# Reversed flue collar, creosote leak...



## apersonnameddan (Nov 29, 2015)

My All Nighter has a flue collar which is sized perfectly to fit in the female end of an elbow. I don't see any good way to make the male end fit inside the collar (6"O.D. 5.5"I.D.). With this in mind I installed most of the stovepipe the correct way (male end down) and cut the male end off of the last pipe to make a gender changer Unfortunately I'm having trouble getting the lower elbow to seal and after a few fires it is showing drip of creosote. Can I use furnace cement, or something to seal that one reversed joint? Is there a better way to do this? 
The manual for the stove actually shows a "drip tee" or "clean out tee" at the back of the stove, which would allow the correct (male down) orientation all the way and a female side to go on the collar, but then instead of running back into the stove to be burned I'll have a collection pan full of flammable creosote in the cap on the bottom of the tee. Would that be a good thing? What precautions would it require? How often will it need to be emptied?
Right now I'm burning a mix of old lath and wood scraps (primarily for kindling), an old maple that has been dead for some time but has been stored outside without shelter, and woodbricks (hardwood sawdust product, like overgrown pellets for a wood stove)


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## claydogg84 (Nov 29, 2015)

You can try the Rutland cement if you want, but that connection would be pretty close to permanent afterwards. Many people, including myself, run a T pipe on the back of stove. It will not fill with creosote unless you have extremely bad burning habits.  You may be able to just get a new elbow that will allow for the pipe to set up correctly.


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## apersonnameddan (Nov 29, 2015)

Since I've already destroyed that length of pipe, and the elbow doesn't have another use I'm thinking I'll probably try some sort of adhesive/sealer. There are other joints I can get apart for cleaning and rework. If it fails completely all I need is a 2' length of pipe, a tee and a cap, but if this works the cement will cost a lot less than the new parts. 
Any thoughts on the high temp RTV? It's rated for 800 degrees and the cement is rated for 2000. I wasn't sure if I should expect temps that high one elbow away from the firebox without a baffle. Would RTV adhere better and be more resilient?


Thanks,
Dan


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## claydogg84 (Nov 30, 2015)

To be honest, neither is the correct way to repair this problem and I think they will both fail. I think the old stove combined with no baffle and you may hit the 800 degree mark at that spot once in a while.


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## bholler (Nov 30, 2015)

use a stub of pipe between the stove and that elbow that way the only jiont that is backwards it the stove collar.  There are also adapters made fot this purpose.  No sealant will hold up well silicone will burn off and furnace cement will crack and fall out.


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## MDFisherman (Nov 30, 2015)

I have the same problem, don't want to put the female end over the collar of my stove(top exit) and have creosote leaking on top of my stove.

I just ordered one of these from lindemann chimney supply.  I hope it fits!


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## jatoxico (Nov 30, 2015)

Aside from getting things hooked up correctly you should be looking at your burning practices and why you're creating liquid creosote. Except for the maple you mentioned the stuff you're burning (lumber scraps and pressed bricks) should be dry. Sounds like you may be shutting the air too much. Of course you want any creosote to be retained in the system but you don't want to be making that stuff in the first place.


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## apersonnameddan (Nov 30, 2015)

Thanks for all the input.

From the suggestions it seems like the adapter would be preferred, but I lack the space to use one. I will probably use the cement as a temporary solution, but need to continue looking for the long term answer.
I'm leaning towards a "tee" but also considering ways to make an adapter fit.

If I use a "tee" is it ok to use the female side leg over the male flue collar? It would seem with the shape of the tee it should all end up in the cap anyway?
Also, this pipe is about 10-15 degrees from vertical. Will this slight angle cause any problems, or should I use an extra elbow to make it vertical? I found this picture in another thread which shows a similar idea to straighten the vertical pipe.
https://www.hearth.com/talk/attachments/dsc07082-jpg.165520/

If I add an adapter and keep an elbow at the bottom, can I add elbows to create space for  the adapter making each bend more like 100 degrees instead of 90? I think I would have to add an elbow or two to create a slight "Z" shape offset between the thimble and collar? 

