Adding secondary burn to a Lopi FL wood burning insert

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New Member
Nov 26, 2020
34
Oregon
Fireplace manual for reference

I’m retrofitting my old Lopi FL from the 80s and want to add a secondary burn and chimney liner. Any comments from the forum are most welcome. Outside surfaces will be painted with fireplace paint after modifications.

So far I’ve used a wire wheel to get the rust off the outside of the body - doors, trim panels, and the blower assembly will be done next. I also started drilling the hole for the 1” secondary burn pipes. They will be angled up to rest just under the brick baffle (which isn’t installed in these pictures - the support is shown in the first pic).
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Here’s a picture of the burner layout. The coupler will go against the inside wall. The 3” nipple will go through the inner wall, convection cavity , and outer wall. The pipe outside is black steel, and everything inside (including the 3” nipple) is 304 stainless. The burners are gas fireplace burners I found on Amazon - the are welded 304 stainless with 1/2” threads and are pre-drilled with burn holes along the 12” upright pipes of the “H” (facing down in this pic). A close nipple and full bore ball valve will control airflow from the outside (not shown).
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For the pipe, I’m thinking about removing the damper and putting in a 8” to 6” reducer, then attaching a 6” flexible 304 stainless liner to that. Any issues with reducing the pipe diameter? I figured it would be more efficient with the secondary burn and require less air.
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begreen

Mooderator
Staff member
Nov 18, 2005
89,580
South Puget Sound, WA
The secondary burn system will require more draft, so reducing to 6" could be detrimental. How tall will the insulated liner be?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,487
central pa
This is in the basement, so 30-35’ to the top of the chimney.
If it really is 30 to 35' you do not want to remove the damper. Sizing the liner for secondary combustion is pretty complicated. You need the proper combination of volume and velocity to make it work.
 

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New Member
Nov 26, 2020
34
Oregon
DB545FA3-EE0F-41F7-BE43-DCA7295D4749.jpeg
Wouldn’t the air intakes (primary ones below the doors, air wash above them, and secondary burn ball valve) control the airflow as much as a damper?
I’m also not sure how I’d install a vertical stove pipe without removing the current damper.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,487
central pa
View attachment 267762 Wouldn’t the air intakes (primary ones below the doors, air wash above them, and secondary burn ball valve) control the airflow as much as a damper?
I’m also not sure how I’d install a vertical stove pipe without removing the current damper.
With that much height you will need the damper to limit draft. A box will need to be fabricated for it
 

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New Member
Nov 26, 2020
34
Oregon
Ok thanks. So should I just put in the secondary burn system and skip the flexible liner? I understand that sweeping the chimney will require pulling the whole thing out.
And I know the “right” answer is to buy a newer stove. Not in the budget this year.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,487
central pa
Ok thanks. So should I just put in the secondary burn system and skip the flexible liner? I understand that sweeping the chimney will require pulling the whole thing out.
And I know the “right” answer is to buy a newer stove. Not in the budget this year.
The liner is absolutely required for use and it needs to be insulated.
 

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New Member
Nov 26, 2020
34
Oregon
Any suggestions on how to attach one while keeping the damper? This older model didn’t use a chimney liner - installation instructions just tell you to shove it in place and open the masonry damper.
 

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New Member
Nov 26, 2020
34
Oregon
I installed it as I had originally intended. Yes I know it’s not ideal for heating, draft, or creosote buildup in the masonry chimney, but it’ll work for now. Honestly it burns pretty well - once the pipes are hot I can turn down the primary draft to ~1/5 open and have the ball valve 3/4 open. Most of the fire is then burning from the tubes. I’ll get some pics posted.

I got this installed just before Christmas, and I’m almost out of wood (I will have burned maybe 1.5 cords of dry hardwood, my entire stack), so it’ll be a short burning season anyway. I will probably pull it out this summer and adjust it some, likely adding a third burner. I want to add the liner as well, and I’ll probably cut out the damper to do that. All of Lopi’s new stoves, including their inserts with more volume, have 6” flue collars and only have a damper as a baffle bypass. Otherwise they’re wide open on top and airflow is controlled entirely by the main draft intake. So to get this connected to a liner I’d cut off the damper and reduce to 6” and install sheet metal plate and ceramic fiber wool to insulate the chimney around the liner to prevent more air leakage into the house.

This is a temporary stove. We are probably going to rip out the entire chimney stack in a few years and build a batch box rocket mass heater instead.

let the hate roll ;)
 
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New Member
Nov 26, 2020
34
Oregon
I’ve tuned my air controls so I can heat my entire 1961 1900sqft 2-story house with a full load + a log or two after the main fire has burned down enough to add a bit more fuel. Winter days have been at the high 40s during the day and between 28 and 35 or so at night. We burned through a lot of wood over Christmas break while we kept the upstairs 78 degrees :ZZZ and learned how not to burn efficiently in this stove. We now get upstairs to peak at 68-70 and are super comfy. When we replace the house’s original doors and windows heat retention should get a little better.

