Chimney Liner for Tall Chimney

[AJ9]

I purchased a Austroflamm Integra II insert to place into my existing masonry chimney. It has it's own flue. The chimney above the damper is 30' tall. There is about 3 feet or so from the damper to the stove exhaust port. So around 33' + the cleanout T into the stove. It is a 2 story house with a 12 pitch roof and the chimney on the side of the house near the point in the roof, hence the really tall chimney.

The Austroflamm Integra II says to use 4" vent pipe over 20 feet but also says to keep the pipe under 30'. I am of course over 30'.

Any suggestions on what I should use for liner?

Someone that also has a tall chimney and the same stove, they have a few feet less than I do, recommended I use ridgid 4" liner for the least resistance and insulate the pipe.

My last resort is to drill a hole through the back of the chimney to vent the stove, but REALLY want to avoid this as it is a very tall chimney and don't want to weaken it.

 

[briansol]

I'm not expert but I think you'll be ok with the 4" liner. 3' is only 10% difference in height. There's enough room for a margin of error there alone. I don't know how you will ever get rigid pipe around the damper block... and I also wouldn't suggest drilling out brick.

 

[fmsm]

If it was me I would connect the 4" liner to a 6" liner for about 15 feet, Install from the top down and secure the 6" pipe to your cap.

 

[AJ9]

If it was me I would connect the 4" liner to a 6" liner for about 15 feet, Install from the top down and secure the 6" pipe to your cap.

Can you run into issues using pipe that is too large? Wondering why I can't just run 5" all the way up. Is it something to do with needing the velocity you get with the smaller diameter pipe to carry the ash particles up?

 

[tjnamtiw]

Since you are talking all VERTICAL pipe, you should see on the installation sheet that the EVL is only 1/2 of 33' or 16 1/2 feet. You should have no problem running 4" pipe up the chimney. What's the max EVL that they recommend?

 

[BrotherBart]

I don't heat with it full time but I have my Englander 25-PDVC vented with 3" pellet vent to the thimble in the basement wall that is connect to a 33 or so foot 5.5" flex liner. I have only burned a ton and a half or so through it but all is well. The liner doesn't get dirty and the fly ash collects either in the tee connected to the liner or the one connected to the back of the stove.

 

[BrotherBart]

Since you are talking all VERTICAL pipe, you should see on the installation sheet that the EVL is only 1/2 of 33' or 16 1/2 feet.

Huh? Please educate me on that one. Vertical rise "reduces" EVL?

 

[tjnamtiw]

Huh? Please educate me on that one. Vertical rise "reduces" EVL?

Hi BB, for every 2 feet of vertical pipe, it is 1 'equivalent foot'. Maybe I didn't use the correct nomenclature.

 

[AJ9]

Doesn't specify separate horizontal or vertical pipe. They are very vague with that. This is what rika says in the pellet stove install manual:

"-Each 90° angle or T-connector adds an effect
of five additional feet of pipe length. Each
45° angle adds an effect of three additional
feet of pipe length.

-4” venting is required in all installations at or
above elevations of 2500 feet.

-4” venting is required in all installations where
the total length of venting is equal to or greater
than 20 feet including the effective length of
any angles.

-The maximum length of any venting
configuration should not exceed 30 feet total,
including the effective lengths of any angles.

-The stove’s exhaust system works with negative
combustion chamber pressure and a slightly
positive chimney pressure. It’s crucial that the air
intake and exhaust system are air tight and
installed correctly."

 

[BrotherBart]

Yeah but those calculations are in regard to the pellet pipe. And with over sixteen EVL he needs to, in theory, go to 4" pellet pipe. But the calculations go out the window when you are talking about five and a half or six inch chimney liner. Restriction drops like a rock at that point. It is pretty much the same as dumping the exhaust into the great outdoors.

 

[tjnamtiw]

Yeah but those calculations are in regard to the pellet pipe. And with over sixteen EVL he needs to, in theory, go to 4" pellet pipe. But the calculations go out the window when you are talking about five and a half or six inch chimney liner. Restriction drops like a rock at that point. It is pretty much the same as dumping the exhaust into the great outdoors.

Totally agree, Brother. I was speaking to his reference of 4" pipe. With that much vertical pipe, his draft will be huge once the air in there warms up.

 

[AJ9]

Totally agree, Brother. I was speaking to his reference of 4" pipe. With that much vertical pipe, his draft will be huge once the air in there warms up.

I'm a newbee on this one. But is that the problem with over 30' of pipe? I was thinking there was too much restriction for the blower for over 30'. Is it that there can be too much draft? Of course Rika doesn't say it shouldn't be over 30' vertical...

