are variants around one theme: providing a non-combustible barrier to radiant heat, followed by a free-flowing air space. If the air behind the barrier cannot move freely, the wall material behind it will eventually become hot. The barrier itself can be a metal board, brick or fire-resistant cement board (not gypsum board) with various decorative coverings. Keep in mind, however, that the air space must be at least 1 inch deep, there must be vents to allow the top and bottom of the barrier to circulate, and the barrier should extend outwards and upwards so that the edge is no less than 36 inches from the furnace. These problems will limit the installation location and construction method. In practice, metal plates are the simplest and cheapest material for barriers. You can buy a suitable No. 24 sheet at a heating store.
The chimney connector gap is usually 18 inches, but a radiation barrier can also be used to reduce it to 9 inches. The wall barrier can extend upwards, or you can consider connecting the barrier to the chimney itself (Figure 8). Not all building codes recognize the latter technology, so please check before use. Of course, you can also completely eliminate the stovepipe by using an insulated chimney on the stove, reducing the necessary clearance to 2 inches in most cases. (Check the chimney manufacturer's guidelines to see if they allow this use.)
Clearance. If possible, avoid passing thin legs through walls or ceilings. It is best to install the wood stove near the chimney, or relocate the chimney when necessary. Nevertheless, in some cases, stovepipes may have to pass through combustible walls to reach the chimney, and there are four approved methods. (Neither NFPA regulations nor building codes allow thin legs to pass through the floor or ceiling; to pass through the floor or ceiling, you must use a factory-built or masonry chimney, which extends uninterrupted to the top.)
The traditional way to pass through the wall is a vented thimble. This includes metal components manufactured on-site with vents and fiberglass insulation that separate the pipes from combustible materials by at least 6 inches (Figure 9). Another commonly used technique was approved by the NFPA in 1986: passing the chimney connector through a section of a factory-made chimney with a clearance of 2 inches from combustible materials (Figure 10). It is also possible to use a double-walled chimney with a 9-inch gap (Figure 11) or a clay liner separated from combustibles with 12-inch bricks (Figure 12).
Based on experience, make the stovepipe connector as short as possible and use the least number of elbows. Although the extended chimney section does extract some extra heat from the flue gas, the cost is reduced ventilation and increased creosote accumulation. Today's low-emission wood stoves are mandated by the Environmental Protection Agency and are particularly sensitive to adequate ventilation required for proper operation. In addition, because their high efficiency reduces the temperature of the flue gas, the benefits of long connectors are relatively small.
Chimneys with a diameter of 6 inches or more should be made of 24 gauge or thicker standard or stainless steel; occasional 5-inch connectors can use gauge 26 metal walls. Avoid using galvanized connectors because zinc is used to reduce the rate of corrosion. The chimney connector is expected to deteriorate-the average life expectancy is three to five years. They should be checked regularly and replaced when necessary.
Place the female thin tube connector facing up so that the liquid creosote does not drip from the outside of the tube. Furnace cement may help seal the joint, but if the joint is upside down, it won’t prevent dripping. (Don't bother with duct sealing tape-even metal varieties-because heat will quickly destroy the adhesive.) Secure each chimney joint with three metal plate screws spaced around the circumference. The magnetic hex driver in an electric drill with appropriate screws (Figure 13) can save you the trouble of drilling pilot holes.
There are two types of commonly used elbows: assembled type, composed of steel belts, which can be rotated to adapt the elbow to different angles, and corrugated flexibility. Splicing elbows may be slightly cheaper, but it is actually impossible to completely seal them. Flexible elbows have no seams (except for the seams where they connect to the thin tube section), but they may be more difficult to clean due to corrugations.
Each chimney should be equipped with a cleaning device (the code may require it), and it is usually the easiest to use the cleaning device T to include this channel in the chimney section (Figure 3). Don't forget to fix the cover with metal plate screws.
Other details of the chimney connector: The horizontal chimney pipe should be inclined 1/4 inch every 1 foot toward the heater to promote ventilation and encourage creosote oil to flow back into the fire box. If for some reason there must be a very long horizontal pipe-it should not exceed 3/4 inch of the height of the chimney-the pipe should be supported every 6 feet. When the stovepipe tube enters the masonry chimney, it should be connected by a ceramic tile or steel sleeve, and should extend into the thimble at least 3 inches, and be close to but not beyond the inner wall of the chimney. In addition, if the chimney enters the chimney of the fireplace below, the chimney must be sealed at the bottom of its flue brick and above the flue chamber of the fireplace-not at the fireplace opening or damper.
Breaking into the masonry chimney of the fireplace connector is not as difficult as you might think. A star drill is actually a chisel-and a 3 pound hammer can work bricks very quickly (Figure 14). Separate an area large enough to install a 6-inch or 8-inch (as appropriate) tile thimble, but do not use a star drill to attack the tile chimney lining. Use a 1/4 inch masonry drill bit and electric drill to drill a series of holes that form a circle with a diameter equal to the outside of the thimble. Use a hammer to carefully knock out the disc, clean up any jagged edges, and grouting the thimble in place with refractory cement, carefully and thoroughly seal the joints. Don't worry too much about the rough appearance on the outside. You can use a cheap decorative ring that fits the diameter of the stovepipe tube you use to make up for the damage.
direct connection. The fireplace seems to be the logical place to connect the wood stove, in fact, in the past, it was a very common practice to seal the surface of the fireplace with a steel plate and pass the stovepipe tube through it. But facts have proved that the violent chimney fire caused by the large amount of creosote accumulated in such fireplaces has become one of the main causes of house fires related to wood stoves, so the revised NFPA standard now prohibits this practice. The new method-direct connection-stipulates that the furnace and fireplace insert must be actively connected to the flue brick itself (Figure 15), and the fireplace baffle must be removed and sealed with steel plates. Many companies have launched toolkits to complete this tricky business, and it is recommended that you use one. So far, the full connection has not been mandated—essentially from the fireplace insert to the relining board at the top of the chimney—but many chimney experts believe this is the ultimate method.
