# Flue Question



## Osage (Aug 22, 2013)

I am going to replace our old Earthstove with a Lopi 520 that caught my fancy. Currently the Earthstove has single wall pipe inside. I would like to reduce the clearance to back wall by using a heat shield on the wall.
The question is, am I better off going to a double wall pipe or going to a heat shield on a single wall pipe.
Thanks


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## begreen (Aug 22, 2013)

Do you want to put up a wall shield or a pipe shield on the pipe? Shielding is less expensive but if this connects to an exterior chimney the double-wall pipe will keep the flue gases hotter. This can help if the interior run is long and creosote accumulation is an issue.


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## STOVEGUY11 (Aug 22, 2013)

Single wall pipe has 18" clearances on its own. If you place a shield on the pipe that is reduced to 9". Double wall pipe will have 6" clearances. Check the specs of the manual of the stove. They typically will show the clearances for all the scenarios.


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## Osage (Aug 22, 2013)

Thanks for the reply guy's. I am going to shield the wall to reduce the clearance on the stove. The inside run of pipe is short, into an 8' ceiling, however there needs to be 2  45 elbows in that run. At the ceiling it transitions to double wall.
 Does it make more sense to go with double wall on the interior if for no other reason than reduction of creosote.


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## Heatsource (Aug 22, 2013)

Osage said:


> Thanks for the reply guy's. I am going to shield the wall to reduce the clearance on the stove. The inside run of pipe is short, into an 8' ceiling, however there needs to be 2 45 elbows in that run. At the ceiling it transitions to double wall.
> Does it make more sense to go with double wall on the interior if for no other reason than reduction of creosote.


 

yes, better draft and performance, lasts longer, looks better


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## oldspark (Aug 23, 2013)

Single wall pipe (good stuff) lasts forever and if you have a short run (what's advised) poses no problem with creosote, and I like the looks of the single wall better.


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## Wood Heat Stoves (Aug 24, 2013)

Osage said:


> Thanks for the reply guy's. I am going to shield the wall to reduce the clearance on the stove. The inside run of pipe is short, into an 8' ceiling, however there needs to be 2 45 elbows in that run. At the ceiling it transitions to double wall.
> Does it make more sense to go with double wall on the interior if for no other reason than reduction of creosote.


 
The 2 45 degree elbows will reduce the draft slightly so the double wall pipe would help by keeping the interior temperature higher for a better draft, especially if the overall chimney run is not that long. Double wall pipe also is stainless steel inside and will last much longer than single wall. The Lopi 520 is a great stove but be sure to follow the manuals specs for clearances with whatever type of pipe you choose. The clearance, especially with double wall pipe, shouldn't need any wall protection to get reasonably close. Just be sure you have the correct specs because there's a 520 and a 520-96. There also may be a tag on the back of the stove with the installation clearances.


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## oldspark (Aug 24, 2013)

Not trying to start a argument but I have 30 year old stove pipe that is in good shape, it is going in my install in the shop, its in that good of shape, I have looked for any recomendation to use double wall for draft and could not find any, just for clearence, if you want it OK but dont think it gains much in a short run of pipe.
Oce again I am not starting an argument just giving facts.
Forgot, stove pipe that does not last long (never seen any body burn even the cheap stuff out in a couple of years) you have a lot of moisture in the stove pipe from wet wood.
If this starts a pissing match and the mods close this thread I give up.


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## begreen (Aug 24, 2013)

Wood Heat Stoves said:


> The 2 45 degree elbows will reduce the draft slightly so the double wall pipe would help by keeping the interior temperature higher for a better draft, especially if the overall chimney run is not that long. Double wall pipe also is stainless steel inside and will last much longer than single wall. The Lopi 520 is a great stove but be sure to follow the manuals specs for clearances with whatever type of pipe you choose. The clearance, especially with double wall pipe, shouldn't need any wall protection to get reasonably close. Just be sure you have the correct specs because there's a 520 and a 520-96. There also may be a tag on the back of the stove with the installation clearances.


 
Exactly right. Warmer flue gas has increased buoyancy. Many EPA stoves have long secondary preheat manifolds. When draft is marginal due to flue height, near negative pressure, or other factors, keeping the flue gases hotter helps keep the draft up. By choosing an easier breathing stove I've gotten away with marginal installs by using a double-wall connector, easing the 90 deg turn by using 2 - 45's going to a 12' exterior flue.


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## begreen (Aug 24, 2013)

oldspark said:


> I have looked for any recomendation to use double wall for draft and could not find any, just for clearence, if you want it OK but dont think it gains much in a short run of pipe.
> Oce again I am not starting an argument just giving facts.


 
A good place to start looking for facts is the manufacturer's website.

