Venting Jotul QT - Hearth Installation

[scottgen20]

Hi Everyone,

I installed a Jotul F100 QT last year and it's performance was less than spectacular.. It seemed to be working well in the fall, but then in early December I had to stop using it because it took forever to get a fire started, drafted poorly, etc. Before I go any further, let me give you a quick run through on my configuration:

Stone fireplace with what I believe was called a "heatilator" insert. (Metal firebox) I lined the chimney (13') with a 6" stainless liner and a cap.

The wood stove is inserted into the fireplace, and is connected to the liner which runs up to the top of the chimney. (The chimney is stone, but lined with clay sections)

When I originally installed the stove, I had to "ovalize" the liner to get it past the opening at the top of my metal fireplace firebox and into the chimney. I think this may have been contributing to my problem. I pulled out the stove in Feb and decided that maybe the jog that the liner was taking out of the top of the old metal fireplace firebox could be part of my problem. I took a sawzall and basically cut out the top of the old Heatilator firebox. (It was rusted and unusable, anyway). This gave me clear access up to the flue lined chimney.

I went ahead and connected the stove back up and had somewhat better results. My fires started faster once I warmed up the flue (by stuffing newspaper above the burn plate and lighting it...) I never seem to have enough draft, though.. I wind up always cracking the door a small bit to induce more air for draft.

I suppose that some of my problem could have been my firewood.. (I had split 3 cords delivered in the summer, and I have a feeling they were not as seasoned as promised) With any luck, the wood was a big part of my problem and this year will yeild much better results.

Here is my question: Does anyone think that I'd obtain any additional draft by venting the stove directly into the clay lined chimney, instead of running the liner all the way to the top? I had the chimney inspected and it's in very good condition. To me, it looks like I'd obtain better draft via the clay lining, instead of the corregated stainless liner. If I did connect directly to the chimney, how do I go about making the connection to the clay lining at the firebox?

As always, thanks to all for your advice! Looking forward to fall

Scott
Scott

 

[BrotherBart]

I don't think you would be doing yourself any favor. I drafted a Nordic into a 30 foot 8 X 12 tile lined chimney last season and draft was not all that good. I am going to line it to the top with SS before the upcoming season to increase draft.

 

[Corie]

The smoothness of the clay liner would help draft, however the area of the clay liner would hinder. In the long run, the draft gained from smooth clay versus rough stainless would be far smaller than the loss you would experience due to the larger flue. Remember, that's a pretty small stove and it's probably barely putting enough heat up the chimney to begin with. Make that chimney area larger and you're only looking at decreasing the draft.


Rather than add height, I would highly suggest insulating the area between the liner and the old chimney. This has been discussed on the forum before and there are a variety of products on the market well suited to this application.

 

[scottgen20]

Thanks for the advice, everyone.. I'll look into insulating the ss liner..

Thanks again!
Scott

 

[Todd]

Keep the 6" stainless liner. Maybe try wrapping insulation around the top couple feet under your cap, between the stainless and clay liners. The air inbetween will heat up keeping the chimney warm. Works for me, and is cheaper than wrapping the whole liner.

 

[BrotherBart]

The Extend-A-Flue of course. Invented and sold by one each Webmaster.

 

[elkimmeg]

International Mechanical Codes 2003

Chapter 8 Chimneys and Vents

801.10.2 Connection to Factory-built fireplace and flue.
An appliance shall not be installed in a factory built fireplace unless the appliance is specifically listed for such installations. The installation shall be made in accordance
with the appliance manufacture’s installation instructions.

I read your installation/ owners manual and this stove is not listed to be installed in a prefab metal fireplace. Further more the minimum vertical height is 14 ‘ I am also willing to bet there is no block off plate to prevent the intrusion of room air. This will cool the flue liner and will lead to poor draft performances. Plus draw heated room air out of the living space. I don’t know how to advise you, as your installation does not legally conform to code.

 

[elkimmeg]

Concerns a metal pr fab was installed in lue of a masonry fire box Meaning I doubt the required masoner exist behind that pre fab.
Code requires 12 " solid masonry or 8" with fire brick.. I doubt there is fire brick behind the prefab. Prefabs were double sheet metal and did not require the existing fire box to be built in a conventional way
Cconcern #2 and posses the most dangerous situation.If the fire place is only 2/3 height. with wood framing members and wood header above this setup. The original protection has been compromised (self admission to it being rusted out) Further compromised cutting into it for the flue outlet.. In a fire place most of the heat exits quickly up the flue . The purpose of a wood stove is to contain that heat Temperatures in that fire box were never designed for 24'7 800 plus heat. The wood stove introduces conditions not designed or tested in that prefab unless the appliance is tested and listed for installation in a prefab. That is, if the Prefab is in good condition which this is not. The model stove used in this situation is not listed nor has it been tested for prefab installation. All it takes is one small fissor crack in the masonry and the framing material is exposed to extreme heat. It may not ignite right away but a process of pyrolasis, wood exposed to extreme heat changes, molecular structure and its flash point is lowered. Even if there is no crack, insuficient thickness of masonry, the process can be progressing as heat transferes threw a thin layer of masonry.