I'd have to measure but I'm pretty sure I have the space for an adapter, just no straight shot to the thimble if I do that. This is the main reason I'm leaning toward the "tee".

Thanks,
Dan


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## apersonnameddan (Nov 30, 2015)

jatoxico said:


> Aside from getting things hooked up correctly you should be looking at your burning practices and why you're creating liquid creosote. Except for the maple you mentioned the stuff you're burning (lumber scraps and pressed bricks) should be dry. Sounds like you may be shutting the air too much. Of course you want any creosote to be retained in the system but you don't want to be making that stuff in the first place.


Since my skill as a wood stove operator is being called into question I might as well get it all out there and hear the critique. I grew up with a wood stove, but my parents monitored it pretty closely, so my training was minimal and more theory and conversation than practice. Any errors I made would be corrected the next time they were near the stove. 
I have been closing the front air vents  (two, screw cap style) to about 1/8" when I'm trying to limit it, and at about 1/4" it's really cooking (sorry, I don't have a thermometer, but the thermostat in the room said 88 at one point). I've been lighting/feeding it with the damper open and running between 50% and 75% open after it heats up. 

Attached is a picture of the pipe and damper about 2' above the elbow. These are all new parts, after burning the stove for 2-3 days. Is this normal, or excessive? If it's excessive then what are my options? At this point it looks like my two options are, open the vents and learn to build smaller fires, or if the stove proves too big in the colder part of winter, downsize to a smaller stove. Are there other alternatives?
I'm afraid it's hard to take a good picture, but the blisters/drips are about 1/8-3/16 thick. There was one big blister just inside from where the leak was. While cleaning and sealing it I realized this was the low point, given the angle of the pipe, where any liquid would run to and try to escape through whatever crack it could find.


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## jatoxico (Nov 30, 2015)

apersonnameddan said:


> Since my skill as a wood stove operator is being called into question I might as well get it all out there and hear the critique.


Don't take it that way! You're not nearly the first that needed some guidance (yours truly included) but what you're making there is stage 3 creosote (google it). And umm yeah, that does look kinda bad for such a short time but you can get it right.

You're on track to build smaller fires if the stove is cooking you out. At this point no matter what add more air to the fire. Forget for the moment trying to get long burns, go for clean first. Avoid the key damper and use only the air controls for starters. If you find you are getting excessive draft and cannot control the fire with the air controls alone then the key damper comes into play.

There are a a bunch of variables but for now split wood down small and build small hot airy fires. Get stove thermo's so you can monitor what you're doing.


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## claydogg84 (Nov 30, 2015)

With a classic stove you're going to get creosote unless you're running it wide open all the time. What you have in your pipe after such a short time is pretty bad - something needs to be adjusted or you'll have a fire, for sure.


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## apersonnameddan (Nov 30, 2015)

jatoxico said:


> Don't take it that way! You're not nearly the first that needed some guidance (yours truly included) but what you're making there is stage 3 creosote (google it). And umm yeah, that does look kinda bad for such a short time but you can get it right.
> 
> You're on track to build smaller fires if the stove is cooking you out. At this point no matter what add more air to the fire. Forget for the moment trying to get long burns, go for clean first. Avoid the key damper and use only the air controls for starters. If you find you are getting excessive draft and cannot control the fire with the air controls alone then the key damper comes into play.
> 
> There are a a bunch of variables but for now split wood down small and build small hot airy fires. Get stove thermo's so you can monitor what you're doing.


Thanks,
I didn't mean to be negative, just realizing that I have a lot to learn. 
If I have "3rd degree creosote" in the pipe, does that mean I probably have it in the chimney too? Do I need to get a mirror and check it out next time I'm home in the daylight, or is 2 days accumulation not enough to justify checking it?


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## jatoxico (Nov 30, 2015)

apersonnameddan said:


> Thanks,
> I didn't mean to be negative, just realizing that I have a lot to learn.
> If I have "3rd degree creosote" in the pipe, does that mean I probably have it in the chimney too? Do I need to get a mirror and check it out next time I'm home in the daylight, or is 2 days accumulation not enough to justify checking it?


