24 foot masonry chimney that is 10 inch by 10 inch........how do we vent a pellet stove..!!!

[Nuke]

My first pellet stove!

Bought a King / Ashley 5500M by United States Stove Company. I am doing the vent and the air intake myself as I have done this to several wood stoves. I KNOW that there are differences, and so the reason for this thread! Note that my house is two story with a nice hearth / fireplace and a 24 foot masonry chimney that runs up both stories. It is 10.5 inches by 10.5 inches on the inside. This results in 18.375 cubic feet of airspace total through the whole chimney. I am not so concerned about plumbing the air intake as I have a nice large ash drop in the floor inside the fireplace......my main concern is the vent exhaust! And I DO want to use my hearth, fireplace, chimney set up ....it is the BEST place to do it!

FIRST QUESTION:

I have read several articles and documents concerning vent exhaust and air intake for a pellet stove including the manual that came with this stove I purchased. Most say to use 4 inch pipe as my house is above 2500 feet (more like 6800 feet..!!) and my vertical run will be more than 12 feet.....most recommend using 4 inch pipe......OK....but all the stoves come pretty standard with a 3 inch exhaust port.....hhhmmm!....restricted already! Another article said to use a "chimney liner" (looked like an oversized pipe...6 inch?....8 inch?).....I had a friend who has pellet stoves say he would try just sealing a 4 inch exhaust at the bottom and then sealing a 4 inch or 6 inch chimney cap (with weather hardware) at the top. But NONE seem to address using a two story masonry chimney like I have...! I KNOW someone has done it and I want to benefit from their experience....

So the three options (so far) seem to be:

1. Use 4 inch pipe all the way, seal at the bottom and the top.
2. Use a "chimney liner"...which I think is just 6 inch or 8 inch pipe...again I would seal at bottom and top
3. Seal at bottom and top (4 inch out of stove, 6 inch for chimney cap) and just use the masonry chimney all the way (22 feet to 24 feet)

I know this is probably a physics problem, and I look at it two ways........the BARE masonry chimney would have the least resistance to air flow as it is much larger than pipes......but then on the other hand you need to "push" against all the air that is sitting in the chimney......??.....so which is it? Will I get the best draft just using the bare chimney, or with pipe all the way?

SECOND QUESTION:

Most of the articles recommend the stainless steel / aluminum pipe that is rated and recommended for pellet stoves......but my Lord! What a price! Seems like you cannot touch a piece of pellet stove pipe for under $40 - $50 bucks! If I run this pipe all 24 feet I will be spending many many hundreds!

I have a friend who said he used just regular double wall stove pipe (galvanized?) to vent his pellet stove, and says he just makes sure he keeps it clean and has had no problem for years..!

I also know that they recommend a clean out "Tee" right out of the stove. This makes sense.

So I am asking WHY is this expensive pipe recommended when it seems regular stove pipe would work if you keep it clean? Seems a pellet exhaust is no where near the high temperatures of a wood burner...??? I know there is ash, but you just make your vents so they are easy to clean...??

Can I get away with using the pellet stove pipe at the bottom and using regular stove pipe up the 24 feet?........

THIRD QUESTION:

Has anybody already done this? And how did you successfully do it? Cleaning tips?

Thanks for reading!

Greg

 

[Harman Lover 007]

My first pellet stove!

Bought a King / Ashley 5500M by United States Stove Company. I am doing the vent and the air intake myself as I have done this to several wood stoves. I KNOW that there are differences, and so the reason for this thread! Note that my house is two story with a nice hearth / fireplace and a 24 foot masonry chimney that runs up both stories. It is 10.5 inches by 10.5 inches on the inside. This results in 18.375 cubic feet of airspace total through the whole chimney. I am not so concerned about plumbing the air intake as I have a nice large ash drop in the floor inside the fireplace......my main concern is the vent exhaust! And I DO want to use my hearth, fireplace, chimney set up ....it is the BEST place to do it!

FIRST QUESTION:

I have read several articles and documents concerning vent exhaust and air intake for a pellet stove including the manual that came with this stove I purchased. Most say to use 4 inch pipe as my house is above 2500 feet (more like 6800 feet..!!) and my vertical run will be more than 12 feet.....most recommend using 4 inch pipe......OK....but all the stoves come pretty standard with a 3 inch exhaust port.....hhhmmm!....restricted already! Another article said to use a "chimney liner" (looked like an oversized pipe...6 inch?....8 inch?).....I had a friend who has pellet stoves say he would try just sealing a 4 inch exhaust at the bottom and then sealing a 4 inch or 6 inch chimney cap (with weather hardware) at the top. But NONE seem to address using a two story masonry chimney like I have...! I KNOW someone has done it and I want to benefit from their experience....

