New guy, old stove, thimble ?

[NickW]

Background - Been in my house 16+ years, built in '78 with a Triumph by Torrid Mfg wood stove. Had the genius idea a couple of years back to install a 2nd heat reclaimer and duct it back to the bedrooms. Started having chimney fires (duh!). Last years was bad enough to call the fire dept, but didn't cause any structural damage. Please, no lectures on my stupidity.... 2nd reclaimer has been removed.

Thinking of upgrading to a new EPA stove with a stainless liner. As I started assessing the chimney I have found a couple of issues. #1. Where the chimney passes through the floor and ceiling they did not leave the 2" clearance to combustibles. I think I can fix that with some effort. #2. This is where I am struggling. The clay thimble liner is inside what appears to be a concrete tube thimble. There is a 1/2" air gap between the clay thimble liner and concrete thimble. Drywall is tight to the concrete thimble and wood studs are 4-5" from it. I can't find anything about this setup. Was such a thing ever commercially made and did this negate the 12" to combustibles requirement?

I am guessing this is a DIY setup that never should have passed occupancy inspection from the beginning...

 

[SpaceBus]

Can you post some photos? I have what most folks would call a "janky" thimble/masonry penetration, but that will be rectified soon with a full insulated liner. You should be quite pleased at the performance from an insulated liner with an EPA stove.

 

[NickW]

First photo shows the edge of the clay flue liner and 1/2" air gap. Second is inside the wall from above through the drop ceiling. The "bricks" are veneer glued to the wall.

 

[bholler]

Yes there are comercially available solutions to this you need an insulated thimble. In addition you should really consider removing the clay liners and installing an insulated liner. If you do this the clearance issues don't matter and the system will work better.

 

[NickW]

Thank you! That's the direction I'm trying to head in. The original question was whether the clay thimble liner inside a concrete tube was a commercially available unit or more likely DIY.

I think I've found a thimble that only needs 2" clearance. Will insulated stainless liners state that they don't require 2" clearance on the outside of the masonry chimney they are inside of?

I knew I'd get help here. Chimney pros are vague because they want the work themselves. Inspector has been pretty good but a bit noncommittal. I wish he would just say "here's what to do in your situation...".

 

[bholler]

Thank you! That's the direction I'm trying to head in. The original question was whether the clay thimble liner inside a concrete tube was a commercially available unit or more likely DIY.

I think I've found a thimble that only needs 2" clearance. Will insulated stainless liners state that they don't require 2" clearance on the outside of the masonry chimney they are inside of?

I knew I'd get help here. Chimney pros are vague because they want the work themselves. Inspector has been pretty good but a bit noncommittal. I wish he would just say "here's what to do in your situation...".

Yes a properly insulated chimney liner will give you zero clearance to combustibles on the outside of the masonry chimney. As far as the thimble goes just take that out and install a proper insulated thimble.

 

[bholler]

The thimble you have looks allot like the old asbestos chimney tiles used for many furnace installs in the 50s. I can't be sure though.

 

[NickW]

So any advice on what to use? I have a chimney that's about 25' bottom of clean out to cap; straight, no jogs. I see pre-insulated flex available, but I was thinking straight sections might be cheaper and easier to work with. Not seeing any pre-insulated though. Old clay liner is 8 3/8 x 12 3/4 outside, so once I make a clay liner removal tool and knock it out I should have room to get it in. I was going to get the flue lining stuff and thimble at Menards and order a Summers Heat 50SNC30 from Rural King, but Menards stock is pretty slim...

 

[begreen]

That's most likely 7" x 11" ID. Duraliner oval is made for this common but narrow flue. It's preinsulated and comes in rigid sections that get pop riveted together as it is being installed. DuraLiner has a 6" round tee snout that connects to the rigid oval pipe.

Chimney Pipe / Venting Pipe :: Wood/All-Fuel Piping :: 6 inch :: DuraVent DuraLiner 6 - page 2

woodstovepro.com

 

[NickW]

Yes, inside measures 6 3/4 x 11 1/8. So I saw that oval duraliner one online, are you saying it may fit INSIDE the clay liner so I might not even have to knock it out? That would be convenient....

 

[begreen]

Yes, inside measures 6 3/4 x 11 1/8. So I saw that oval duraliner one online, are you saying it may fit INSIDE the clay liner so I might not even have to knock it out? That would be convenient....

