# relocating rear flu to top flu- Issues?



## beergut (Aug 31, 2014)

I just doubled the size of my house and as a result, had to buy a larger wood stove to heat it (about 3000sf with vaulted ceilings)
I picked up a nice All Nighter "Big Moe" stove- and I was contemplating welding the factory rear flu closed and cutting / welding a new 6" flu on the top of the stove. This would save me a lot of work relocating my roof stack and extending my floor pad. Wondering if that would change the dynamics of the stove a great deal? It's just one huge firebox inside- I'm an experienced welder and metal worker. your thoughts?


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## Grisu (Aug 31, 2014)

I assume such a modification would void the stove's UL listing meaning you would need to install it according to the specs for unlisted stoves (see NFPA 211). Looking at the manual that may not mean much of a change: https://www.hearth.com/images/uploads/AllNighterman.pdf 
The stove needs a 36" clearance to the back wall. When relocating the exhaust your flue should be about 40" off the wall. I would also check with your local building inspector and your home insurance about their requirements for an unlisted stove install. 

Another problem could be that the stove will be even less efficient. With your planned modification the hot gases are no longer flowing along the top to release some of their heat to the top-plate but go right up the chimney. You will need A LOT of wood to heat 3000 sqft with that stove. 

On a personal note: Not sure if you will be really happy with this inefficient "smoke dragon" when a new, EPA-approved secondary burn stove can be bought for ~$900 (e. g. the Englander 30NC). Such a stove will be twice as efficient (60% to 70% versus 30% to 40% for your old-fashioned stove) meaning you will need only half the wood for the same amount of heat.


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## beergut (Aug 31, 2014)

Grisu said:


> I assume such a modification would void the stove's UL listing meaning you would need to install it according to the specs for unlisted stoves (see NFPA 211). Looking at the manual that may not mean much of a change: https://www.hearth.com/images/uploads/AllNighterman.pdf
> The stove needs a 36" clearance to the back wall. When relocating the exhaust your flue should be about 40" off the wall. I would also check with your local building inspector and your home insurance about their requirements for an unlisted stove install.
> 
> Another problem could be that the stove will be even less efficient. With your planned modification the hot gases are no longer flowing along the top to release some of their heat to the top-plate but go right up the chimney. You will need A LOT of wood to heat 3000 sqft with that stove.
> ...




thanks for the reply-
been thinking and working on this project a lot today.
I'm not worried about the clearance; the wall it's next to is solid brick and field stone all the way up to the zc pipe.
the stove back will be about 11" from the wall.
I had the same thought about the stove being less efficient with the convection heat going up the pipe- but I balanced that notion with the fact that I'll be utilizing a damper in the pipe, the black stove pipe has a 20' run before it goes through the roof (vaulted ceiling) so the pipe will release some of that heat, and I was thinking of welding a long baffle shaped like this:  " ) " with the cup facing the front of the stove- this would create a heat "dam" in effect and allow that top plate to catch some of that convection heat before heading up the smoke stack... also, that rear exit is only 2" down from the top plate, so I just can't see it making all that much difference. 
this stove is rated to heat a 3000+ sf area. I must've read a hundred posts on various stove forums that regard this stove as one of the best stoves to heat a large area- locally, these stoves still sell for over $1200- I paid under $200 for my Big Moe- so I'm not staying awake at night worrying about having to buy another stove if this doesn't cut it. 

Wood isn't an issue either; I have 14 acres of hard woods (oak & maple) and another 30 acres up in main of dense forest.


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## begreen (Aug 31, 2014)

What is behind the brick and fieldstone, stud wall?


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## BrotherBart (Aug 31, 2014)

Moving this one over to the Classic Stove room.


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## beergut (Aug 31, 2014)

begreen said:


> What is behind the brick and fieldstone, stud wall?



cinder block core with field stone and brick. it's about 10' wide all the way up to the vault.
but even if it was stud- having field stone and brick between the stove and the stud is more than adequate- especially fieldstone.


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## beergut (Aug 31, 2014)

similar to this- except I have a triple bay window on either side of the stone- but the stone design and location is similar to this pic here:


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## Grisu (Aug 31, 2014)

beergut said:


> but even if it was stud- having field stone and brick between the stove and the stud is more than adequate- especially fieldstone.