So the three options (so far) seem to be:

1. Use 4 inch pipe all the way, seal at the bottom and the top.
2. Use a "chimney liner"...which I think is just 6 inch or 8 inch pipe...again I would seal at bottom and top
3. Seal at bottom and top (4 inch out of stove, 6 inch for chimney cap) and just use the masonry chimney all the way (22 feet to 24 feet)

I know this is probably a physics problem, and I look at it two ways........the BARE masonry chimney would have the least resistance to air flow as it is much larger than pipes......but then on the other hand you need to "push" against all the air that is sitting in the chimney......??.....so which is it? Will I get the best draft just using the bare chimney, or with pipe all the way?

SECOND QUESTION:

Most of the articles recommend the stainless steel / aluminum pipe that is rated and recommended for pellet stoves......but my Lord! What a price! Seems like you cannot touch a piece of pellet stove pipe for under $40 - $50 bucks! If I run this pipe all 24 feet I will be spending many many hundreds!

I have a friend who said he used just regular double wall stove pipe (galvanized?) to vent his pellet stove, and says he just makes sure he keeps it clean and has had no problem for years..!

I also know that they recommend a clean out "Tee" right out of the stove. This makes sense.

So I am asking WHY is this expensive pipe recommended when it seems regular stove pipe would work if you keep it clean? Seems a pellet exhaust is no where near the high temperatures of a wood burner...??? I know there is ash, but you just make your vents so they are easy to clean...??

Can I get away with using the pellet stove pipe at the bottom and using regular stove pipe up the 24 feet?........

THIRD QUESTION:

Has anybody already done this? And how did you successfully do it? Cleaning tips?

Thanks for reading!

Greg

First of all, Greg, welcome to the Pellet side of hearth.com. You are about to get a ton of answers and opinions to your questions. My quick response is use the chimney for it's intended purpose. Question: is it lined? It must have a natural draft since you had a wood stove in there. "Pushing" the air is a non issue. My two stoves replaced a woodstove and I have had no issues in 17 years of pellet burning. There will be many who disagree so hang on for the ride and have some fun.

 

[Nuke]

So you are saying just seal it at the top and bottom and let the chimney do its regular job? Sounds like I can use 8 inch or so at the top to allow the best draft?

 

[Delta-T]

you prolly want to use a 4" Stainless Steel liner...looks like a dryer vent, but its Stainless and NOT aluminum. You can pick them up in "kits" that will have a flashing and some type of cover for the top of the chimney. If the stove you have has a rear facing vent, you'll want to get a "T" to put on there, then the liner...makes for cleaner install, and somewhat easier cleaning.

Look at the flange on the stove, is it 3" or 4"? if its 3" and the manual calls for a 4" liner, get a "T" that transitions from 3"-4", or get an increaser. Whatever you do, do not skimp on the pipe and pick up some aluminum...it will deteriate and you will have a problem. The reason its stainless is because the exhaust contains carbonic acid...corrosive to aluminum, the reason that pellet pipe is so expensive is because its build to withstand heat, and pressure.

 

[Nuke]

Thanks!........the heats and pressures of a big wood burning stove far exceed what a pellet puts out.........but carbonic acid!......now I see the reason for stainless....BTW the pipe I looked at was aluminum with a stainless steel liner inside.....so I assume it would work.......(I would NEVER consider just aluminum pipe, you misunderstood me).......I would like to get an "increaser, cleanout T, and 90 degree elbow" all in one pipe as I only have 7 inches of travel from the back of the stove to where it has to turn upwards to the chimney....!...get the feeling I will have to use some flex to come back a little and go up.........

No one has successfully explained why stainless is superior to regular double wall galvanized steel stove pipe!......Unless it is the excess carbonic acid........when you burn wood you MUST be expelling carbonic acid, as wood pellets are.....WOOD.....right?.....I am thinking it might be the CONCENTRATION of carbonic acid....BTW "carbonic acid gas" is just carbon dioxide....but it has energy and can cause damage.......

OK.....Thank you for your input.....all info is helpful!