The air outside. Should you equip your wood stove with an external combustion air supply device? If you live in a mobile home and you need outside air, you should look for wood burners designed specifically for mobile homes. However, for owners of traditional houses, outdoor air is an option, and there are several issues to consider.
First, let us debunk a few myths. Outside air will not significantly increase the efficiency of your wood burner. The use of household air will not cause performance loss, because the cold outdoor air must be heated in the fire box. Therefore, the energy lost due to the increase in air permeation caused by the intake of indoor air for combustion can be balanced by increasing the efficiency of the furnace. Wood stoves are also unlikely to use enough air (they usually use less than 50 cubic feet per minute) to deplete the oxygen in your home. Few houses can completely prevent the air from being replaced due to leakage of walls, ceilings, windows and doors.
However, internally supplied wood burners can cause potentially serious problems. Because wood stoves exhaust household air, it causes a difference in air pressure between indoors and outdoors. When the house air pressure is lower than the outdoor air pressure, natural ventilation burners (including wood stoves, water heaters and stoves) may operate in reverse. The combustion air can be exhausted from the chimney, and the exhaust gas is ejected from the indoor air intake.
If this happens on a wood stove-this phenomenon is called flashback-it is obvious. You can see and smell the smoke. However, back-suction gas stoves and water heaters will not provide such obvious symptoms. If the wood stove happens to be well ventilated—perhaps because you have installed such a large chimney—but other burning appliances, in turn, you and your family may die in carbon monoxide poisoning sleep without any warning. (Carbon monoxide is colorless and odorless.) Similarly, indoor pressure lower than outdoor pressure can cause another health problem: the presence of radon and its decay products. The pressure difference is the main driving force for this radioactive carcinogenic gas to enter the building from the soil.
Therefore, the wood stove that obtains combustion air from the house has little impact on life-threatening health problems, but it may be an important factor. Although outside air has not yet been universally mandated, we predict that the regulations will eventually require all combustion equipment to obtain combustion air from outside. This is your chance to join the vanguard. To do this, buy a "mobile home" stove and follow its installation instructions.
An important part of the installation of a safe wood stove is the purchase of appropriate safety equipment. Of course, you have installed the smoke detector in the recommended location. Some people also put one near their stove, but if the wood burner easily goes backwards, it may give off annoying false alarms. You should place an ABC-class fire extinguisher with a capacity of at least 5 pounds in a conspicuous location, and everyone in the family should know where it is and how to deal with it. You also need to buy a chimney fire extinguisher, which can be a dry chemical pressurized tank or a highway flares-like type.
You may also want to consider buying a stovepipe thermometer or even an alarm to help you operate the stove in the best way and warn the chimney of a fire. These devices range from simple, inexpensive bimetallic coils (ask your dealer for a Condar stove thermometer or equivalent) to more complex electronic thermometers (available from Condar and other companies) to alarms triggered at a set temperature ( FASCA, Inc., Spencer, WI).
Now that you understand the requirements for safe and efficient wood stove installation, let us finally introduce some details about the tools and techniques. Once you have the right tools and know how to use them, using metal plates (whether thin tubes or thermal barriers) will become easy and beneficial.
Metal cutting tools. The most common metal scissors, tin scissors, look a lot like scissors that are too big. These are very useful for fine work on thinner soft metals, but they are not what you need for thin tubes and duct steel. You need compound, offset, and lever shears, usually called aviation shears. These increase your grip by 10 to 1. Aviation scissors usually come in two versions, right-handed and left-handed. This refers not to the hand used to manipulate them, but to the metal side and the direction of the curve that will become waste (Figure 16). The right hand scissors are green and the left hand is red for easy identification. Since you won't cut many curves and may be able to flip the material you are working on anyway, you can use a pair. Most right-handed people start with green.
However, for discerning tool collectors, the local heating store also offers several other metal processing tools to make sheet metal processing easier. For example, although "manual" scissors will cut straight, straight cut (yellow) or better yet, center cuts cut better because they remove a small part from the center of the paper, leaving no distortion on either side. In order to pass through the seams, a pair of super heavy scissors is also very convenient. An almost indispensable tool for forming custom-length stovepipe sections is a crimping machine. This tool creases the shortened pipe to form a male end for insertion into another section of pipe, elbow, outlet or thimble. In order to fold the periphery of the metal plate thermal barrier to remove dangerous jagged edges, handbrakes called "pliers" are very useful. Full-size brakes are great but expensive. To make a big bend on several metal plates, sandwich the steel between the two plates, and then hammer with the other plate. Finally, don't even try to handle metal plates without wearing a pair of thick leather gloves to protect your hands. Blood is the wrong medium for signing your work.
Although it is said over and over again, it cannot be repeated too often: the installation of a wood stove without proper maintenance is safe. After your furnace is in and running, check every week for creosote in the chimney until you understand how quickly the system tends to become sticky. Remember also that creosote will accumulate at different rates, depending on how you operate the heater. Many new wood stove owners are surprised to find how fast the chimney can be blocked in spring and autumn. At that time, very little wood was used, but the fire would be greatly reduced to prevent the house from overheating. Whenever creosote reaches a thickness of 1/4 inch, clean it up or clean it up for you. Most importantly, never let the gentle, soothing heat make you forget what is in the wood stove: a faintly domesticated monster called fire.
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