M&G:
"DVL's double-wall, air-insulated design reduces clearances to combustibles from 18" to 6", the closest clearance to a wall of any connector pipe. DVL *improves stove performance by maintaining high flue gas temperatures for a strong, steady draft*. Because the inner wall is stainless steel the flue *heats up faster, stays hot longer, minimizes the formation of creosote*, and has the same life expectancy as the chimney. Adjustable lengths eliminate the need for cutting or crimping."
http://www.duravent.com/Product.aspx?hProduct=11

Excel:
Double Wall Construction with a 3/8” air space between inner and outer pipes provides superior insulating value to single wall pipe. Better insulating value keeps flue gas temperatures higher. This helps your woodstove perform with an enhanced draft, which provides:

less chance for moisture or soot build up within the vent
reduced smoking of the stove at start up
increased efficiency
ULTRABlack not only keeps the flue temperatures higher, it keeps the outer pipe temperatures cooler. This allows *ULTRABlack *to be installed with only 6” clearance to combustible materials. Single wall stove pipe requires an 18” clearance, which typically means your wood stove sits further away from the wall and takes up valuable space within the room.
http://www.icc-rsf.com/en/ultrablack


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## oldspark (Aug 24, 2013)

Well I was on some of the sites but did not find the info you have, I will look into it more, I question the stainless steel claims as I used to weld SS at my old job, does not transfer heat that well.
I wish I would have saved the post by the guy who was talked into double wall pipe and 2 45's spend a lot of money only to have it not help enough, IMHO it's not worth the extra cost in a good working chimney.
Have read some posts where people said the same, I think one guy did a test with the 2 types but dont remember the results.


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## begreen (Aug 24, 2013)

oldspark said:


> Well I was on some of the sites but did not find the info you have, I will look into it more, I question the stainless steel claims as I used to weld SS at my old job, does not transfer heat that well.


 
As Martha would say - this is a good thing.


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## oldspark (Aug 24, 2013)

begreen said:


> As Martha would say - this is a good thing.


Not sure you understand if you get a hot spot in tends to stay in that spot not transfering through the pipe, probably not a big deal but they are trying to sell you something.

Just trying to give opinions on the subject, I get tired of the single wall pipe not lasting comments as I know better, I know I am not the only one getting long life out of single wall.

This was one of the threads about single wall pipe with many good points brought up.
https://www.hearth.com/talk/threads/single-or-double-wall-stove-pipe.83844/page-2


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## Osage (Aug 25, 2013)

begreen said:


> Exactly right. Warmer flue gas has increased buoyancy. Many EPA stoves have long secondary preheat manifolds. When draft is marginal due to flue height, near negative pressure, or other factors, keeping the flue gases hotter helps keep the draft up. By choosing an easier breathing stove I've gotten away with marginal installs by using a double-wall connector, easing the 90 deg turn by using 2 - 45's going to a 12' exterior flue.


Begreen
 Would you consider the 520 (not the 520-96) an easy breathing stove? After the entry of the ceiling there is about 9' of double wall to the cap. (Single story house).
Thanks


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## Osage (Aug 25, 2013)

Lets try this again! Here is a photo of the current setup. Plans are to install the 520 the same way, but with new pipe. The pipe that currently on is over 30 years old.


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## begreen (Aug 25, 2013)

The 520 preceded the Liberty I think, is that correct? I don't recall it being particularly a problem for draft, but it's been awhile since I have seen one in operation. It's going to have to pull air a little harder to the front of the secondary manifold than a stove without any secondary like the old stove. I would install the new connector with 45's, similar to the current install. Watch clearances to combustibles behind the stove. The current installation looks close, but that may be just the picture. The 520 is going to want 19" from the flue collar if used with single-wall.

http://www.lopistoves.com/TravisDocs/93508003.pdf‎


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## Osage (Aug 26, 2013)

The current setup is 12" from the back of stove to the heat shield. I plan on using new double wall. Thanks for the reply.


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## begreen (Aug 26, 2013)

Good plan. That will help. What is being used for a heat shield? It doesn't appear to have the required 1" spacing behind it.


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## Osage (Aug 26, 2013)

begreen said:


> Good plan. That will help. What is being used for a heat shield? It doesn't appear to have the required 1" spacing behind it.


The photo is deceptive, there is 1 1/2" between the wall and shield.


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## begreen (Aug 26, 2013)

Nice low key shielding there. It's simple and elegant. What did you use?


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## mepellet (Aug 26, 2013)

oldspark said:


> Well I was on some of the sites but did not find the info you have, I will look into it more, I question the stainless steel claims as I used to weld SS at my old job, does not transfer heat that well.


 
If SS does not transfer heat that well, then more heat would stay in the chimney no?


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## oldspark (Aug 26, 2013)

mepellet said:


> If SS does not transfer heat that well, then more heat would stay in the chimney no?


 I dont think its a problem at all not sure why I said that, it is a poor conductor of electricity and heat, my thought was it might not trasnfer the heat through the pipe (for an even flue temp) as well but we all know that class A pipe works well.


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## Osage (Aug 26, 2013)

begreen said:


> Nice low key shielding there. It's simple and elegant. What did you use?


 It is cement board. I spaced it away from the wall with 11/2" aluminum box tubing, then painted it the same color as the wall.
On a side note, I have a Son & Daughter-in-law that live in Bellingham. He just got out of the Coast Guard. Is going back to school at Western Washington to work on a masters in business. We get up there at least 1 per year. We enjoy hiking the Mt. Baker area. or getting on a ferry at Anacortes and go to the islands. You don't happen to live in that area? I have been to some beautiful places including Alaska, but none were anymore inspiring than east of Bellingham. You lucky suckers!


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## begreen (Aug 26, 2013)

Bellingham is north of us. It's a nice spot. Next time you are there stop in and say hi to Tom and the crew at the The ChimneySweep.It's a classic stove shop!
http://www.chimneysweeponline.com/


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