 

[AbetterChimneynm]

First off i would not let a pellet stove just "vent" into a chimney the cleanup at the end of the year would be horrid, IF i was the one installing it since it is a 25 ft run of pipe i would use four inch stainless steel flex pipe, but that is just what i would do

 

[AbetterChimneynm]

The reason I use flex in the fireplace is because it is flexible and can bend easy around a smoke shelf or damper where as stright solid pipe does not.

 

[ROVERT]

No one has successfully explained why stainless is superior to regular double wall galvanized steel stove pipe!.

OK.....Thank you for your input.....all info is helpful!

When you are referring to regular double wall galvanized, I assume you mean B vent. I don't know much about pellet stove venting, but B vent is only for use with gas appliances.

 

[Delta-T]

if you are asking "why S.S. Liner instead of PL type venting" (specific for pellet appliances) then the answer is:
1-less expensive, single wall s.s. flex liner is significantly less expensive that rigid PL type venting for the same length, but liner is only to be used inside of masonry chimney.
2-easier to work with, s.s. liner can be affixed at the top, and the bottom and attached to the stove, PL type pipe has to be supported with brackets every few feet, and would be no fun at all to run up/down a chimney, especially if there is a jog in the flue.
3-single piece, no have to worry about leaking.

 

[Nuke]

I am asking.....WHY A PIPE AT ALL?

 

[smwilliamson]

The reason I use flex in the fireplace is because it is flexible and can bend easy around a smoke shelf or damper where as stright solid pipe does not.

You can also pull the stove forward with flex when you need to service it. Rigid doesn't move forward too well.

 

[smwilliamson]

I am asking.....WHY A PIPE AT ALL?

I'm not sure of what the codes are there in NM but you can vent into a regular masonry or class A chimney, the issue is that pellet stoves have heat exchangers to remove the heat from the exhaust. This requires residency time of the combustion gases to heat the exchanger up. If you have a hot flue with a lot of surface area...you get a lot of draft, that decreases the the exchangers efficiency. Secondly, pellet stoves must maintain a close 35/1 ratio of air/ fuel in the combustion zone, the auger doesn't feed in relation to the air flow so your fuel delivery is what it is depending upon the heat level desired. The air needs to be controlled. Chimneys with excessive draft have problems running on lower settings.

Follow directions and avoid problems. Nearly every stove I look at that is having unexplained operating problems is resolved when the installation recommendations are followed.

 

[AbetterChimneynm]

We will not install a stove without piping it all the way to the top

 

[DexterDay]

A 4" liner all the way up and a Clean-out-T that is a 3" to 4" increaser on the back of the stove...

Only use Pellet vent, no gas vent, etc...

Lots of people here have gone up a chimney. Most have ran a full length liner. Its the safest way (costs more), but my families safety is #1. Cost can be higher if I know I am going to do it right the first time and have no regrets. As I get older, I dont "Settle" as much as I used to. I prefer to spend the money and do it right.

 

[katman]

Probably not a huge issue but I would also be concerned about the gradual buildup of ash in your masonry chimney if you only run the vent partially up. I assume you would seal the damper area around your pellet vent, so it would seem whatever draft you had in the masonry chimney would be reduced because the intake flow at the bottom would be reduced. Your pellet vent would in effect have to push the air volume in the chimney to exit so any heavy particles in the exhaust could possibly fall to the bottom, gradually building up in the damper area. I'd run flex suitable for a pellet stove all the way up and be done with it. It will exhaust correctly, be easier to keep clean and negate the need to revisit your install if you find relying on the masonry chimney doesn't work right. Off course, if you have plenty of spare time and want to try saving a few bucks then by all means go for it. You can probably go out for dinner a couple of times with the money you might save, but I think you will be on a ladder in the winter running flex down the chimney or cursing the stove because it doesn't appear to be putting out much heat.

 

[Don2222]

I'm not sure of what the codes are there in NM but you can vent into a regular masonry or class A chimney, the issue is that pellet stoves have heat exchangers to remove the heat from the exhaust. This requires residency time of the combustion gases to heat the exchanger up. If you have a hot flue with a lot of surface area...you get a lot of draft, that decreases the the exchangers efficiency. Secondly, pellet stoves must maintain a close 35/1 ratio of air/ fuel in the combustion zone, the auger doesn't feed in relation to the air flow so your fuel delivery is what it is depending upon the heat level desired. The air needs to be controlled. Chimneys with excessive draft have problems running on lower settings.

Follow directions and avoid problems. Nearly every stove I look at that is having unexplained operating problems is resolved when the installation recommendations are followed.