Believe it or not I have found chimneys in new construction where I have actually seen the wood framing in the void left between the angle iron and brick courses. That crack and it is common to find, is present more than people care to know, a common flaw
Two towns away that crack was deemed the cause of a major fire.. The home was 5 years old. This is why code requires a through inspection of masonry chimneys prior to issuing a permit, For all reading this post get a flash light and look up at the top of your brick facing,, just inside the fire box ,inbetween the front row of bricks and the angle iron. Is it solid masonry?

This issue is less of a problem, where floor to ceiling is solid masonry no framing members imediately above the fire box

I could go on and on, the dangers of fireplaces built incorrectly, Craig and are in agreement, that many are not as protective as people believe. My town requires a throat inspection, where I view the construction and can actually see the required thickness in place

 

[elkimmeg]

This was discussed in Early Dec follow this thread threw
https://www.hearth.com/talk/threads/393/

 

[scottgen20]

Hmm.. Now everyone has me thinking.. When I originally had my fireplace inspected, it was the chimney sweep who recommended installing a wood stove with a liner.. I can't say whether the chimney was always a Heatilator or not. The fireplace mass sticks out 14.5" from the finished wall. The firebox depth (back to front opening) is 33". The floor of the firebox is lined with brick. The chimney is built out of fieldstone. After removing the back and top of the rusted out Heatilator box (it was just single wall metal) I could see that the firebox is made out of fieldstone and is fieldstone up to the clay chimney flue. The sides of the fireplace going back to about 14.5" (matching up with the mass that sticks out 14.5" from the wall) is mortar, followed by the original heatilator walls. The opening of the fireplace is centered and has 22" of mass on either side. The wood stove resides at the front of the firebox.

My wood stove dealer came out to do the measurements and actually recommended the Jotul, so I was relying on their expertise as far as safety is concerned. It would look to me as if my installation could be safer than most because the stove is very isolated from any structure.. (see the attached pics).

If it is a problem, I suppose that I can pull it out of the fireplace further, although I'll need to deal with extending the hearth out further into my small room..

What does everyone think?

Thanks again for the advice!
Scott

 

[scottgen20]

Here is the picture of the full fireplace, giving an orientation of the stove placement.. The stove is vented at the rear since there was no way to top vent, as the lintel is 14" wide. (I should mention that I know that is pre-fab stone on the outside of the fireplace, not fieldstone. The prefab stone on the outside is covering fieldstone and mortar. Must have been someones remodeling project sometime or another. This fireplace is located in an early 1940's addition on a house built in 1750. What makes me wonder if the Heatilator firebox was added at a later date is how far the fireplace sticks out into the room. It's not like the heatilator firebox was flush with the finished walls of the room, like a normal fireplace... I'm guessing they recommended installing the stove in the firebox, as my whole fireplace is so large (not the firebox, but the actual mass) I was going to get a Jotul insert, but because of the 14" lintel, it would not fit...

 

[elkimmeg]

Scot as for your dealer he recomended the setup then sold you the stove. His only inspection ( I guessing here)was to see if it physically fit. You revealed another piece of the problem Chimney length is 13' witha 90 degree elbow. The Elbow Produces friction that effectively reduces your flow to 8'. Inorder to meet miniumm verticle height, your chimney would have to be 19'. You have less the 50% of the verticle height and you are wondering why you do not have proper Draft? The guy that inspected the setup, that sold you the stove seems, to missed that point. I would give no creedence to what he said as far as the inspection. Like I said to see if the unit fit and only that. If you lived near me, I would check it out to see how safe you are. I cannot say for sure even with the pictures. You did not mention or confirm the existance of a metal damper block off plate either? Did you local building or /fire inspector approve the installation? Safety should not be compromised. I do two types of inspections one to make sure I will not be re-visiting you home because I did not do my job the first time. I make sure it is safe. The second trip is to figure out what went wrong. So far in 11 years of insppections, I have not had to figure out what went wrong after my first inspection, Usually the what went wrongs, were never permitted or inspected in the first place

 

[precaud]

My 2 pence:
First, burying a radiant stove inside an alcove like that is bound to lead to disappointment.

Second, I started out last year's heating season with an F100. Sorry to say, the QT is a sedate heater, whose design is unsophisticated and fraught with compromise. When rear venting, heat output suffers more than most stoves, as the exhaust is pulled under the "increased surface area" nibs cast into the top plate. So top venting is a must with the Nordic.

But the biggest booboo is it's "Simplex" secondary air system (ah, marketing...) which is little more than holes in the backplate - it is not preheated. So alot of the secondary air becomes little more than dilution air, which cools the stove. As such, this design requires everything to be "just right" to function properly. Wood MUST be fully seasoned. Draft MUST be sufficient. Wood placement in the firebox is very finicky.

Well, I've spent my twopence. But whatever you do, I'd replace the stove with an appropriately-designed insert.

 

[elkimmeg]

Scott just to clear up any missconceptions
: I am trying to help you. I wish you had posted your situation before you bought and installed your stove. Forum members would have pointed you in a direction, where these recent post would have been unecessary
Part of my response was this is a re-occuring guestion. What can go into prefabs? It was not directed soley at you but the situation.