Check what you can if for no other reason than to see if things are getting better or worse. Have a look at the cap if you have one (get on the roof or use binoculars if you have to), that's the coldest part of the system and they can clog. Most likely 2 days of burning didn't foul the whole system but change is in order.

The old way of burning wood was to split in fall and burn in winter and even have the occasional chimney fire. Never mind that it's dangerous as heck and a waste of fuel. We know better now and you should burn dry wood that's been seasoned (cut/split/stacked) in a good location for a year or more.

New stoves require very dry wood (<20% moisture). Your old stove will tolerate wetter wood better than a modern EPA stove but will still benefit from using good dry fuel. You'll get more heat, use less wood and burn cleaner.

Even using good practices expect to sweep once if not twice a year depending on amount of wood burned. The pipe ideally should contain light fluffy ash not the glaze you got with you're first couple of fires. BTW welcome.


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## coaly (Nov 30, 2015)

What little drips into a cap in a T evaporates.
The normal way was to over-crimp the elbow or pipe going into stove with hand crimpers. As you go around it and squeeze it down, pry outward to keep the crimp from tilting inward like a funnel too much.
The reason, is the first steel plate stoves used thin wall 6 inch OD pipe before thicker wall pipe was made having 6 inch ID to fit connector pipe.
Do you know which model stove and how many square feet you're heating?

Under normal circumstances most water vapor rises out with exhaust gasses and is not a problem.
If the chimney flue goes down below the thimble to a clean out, any liquid from the flue should drop there. You shouldn't get much from the thimble down. Your flue temperature is going to drop at that increaser causing creosote higher in the flue. A 6 inch insulated liner all the way up requires half the heat you need to leave up the larger 8 inch flue. If that is a Little Moe or Mid Moe, you may not have enough stove for a tall chimney of that diameter. As jatoxico suggested, a thermometer on the pipe just before chimney or IR thermometer to check surface temps will give you an idea if you are running stack hot enough. The key is keeping the flue and flue gasses above 250* all the way up when particulate (smoke) is present. Flue gas temperature is 30% to 50% higher than surface temperature depending on a lot of variables. 6 increased to 8 inch flue diameter is almost twice the square inch area to heat, so you need to guess how hot the temperature at upper elbow has to be to keep above 250* to the top. Checking creosote formation near the top will tell you when you're hot enough. With an IR, I've found 300* f at the 6 inch side of increaser decreases all the way to 170* on the 8 inch side. This also slows the flow in the larger flue to allow smoke particles to stick. If your chimney flue extends down below the thimble, the increaser is probably the condenser causing liquid.


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## Jay106n (Dec 1, 2015)

I came across the same problem on my All Nighter Mid Moe. I bought new pipes and I had to reverse to collar for it to fit the stove, because it does not fit the proper direction. I just installed today, so I have not experienced any leaks of any kind yet.

https://www.hearth.com/talk/threads/stove-pipe-reverse-flow-direction.150089/


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## rippinryno (Dec 1, 2015)

mine drips through the exact same spot.  i was able to seal it off with cement this past weekend.  so far no leaks and it's been getting use!


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## coaly (Dec 1, 2015)

Depends on year and UL Listing of stove.
NFPA 211 and local codes state any appliance must also be installed as per manufacturers installation instructions.
So a drip Tee is required on UL Listed stoves and joints can face downward to prevent condensed water vapor from leaking out.
https://www.hearth.com/images/uploads/ALLNIGHTERmanualwiki.pdf

It was common procedure before manuals to over-crimp the male end at the stove and install all male crimped ends down.
This was common on all stoves since the outlet pipe was 6 inch OUTSIIDE  before pipe was made 6 inch INSIDE to fit connector pipe.

Water vapor is a by product of combustion when hydrogen is present. Oven dry wood contains 6% hydrogen. One pound oven dry wood produces .54 pounds of water vapor. wood with moisture content of 25% contains another 1/4 pound of water vapor. *When entire vent system is above condensing point of 250* flue gasses rarely condense.*
The formula for calculating water vapor formed burning any fuel is 9 being the ratio of the molecular weight of water to hydrogen. Every pound of hydrogen becomes 9 pounds of water. So a fuel containing approx. 6% hydrogen such as dry wood produces .54 pounds water for every pound burned.