You can also put in flexible Metal Liner in your chimney with a cap to reduce the draft. That is how a pellet stove insert is installed.

 

[SmokeyTheBear]

Nuke, welcome.

If that flue is 10" by 10" you may find it can cause draft issues, consult the installation instructions for your stove. The combustion fan will have to be able to overcome the back pressure in the flue when it is cold and when the flue starts drafting it may remove far more heat up it than it normally would. A liner takes care of both of those issues.

 

[Don2222]

Nuke, welcome.

If that flue is 10" by 10" you may find it can cause draft issues, consult the installation instructions for your stove. The combustion fan will have to be able to overcome the back pressure in the flue when it is cold and when the flue starts drafting it may remove far more heat up it than it normally would. A liner takes care of both of those issues.

I am running an Avalon Astoria into a 25' 8x8" clay lined block chimney. I only find a small issue of too much draft when trying to burn on heat setting 1 which is approx 1.7 lbs per hour of pellets. This can be easily compensated by closing down the air intake damper. Heck the Hudson River West Point with the 3" intake needs a damper anyway to burn on heat setting 1 because the 3" intake draws in too much air!

If you do not have a damper built into the stove you can get them for the back of the stove!
This is another way to obtain that 35/1 Fuel Air Mixture!

Remember what goes in, is what comes out.

Hope this helps?

 

[pell it]

http://providence.craigslist.org/mat/3218199104.html

Maybe they will ship it?

 

[SmokeyTheBear]

...
If you do not have a damper built into the stove you can get them for the back of the stove!

Remember what goes in, is what comes out.

Hope this helps?

Make certain than any damper you put on the stove is on the air intake not the exhaust side and there is a world of difference between an 8" x 8" and a 10" x 10" follow the manufacturer's venting instructions.

 

[Nuke]

From Nuke:

THX guys........I am going to buy a MagnaFlex 4" X 25 foot pellet stove liner kit.....$420, and it has the liner, chimney cap, cleanout T, and 3" to 4" adapter for the stove..........

1. What everyone says about the draft makes sense....I feel the best thing is to just have it exhaust 4 inch pipe all the way .............I can especially see the case where there is no draft at the beginning of a burn and then too much once it gets going.........I noticed this when I used the chimney for wood burning!

2. No one has yet successfully explained the need for stainless steel............one explanation was "carbonic acid" which is just carbon dioxide....which is a by product of burning ANY kind of wood....???...others say...."It is the ash clean up".......well, I have cleaned regular wood stove pipe, single, double, and triple wall, and it is not that difficult...????.....obviously you need it ....BUT WHY?

Nuke

 

[camdids]

As Warned. lots of suggestions. I have 27ft of masonry chimney, with 10x10 line. The air in the chimney being on the outside, would cool the air too much that fumes came back down into the house. I had installed a 4inch full length SS flex liner to th etop. No problems at all now, and easier to clean with chimney brushes

 

[smoke show]

2. No one has yet successfully explained the need for stainless steel............one explanation was "carbonic acid" which is just carbon dioxide....which is a by product of burning ANY kind of wood....???...others say...."It is the ash clean up".......well, I have cleaned regular wood stove pipe, single, double, and triple wall, and it is not that difficult...????.....obviously you need it ....BUT WHY?

Nuke

Lower temps, more corrosiveness. Whats the other options? b-vent is aluminum.
So have tried PVC, without success.

 

[SmokeyTheBear]

The need for stainless is for corrosion resistance which can be severe due to the relatively low flue gas temperature. There is a difference between carbonic acid (H2CO3) and carbon dioxide (CO2), one is a gas which is noncorrosive and the other is a liquid that is corrosive. Carbonic acid is formed when carbon dioxide reacts with water. The relativity low flue temperatures can lead to water condensing and the reaction taking place. Thus the need for the stainless.

You really need to pay attention to the grade of stainless if the stove is a multi-fuel unit as other biomass fuels produce a number of even more corrosive combustion by products.

 

[Nuke]

OK....I knew that when carbonic acid went through the phase change it became carbon dioxide.....did NOT know the further chemistry of corrosion......making more sense to me now.........although in New Mexico, nothing rusts as we have no moisture to begin with!......believe it or not, but our cars do not rust!........

BUT I know that in the environment of the pellet stove you would still have the carbonic acid issue........

Thank you for the explanation!....I have ordered a complete stainless kit from MagnaFlex......

Nuke