How to Vent your Pellet Stove
The vent your pellet stoves are utmost importance for the correct operation of your pellet stove.
To start let's examine the different vent pipe types in the market. The primary different chimney pipes can be categorized into 5 different types of vent pipe used in the heating industry.
- Gas vent pipe, which has an aluminum core for the inner portion of the two-wall chimney. The chimney pipe looks almost identical to Pellet Vent chimney. Be very careful to read the label to make sure it identifies itself as B-Vent or Std. Vent pipe. Under no condition should gas chimney pipe be used in instead of Pellet Vent Pipe, as the inside aluminum wall will not withstand the pellet stove exhaust and gas vent chimney pipe will fail very quickly.
- Pellet Vent pipe, pipe is classified as L-Vent pipe, can be bought in two sizes, either in 3 inch or 4 inch diameter. The L-Vent pipe is the correct type of pipe for your pellet stove. The inside portion of the chimney is made from Stainless Steel and can last as long as your pellet stove.
- Corn Vent pipe is normally used for corn burning stoves however, it is tested for pellet stoves as well as many times it is regarded as a higher grade of pipe, many L Vent pipes are test both for corn stoves or pellet stoves and will work satisfactory either way. Corn Vent also comes with an inner liner of stainless steel, and should last the life of the stove.
- Manufactured wood stove pipe, classified as Class A chimney pipe, for residential uses the pipe is normally either in 6 inch, 7 inch, and 8 inch inside diameters. Class A type of chimney can also be adapted to work with pellet stoves as it also has and inside stainless steel inner chimney. Normally the only time Class A chimneys are used with a pellet stove is when the pipe is already installed and the pellet chimney can be either adapted to the Class A pipe or install the pellet vent pipe thought the center of the Class A pipe.
- Existing masonry wood stove chimneys with clay liner are also classified as a Class A chimneys and comes in various sizes. Many older masonry chimneys do not have an inner clay liner and will require that Stainless Steel flex or ridged liner be installed prior to installing a pellet stove into the chimney. This also works very well with a pellet stove. Pellet vent pipe can vent directly into Class A chimneys.
A basic knowledge of the different types of piping will help to understand how to configure for different venting application. Always adhere to all clearances and specifications from the manufacturer of the pellet stove you bought as all pellet stoves will include its own installation manual. These installation instructions are to be followed exactly, and will override any suggestion printed below. Inspectors at your local municipality typically base their inspections on the manual, however the local inspector has the power to override the Manuel, but rarely do they as the pellet stove has already gone through rigorous testing at a certified laboratory.
To begin lets understand what we can and cannot do. Once you decide on the location in the room that would best fit your needs, the next step will be to make sure that the venting pipe will meet the clearance requirements that are specified in the owners Manuel. Listed below are most of the clearance restrictions, if any of the restriction is not met then it becomes necessary to use and alternate piping configuration or relocate the pellet stove. Do not compromise as the safety of your family and others will be at risk.
- Cannot be less then 3 feet above any forced air inlet located within 10 feet of the exhaust pipe.
- Cannot be less then 4 feet below or horizontally from, or 1 foot above, any door, window or gravity air inlet into any building.
- Cannot be less then 2 feet from an adjacent building and less than 7 feet above grade when located adjacent next to a public walk way. Mobil home installations must use a spark arrester.
- Termination should not be located where it might ignite trees, shrubs, dry grasses or be a hazard to children as exhaust gases can reach 500 degrees and cause serious burns if touched.
- Do not install vent pipe into chimneys shared by other appliances, as you can get a back draft and causing the exhaust from one to the other appliances to come back into the home through the other appliance.
Pellet stoves are bring in the air into then through the burn chamber up through the burn pot through the heat exchangers finally blowing the exhaust air into the vent pipe with the stove's exhaust fan. The less restriction your pellet stove encounters through this process will allow more air flows making the appliance burn more efficiently. First let's clarify the word restriction. Restrictions can come from several different components and methods that you can use when you install the stove.
- 45 degree elbows
- 30 degree elbows
- Horizontal distance
- Vertical distance
- Elevation where you live
All of the above variables will figure in when you figure the resistance EVL equation that has been adopted by most pellet manufactures has proven itself over many years. The equation is referred
To as the sum of Equivalent Vertical Length (EVL). All of the above mentioned venting restrictions have been assigned EVL values.
- Each 45 degree elbow = 3 EVL
- Each 90 degree elbow and Tees with cleanout = 5 EVL
- Each foot of horizontal run = 1 EVL
- Each foot of Vertical run = 0.5 EVL
- Elevations above 3000 ft with an EVL of 6 or more must adapt to 4-inch diameter vent pipe.
If your installation were below 3000ft, we would need to do some math. The rule of thumb equations is that if the sum of the EVL is 15 or greater, then the pellet vent pipe would be increased to 4 inch diameter pellet vent pipe.
Of course there may be different variables to this equation that we used, but still it works quite well. Let's try out this EVL equation using several different types of installation configurations that are might encountered.
