My Chimney: 6" -> oval -> 12x8 masonry. Should I upgrade everything to 6" stove pipe?

[NewtownPA]

I bought my house with the wood stove already installed. Just last week I discovered that my stove has a 6" output which goes to an oval pipe about 6 feet long and then merges with a 12x8 masonry chimney.

I was talking to the chimney cleaning company on the phone and based on what I told them they said that in it's current configuration its:
1. Not up to code
2. Not as efficient as it should be
3. Results in more creosote

So, what's your take, should I have 6" stove pipe installed throughout the entire length of my chimney?

If so, what sort of cap should I put on the top? And how much would something like this cost (ballpark range)?

My house is a standard two floor colonial style with the chimney going up two floors plus the attic.

Here's a photo of my house. (you can *just* make out the chimney behind that tree there).

 

[BrotherBart]

Yeah you need to line that chimney with a stainless liner. Either rigid or flexible. You can purchase a flex liner kit that includes stove top adapter and top plate with cap for five hundred or so. More to add insulation around it. If that stove is on the first floor you will need a 25' liner, basement 30'. If you have the chimney guys supply the liner kit and labor it will usually run you in the neighborhood of $1,200 to $1,500 installed.

What you get for that is not only a current code compliant installation but that Avalon is going to perform like a whole new stove due to having better drafting in the chimney. And much less creosote accumulation and cleaning difficulty. The current setup is just dumping the stove exhaust into an entirely too large cross sectional area to ensure good draft and burning. I know, I burned into exactly that same size flue for years and thought I had a good draft. My eyes almost popped out at the difference after I lined it. And cleaning the chimney now is a twenty minute job.

 

[webbie]

I bought my house with the wood stove already installed. Just last week I discovered that my stove has a 6" output which goes to an oval pipe about 6 feel long and then merges with a 12x8 masonry chimney.

I was talking to the chimney cleaning company and they said that in it's current configuration its:
1. Not up to code
2. Not as efficient as it should be
3. Results in more creosote

Let me try to answer these questions fully - to some level.

First of all, have you used the stove extensively? How does it burn?

OK, I am going to go backwards and start with #3...

Results in more creosote:
The answer to this is the amount of creosote that is in the chimney. I have installed many hundreds of Avalons into similar situations with similar piping, and our sweeps have almost always reported that they get almost NO creosote out when cleaning...and perhaps less than a gallon can of soot and loose particles (which pose no ignition danger).
So, unless you have seen for yourself that you have a lot of black tar creosote from this stove, I would question this assumption.

Not as Efficient
This relates also to how the stove operates for you. If the stove burns well at most levels of operation, then it is burning efficiently. Efficiency relates to the wood, the operator, the stove and the chimney. It is also a hard EXACT figure to put your head around. In other words, if you stove was burning at 2% less efficient than it "might", is that classified as "not as efficient". On both these questions, the proof is in the pudding.

Not up to Code
First, check your owners manual and see if the stove was installed in the fashion required there. After that point, we can consult the NFPA code which was in effect at the time of your installation - chances are that was the previous version of NFPA 211 - the new one is just getting distributed recently.

That version would state (I think) that the masonry chimney cross-section should not be more than 3x the size of the pipe if the fireplace chimney was outside, and 4x if the chimney was inside. Your chimney is somewhere in between, since it appears it may be in a garage or other room for part of the run.....

An 8x12 chimney is usually about 6.5 x 10.5 ID, which is about 70 Square inches of flue area. A 6" pipe is:
pie x (times) the radius squared, or about 28 square inches, meaning that your installation would pass the previous version of NFPA.

The brand new version of NFPA211 has taken the figures down to 2x if chimney is exterior, and 3x if the chimney is interior. So depending on exactly how an inspector would classify your chimney - it would pass current standards if interior, and not quite if exterior.

Chimneys do not have to be "upgraded" to current code changes, but new installations must follow these standards.

All in all, the biggest question is how well the stove starts and operates, and how clean the chimney stays.

Summary - your installation is probably approved by the manufacturer and test lab as per the manual and probably also kosher as to when it was installed. It would easily pass muster from 1979 to 2006......but as a NEW installation, it would depend on whether the chimney was classified interior or exterior as to whether it would meet NFPA 211.

 

[BrotherBart]

My experience with two of those 12X8's that are 7X11 inside dimension are that the direct dump stove and the 2005 EPA stove I burned hot into both of them crapped up the chimney something fierce and had caca for draft, I now know but thought it was great at the time. I think the code change was years behind when it should have been.