Yes, if it's a straight shot down the chimney, without offsets, the oval DuraLiner will fit in that space without removing the tile.

 

[NickW]

Ok guys... I bought a Summers Heat 50-SNC30 from Englander, Double wall DVL chimney pipe & the oval Duraliner (which shipped partially wrong ... still waiting). I did a low burn the other day in the driveway with just really little stuff and was seriously impressed by the heat and burn time. Today I'm trying to do a little hotter & longer burn with not a lot of luck. I can only get a stovetop temp of 430 and the secondary burn won't stay kicked in (at least visibly). Smoky too. Wood is 15-20% on a fresh split. Do you think it could be weak draft because I only have 3' of pipe on? Am I not hot enough? Fires right back up when I open the door a bit, then I shut it and get secondary burn for a while but it goes out and starts smoking... I have the air supply open all the way, what's gonna happen when I choke her down?

 

[begreen]

Definitely because there is not enough flue on the stove. Once it has 15' of stack it will be ok.

 

[NickW]

Ok. Looking forward to having it in one of these weeks. What about split sizes? My old smoke dragon I left the splits big (7×7 wedges) so I still have a few coals in the morning. Is that too big to burn efficiently in an epa stove?

 

[weatherguy]

Ok. Looking forward to having it in one of these weeks. What about split sizes? My old smoke dragon I left the splits big (7×7 wedges) so I still have a few coals in the morning. Is that too big to burn efficiently in an epa stove?

Not if its dry, or below 20% moisture.

 

[begreen]

Ok. Looking forward to having it in one of these weeks. What about split sizes? My old smoke dragon I left the splits big (7×7 wedges) so I still have a few coals in the morning. Is that too big to burn efficiently in an epa stove?

If the wood is fully seasoned, thick splits are fine.

 

[NickW]

Thanks! I will post again when I have it installed.

 

[NickW]

Finally have the new stove & flue installed! First fire is lit. Kinda struggling to get the temp up to where it should be from what I understand (stovetop 450-550.... correct me if I'm wrong...). I am being a bit cautious with the wood load though. It seems like keeping the door cracked allows too much air in keeping it cool, but closing the door with the air control all the way up I'm still only at 370. Draft seems pretty strong. I'm going to try closing the air control some and see if that helps the temp go up. Maybe I have a bit too much draft. More likely I don't have enough wood in? Only put 2 medium size chunks in after I had it established.

 

[NickW]

So that last post was supposed to be last night.... forgot to hit "post" - duh! Stove is a Summers Heat 50-SNC30 by Englander. I found another post about an NC30 that I assume is the same or similar stove that gave me some tips. I had the air shut down all the way overnight (6 hours) with 3 good size chunks on the bottom and 1 med & 1 small on top of them. Firebox was not full. Got up to 470 at the collar and backed it down slowly. Still had 2 fairly solid chunks left but temp was only 250 this morning. Added another small and medium chunk and got up to 500 (at the collar) and backed it down but it settled in at only 300 or so an hour later.

So from the other post I seem to need to move my thermometer to the back edge of the lower step to get a more accurate reading because this is the "hot spot". My next steps are going to be leaving the air a little more open and loading more wood (not both at the same time though to start). The temps of 500-600 in that other post sounds really high to me, but I'm used to the old smoke dragon...

My wood is well seasoned, under 18%; but the glass is getting black already. Am I not running hot enough? Do you agree with my plan with leaving the air more open and trying more wood? Would it be wrong to add more wood already to try to get the temp to cruise higher? Comments?

I'm in WI. It's not super cold (yet), but I've got 2400sqft and baseboard electric heaters and hate hearing them kick in. I have a 2x4 grille in the drop ceiling near the stove and ductwork with a fan to help move warm air from the stove room back to the bedrooms and cold air returns. Looking to get the max out of this stove.

 

[MAD MARK]

Not running hot enough. Shutting air down too early causing the blackened window.

Add more wood. My normal load is within 2 inches of the top reburn tubes. I do top down fires.

I run my NC-30 to 700°F everytime I use it. This is measured on the step up on top.

Light fire with door open 1" for 10 mins.
Shut door for another 5.
STT will be about 450.
Start closing air down to about half. (Weak draft here)
STT will end up max 750°F.

 

[NickW]

So you do front of top step, not back of bottom step. 700 sounds really high! I hit 650 for a while this morning and the smoke detectors didn't like it, but it's only day 2... I did do a couple of burns in the driveway, but could only get so hot; so I'm guessing I'm still burning the chemicals out. Might be time for new batteries or new detectors.

