New coal stoker, install question

[Dark Jedi]

We just bought a new coal stoker and replaced the old Franklin fireplace. We did use the Franklin, and it worked fine. My question is what do I need to put through the wall for the coal stove. The existing masonry chimney has been inspected and is good. It is of course lined. The hole through the wall is 8" and is lined with what appears to be a clay like stuff. It has a couple cracks in it, and I'm not sure I'm completely comfortable with it - but it's not going anywhere. Since the coal stove has a six inch pipe, is there some type of replacement liner I could use to put through the 8" hole and make it 6 or 7"? I can use a reducer if need be to connect to that. Also, I was at Lowe's today looking at double wall pipe. Some of it doesn't say anything about coal or wood, and some says for wood and gas use. If I am not mistaken, coal burns hotter than wood, so I would need to avoid the wood/gas use stuff, right? How do I know the other stuff that doesn't say is OK?

Just to be clear, here are the questions:
1. Can I just put a new type liner through the existing old liner that goes through the wall, and if so, what am I looking for? (The Lowes folks weren't much help).
2. What kind of double wall pipe am I looking for? None of them said they were specifically for coal, but some were for wood/gas.

Thanks in advance! May the Force be with you.

 

[Dark Jedi]

The stove came with the barometric damper, CO detector, and thermostat. And some free coal, too. It was a good deal without all of that based on my research and shopping around.

At any rate, I can't follow your link Sawdust, it asks me for a username/password. You mention the proper adapter for the chimney, and that is one of my questions - what is the proper adapter? Why single wall as opposed to double wall?

 

[Corie]

You can use single wall chimney connector from the flue collar of the stove to the thimble of the masonary chimney. Then, use a 6" to 8" stovepipe increaser to connect to the thimble. Seal the pipe to the thimble using furnace cement if possible. Make sure you hook up that barometric damper.

 

[Dark Jedi]

You can use single wall chimney connector from the flue collar of the stove to the thimble of the masonary chimney. Then, use a 6" to 8" stovepipe increaser to connect to the thimble.

This is where I'm a bit confused, I guess. When I took out the old woodstove, I removed (with some difficulty) the old black pipe that was inside the masonry thimble. It needed to be removed as it was corroded. The old pipe stuck out a few inches from the wall, thus allowing a connection to the rest of the flue. Now the masonry lining (looks like clay) is flush with the wall, so there is nothing there to connect to. So, I need to either put in another pipe like the one that was there or put in something different. Again, although the cracks are small, I am not entirely comfortable with the masonry thimble that is there. So, I would rather put in a new, metal thimble. The question, then, is do I just get a piece of black or galvanized pipe like what was there and use a reducer, or is there something better out there? What is the somehting better?

 

[Corie]

Masonry thimble flush with the wall? That sounds like an unsafe thimble to me. You may need an inspection, but at the very least pictures would be helpful so that I can walk you through what you need to do.

THe coal stove forum is helpful, but I assure you there are few questions regarding coal burning that we can't answer here.

 

[Michael6268]

What kind of wall is the clay thimble in? Im assuming its in a concrete wall. If so you are fine with a clay thimble. You just cant finish the inside of the wall up to the thimble opening with anything combustible or you will have to get an approved wall thimble if you wish to finish the wall up close to the thimble with something combustible like sheetrock or paneling. Class A double wall at Lowes is fine for coal you probably dont need it. If you clay thimble has a few hairline cracks in it and indeed it is in a concrete wall all you really need to do is patch the cracks with some furnace cement. Coal doesnt produce creosote so you dont have to worry about fire going up the chimney and the heat going up the flue is usually less than 400 degrees, so unless the thimble is in total disrepair you should be all set. You can use single wall 24 gauge black stove pipe or if you want single wall stanless as stainless will last longer, and insert it into the thimble making sure it doesnt stick out into the actual vertical clay liner. You want it just to the back edge of the thimble. Attach a 6-8" reducer on the front of that piece and from there go to the stove with the six inch black or stainless. Use a baramentric damper too. Again, this is assuming you have a concrete wall situation with no combustibles. If you are going through combustibles you need an approved wall thimble kit.

 

[ansehnlich1]

What kind of wall is the clay thimble in? Im assuming its in a concrete wall. If so you are fine with a clay thimble. You just cant finish the inside of the wall up to the thimble opening with anything combustible or you will have to get an approved wall thimble if you wish to finish the wall up close to the thimble with something combustible like sheetrock or paneling. Class A double wall at Lowes is fine for coal you probably dont need it. If you clay thimble has a few hairline cracks in it and indeed it is in a concrete wall all you really need to do is patch the cracks with some furnace cement. Coal doesnt produce creosote so you dont have to worry about fire going up the chimney and the heat going up the flue is usually less than 400 degrees, so unless the thimble is in total disrepair you should be all set. You can use single wall 24 gauge black stove pipe or if you want single wall stanless as stainless will last longer, and insert it into the thimble making sure it doesnt stick out into the actual vertical clay liner. You want it just to the back edge of the thimble. Attach a 6-8" reducer on the front of that piece and from there go to the stove with the six inch black or stainless. Use a baramentric damper too. Again, this is assuming you have a concrete wall situation with no combustibles. If you are going through combustibles you need an approved wall thimble kit.

Michael is correct here. If your clay thimble goes through a solid masonry wall, which it should, then you could use 6 inch pipe to an 8 inch stove pipe slid through the clay thimble, but not jutting into the chimney itself any further than the thimble.

You may have a 16, 18, 24, or 30 inch square brick or masonry wall through which the thimble passes. Code in our new home was 12 inches of masonry all around the thimble if I recall, meaning for a 6 inch thimble it would have to be 30 inches square.