 

[mikkeeh]

My assumption would be....sine cold air is heavier...these a lot of cold air laying in 30' of pipe. That resistance must be overcome by the exhaust fan. I would think that over 30' of pipe would hold too much cold air for the exhaust fan to overcome. Now.....although the EVL # gets better with larger pipe...it seems to me that the volume of cold air in a 6" pipe....would compound the problem.....No??

 

[AJ9]

My assumption would be....sine cold air is heavier...these a lot of cold air laying in 30' of pipe. That resistance must be overcome by the exhaust fan. I would think that over 30' of pipe would hold too much cold air for the exhaust fan to overcome. Now.....although the EVL # gets better with larger pipe...it seems to me that the volume of cold air in a 6" pipe....would compound the problem.....No??

That makes sense.

Now that we are talking about EVL and I'm lower than the pipe length i thought because its all vertical...I'm thinking I should just buy a 4" x 35' smooth wall flex liner and insulate it. Called Rockford Chimney Supply and the guy I talked to said the smooth wall pipe vs the rigid I won't see much of a difference in terms of resistance. Then I can avoid the 45 deg bends around the damper as well. But since I'm at such a ridiculous installation height at around 38-40 ft up on a ladder or manlift, it would make install much easier with the smooth wall flex pipe than the ridgid. I have read that I really need to make sure i don't kink the smooth wall flex pipe. Hopefully I can manage that if I go this route.

If i use the smooth wall flex, should I use a T so the ash doesn't slide all back down to the blower? Or is that not really an issue and I can connect right to the back of the stove.

 

[stoveguy13]

The instruction are telling you more then 30 ft of total venting from the standpoint that stove may not operate correctly this is for a vertical or horizontal per the installation instruction you posted the reason for this is in some case the stove may not be able to generate enough pressure to pull enough air in for combustion and exhaust the flue gas from the stove or it may pull to hard and you won't be able to slow it down. You have two options i can think of install it with 33ft of liner and see how it works. My guess is it will most likely be fine if you had 40-50ft i would be concerned. Second option is bust a hole in the back of the fireplace and horizontal vent it. I would try option one first.

 

[Madcodger]

I'm running about 30' of 4" liner straight up a chimney (slight bend with the damper at bottom). Stove on is a little Whitefield Quest (19 years old). Burns like a champ, no problems at all. Can't speak to this situation, but when I go outside and look at the cap there is clearly some very warm air exiting so it hasn't cooled much in its ascent.

 

[SmokeEater]

I ran my 4" pipe to a 32 foot masonry chimney that I used for my wood furnace for 30 years. It's a masonry unit with 8 in square tile liner. That 8 inch dimension is outside to outside. I was going to line it with a 7 inch stainless liner and bought it. I could not get the liner to fit so had to order another at 6". I have the 7 in its original box if anyone wants it. I paid about $600 for that with the cap and the horizontal T connector. My point is that my PB105's 4" pipe connects to that 6 inch stainless liner at the masonry wall. I put a damper in the 6 inch portion in case my draft was too high, Using the Magnahelic instrument I easily set the max and min settings according to the Harman manual with the damper and the draft pot on the the control board. After removing and cleaning this past Spring, I reassembled the pipes and reset the correct draft. My boiler runs very well on a feed setting of 5 and makes only white to grey ash with no unburned pellets in the ash pan. I just emptied the pan Saturday after burning 1 1/2 tons. The ashes were just below the top edge. I know that the manual says not to put a damper in the vent, but it is in the 6 inch section, and it works just fine keeping the high draft that I would have moderated.

 

[skibumm100]

The only concern I would have with the Rika is that you don't have an inlet damper and you may not be able to keep the air flow low enough. A tall, hot flue with draft like crazy once it gets hot and you may have too much combustion air. The Rika uses an airflow sensor to tell the computer card how fast to spin the blower to supply the required combustion air for the fuel feed rate. There is no restriction (damper) in the inlet air path like you find on a lot of stoves. I would install it as you are planning with 4" vent and see how it runs. If the stove has too much air flow, you could consider installing a damper on the combustion air inlet at the back of the stove. You don't want to blow all of your heat up the flue. This is just something to keep in mind and may not be required as long as the combustion blower is still able to control the air flow.

 

[steamguy]

Maybe I can help, speaking from a little practical experience: We had an Austroflamm Integra for many years (14 years) and it was the best heating pellet stove we've ever owned. When we had it installed, we used 36' of 4" flex to get from the tee+cleanout to the wind cap on the top of the chimney. We live in a VERY windy part of the country, and never, ever, had a problem with the stove as for draft or heating capability. Never, ever a problem starting the stove.

We put a bracket in to hold the bottom of the pipe steady, and one at the top of the chimney to secure all that length. Did not insulate the chimney pipe, except at the bottom to stop drafts.

Just a data point from some practical experience from an Austro owner. Hope that helps you sort through the other stuff as well.