So you don't ever get to shut the air down all the way and keep it going? It's been calm the last couple of days, but I live on Windy Acres so I bet I'll be able to get close to shutting all the way - it's an appropriate road name. I've got decent draft - 20' of insulated Duraliner and about 7' of DVL double wall.

Do you spread the coals out with a trough like the manual says or rake to the front like most people do (or so it seems)? How long is your burn cycle with the box loaded like that (down to 250-300)? Also noticed more smoke out the chimney when I shut it down, but again not enough draft in the calm.

I can tell already I'm using less wood for more heat and the outside of the chimney is now cool to the touch when burning. The old smoke dragon and clay flue really radiated the heat through the concrete chimney. I love it already and I'm sure it'll only get better as I learn how to use it better. Thanks for your input Mark!

 

[MAD MARK]

I never have air closed the whole way because of my weak draft and short chimney.

I do pull the lump coals to the front on reloads or to burn them down.

Below is a picture of what I lit 30 minutes ago, and also a picture of where the STT was. Probably got near 800 because I was checking up on the young one. That's where my STT reads from, your stove might be a little different setup.

 

[MAD MARK]

And with the box loaded like that I'm expecting burn time to be about 5-6 hours with a 3-4 coaling time. All cherry.

 

[Woody Stover]

I had the air shut down all the way overnight (6 hours)....Got up to 470 at the collar and backed it down slowly.....got up to 500 (at the collar) and backed it down but it settled in at only 300 or so an hour later.

How were you taking temps at the flue collar, infrared thermometer, magnetic surface meter or what?

My next steps are going to be leaving the air a little more open and loading more wood (not both at the same time though to start). The temps of 500-600 in that other post sounds really high to me

wood is well seasoned, under 18%; but the glass is getting black already. Am I not running hot enough? Do you agree with my plan with leaving the air more open and trying more wood? Would it be wrong to add more wood already to try to get the temp to cruise higher?

To get accurate wood moisture reading, take a few of your large splits and get them to room temp for a day or more, then re-split and test on a fresh face. Black glass is from wet wood, or as Mark said, cutting the air too much, too soon.
You can do different things with the coal bed when you reload, depending on how your loads are reacting. If you find your wood is a bit damp (>18%) you might need more coals under the wood when you reload. If your full loads are hard to control, you might burn the coals down more before reloading, so that coals aren't under as much of the wood and the load will burn slower.
A top-down start, mentioned by Mark, will get the top re-burn section of the stove up to temp faster, while not burning up as much of the load early. You need dry wood for it to work well, however.

Not running hot enough. Shutting air down too early causing the blackened window.
Add more wood. My normal load is within 2 inches of the top reburn tubes...
I run my NC-30 to 700°F everytime.

With dry wood, once you start to see the first signs of secondary burn at the tubes, start cutting air in increments, but not so much that the secondary dies. Your goal is lazy flame coming off the logs, but a strong secondary burn.
This high-output phase of the burn will last a few hours, then a slow decline in stove temp over the next several hours. If you need more heat, you can open up the air slightly on the coals to get more heat while making room for a bigger load. You want to open the air enough to fire up the coals, yet not so much that the heat goes up the chimney too fast. The secret to extracting the most heat at any stage of the burn is to have the least possible amount of air going through the stove, while maintaining a strong burn. This is a better approach than opening the stove more often and just throwing in a split or two. Every situation is unique though..you just have to experiment and see what works. Don't fall into a pattern too early, keep trying different things.

noticed more smoke out the chimney when I shut it down, but again not enough draft in the calm.

If you have a strong secondary burn going, there should be no smoke. If you don't, your wood is wet or you've cut too much air and killed it. The fact that there's "not enough draft" on 25' of liner might be pointing to wet wood. I often talk to my brother up there, and my buddy, and it hasn't exactly been hot, so I'd expect decent draft.

with the box loaded like that I'm expecting burn time to be about 5-6 hours with a 3-4 coaling time. All cherry.

Cherry is decent medium-output wood, but I know that higher-output woods are available in SE WI. Those will stretch your burn times a bit.

 

[Woody Stover]

If you put a flue probe thermometer in the double-wall connector pipe, 18" above the stove top, it will give you more immediate feedback on the current state of the fire than a stove top meter will.