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)

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.

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

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.

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.

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!

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.

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

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.

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.

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.

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?

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.

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.

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/

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!

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.

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

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.

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

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.

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.

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?

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.

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.

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.

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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