How do you know? Have you looked at NFPA 211 to see by how much a non-combustible surface reduces the required clearance? Before you tell that someone else who may have studs behind the wall take a look at this, especially table 2: http://www.maine.gov/dps/fmo/documents/standardsfor_solidfuel_stoves.pdf 

Regarding your plans: Make sure to brush your chimney often. With all those elbows and the damper in there you likely will accumulate quite a bit of creosote. Are you seasoning (aka split and stack 1 to 2 years in advance) your wood? 


beergut said:


> I must've read a hundred posts on various stove forums that regard this stove as one of the best stoves to heat a large area



Let me guess: This one was not one of them.


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## beergut (Aug 31, 2014)

Grisu said:


> How do you know? Have you looked at NFPA 211 to see by how much a non-combustible surface reduces the required clearance? Before you tell that someone else who may have studs behind the wall take a look at this, especially table 2: http://www.maine.gov/dps/fmo/documents/standardsfor_solidfuel_stoves.pdf
> 
> Regarding your plans: Make sure to brush your chimney often. With all those elbows and the damper in there you likely will accumulate quite a bit of creosote. Are you seasoning (aka split and stack 1 to 2 years in advance) your wood?
> 
> ...



*I'm not using a single elbow- straight pipe all the way up (20' black / 16' zc) not sure how you came under that impression.
*I've never seen a fieldstone wall less than 3.5" (unless you're referring to a stone veneer- in which case, it's not a "fieldstone" wall) - so even if there were studs behind the fieldstone wall, it's irrelevant. Like I said, this isn't an issue; whether the NFPA 211 says it is, or not.... it's not.
*I've been burning wood in this house for almost 20 years- 3 different stoves- swept the chimney all of maybe 4 times. I'll typically "over-fire" the stove twice / year to clean any tar out of the stack.
*My wood is aged anywhere from 1yr to 5 yrs, depending on where I take from the pile. I burn about 3.5-4 cords per year between October - may. This will be the second year with the new addition, hence the bigger stove. the russo didn't cut it last year.
* quote: "Let me guess: This one was not one of them" .... I have no idea what you mean by this comment; I've read a ton of threads from this site on "all nighter" stoves that've been positive.


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## begreen (Sep 1, 2014)

Actually, if there is wood in the wall behind the stone/brick it's pretty important. They can act as a heat shield but are also heat conductors and over time the bigger concern becomes pyrolysis. This issue recently hit a friend's dad's house after 35 yrs of burning.


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## beergut (Sep 2, 2014)

begreen said:


> Actually, if there is wood in the wall behind the stone/brick it's pretty important. They can act as a heat shield but are also heat conductors and over time the bigger concern becomes pyrolysis. This issue recently hit a friend's dad's house after 35 yrs of burning.


 

sounds strange- I read up on it a little...
pyrolysis occurs with organics over the temps of 390*F - in the absence of oxygen.
I can't see how this can occur behind a thick wall of masonry or stone. even stone veneer is at least 3"+ thick of actual earth stone, then the mortar and at least 1/2" cement backer board or 5/8" fireboard. Then you also have an air gap between the stove and the masonry- if he had a masonary or stone wall behind his stove, I can't see how the air between your walls could get over 390* ? Did he have the steel pipe also going through the wall? If so, then I can see how he could reach those temps.

we just remodeled out lake house up in acton maine a few years back- has a wood stove and black pipe about 12" away from the wood paneling and nothing but studs behind it. this stove has been used for over 40 years all winter long while we'd head up for ice fishing and sled riding- I remember the pipe glowing red hot. the wall paneling is 3/4 pine t/g and has a slight discoloration and warpage to where the heat hits it. the studs behind the wall are true 2x4 (not 1.5x 3.5) - they look as good today as the day my grandfather built it.


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## Grisu (Sep 2, 2014)

http://inspectapedia.com/chimneys/Pyrolysis_Definition.php

"The chemical change of pyrolysis lowers the temperature at which a substance will catch fire. What may be surprising is that wood exposed to temperatures as low as 200 degF. can over time be changed such that its ignition point or combustion point is significantly lowered."


beergut said:


> the wall paneling is 3/4 pine t/g and has a slight discoloration and warpage


 

That's like driving with bad brakes and saying, because you did not have an accident so far, the car is fine.