New gaskets on the doors & glass. I need to replace one pane eventually - the small crack lets in a minimal amount of air.
EC8AB23A-441A-418E-B87D-6F7E1B721FDC.jpeg 1309155E-BFD5-4291-B505-89437EF4077C.jpeg 5D4F0590-8BA5-4FA5-9F9B-573783B17EC5.jpeg 9646B793-D3CE-4F08-A566-316D2DB24587.jpeg
 
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Turbo_B

New Member
Dec 13, 2019
15
South Carolina
awesome! any pics of it in operation?

I tried the firebrick baffle, then bought 1.5" thick vermiculite board and got a better secondary burn in my old Suburban.
 

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New Member
Nov 26, 2020
34
Oregon
I’ll take some good pictures this week. I tried uploading a video but it must be too big or a bad format or something.

One of the new pumice bricks broke already, but I had another spare. It was probably the heat of the direct fire on cheap brick. I’ll check out the vermiculite board - it would be nice to have something that seals up the baffle better since the bricks I have seem to walk a bit as they expand and contract, opening small gaps in the baffle. I did take some of the old broken bricks and placed them on the ledges beneath the baffle to better insulate the fire box, not sure it helps any.

image.jpg
 
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Hoytman

Feeling the Heat
Jan 6, 2020
356
Ohio
There were three posts above that I disagreed with. You've obviously been able to do what you wanted and it looks nice. You've proven it can be done. Not as complicated as some would have you believe. Good for you!
 
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Turbo_B

New Member
Dec 13, 2019
15
South Carolina
Looking good!

Perhaps more info than you want this morning - My old Suburban and my Appalachian stove both had rectangular outlets with no flue connector. I picked up these for my stoves and have been working well. Connecting these to a proper flue liner helps keep the heat in the room and really improved the draft on my old stoves.
Flue pipe adapter
 
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[email protected]

New Member
Nov 26, 2020
34
Oregon
Looking good!

Perhaps more info than you want this morning - My old Suburban and my Appalachian stove both had rectangular outlets with no flue connector. I picked up these for my stoves and have been working well. Connecting these to a proper flue liner helps keep the heat in the room and really improved the draft on my old stoves.
Flue pipe adapter
My stove has a 8” round opening, so I should be able to just use a round 8” > 6” reducer after cutting off the damper. Next season I’ll do some upgrades like adding a third burner and hopefully a chimney liner. You aren’t the only one who’s mentioned how much better these burn with a liner
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,487
central pa
I installed it as I had originally intended. Yes I know it’s not ideal for heating, draft, or creosote buildup in the masonry chimney, but it’ll work for now. Honestly it burns pretty well - once the pipes are hot I can turn down the primary draft to ~1/5 open and have the ball valve 3/4 open. Most of the fire is then burning from the tubes. I’ll get some pics posted.

I got this installed just before Christmas, and I’m almost out of wood (I will have burned maybe 1.5 cords of dry hardwood, my entire stack), so it’ll be a short burning season anyway. I will probably pull it out this summer and adjust it some, likely adding a third burner. I want to add the liner as well, and I’ll probably cut out the damper to do that. All of Lopi’s new stoves, including their inserts with more volume, have 6” flue collars and only have a damper as a baffle bypass. Otherwise they’re wide open on top and airflow is controlled entirely by the main draft intake. So to get this connected to a liner I’d cut off the damper and reduce to 6” and install sheet metal plate and ceramic fiber wool to insulate the chimney around the liner to prevent more air leakage into the house.

This is a temporary stove. We are probably going to rip out the entire chimney stack in a few years and build a batch box rocket mass heater instead.

let the hate roll ;)
The requirement for a liner has much more to do with your safety than performance. Codes don't care much about performance they are in place to help keep people safe. Ignore them if you want but you are doing something we have seen end badly many many times. And do not cut that damper out I really think you will regret that if you do with the height of your chimney. I have been doing this a long time and installed hundreds of stoves and inserts. You want that damper.
 

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New Member
Nov 26, 2020
34
Oregon
The requirement for a liner has much more to do with your safety than performance. Codes don't care much about performance they are in place to help keep people safe. Ignore them if you want but you are doing something we have seen end badly many many times.
Yep, well understood. The plan is to get the chimney swept before next fall (we also had it inspected this year before we burned anything) and get a liner installed to improve both safety and performance. I have no desire for a chimney fire.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,487
central pa
There were three posts above that I disagreed with. You've obviously been able to do what you wanted and it looks nice. You've proven it can be done. Not as complicated as some would have you believe. Good for you!
You are assuming there is a benifit to this system and that it will hold up. The pictures of the fire I see look pretty much like the fire in any old stove with a baffle installed. But I see no problem with trying a secondary combustion system. There is a big problem with running a slammer
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,487
central pa
Yep, well understood. The plan is to get the chimney swept before next fall (we also had it inspected this year before we burned anything) and get a liner installed to improve both safety and performance. I have no desire for a chimney fire.
You can have multiple chimney fires in one year especially with a slammer.