quick question, lining old flue

[Riverstone]

Recently bought a house and am looking into an insert for an existing masonry fireplace. We got rid of the previous (very old) insert, which had been shoved in there with a short section of pipe just sticking up into the 9x13 clay flue--when we pulled it out there was creosote all over the top of the insert and around the pipe--a disaster waiting to happen. Anyway, my sweep says he can put in a new insert and connect it with flex pipe to the bottom of the clay liner (again, 9x13). The flex pipe would connect to the clay liner with some kind of plate to make a seal.

I'm new to this, but from what I've read here it struck me funny--do I not need to line the entire 9x13 clay flue with insulated SS? Or can I just connect to the old flue like the sweep says?

Thanks all.

 

[jtp10181]

In some situations you may be able to get by with just the stubby liner, but as you saw this can make a big mess and it also makes the chimney hard to clean. The optimal way to do it is a full liner to the top.

 

[RonB]

You will be happiest in the long run and your stove will run better if you do the whole reline with the SS and install a block off plate just above your insert. Other members are very knowledgeable in this area and will advise you shortly. Do a search on this issue as there are lots of threads that relate to this issue.

 

[webbie]

Are you still using the old stove? Is is a newer EPA type appliance.

The job with the flex direct connect is probably adequate in the case of 8x12, but make certain the sweep fabricates and installs a block-off plate - not up in the tile (almost impossible to do), but rather at the fireplace top, as in:
https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/

Chimney can optionally be lined - or should be lined if tiles are cracked, missing, etc....or if chimney is constructed improperly. It will be tough to get anything insulated down an 8x12, which are usually barely over 6" in ID width.

The reason you hear various opinions is that codes and "in the field" practice change over the years. The vast majority of inserts out there in the field only have the Direct Connect that your sweep mentions because it was the proper way to do it for many years, and met at least minimum code. These days, almost all new installs need lined, because most chimneys are larger than yours (12x12) and therefore way too large to vent a 6" pipe into and still have proper draft.

Any of these jobs are a vast improvement over what you had - so it becomes a question of your budget, what the existing chimney condition is, etc.
One problem with lining entire chimneys which is often overlooked is that they often have tar and creosote buildup. In this case, measures have to be taken to properly clean (sometimes very difficult) the chimney before installing a top to bottom liner. Some companies go as far as to bust out all the flue tiles so as to not deal with the cleaning and have more room for the insulation.

 

[begreen]

What insert are you considering? Most new inserts are connected to a 6" r pipe. The 9x13 flue has a lot larger area and may not draw well, especially if this is an exterior chimney. If exterior chimney, put in a six inch, insulated liner with a top cap and bottom block off plate, for best stove performance.

 

[Riverstone]

gotcha. assuming current tile flue is in good shape, then it's really an issue of performance--i.e. will 9x13 draw too much for the insert.

we've discarded the old insert, and were planning to use use an open fireplace for occasional ambiance fires. i then had it swept for safety's sake, and the reason i got into this is the sweep said he had a 10-yr old buck stove insert that he took out of another job, in good shape, that he'd sell for a $100. i haven't even seen it yet, and maybe it's a wreck, but i wanted to check on his flue methodology before i did. i guess i'd rather have a safe insert in there, throwing some heat, than an open fireplace wasting it all, but i'm not ready to pony up for a new insert and a new liner--saving that money for the house we're building two years out, where i can start fresh with floorplan, stove size, etc. etc.

so, any advice on the 10-yr old buck stove insert connected with a plate to the 9x13 tile flue? sweep says the clay tiles are good, and i know they're pretty clean.

 

[webbie]

Don't know the flue size of the Buck - many were 8", although if really only 10 years old (EPA model), it would be 6.

9x13 tiles are usually 6.5" x 10.5" ID.....so they are not tremendously oversized for 6" - about 2.2 x the size in square inches. As mentioned, the guidelines used to be that flue could not be more than 4x the size of the pipe, then it was 3x, now it is 3x for interior and 2x for exterior.

It is not a matter of draw TOO MUCH, but too little! A larger flue cools down the flue gases, therefore they lose velocity. Complicated, I know!

And confusing. But check with the sweep - he is the one on the job, and I would only take that stove if it is EPA. If it is not, he is lying about the age, since anything produced after 1990 would HAVE to be. The stove should have a label on it.