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## beergut (Sep 2, 2014)

Grisu said:


> That's like driving with bad brakes and saying, because you did not have an accident so far, the car is fine.


 
yep- sorta. always told dad to fix the wall before nature does it for him.
when we did the house over a few years back I found a large slate slab about 6' x'5 x 1" thick and now it sits against the wall with 3/4 spacers behind it.


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## bholler (Sep 2, 2014)

beergut said:


> *I've been burning wood in this house for almost 20 years- 3 different stoves- swept the chimney all of maybe 4 times. I'll typically "over-fire" the stove twice / year to clean any tar out of the stack.



And you think this is a good practice?  I am sorry but you are asking for trouble if you continue doing this.   Also what are you referring to as zc pipe?  do you mean class a if so it need 2" not zero clearance at all.  I would also recommend running double wall instead of single if it is running 20' because it will cool allot in that distance causing more creosote buildup.


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## beergut (Sep 2, 2014)

bholler said:


> And you think this is a good practice?  I am sorry but you are asking for trouble if you continue doing this.   Also what are you referring to as zc pipe?  do you mean class a if so it need 2" not zero clearance at all.  I would also recommend running double wall instead of single if it is running 20' because it will cool allot in that distance causing more creosote buildup.


 

zc = zero clearance. it requires zero clearance, as the name implies.
and yes- there's nothing "wrong" with over-firing a stove to clean a smoke stack every now and then- if YOU don't like the idea of it, then YOU don't have to do it; I've been doing it for over 20 years with no ill effects and it keeps my pipes clean and tar free...
And no. I would not run zc instead of steel pipe up the 20' interior span- total waste of heat & money. ZC runs from the roof box up through the roof and above the roof ridge- that's it.
Came here to get thoughts on modifying my big moe and to discuss the dynamics of such modifications; not to discuss wall clearances, building materials and be given advice on how to burn wood and assemble pipe- I'm 43, 15 years as a frame / finish carpenter, 5 years as a roofer and 6 years as a USMC Combat Engineer (building and blowing stuff up) I've installed many stoves and stacks. I've been burning wood personally for over 20 years and grew up in northern NE with my father who has burned wood for the last 45 years.
Thanks for the "advice" on how to burn wood, season wood, build a wall or read local code on stove installation.... All set with that.
If you'd like to stay on topic and discuss the stove modification.... wonderful, otherwise I don't need advice on how to own & operate a wood stove


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## bholler (Sep 2, 2014)

Well by modifying your stove you change the clearance requirements as stated before.  Also what brand pipe are you using that is zero clearance?  Not saying it doesn't exist but i have just never heard of it i am curious.  Now as far as nothing wrong with purposely starting a chimney fire instead of cleaning your chimney you ar every wrong there.  If you want to do it that is your prerogative but i don't want anyone to read this and think that it is in any way safe to do so.  And by the way i am a certified chimney sweep been doing it for 7 years i work for my father who has been a sweep for almost 40 years so i think i know a little about installing stoves safely.  Also i was not saying to use insulated pipe instead of single wall i was referring to double wall connector pipe.


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## bholler (Sep 2, 2014)

beergut said:


> I've been doing it for over 20 years with no ill effects



When was the last time you scanned your chimney to check the condition.  If you haven't how do you know there are no ill effects.  Just because you have done something for a long time doesn't make it right.


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## beergut (Sep 2, 2014)

bholler said:


> Well by modifying your stove you change the clearance requirements as stated before.  Also what brand pipe are you using that is zero clearance?  Not saying it doesn't exist but i have just never heard of it i am curious.  Now as far as nothing wrong with purposely starting a chimney fire instead of cleaning your chimney you ar every wrong there.  If you want to do it that is your prerogative but i don't want anyone to read this and think that it is in any way safe to do so.  And by the way i am a certified chimney sweep been doing it for 7 years i work for my father who has been a sweep for almost 40 years so i think i know a little about installing stoves safely.  Also i was not saying to use insulated pipe instead of single wall i was referring to double wall connector pipe.



