replacing insert with freestanding stove - need installation advice

[questforfire]

Hi everyone - as the title suggests, we have decided to replace our insert with a jotul F400. ive been looking through old posts to figure out how to do it (i called a local company to see if theyd do the install but they refused, saying i just needed a better insert). There is already a flexible liner running all the way up the masonry chimney. Ive figured out that i need to make a blockoff plate, and insulate with rockwool. the plan is to push the flexible liner up a few inches, along with the existing 'collar' (i dont know the technical term) that was used to run it into the insert (it is a male connector), and have it sit on/run through the block-off plate, into a T-piece which will then run into the stove (with rear-vented configuration, obviously). So here are my questions:
1. are there any issues with pushing the flexible liner up 6 or 7 inches (ie. condensing it)? or maybe a bit more than that, depending what the T-connector looks like...? i have never worked with it before, no idea how fragile or if it has a propensity to lose its shape with such manipulation...
2. it seems to me that the blockoff plate will be performing a structural role here, in holding the flexible liner in place...is that ok?
3. any other general caveats/concerns/ 'youre f-ing crazy' comments appreciated also (i did already extend the hearth pad, clearances should not be an issue )

thanks for any advice/input!

 

[EbS-P]

How tall is you fireplace opening. How tall is your liner?

I have an F400 top vented (with short legs) inside my fireplace. See my avatar. I like the F400 but it’s not a big stove.

I do have 100$ blower on the firebox floor pointed up. It’s really useful to maximize heat into the room when it’s cold. Top vent F400 is better as a rear vent can spill smoke on a reload. I have run a top vent in 30+ feet no damper and mine is better top on 14 feet.

 

[questforfire]

oh, forgot to say that the whole fireplace cavity is lined with a very sturdy metal liner/reflector, which has a big cutout, i guess so they could install the liner, so that is what i would attach the block-off plate to, probably considerably lower than where the damper would have been...id attach it more-or-less at the height of the fireplace opening.
i guess the fact that it was left completely open like that, with no block-off or insulation, may be one big reason why the insert never heated very well (!)
also, i know pictures would help a lot here, unfortunately i am technically unable to do that at the moment...

 

[questforfire]

the chimney is 1 storey - im going to say 15 ft? the fireplace height is 26.5'' - our jotul has the long legs, unfortunately (we got it second hand). we plan to put it in front on a tiled hearth pad that is 3or 4 '' lower than the stone hearth base of the fireplace. so not even sure the short legged version would fit inside. Also i guess i was convinced by others that having it out front would make a big difference in its heating efficacy. good to know about the smoke issues though...hmmm....

 

[jbart]

I installed my MF Fire Nova 2 stove in a similar way you are describing. 6in tee vented out the back of the stove with block off plate. I actually set a brick under my tee because I was worried the block off plate would not be sufficient to hold the liner in place. Probably just paranoia but it definitely isn't going anywhere now! I never had a fireplace insert but I do like having the stove out on the hearth. It allows me to boil water and the such. I also wanted to avoid having to listen to a blower. I do have a ceiling fan in the room to move air but it has a DC motor and is virtually silent. My stove does suffer from smoke roll out but it seems like everyone that owns one has the same issue regardless of how it is installed. It heats my 1400 sq/ft house all winter without a problem.

 

[EbS-P]

You will need short legs top or rear vent. I believe the short legs take 3 1/4” off the height. To rest outlet is a touch higher Than the top. Short legs can be purchased. At that point with a single story I suggest the top vent using an appliance adapter.

I use the blower 1/2 the time now. Your really need a block off plate and if it’s an external chimney a lot of the radiant heat will go out side (maybe a rear vent out front is better) from a really radiant stove.

 

[begreen]

The F400 with a 1.7 cu ft firebox is not a large stove though it will be a lot more radiant. I am concerned about hearth protection with the short legs. These normally are only meant for fireplace hearth installation. With the standard legs the F400 requires R=2.0 hearth protection unless the stove has the bottom heat shield attached. Do the used stove have this bottom heat shield? Another issue may be drafting with the rear vent attached to a 24" horizontal pipe then a 90º turn at the tee. This is going to need a decent chimney height to draft well, especially when the door is opened for starting or reloading.

What is the insert that is currently installed? How tall is the current liner on the insert?

 

[questforfire]

Ebs-P : Im not sure I understand why you say i will need short legs even with rear vent -- i have about 30'' height if the stove is out on the lower hearth (which would require about 19'' of horizontal pipe to the Tee, it looks like to me). i understood that you need 29 and 1/4 '' minimum with standard legs...is that not correct?

begreen : I dont see any heat shield on the bottom, just the ash tray. how can i know the r value of my hearth protection? re: drafting - its an exterior chimney, and i just went out to get a look at it and its actually quite high off the roof...i would say at least 20ft? and i believe the liner goes all the way up the chimney. the insert has a label that says Escape 1400; SN: 8108

jbart : thats a lovely setup

So im sensing the consensus is that my proposed setup isnt a good idea, mainly due to poor drafting b/c of 19'' horizontal pipe and 90 degree Tee. Is there any sense in trying it out for a season, and if its really no good i could get some short legs and push it inside and try to figure out a top vent configuration...

 

[EbS-P]

the chimney is 1 storey - im going to say 15 ft? the fireplace height is 26.5'' - our jotul has the long legs, unfortunately (we got it second hand). we plan to put it in front on a tiled hearth pad that is 3or 4 '' lower than the stone hearth base of the fireplace. so not even sure the short legged version would fit inside. Also i guess i was convinced by others that having it out front would make a big difference in its heating efficacy. good to know about the smoke issues though...hmmm....

If you have 30” opening height to the lintel you are ok.

 

[begreen]

The Drolet Escape 1400 is a 1.8 cu ft stove. Virtually the same size firebox as the F400. I don't see much gain here other than more radiant heat.

 

[EbS-P]

The escape 1400 is about the same size. As the jotul. Diagnosis as to why it’s not heating well will ensure you don’t make the same mistake.

 

[questforfire]

thanks so much for all your input, I will be rethinking my plan...