 

[Riverstone]

Were Buck stoves of that vintage (mid 1990s) generally good?

I'll check out the insert and see what I can see--I'll post pics and/or questions then. For now, thanks! It'd be great to get some extra heat in here...

 

[begreen]

Is this an interior or an exterior chimney?

 

[Riverstone]

exterior--the outside brick is 4 feet wide and 1 foot deep, and it stands in a 12x12 alcove made by the house footprint. it also used to house the chimney for the old oil furnace, which i just replaced with high-efficiency natural gas...i'm sure being outside affects draft by cooling the chimney. would it be enough to rule out using the 9x13, BG?

 

[webbie]

Were Buck stoves of that vintage (mid 1990s) generally good?

I'll check out the insert and see what I can see--I'll post pics and/or questions then. For now, thanks! It'd be great to get some extra heat in here...

Similar to current models if mid to late 90's.

If it looks like the "old" buck stoves, then it IS one.....the two doors on the front, the fan in the rear of firebox, etc.

In that case, stay away from it.

The newer models look similar to other EPA stoves - large clean glass, etc. - mostly all single door.

 

[webbie]

exterior--the outside brick is 4 feet wide and 1 foot deep, and it stands in a 12x12 alcove made by the house footprint. it also used to house the chimney for the old oil furnace, which i just replaced with high-efficiency natural gas...i'm sure being outside affects draft by cooling the chimney. would it be enough to rule out using the 9x13, BG?

As mentioned, the current (2006 on) rule is 2x. So if the Buck is 8", it is OK. If 6", that is about 29 square inches and your flue is 70 square inches, so it does not meet the current guidelines. Some would argue with that based on the fact that it has been proven that masonry flues only actually use the oval or round part of the flue (like a 12x12 is actually only a 10.5" round), but those are the NFPA guidelines.

I have seen 8x12's that are 6 x 10 inside, which actually means they are extremely close to the guidelines. On the other hand, some are 7 x 11 inside, and then almost 3x the 6" flue size.....

As mentioned, exterior guidelines are the masonry flue can be at most 2x the square inches (cross section) of the stove flue.

 

[Riverstone]

Thanks, Craig. I guess it depends on whether that stove is 8" or 6"--not to mention how old it actually is. If it's real old, I agree, I'd rather forget it. Already have one old stove, a jotul #1, in the barn.

 

[jbrown56]

Hi, I just got my stove about seven weeks ago after using an old steel box stove for 26 years. For about 5 weeks I exhausted into an 8 x 12 clay flue which is on the inside of the house. I would have to leave the side doorcracked for 15 - 20 mi. to get a good fire going. Two weeks ago I installed a 20' rigid liner and now only have to crack the door for 1 - 2 min., close the door, set the damper on 1/2 and in 20 min. I have stovetop temp. of 500*. It has greatly improved the performance of the stove and the airwash works better too.

Jim

 

[JimWalshin845]

Your new appliance will not meet flue specs so you really must line it.

Second recommendation is to start looking at installing a stove rather than a insert. The amount of heat generated will far outway putting in an insert.

Wecome aboard and good luck with your project!

 

[Riverstone]

I'd much rather put in a stove, actually, but my hearth makes it near to impossible, as far as I can tell. It's brick, and raised off the floor by 12 inches. It sticks out from the front of the opening only 12 inches, too (in the case of an insert, I do know I'd have to add a hearth pad in FRONT of the existing hearth, even if it wasn't at the same height). Anyway, if I wanted a stove I'd have to build out the hearth at a full foot thick, or else remove/lower the existing one. I'll probably just line the whole thing, and if I'm making that investment, I may as well look at a good new (or newer) insert at the same time.

I appreciate all the advice--I think I'll start looking at new inserts and assessing my needs, which are for a supplemental heater with good fireview. I'd like to be able to get some radiant heat (feels nice) without the noise of a blower while I sit in here, and then run the blower while I'm in other rooms. I've got a one-level house, fairly open, 1000-1200 square feet, and again, I'm just looking to supplement. Perhaps another consideration is that if I sell the house to build from scratch, I'd like the appliance to be fairly straightforward--don't know if everyone wants to obsess over operation the way we do...

Any thoughts?

Thanks again!