Reversed flue collar, creosote leak...

[coaly]

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.

 

[Mybooman]

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.

 

[coaly]

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.

 

[apersonnameddan]

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.

 

[coaly]

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.

 

[bholler]

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'

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

Not inside that line no

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

 

[apersonnameddan]

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...

 

[bholler]

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'

 

[apersonnameddan]

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...

 

[bholler]

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

 

[apersonnameddan]

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.

 

[bholler]

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

 

[apersonnameddan]

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.

 

[coaly]

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.

 

[apersonnameddan]

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

 

[bholler]

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.

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.

 

[coaly]

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.

 

[coaly]

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

 

[bholler]

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

 

[coaly]

Good thing I suggested it for temporary use.