Venting your Pellet Stove

Venting your new pellet stoves is crucial for optimum operation of your stove.

To begin let's first talk about the different types of vent pipes in the market. There are five different types of vent pipe used in the heating industry.

1. Gas vent pipe, which uses aluminum for the inside wall of the chimney. The chimney itself looks very similar to Pellet Vent pipe. Read the label to make sure. Under no circumstance should gas vent pipe be used for Pellet Vent Pipe, as the inner wall will not stand up to the pellet vent exhaust and pipe will fail very rapidly.
2. Pellet Vent pipe, referred to as L-Vent pipe, can be purchased in 3 inch and 4 inch diameter sizes. The L-Vent pipe is the correct type of pipe for your pellet stove. The inner chimney is made from Stainless Steel and will last as long as your pellet stove.
3. Corn Vent pipe is usually for corn burning stoves however, it is OK to be used for the pellet stoves as well. Corn Vent also comes with a stainless steel inner chimney, and should last the life of the stove.
4. Manufactured wood stove pipe, classified as Class A pipe, usually comes in 6 inch, 7 inch, and 8 inch diameters. This type of pipe will also work with your pellet stove as it also has a stainless steel inner chimney. However, it is not necessary to be used for the pellet stove since this type of pipe is very expensive.
5. Existing masonry wood stove chimneys with clay liner are also classified as a Class A chimneys and comes in various sizes and must have a clay inner liner. This also works very well with a pellet stove. Pellet vent pipe can vent directly into Class A chimneys.

Having talked about the different types of pipe, we now move on to our main topic which is how to vent pellet stoves using the using pellet stove vent pipes or in conjunction with an existing chimney. The purpose of this article is to discuss how to configure your pellet stove vent System. It is critical to adhere to all clearances and recommendation from the manufacturer of the pellet stove you bought. All pellet stoves come with its own installation manual. These installation instructions are to be followed exactly, and will override any suggestion printed below. Inspectors at your local municipality based their inspections on the manuals along side any local codes that need to be enforced. As such it is imperative that the installation manual be adhered to.

First let us understand what we can not do as to the location for the termination of the vent pipe. If your planned termination location falls at any of the below described location, it is critical to select an alternative location. Do not compromise as the safety of your family and others will be at risk. 1. Less then 3 feet above any forced air inlet located within 10 feet 2. Less then 4 feet below or horizontally from, or 1 foot above, any door, window or gravity air inlet into any building. 3. 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. 4. 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. 5. 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 have to push the exhaust air through the vent pipe with the stove's exhaust fan. With less restriction your pellet stove will breathe easier and burn more efficiently. First let's clarify the word restriction. Restrictions come from several different items.

1. 45 degree elbows
2. 90 degree elbows
3. Horizontal distance
4. Vertical distance
5. Elevation where you live.

A rule of thumb equation we are using has been adopted by most pellet manufactures. The equation is called the sum of Equivalent Vertical Length (EVL). All of the above mentioned venting restrictions have been assigned EVL values as follows:

1. Each 45 degree elbow = 3 EVL
2. Each 90 degree elbow and Tees with cleanout = 5 EVL
3. Each foot of horizontal run = 1 EVL
4. Each foot of Vertical run = 0.5 EVL
5. Elevations above 3000 ft with an EVL of 7 must adapt to 4 inch vent pipe.

If your installation is 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 equation using several different typical installation configurations we encounter.

The first typical installation is out the back of the stove and straight through the wall with 10 to 12 inches protruding chimney past the outside wall with an installation altitude of less than 3000 ft. Do make sure that the pipe outside is clear of walkways, shrubs, and at least 24 inches above the ground. Looking back at our chart, we know that each horizontal foot equals 1 EVL. For this installation we have about 2 and no more than 3 horizontal feet which equals to no more than 3 EVL. This is of course way below the EVL of 15 so 3" pellet vent pipe would be very adequate size pipe to operate the pellet stove. The through the wall and terminate is the least desirable of installations as it is not uncommon for soot to stain the outside of the home and is more prone to high winds blowing back into the stove causing poor burning of the stove and even have the exhaust blown back into the home.

Another popular type of venting installation is in the corner of a home and an installation altitude of less than 3000ft. This is similar to the first style of installation with the addition of a 45 degree elbow is added to compensate for the corner. In this type of installation a 3 foot pipe is usually required to exit the home in order to maintain the one foot clearance on the outside. So let's start with the calculation. A 3 feet horizontal run has an EVL of 3. The 45 degree elbow has an EVL of 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 very adequate size pipe to operate the pellet stove. The above two examples are the most common method of vent a pellet stove, because of the cost of the pipe, but also the least desirable method. READ ON.

The main reason for these types of installation is cost efficiency. There is however, a word of warning. If the exhaust is located in a breeze way or prevailing wind side of the home, this would not be a suitable installation. A drawback on the through the wall and terminate installations is that it is not uncommon for soot to stain the outside of the home and it is more prone to high winds blowing back into the stove causing poor burning of the stove and even have the exhaust blown back into the home. High wind problems can be overcome by using the Up and Out or the Out and Up method of installation, but we want to terminate closer to the eve of the house or above the roof of the house.

OK let's do the math. The home is located less then 2000 elevation. We will put a Tee with a clean out on the stove, or out side the home depending on the method decided on. A Tee is basically a 90 degree elbow, EVL=5. Next we have to go up, usually about 3 feet, EVL=1.5 another 90 degrees at the top of the 3 foot section EVL=5. Two foot through the Wall EVL=2. Now lets add, 5+1.5+5+2=13.5 EVL, still OK for 3 inch pipe.

The third and a better installation is call the Up inside the room then Out through the wall configuration. The advantage to going up and out is that the stove now has some natural draft. This advantage is more clearly seen in the case of a power outage and the exhaust fan on the stove stops. Without this natural draft this type of installation creates, the smoke coming from the live flame still going in the stove will exhaust into the home. But the draft created by this type of installation allows the smoke to be drawn up into the hot chimney and exhausted outside since hot air (and smoke) rises naturally.

The forth and still a very good installation is straight up through the ceiling and roof. Let's do the math. Home is located at an elevation of 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 configuration to consider, an existing wood stove chimney on the out side of the home and we want the pellet stove to vent into the chimney. The home is located at 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 for this example for the existing chimney EVL=3. Lets do the math, 5+3+5+1+5+3= 22 EVL. 4 inch chimney is required for this type of installation.

The sixth configuration we will consider is up and into an existing wood stove chimney located in the ceiling above the pellet stove. This will be the most complicated configuration to figure out, but with a knowledgeable person, this can be a very good installation with a minimum of problems. Usually the Wood Stove pipe is not directly in the right place for the pellet vent to vent into the existing pipe requiring 2 additional 45 degree elbows. This example is only an example, as every existing stove pipe will have different distances for the configuration. The 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 of 2. 45 degree angle EVL=3. Vertical run on a one story home 6 feet EVL=3. Lets add 5+2+3+2+3+3=18 EVL. Once again we must use a minimum of 4 inch pipe.

The last configuration we will consider is for Pellet Stove Inserts. One story liner kits. The home is located less then 2000 feet elevation. 90degree on back of stove EVL=5. 15 feet of vertical elevation EVL=7.5. Do the math 5+7.5= 12.5 EVL. Two Story Liner kits. The home is located less then 2000 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.

As you can see, using the EVL equation it is not hard to find out for yourself what your venting requirement for your stove. We hope this article gives you some guidelines in the placement for the venting options for the pellet stove of your choice.