Thanks again for your OPINION on chimney sweeping & burning, but I'll heed the 65 years of knowledge & experience accumulated (collectively speaking) between my father and I. Like I said- I've never had an issue over-firing my stove at the end of the season to clean the pipe out, and it would take A LOT more than the opinion of a 7 year experienced chimney sweeper to convince me to toss my knowledge & experience to the side. Today's zc stove pipe is VERY CAPABLE of sustaining and containing a chimney fire; unlike yesterdays single-wall stove pipe running up between rafters that would turn cherry red and ignite any organic material within a few inches of it. Regarding the double wall connector pipe for in the house; I haven't needed it over the past 20 years, nor has my father, or any of our neighbors (who are much older than I)... maybe for some applications it could be useful, but TOTALLY useless in my application and a complete waste of money. Having the knowledge is only one part of the equation; knowing when & where to apply it properly is another aspect.    

I have no idea what brand zc pipe it is- as I'm not climbing up on my roof to find out- I know it's triple insulated stainless pipe (that won't even melt snow when my stove is fired up!)... but it's irrelevant. Whether zc requires 2" of space between a surface and the pipe is also irrelevant, since all of the zc is above my roof- and, even if I did have any zc (or double wall connector) between the ceiling and the stove, it would be in front of a field stone wall- where there is no code requirement for clearance. moving on...

The only difference in heat transfer I can expect by relocating the flue from the rear to the top, is a minor change in convection heat transfer- but I suspect very little change by way of the baffle design I'll be implementing which will prevent the heat currents from going straight up the pipe. The modification is actually quite minor- as the rear flue is already practically at the top plate to begin with.


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## beergut (Sep 2, 2014)

bholler said:


> When was the last time you scanned your chimney to check the condition.  If you haven't how do you know there are no ill effects.  Just because you have done something for a long time doesn't make it right.



huh? "scanned" a chimney? it's triple wall stainless steel from the roof up. I built the house (and recent addition) 20 years ago.


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## bholler (Sep 2, 2014)

Ok as far as modifying the stove in that stove it probably doesn't matter very much and as long as you have no combustibles in the wall behind it clearance is not an issue.  And yes scanned a chimney modern insulated chimneys are only designed to stand up to occasional chimney fires and are supposed to be thoroughly inspected after any fire they can become seriously computerized by repeated fires.  And by the way these are not my opinions These are code and recommendations from CSIA.  



beergut said:


> I know it's triple insulated stainless pipe (that won't even melt snow when my stove is fired up!)... but it's irrelevant. Whether zc requires 2" of space between a surface and the pipe is also irrelevant, since all of the zc is above my roof



It is relevant where it passes through the roof there have to be combustibles there.  And i am sorry but working as a professional chimney sweep for seven years counts for allot as well as growing up with a father who has been a chimney sweep my whole life and heated with wood the whole time also counts.  I also go to several continuing education classes a year on all aspects of chimneys.  How much education have you had on the subject?  And you are contradicting yourself is it " triple insulated"  or triple wall or zero clearance?  

Like i said before if you want to risk you house by burning your chimney out that is up to you but it is a very dangerous old school way of doing things and i don't want anyone else to think it is in any way safe or advisable.


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## bholler (Sep 2, 2014)

beergut said:


> we just remodeled out lake house up in acton maine a few years back- has a wood stove and black pipe about 12" away from the wood paneling and nothing but studs behind it. this stove has been used for over 40 years all winter long while we'd head up for ice fishing and sled riding- I remember the pipe glowing red hot. the wall paneling is 3/4 pine t/g and has a slight discoloration and warpage to where the heat hits it.



Is this part of that 65 years of knowledge?  Another great example of chimney saftey


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## beergut (Sep 2, 2014)

bholler said:


> Ok as far as modifying the stove in that stove it probably doesn't matter very much and as long as you have no combustibles in the wall behind it clearance is not an issue.  And yes scanned a chimney modern insulated chimneys are only designed to stand up to occasional chimney fires and are supposed to be thoroughly inspected after any fire they can become seriously computerized by repeated fires.  And by the way these are not my opinions These are code and recommendations from CSIA.
> 
> 
> 
> ...




no- it's not relevant where it passes through the roof- makes no difference at all- as long as I have the proper height on the stack.
No again; your "education" means zippo to me. I also know many certified ASE mechanics that I wouldn't trust for a second working on my truck.
Just because you THINK you know something, does not mean you do.