And both of them, now lined, draft beautifully and don't accumulate ANY crust and just a little dust in the pipes. Some updates are worth paying attention to and applying grandfathered codes or no grandfathered codes.

 

[webbie]

BB is correct in that a balanced chimney makes everything much more pleasant.

My answer was just to address the questions without opining on what you should do - because I am not you and don't know your chimney, your bank account and a lot of other things.

I used a fireplace similar to yours (partially interior) with a Resolute Acclaim - a tough stove in terms of draft, and my "years ago" solution (12x12 flue) was running the pipe 10 feet up instead of the usually 5 feet - worked like a dream. But as BB says, sometimes we don't know what we are missing!

The two folks who introduced clean burning (cat) stoves to the market talked often about the fact that an idea chimney is EVERYTHING when it comes to performance.

 

[NewtownPA]

Here is a pic of the top of my chimney. Does it look to you like I have a lot of creosote?

My last cleaning was December 2005 - so that's almost two seasons without cleaning.

-njm

PS. It's rather scary being up there Yikes I don't like heights at all.

 

[NewtownPA]

Inside

 

[NewtownPA]

Thank you for all the advice you two have posted so far. I know there's a lot I need to consider.

This is my first wood stove and I don't have anything else to compare it to. I know it produces a lot of heat, but I don't know if I'm at 98% efficiency or 50% efficiency.

This weekend I'm having the professional company come out and take a look at it. At the moment I can't afford $500 let alone $1500! I've got a new baby on the way - due in November so I've been saving up!

-Nathan

 

[elkimmeg]

3 years ago bb challenge me every step of the way about block off plate full liner the whole process we e when back and forth code ,code interpretation on and on.

And way back quite a few members sided with BB they did not want to hear their set was a bit less than it should be. Finally after a few PM and BB experiences or near experiences with the Jet engine roar in this chimney, he decided to find out for himself. Sorry listening to me lightened his wallet . The difference was like night and day he had capacities he never thought his stove could obtain he had control and heat volumes he never had before. And the wood and constant fiddleing with controls just to get it working and heat he needed.

AAwh he tells it better than I can. But you will never know if there is a whole other level of performance your current setup can't deliver

I assume the connector pipe makes a 90 degree bend goes to oval and ends in the first clay flue liner Hopefully there is a good steel block of plate at the damper pass threw

Oval pipe creates more resistance to draft than round pipe
Step one of reduced performance

As mentioned your chimney is considered exposed so a lot of normal heat loss weakens draft to the outside coupled with trying to heat that 8/12 flue exposed a lot of energy

is used / wasted

Creosote warm smoke contacting an exposed chimney will condensate against outside walls ones moisture collects it collects smoke particles and it becomes a continuing process

Creosote is highly combustible highly combustible fuel is accumulating on those clay flue walls. Non hot burn night a p creosote starts melting and moving dripping down the chimney getting closer and closer to hotter and hotter chimney entrance on spark is all it takes and you will swear a 747 jumbo jet is taking off in your living room fireplace. The goes out foe help and the 9121 call soon guys driving Big red trucks arrive but each second you are hopeless waiting for their arrival If the can control it it just a bad experience but chances are your chimney liner is totaled. Hopefully it stays contained in the liner and that hot blast of 2100 degrees flame does not blow out and tough off combustible materials in the rest of the house.

Thank god you had the damper block off plate because it prevented the 2100 degree of blow back into the living room ,it forced it upward Simple sicence the fire will follow the source of oxygen and follow the path of least resistance which was to the top..

But you have nothing to worry about. Back when your stove was installed it was done legally. Do you think this scenario was played out a few times, that fire masrhalls looked at this situation and changed the code? What a mess you home now looks the smell. Time to call Serve Pro and start the recovery process all this is going on in your mind as you can barely hear your thoughts over that wirl of all those big fans

 

[webbie]

Here is a pic of the top of my chimney. Does it look to you like I have a lot of creosote?

My last cleaning was December 2005 - so that's almost two seasons without cleaning.

-njm

PS. It's rather scary being up there Yikes I don't like heights at all.

That is certainly not a large accumulation, but that doesn't tell us much. You mentioned that you talked to a sweep - did he just get finished cleaning it?

More importantly, was there a different insert and installation in the fireplace prior? It might be hard for you to know these things. This deposit could also be from way back when it was used as an open fireplace. Maybe the same sweep has cleaned it for awhile?

That is black tar creosote - perhaps an 1/8 inch or so on some surfaces. It certainly is not enough to do the 747 or space shuttle deal (sooty bob made that up years ago - although as I remember, they used "freight train")........