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## apersonnameddan (Dec 1, 2015)

coaly said:


> Depends on year and UL Listing of stove.
> NFPA 211 and local codes state any appliance must also be installed as per manufacturers installation instructions.
> So a drip Tee is required on UL Listed stoves and joints can face downward to prevent condensed water vapor from leaking out.
> https://www.hearth.com/images/uploads/ALLNIGHTERmanualwiki.pdf
> ...



WOW! I knew that combustion makes water, but I never really thought about the ratio of fuel to water and CO2 produced. 
I'm curious where the 250* comes from. Water boils at 212* is  250* just rounded up to account for cool spots, or are we talking about something else condensing?

Thanks,
Dan


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## coaly (Dec 1, 2015)

250* is the threshold of expanded flue gasses no longer able to suspend vaporized water.
So it will form as moisture on flue walls allowing smoke particles to stick forming creosote.
That is the key to keeping your chimney clean. If you had a 6 inch insulated liner, you could do that with a lot less wasted heat. The liner pays for itself in fuel.

Now think about how much water vapor is in flue gas that also carries away sensible heat that is not used in the stove or chimney. That is another reason why old and new stoves benefit from dry wood.


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## coaly (Dec 1, 2015)

Complete combustion means the conversion of carbon to CO2 and hydrogen to water.
When gasses are emitted from wood, it forms a charcoal layer. It can't burn because oxygen can't get to it as it is still emitting gasses out. Charcoal is mostly carbon but also contains hydrogen, oxygen and minerals that form ash. Oxygen that wanders on the surface combines with carbon to form carbon dioxide and carbon monoxide which is a flammable gas and can be seen as a faint blue light.
Approximate elemental composition of dry wood is carbon 49%, oxygen 44%, hydrogen 6% and ash 1%. So you can see how much more carbon is converted than hydrogen.
Figures and formulas are from Jay Shelton's book The Woodburners Encyclopedia from 1976.


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## rippinryno (Dec 1, 2015)

Every time you light a cold stove you create condensation.  Is this so minimal that it is not a factor in the long run?  Also what about long chimneys that go 15ft and probably never reach 200 degrees on the top sections?  Do these tend to gather creosote?


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## FishKiller (Dec 1, 2015)

That certainly seems to be excessive amounts of creosote build up, especially with the fuel you are using, my stove pipe never collects creosote south of the 90...just some fly ash. seems to me that your condensation point is in your stove pipe.  which means you might be getting great stove top temps, but your stove pipe is way to cold.  you should clean out all that gunk, inspect your flue for build up, and seal that crack with stove cement.  then change your burning habits and get a couple of thermostats or an IR gun....  run the stove with damper wide open and control the stove with the air controls.. if your damped down all the way and can't get control of the fire, then start using the damper to slow the draft down.  you want a nice hot stove pipe and a hot flue.
all that talk about how much water wood produces is pointless if your running the stove right.


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## coaly (Dec 1, 2015)

rippinryno said:


> Every time you light a cold stove you create condensation.  Is this so minimal that it is not a factor in the long run?  Also what about long chimneys that go 15ft and probably never reach 200 degrees on the top sections?  Do these tend to gather creosote?


The same moisture is always present, you just see it on the glass and stove walls when they are cool enough to condense it. Once hot, it evaporates back into water vapor and condenses again if cool enough in higher portions of flue. As flue heats, it eventually gets hot enough to the top and rises out. When the water vapor exits chimney into cold enough air, it will appear as steam or condensing water vapor looking like white smoke that drifts away.
Yes, creosote forms more at the top and is the reason for an insulated flue so it does stay above condensing point. Checking surface temperature isn't flue gas temperature, only an internal probe or thermocouple can tell you that. Most calculations figure 30 to 50% higher but can be even higher.
The coldest part is the screen and top cover that come into contact with outdoor air. That can be a good indication from the ground what to expect in the flue and is usually the first to block up.