How much education do I have on burning wood and building code? well, it would take a very long post and honestly- I just don't respect your opinions or recommendations enough to vest that kind of energy into listing my credentials; we'll just say, I'm very qualified (and well licensed) and I've dealt with "chimney sweepers" on projects before-  and lets just say... dealing with a "chimney sweeper" on a project is like dealing with a security officer who thinks he's a cop.
EVERYTHING you've covered in your "continued education" on chimneys, I've covered as well- plus some, and some more. I'll leave it at that. There's no knowledge you posses that can't be obtained via 1 week of google a few hours a day.

"triple insulated"  or triple wall or zero clearance".... now you're just be silly. obviously meant to say triple wall- and you knew that.

regarding your last post about the lake house.... read the above thread again; like I said above, that lake house was built by my grandfather, inherited by my father and then sold to me. I renovated the lake house and FIXED my grandfathers shoddy install (which lasted what, 50+ years the way it was... no fire... no issues.)

enough with this. getting feedback with a stove modification on this site is akin to asking a waiter what dinner he recommends on the menu and the waiter responds by telling you how to plant crops and feed cattle.
Here I expected to engage in an intelligent conversation on the physical characteristics & thermal dynamics of a particular wood stove- expecting some input from someone who's performed such a mod, or even maybe a little math to assist in my flue design and stove mod. Nope. just a bunch of irrelevant questions, opinions and recommendations that have ZERO relevance to the original topic.

and I'll leave it at that.


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## bholler (Sep 2, 2014)

beergut said:


> "triple insulated" or triple wall or zero clearance".... now you're just be silly. obviously meant to say triple wall- and you knew that.



Ok then you obviously know that most triple wall is only tested to 1700 degrees and not the 2100 needed for a wood stove.  I hope you picked the right one.  I guess you have it all figured out i hope If there ever is a fire your insurance company doesn't check it to close because by your comment that it doesn't matter what is behind the stone i can tell you have no understanding of fire code and there are probably multiple violations.  And by the rest of what you have said you obviously have zero idea about how to properly operate and maintain a stove.  And i will say it again most of what i have said here is not my opinion it is a combination of code and csia recommendations.  I am done wasting my time on someone who obviously isn't going to listen to anyone and has no concern for their safety or the safety of their family.


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## begreen (Sep 3, 2014)

Don't take offense. The primary focus here is safety. We get too many "pros" here that have always done it this way or that only to find out it is not the right way. What one does in their own home is their business, but we have to also think about the next person that reads this thread and decides whether to copy or not the practices mentioned. 

As for the stove mods, I don't think it would be a huge change, but I would also consider adding a baffle plate to help force more of the unburnt gases into the basic secondary air supply coming from the door.


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## bholler (Sep 3, 2014)

I am sorry i got a little pissed begreen i started with safety in mind and then he just got ignorant.  I just take offense when some one says it is ok to do something so unsafe


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## mellow (Sep 3, 2014)

While you are at it add some stainless steel tubes and set it up for reburn with a nice baffle, sounds like you got the welding knowledge to do it.  Those big moe's are pretty much bulletproof, would take a lot to damage it, but they can be warped beyond repair.  Make sure and weld that rear exhaust plenty good, check the weld around it with a flashlight as it might need some touch up after all these years of burning.

Here is a good thread on setting it up for secondary reburn:  https://www.hearth.com/talk/threads/bullard-secondary-air-retrofit-project-complete.55033/


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## coaly (Sep 5, 2014)

I second the baffle plate to prevent more heat rising directly out of the stove.

More info here; https://www.hearth.com/talk/threads...less-smoke-under-25.74710/page-4#post-1748825

The first (Fisher) steel plate stove was side vented to sit across the hearth and not extend out into the room farther than necessary. Then they were built with rear or top vent. Baffle plates were developed for double doors around 1980 but were never used on single door stoves.

The main thing is that you make the new collar long enough to extend down into the stove. Length was 5 inches long, extending into stove I believe 3 inches. That way the rising heat goes to the top and has to be pulled down to go up the stack. If the flue collar is even with the inside of stove too much slips up the flue.

Keep the baffle plate "smoke space" or the square inch area the exhaust flows through at least the square inch area of the flue outlet on stove. No smaller. And use a damper in the first section of pipe if possible.


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