In a stainless liner and in interior black pipe you get the same buildup - but because it is in a small hot area, it tends to ignite and burn off regularly. It is pretty amazing how a relatively small amount can burn hot.....I've taken black piplng outside and ignited it, and did have a mini-jet engine.

The main thing about ANY of these situations....is that if you can limit the air to the chimney, than your chimney fire cannot easily get out of hand. That is why a tight block off sheet metal plate at the damper is very important.

Truth be told - and this comes from the 4 chimney sweeps that serviced about 2,000 stoves in conjunction with our shop - that the newer stoves (1990 on) are extremely unlikely to cause the "old" type of destructive chimney fire. Certainly it is possible, but NOTHING like what could be created with an old Smoke Dragon. An improperly burned Fisher, for example, could cause a bad chimney fire after 6 weeks of use.

As far as whether you should line to the top - all the advice given here (well, perhaps except the meltdown and 747) is quite accurate - but we are not in your shoes, and don't have your stove or installation or bank account. Rather, we (I) were simply trying to add the "longer" story to the simple statements of the sweep. As I repeat often here, there is:
adequate
decent
good
better
and
best

If you were Bill Gates, I'd say to remove all the flue tiles, and pour a Ahrens insulated cement flue liner. That is the "best" on the list above. Your existing setup (with the addition of a metal plate at damper) might be adequate, but maybe you want decent, good or better....that means a stainless liner (thicker and rigid are best), and maybe even insulated (that is the "better")........

For all we know, you use 3/4 of a cord of wood each year for weekend burning. Someone else might put 5 cords through the stove - lots of variables. I think you have the info you need to make decisions.

 

[webbie]

Thank you for all the advice you two have posted so far. I know there's a lot I need to consider.

This is my first wood stove and I don't have anything else to compare it to. I know it produces a lot of heat, but I don't know if I'm at 98% efficiency or 50% efficiency.

This weekend I'm having the professional company come out and take a look at it. At the moment I can't afford $500 let alone $1500! I've got a new baby on the way - due in November so I've been saving up!

-Nathan

Do you have a pic of the stove ?

If it is installed decently, you are probably getting 60% efficiency out of it - if it has a blower, maybe a few more points if a blower and tight plate. Assuming it drafts decently, you will not be able to increase that number too high - say maybe 70% for a perfect situation.

Congrats on the new addition to the family. Too bad you are not around the corner from Elk (and Corie moved), or we'd have a crew over there for beer - after the liner was installed. Still would be $350 or so in material.

 

[BrotherBart]

And way back quite a few members sided with BB they did not want to hear their set was a bit less than it should be. Finally after a few PM and BB experiences or near experiences with the Jet engine roar in this chimney, he decided to find out for himself. Sorry listening to me lightened his wallet . The difference was like night and day he had capacities he never thought his stove could obtain he had control and heat volumes he never had before. And the wood and constant fiddleing with controls just to get it working and heat he needed.

Yep Elk. I lined it and the first time I lit it off the stove ran out of control for the first time in 20 years and I had to replace it. Thanks a lot buddy.

The jet engine roar was at my neighbors house in 1988. I gave him a chimney brush for Christmas. He still runs without a liner.

 

[NewtownPA]

That is certainly not a large accumulation, but that doesn't tell us much. You mentioned that you talked to a sweep - did he just get finished cleaning it?

More importantly, was there a different insert and installation in the fireplace prior? It might be hard for you to know these things. This deposit could also be from way back when it was used as an open fireplace. Maybe the same sweep has cleaned it for awhile?

Hi,

The chimney guy has not come out to see it yet - I scheduled him for Saturday morning, but I figured I'd ask my questions here first so I can know what to ask him when he does come. I had a guy come out to clean it back in December 2005 but I didn't like him and I don't think he did a very thorough job, he certainly wasn't very "professional" - so I don't know. Last week was the first time actually got enough courage to stand on the ladder and take those pics.

I'm sure I will find out a lot more information when the guy comes on Saturday. He said he would pull the stove out and take a look at exactly what I've got for a chimney and make any recommendations.

I am including some pics of my stove that I took last winter to show you the setup and the burn.

-Nathan

 

[NewtownPA]

My Avalon Rainier Insert. (Yes I know, I need some more hearth space in front. I've been talking to Hogwildz about it but I just have not had time to make my hearth extension yet. I'd better hurry up!)

 

[NewtownPA]

Front glass.

 

[NewtownPA]

Secondary combustion.