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## apersonnameddan (Dec 4, 2015)

It's been too warm for the stove the past couple days but I finally lit it again last night. I have 2 magnetic thermometers 18-24" above the stove I had to pack it about 50% full and run it wide open to get them both into the burn zone. Closing the vents to 2-3 turns open trims the temp to the bottom of that range with one sitting a little below and the other a little above the creosote/burn zone. I read somewhere that most stoves run at 1-2 turns open, but that just chokes the fire down to a smolder. I'm using hardwood bricks with lath as kindling at this point.


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## Mybooman (Dec 4, 2015)

So, Coaly, using your formula above, I think you may have helped me figure out what is going on with my Resolute III / 6" stove pipe / 8" chimney.  Dan, you are not alone with the significant amounts of creosote build up in a short period of time and I have been through this site trying to find answers that make sense for the past week to no avail.  So I thank you for putting it all out there.  Sounds like my 8" chimney may be too fat and tall for my little stove and I may be in for some real trouble when it gets truly cold, does this sound accurate?  And if so, what are my options?  Start another thread, to begin with?


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## coaly (Dec 4, 2015)

Mybooman;
Is your chimney also exterior? 6 inch outlet on stove? 8 inch masonry or insulated prefab? Do the installation instructions require the pipe and chimney to be the same size as stove outlet?
All the principals apply to all stoves and the more efficient the design or smaller the firebox the more critical a larger flue becomes.
It's common to have a small stove and people think the stove won't heat enough so are looking for a larger stove when the problem is the chimney is so big the stove is having a problem heating it before it can heat the house. They think a larger chimney creates more draft so it should be fine. A larger flue is *capable* of more draft when more heat is left up it, but if you have an efficient stove with less heat loss it becomes much weaker than the correct size. Any stove benefits from not increasing the flue larger than the stove outlet.


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## Mybooman (Dec 4, 2015)

coaly said:


> Mybooman;
> Is your chimney also exterior? 6 inch outlet on stove? 8 inch masonry or insulated prefab? Do the installation instructions require the pipe and chimney to be the same size as stove outlet?
> All the principals apply to all stoves and the more efficient the design or smaller the firebox the more critical a larger flue becomes.
> It's common to have a small stove and people think the stove won't heat enough so are looking for a larger stove when the problem is the chimney is so big the stove is having a problem heating it before it can heat the house. They think a larger chimney creates more draft so it should be fine. A larger flue is *capable* of more draft when more heat is left up it, but if you have an efficient stove with less heat loss it becomes much weaker than the correct size. Any stove benefits from not increasing the flue larger than the stove outlet.


My Resolute III 6" stove pipe goes straight up almost 10' where I put an adapter 6 -> 8" which attaches to the black box, through the roof, where it then becomes a double wall still straight shot another 7' or so.  I do not have any trouble lighting the stove or keeping it at appropriate temps, but I have dangerous amounts of creosote accumulating in very short periods of time, even when burning biobricks, so it's not all related to my wood, which is good, but not stellar.


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## coaly (Dec 4, 2015)

Yes, your chimney is too cold. 10 feet of single wall pipe is going to cool a lot before dumping into chimney. Even a 6 inch chimney flue needs more heat than it's going to get that high unless you burn exceptionally hard. You should get an IR thermometer (or check multiple places with magnetic) and see how much the surface temp drops from stove to support box. You'll be surprised. Don't think that stove will get you 300 or 350 that high. Remember the inner flue gas temps are going to be 30 to 50% higher than surface, so it's not as bad as it looks. Double wall pipe up to that height will get you hotter, but expanding to 8 is still going to cool possibly too much. It would be better than what you have, but not eliminate the problem. Only a probe type will get you accurate readings below the ceiling box with double wall. Then you will know by accumulation if you have to reduce to 6 all the way. If you're happy cleaning mid season, that may be enough.