No one here has viewed your unique setup we only can make suggestions. My statements were made based on general assumptions of a fireplace 2/3 height they may not apply to your situation. Better yet what did the local inspector say? He is the one that its his jusirdiction. He is the one viewing your setup first hand.

 

[scottgen20]

Hey Elk,

No problem.. I realize that you're just trying to give me advice... I misstated the chimney height as 13', it is actually 15', but as you mentioned, with a T at the back of the stove, I'm reducing my effective height.

I havent had an inspection other than by the dealer and chimney sweep, so I'll give the local building/fire inspector a call and have them come out. Believe me, the last thing that I want is a fire outside of the stove.. I hadnt really given the fire issue any thought since the stove is placed far from the back of the firebox (and it has a heat shield) and as for side and top, it is sitting well away from any structure (other than masonry).

As far as chimney height, I suppose I'm limited in my options..

Precaud.. Thanks for the review of the F100, it's small firebox has been causing me greif (with split length) from day one. You also mention some very good points..

I'll get someone out to inspect, and post the results..

Thanks again!

 

[Corie]

The reason I didn't recommend adding length to the chimney is because that isn't the fix all solution to draft problems. What good does adding another 3 feet of chimney do if the stove can't even keep the existing flue warm? It's just more cold chimney, further from the stove which I think will decrease, rather than increase the draft in this case.

It's a different situation when you have a stove putting plenty of heat up the chimney, but not giving that heat sufficient rise to gain velocity. However I don't think that's the case here. But that's just my humble opinion

 

[HarryBack]

also, correct me if Im wrong Elk, but isnt it up to the manufacturer of the stove as to whether of not the stove can even be installed in alcove situations such as this? I know of a few stoves that dont even allow alcove installs. Im sure the shortness of pipe is a major hindrance as well. Also, a question......what about the use of vermiculite as insulation in the annular space between the liner and the tile? (im assuming theres a block-off plate there).....might be a bit of a mess if there isnt!

 

[Corie]

yeah that's what I was suggesting harry! I know there are other products for this purpose on the market, I just have no idea what they are called.

 

[HarryBack]

Im not sure its Kosher, Corie, to do so, but it seems an easy way to insulate a chimney with liner in place...ive tried to torch Vermiculite with my OxyAcetylene torch, and it didnt do anything....seriously doubt a stove gets that hot.....Maybe Elk can give us advice here as to whether its ok to use vermiculite? I understand it would be a mess if a guy had to pull the liner, but sounds easier than using insulating wrap....

 

[Corie]

Agreed. And i think insulating like that would improve his draft big time. Then maybe he could consider adding height, since the chimney temperature would be high enough to actually gain velocity from a longer chimney.

 

[scottgen20]

Thanks guys.. I'll look into insulating the chimney.. At this point, I'm wondering what would be more cost effective -- trying to increase the chimney height, or to install something like an Exhausto chimney fan to induce some draft..

I checked the instructions and it is approved for both fireplace and alcove installation. Looking at the clearances, it would appear that I should be fine. My fireplace mass is very large, so the nearest place that could actually contain framing is outside of the clearance areas..

 

[elkimmeg]

The reason I didn't recommend adding length to the chimney is because that isn't the fix all solution to draft problems. What good does adding another 3 feet of chimney do if the stove can't even keep the existing flue warm? It's just more cold chimney, further from the stove which I think will decrease, rather than increase the draft in this case.

It's a different situation when you have a stove putting plenty of heat up the chimney, but not giving that heat sufficient rise to gain velocity. However I don't think that's the case here. But that's just my humble opinion

Got to differ with your explanation: Same caliber bullit leaves a pistol barrell witha lot less velosity than same caliber in a rifel

What's the difference the length of the barrel. One would think the longer barrell would produce more friction and that the bullit stays in the barrell longer. I think you can apply the same principle to verticle length of draft

 

[elkimmeg]

.

Maybe Elk can give us advice here as to whether its ok to use vermiculite? I understand it would be a mess if a guy had to pull the liner, but sounds easier than using insulating wrap...

I think the product is called thermax combination of Vermiculite mix Harry. I hope this i does not get you in a tizzy I not peod at your very informational post. Besides I would have a hard time walking in your boots. Have you ever thought of asphalt paving, no need for a Tamper with Harry around. Another Eddie Rabbit night

 

[Corie]

I don't think the bullet leaving a barrel is synonomous with smoke going up a chimney. Remember, a bullet is propelled, whereas the smoke only rises based on a temperature differential.

We all agree that a cold chimney doesn't draft well at all, and in this case we have a stove that is too small to keep the flue warm for draft. I don't see how adding height will help the small stove keep the flue warm enough to maintain draft?

 

[HarryBack]

ggez, elk, Im only 220 lbs!.......thinking of going as Sasquatch tho next halloween, but Im afraid everyone would recognize me.....I know! I'll get a pair of those Matterhorn Search and Rescue boots! even if they DO recognize me, they'll be afraid to say anything but "hi"......