The first configuration example is straight out the back of the stove and through the wall with at least 10 to 12 inches protruding past the outside wall and the altitude being less than 3000 ft. Looking at the EVL parameters, we know that each horizontal foot equals 1 EVL. For this installation typically we have about 2 horizontal feet, which equals to no more than 2 EVL. This is way below the EVL of 15 so 3" pellet vent pipe would be the correct size pipe to operate the pellet stove. The through the wall and terminate is most popular and the least desirable of installations as it can soot and stain the outside wall of the home.
Another example of type of venting installation is in the corner of a room and the altitude is less than 3000ft. This is comparable to the first style configuration with an added 45-degree elbow to allow for the corner. In this configuration a 3-foot pipe is usually need to exit the home to maintain the one-foot clearance on the outside. So let’s begin the calculation. The EVL of 3 feet horizontal is 3. The EVL of the 45-degree elbow is 3 as well. Adding that together you get a total EVL of 6. This is way below the EVL of 15 so a 3" is adequate size pipe to install for the pellet stove.
The main reason for these first two types of installation is that cost a less to install. There is however, a word of caution. If the termination is located in a breeze way or prevailing wind side of the home, this could cause a back draft condition. In case of power outages, there is no natural draft on the stove so that the smoke will come back into the home. Still another drawback on the through the wall and terminate installations is that it is not uncommon for soot to stain the outside of the home All of these problems can be overcome by using the Up and Out or the Out and Up method of installation
The third and a better installation is the out through the wall and up configuration. This example could just as well gone up inside the room then out. The advantages to going up are that the stove now has some natural draft. This advantage is appreciated in the case of a power failure, which would cause the stove exhaust fan to stop. Without the natural draft this type of configuration creates, the smoke coming from the ember in the burn pot that are still glowing will come into the home. Instead the draft created by the chimney exhausting above the stove allows the smoke to be drawn up into the hot chimney naturally and exhausted outside since lighter hot air (and smoke) will rise naturally. Lets do the EVL to check for the pipe size needed, from bottom to top for this example. First we need 1.5 feet of pipe through the wall (1.5 EVL). Next is a tee with a clean out which is same as a 90 degree (5 EVL) next lets assume 3 feet up (1.5 EVL) another 90 degree (5 EVL) next 6” out (EVL .25) OK lets add 1.5 + 5 + 1.5 + 5 + .25=13.25 Still ok for 3” pipe.
The forth and still a very good installation is straight up through the ceiling and roof. Could also be out and up through the roof. Let's do the math. The elevation of the home is less then 3000 feet above sea level. One 90 degree on the back of the stove EVL=5, 12 feet of vertical pipe EVL=6. Now let's add 5+6=11, still OK for 3 inch pipe.
The fifth example we can examine, will be into existing wood stove chimney located on the out side of the home and we will vent the pellet stove into the chimney. The location will be less then 3000 feet elevation. Tee with cleanout on back of stove EVL=5. Vertical elevation in the room for this example will be 6 feet EVL=3. A 90 degree elbow to go into the chimney EVL=5. 1 foot piece of pipe to go into the chimney EVL=1. The Chimney now 90 degrees up EVL 5. Another 6 feet of vertical rise inside the existing chimney for this example EVL=3. Lets do the math, 5+3+5+1+5+3= 22 EVL. 4-inch chimney is definitely required for this method of installation.
The sixth method we will understand is up and into an existing Class A wood stove chimney pipe located in the ceiling. This configuration will be the most complicated to figure out, but with a knowledgeable person a couple of measurement the calculation are very easy with the right tables for reference. The installation can go with a minimum of problems and work very well. Rarely does the wood stove pipe align up for the pellet stove as the Wood Stove pipe is not directly in the right place for the pellet vent to align into the existing pipe thus requiring 2 additional 45-degree elbows plus some pipe in between the elbows. This example is used only as an example, as all existing stovepipe will have different distance measurements for the configuration. Let’s calculate, stove will be located less then 3000ft above sea level. Tee with cleanout on the stove EVL=5. Vertical pipe, for this example, will be 4 feet, EVL=2. 45 degree elbow, EVL=3. 2 feet of pipe running at a 45-degree angle has an EVL =2. 45 degree angle EVL=3. Vertical run on a one story home 6 feet EVL=3. Lets calculate 5+2+3+2+3+3=18 EVL. And again we definitely must use a minimum of 4-inch diameter pipe.
The last installation type we will analyze is for Pellet Stove Inserts. One-story liner kits and two story liner kits. First the home is located less then 3000 feet elevation. 90 degree on back of stove EVL=5. 15 feet of vertical elevation EVL=7.5. Do the math 5+7.5= 12.5 EVL. Next the two Story Liner kits. The home is located less then 3000 feet elevation. 90 degree on back of stove EVL=5. 25 foot vertical liner pipe EVL=12.5. Let's do the math 5+12.5=17.5 EVL. A 4-inch liner is required for a two-story home.
These examples should help you to figure your own installation requirements using the EVL equation. The EVL venting equation it is not hard to find out for yourself what you need for your venting requirement on your stove. We hope this article helps you to know the guidelines in the placement and best venting options for the pellet stove of your choice.