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## apersonnameddan (Dec 5, 2015)

I got a couple more pictures of "normal" operating temps with the vents open 2-3 turns. It seems low to me, but maybe someone with more experience can confirm or correct that?
Also I'm not sure if I shared the chimney info before.  It's a rectangular flue, with concrete chimney block, about 6 5/8"x11" inside. 2' above the peak, and about 15' from thimble to crown. The bottom section is wrapped in an un-heated sunroom, and the top 12' (3/4 of the used section) is exposed.  When the thimble was open there was a continuous draft year round, but I don't have any measurement of that.
Questions
1 Is it tall enough, and high enough above the peak?
2 a. Does the narrower dimension (6 5/8") allow for an insulated round liner? 
2 b. If it's not large enough should I skip the insulation, or do I need to get a rectangular or oval liner, knock out the clay, or find some other way to insulate?

Here are the thermometers at my current "normal" operating temps.


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## coaly (Dec 5, 2015)

That flue is way too large for a 6 inch stove. You're dumping a 28.26 square inch pipe into a 72.87 square inch area. That's expanding almost 3 times the size so you can't keep it near hot enough all the way up. Cooler flue temp = less draft = less air into stove. Like I stated above, it's condensing in the increaser from expanding and cooling.
The chimney needs to be 3 feet above roof penetration point, and 2 feet above anything horizontally within 10 feet.
The chimney pros here can tell you what liner you need.
I have no idea what the normal intake opening for the All Nighter may be. Depends on opening size in door and threads per inch. You're going to have it far more open since you have very little draft. The correct draft creates a low pressure area or vacuum in the stove which allows atmospheric air pressure to push air into the stove. Since you don't have low enough pressure, (lowest at the stove collar) you are trying to make up for it by opening intake farther. That is not the same as the correct pressure differential pushing oxygen into the stove. You want a small opening moving fast, not large opening moving slow. Air flow and turbulence mixes air with flammable gas being expelled from wood for better oxygen and fuel mix.


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## bholler (Dec 5, 2015)

apersonnameddan said:


> 1 Is it tall enough, and high enough above the peak?


Like coaly said 3' above the roof penetration or 2' above anything with in 10'



apersonnameddan said:


> 2 a. Does the narrower dimension (6 5/8") allow for an insulated round liner?


Not inside that line no



apersonnameddan said:


> 2 b. If it's not large enough should I skip the insulation, or do I need to get a rectangular or oval liner, knock out the clay, or find some other way to insulate?


No you should not skip it.  Infact it is usually required by code.  What i would do would be to break out the old liners.  But an ovalized 7" liner will work just fine.  The liner on the oval will cost quite a bit more but the labor will be less .  But i would prefer round over oval for sure


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## apersonnameddan (Dec 5, 2015)

Thanks,
I had read somewhere that 3x the cross section was ok, but I'm guessing that's the difference between the rules to meet code and the rules of physics and chemistry...

Would a 5" or 5.5" liner be an option? It doesn't say in the manual, but I'm guessing they didn't exist when it was printed...


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## bholler (Dec 5, 2015)

apersonnameddan said:


> Would a 5" or 5.5" liner be an option? It doesn't say in the manual, but I'm guessing they didn't exist when it was printed...


I would not use a 5 or 5.5 on an old stove like that and your chimney height.  You will be much better off with a 6" or ovalized 7".  If your chimney was 25' or more it may work ok with a 5.5 but i doubt it with that stove at 15'


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## apersonnameddan (Dec 7, 2015)

Hmm... I just called chimneylinerdepot and they tried to sell me a 5.5"... 
bholler is obviously a respected member and a professional in the field. How do I resolve that with a  salesman selling liners from what seems to be a respected vendor? Do you guys trust chimneylinerdepot for their technical advice? The salesman told me downsizing to 5.5 has "never" been a problem, but to put the customer at ease he recommends calling the manufacturer to confirm. Unfortunately this isn't an option with an All Nighter. 

Based on measurements I've decided the stove is a Mid Moe, and Big Moe had the same 6" collar. Does that buy me some wiggle room to downsize the chimney? I would like for it to work with the 5.5", because it's the least expensive option and simplest install. That said, I also need it to work and be safe...


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## bholler (Dec 7, 2015)

apersonnameddan said:


> Do you guys trust chimneylinerdepot for their technical advice?


No I have heard some pretty bad advice they have given.  Usually about insulation and the fact that it is not needed


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## apersonnameddan (Dec 7, 2015)

bholler said:


> No I have heard some pretty bad advice they have given.  Usually about insulation and the fact that it is not needed


Interesting... he was pushing the 5.5" liner to allow for 0.25" insulation. So I guess it's up to me with help from people like you to decide what's right and safe.


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## bholler (Dec 7, 2015)

apersonnameddan said:


> Interesting... he was pushing the 5.5" liner to allow for 0.25" insulation. So I guess it's up to me with help from people like you to decide what's right and safe.


Yes and .25" insulation does not meet code for a wood burner


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## apersonnameddan (Dec 8, 2015)

I'm afraid I may be caught in the position of the guy asking for advice when he's already decided what he wants the answer to be... I don't mean to disrespect bholler but am curious to hear from Pen and coaly on this one.

I've seen Pen suggest that the smaller I.D. of a flue collar would have some value in deciding what size liner to use. Since the collar is 5.5" I.D. should that buy me enough wiggle room for the 5.5" liner?

The other thought I had was given that this is an established chimney which burned for decades with a larger stove. (Unsure of code but seems to be safe) Would a 6" liner  with whatever insulation I can pour in be the best bet? Because it's a rectangular flue there would be good insulation around 90% of the circumference with thin insulation near the two small contact points.

I think my main fear of removing the tiles is that I can't afford to pay the extra to have it done, but if I do it myself the chimney will be totally out of commission until the job is done, and who knows what I'll run into along the way.


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## coaly (Dec 8, 2015)

The question you're asking is if the draft produced by your flue will be enough. We don't know that since we don't know what the required draft is for your appliance. I have lots of testing criteria and literature from Fisher and contacts withn the industry to answer most any Fisher model questions, but the family from your fabricator is now a Ford dealership that either doesn't have the information or refuses to be of any help. I was threatened by a family member and refrain from commenting on the brand.  I responded to this thread due to the picture of the increased flue size from 6 to 8 inches, but your flue is actually much worse.

If the outlet pipe on the stove measures 5 1/2 inside, that is the stove outlet size, so 5 1/2 would probably be fine. You're not actually decreasing the square inch size of the stove outlet. The difference is a little more resistance to flow in the smaller pipe. I'd use solid smooth bore liner if possible to prevent more resistance. bholler would know more about resistance to flow in the different types of liner than me. It could cause smoke roll in problems when opening the door. That is more a stove design issue and was the reason for the Fisher step top design of the first air tight stove. Bob Fisher built his first stove with the step top making the exhaust outlet higher than the door opening to prevent smoke from rolling in. That was one of the patent right infringements the Fishers had a problem with. A judge made the decision against them since "you can't patent the way something naturally works". So that opened the door for others to make stoves of the same design that work very well with less draft. Some stove designs will not like that liner size and height at all. It will probably work fine, but we don't know the details of installation like possibly being in a basement that you can close doors and run a clothes dryer, gas water heater, gas or oil burning furnace that all exhaust indoor air outside. An outside air intake could be the difference of the smaller diameter chimney working or not.
 I helped a member here convert a Fisher Coal Bear to a wood burner last year, and when working on the stove, I got the smell of dirty chimney through the stove before lighting. Couldn't figure out why the chimney was acting as an air inlet into the house with everything off. Last month he messaged me that he realized a radon fan under the slab runs constantly. An outside air intake would be necessary in that case for the chimney to draft properly.
 Yours may also work fine when you first try it until every time you get a low pressure area move over your house it may smoke a bit when opening door too fast or be extremely sluggish without the higher air pressure working to push into stove inlet. Altitude affects air density and pressure, so a sweep in one area knows what is required by his customers and where to draw the line with what works and what doesn't. When factoring in all these variables he is going to make sure the product he installs is going to have an abundance of draft in case these variables come into play someday.
Only when you connect a draft gauge at the flue collar will you know if you have adequate draft at any given time. The flow it creates through fire is more important through a coal fire bed than wood stove. The pressure difference between inside the stove and out is very minute and varies with temperature, weather, even opening and closing an outside door in the house. To give you an idea of the pressure differential, the measurement used is "inches of water column" like blood pressure uses inches of mercury. A U shape clear tube is filled with water open to the atmosphere on one end, and the other end is inside the flue collar. Atmospheric air pressure pushes the water down through the open end and the drop is measured in inches. This drop corresponds to an even rise on the other side of the U bend. Added together is the total inches of water column. 1/2 PSI or 11" WC is normal propane pressure a low pressure appliance requires. Natural gas is HALF that, which is less than your breath. The inches of water required to allow the correct amount of air through solid burning appliances is much less. A measurement in excess of *.05" WC* (Notice the decimal is 5 hundredths inch WC) requires a damper to slow the draft to a range closer to .03 - .04" WC.  

If you can get a round 6 inch liner in, I'd do that and insulate as much as possible. It's far better than what you have and should solve the cool flue problem. If you use soft dry fill you can always pull the liner and take time to remove tiles to add more insulation at a later date. It's more labor of your own than dollars and gives you the best chimney when done.


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## apersonnameddan (Dec 8, 2015)

Thanks for your very detailed answer. The local sweep said he wouldn't insulate unless I insisted on it. So I like coaly's answer of insulating in the space available and doing it in a way that can be modified later.
What is out there for loose insulation options? Should I be looking at hardware stores, HVAC suppliers, stove shops, or am I going to have to have it shipped?

Thanks,
Dan


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## bholler (Dec 8, 2015)

apersonnameddan said:


> I'm afraid I may be caught in the position of the guy asking for advice when he's already decided what he wants the answer to be... I don't mean to disrespect bholler but am curious to hear from Pen and coaly on this one.


No dissrespect taken at all.  



apersonnameddan said:


> he local sweep said he wouldn't insulate unless I insisted on it. So I like coaly's answer of insulating in the space available and doing it in a way that can be modified later.


The biggest question that needs answered as far as the insulation goes is do you have the required clearance to combustibles from the outside of the masonry to any combustible materials?  In your case because the chimney is partially enclosed at the bottom it would be 2" for that section and then drop to 1" once the chimney is exterior on 3 sides.  If you dont have this you are required to insulate the liner properly to meet code.  That means either 1/2" insulation wrap or 1" or pour in.  Yes i know it has been used for many years but over time the wood in contact with the chimney will go through a process called pyroisis.  This means the ignition point is lowered slowly.  And if you have a chimney fire there could potentially be enough heat tranferred through to that wood to ignite it.  If your sweep does not insulate liners he is not installing them to code in most cases and is not following the manufacturers instructions.  Due to that i would question where else he may cut corners.  I do agree that pour in would be better than nothing but it will not bring it up to code and there could potentially still be an issue with heat transfer.  I am not telling you this to try to scare you at all i just want you to be able to make an informed decision.  And yes there are many liners out there that are not insulated and have not burnt the house down so you need to make the decision based one the info you now have.


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## coaly (Dec 8, 2015)

https://www.perlite.org/library-perlite-info/insulation-perlite/Perlite_Chimney-Lining-Systems.pdf

When you pull a liner with this stuff, it's like a wheelbarrow of Rice Krispies to vacuum up.

I went to look at a truck for my grandson last month. Rotted away Ford with a stack of ladders, chimney brush and beat up Rigid vacuum in the back. I asked if that was his Loveless vac. He smiled sheepishly and I asked if he was familiar with Hearth.com. He never heard of it. Got home to find his girlfriend had called my home with her name on my caller ID. Searched the name to find he and his girlfriend were on national news defrauding elderly people for chimney repairs on Long Island, New York. Now in business in PA. We didn't buy the truck.

If they don't realize their job is to keep the inside of the flue warm, you need someone else.


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## coaly (Dec 8, 2015)

I think bholler might be Santa. He knows a lot about chimneys.


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## bholler (Dec 8, 2015)

Fyi loose perlite or vermicultie is no longer an accepted chimney liner insulation.  It does not meet code because over time with the expansion and contraction of the liner it will settle and get packed in very tight leaving a section at the top uninsulated and not allowing for expansion and contraction at the bottom.  It is now recomended that you use a cement and vermiculite mix that will stay in place.  There are many of these products on the market


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## coaly (Dec 8, 2015)

Good thing I suggested it for temporary use.


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