I actually have an 8 inch clay thimble which was first installed because we thought we'd buy a stove needing an 8 inch pipe, the vermont castings defiant, however we went with the oslo which uses 6 inch pipe... so, we just mortared a 6 inch clay thimble right inside the 8 inch thimble, and slid our 6 inch stove pipe through that.

So, what's your thimble pass through, that's the question???

 

[Dark Jedi]

Thanks for your input guys. The wall is not concrete, it is a wood house. The masonry "thimble" could probably be better described as a liner. I removed the old metal "thimble" which was actually just a length of black pipe cemented in. The advice about the cracks is good - they are small, hairline cracks which it would seem would be easy to cover with furnace cement. And thanks for the clarification on the double wall pipe. Clearance isn't an issue, but we don't want it to be an issue, either.

That brings us to the thimble kit you mentioned. I didn't see anything like that at Lowe's, but then again I wasn't specifically looking for that. There is also a hardware store nearby that has stuff as well as the place I bought the stove. I haven't been to TSC yet. So, are these thimble kits generally available at Lowes. TSC, etc.? Are they difficult to install? Can I actually put in one to fit the 8.5" hole then another smaller one inside of that one? Should/can I put in a stainless pipe then the kit?

 

[Dark Jedi]

Updating: I have done some more research and I think a plan similar to yours, ansehnlich, may work very well for us. Just so I'm clear here: I can get another, smaller liner to put inside the old liner, then put the new metal thimble through that, or I can actually get 2 thimbles, a larger one to fit the 8.5" hole, then another to go in there. Is this right? I would still need a reducer for the 6"pipe, I assume. That said, if I went with a new liner for through the wall, where do I get the clay/ceramic stuff to do that with? I didn't see stuff like that at Lowes or the hardware I go to. Where do I find them? (I haven't been back to Lowes since my first post, but will have time this weekend.)

 

[Michael6268]

So when you say it "goes through the wall" are you talking about a chimney/brick structure? Surely you dont have a clay tile liner in a wood framed wall. I would think it has to be in some kind of masonry. You can never be too careful but the one thing with coal is there are no vigorous flames burning in the stove. All that is going up the pipe is warm gases. The risk of chimney fire/pipe failure leading to anything catching fire is not as much of a factor as it is with wood stoves. As stated previously if the clay is totally deteriorated I would either chip it out and install a new one or cement a 6" inside the old 8"

 

[ansehnlich1]

Dark Jedi,

there are strict codes involved when a wood/coal stove chimney passes through a wall. Wood is different than coal, but chimney construction code I think is the same.

Look at this link,

http://www.jotul.com/FileArchive/Technical Documentation/Wood Stoves/Jøtul F 500 Oslo/Manual_F_500_USA_P11_180808.pdf

You may need to cut and paste the above link in your browser.

Check out Page 14, figure 4, it shows a thimble passing through a wall. If your thimble does not pass through masonry as pictured in figure 4 I am afraid you are at risk for fire.

For example, if you have a 6 inch thimble, it is required to have 12 inches of masonry surrounding it all around, meaning you would need a brick/masonry square of 30 inches for the 6 inch thimble to pass through the middle. This is exactly the stove we used and exactly how we built our chimney.

I highly advise you check to see what your thimble passes through and make it to code, maybe you could post a picture of this setup here.

 

[ansehnlich1]

And if you are seeking a clay thimble, you would find them at concrete block/brick manufacturer supply places, local masons could help you find them too.

I must add that when we slid our 6 inch thimble through the 8 inch thimble it was mortared in place, not just slid through there loosely.

So, assuming your current thimble passes through the wall "to code" as outlined in my previous post, you could mortar a 6 inch clay thimble inside the current cracked 8 inch clay thimble. Then you could use single wall steel pipe to pass through the 6 inch clay thimble.

 

[Dark Jedi]

I apprecite y'all's concern for that the current system meets code, and I assure you it does. It does pass through a wood wall to an exterior block chimney that is properly lined, and there is indeed a huge block of masonry through the wall. The clay liner I refer to is part of that masonry. I have removed the old thimble because it needed to be replaced even if I were to keep the old Franklin fireplace, which we haven't used in about 5 years. Replacing it with a coal stoker is meant to reduce our dependence on oil, which I am sure y'all realize has increased greatly in price the last two heating seasons. I do not intend to be rude and do appreciate your input, however, I do assure you the chimney is up to code and remind you that it has been properly inspected by a local licensed inspector who runs a chimney cleaning service. This is NY where everything is regulated, taxed, or both (most likley both).

That said, back to one of the original questions. With the input here and other research, I have come to the conclusion that all I really need to do is seal the small, hairline cracks in the liner if I desire and put in a new thimble. I would prefer to put in a thimble where I don't have to use a reducer (from 8" to 6") and I am there fore asking the following:

Is it possible/advisable to put a thimble inside a thimble, all of which would go through the current, code approved, properly inspected masonry to the chimney? I still intend to use double wall pipe, even though I don't "need" it.

 

[ansehnlich1]

Is it possible/advisable to put a thimble inside a thimble, all of which would go through the current, code approved, properly inspected masonry to the chimney? I still intend to use double wall pipe, even though I don't "need" it.

You can mortar an 8 inch thimble through there, then mortar a 6 inch thimble through the 8 inch, as long as you have solid masonry/mortar surrounding the thimbles.

My stove has double wall going to the thimble, but single wall passing through the thimble, I'm not certain double wall pipe will slide through a 6 inch clay thimble.

 

[Dark Jedi]

Thanks, an. I was actually looking at using a metal thimble since it appears they are much easier to come by. Is it still possible using metal thimbles?

 

[ansehnlich1]

As long as the thimble you are using is installed properly AND rated for use with a coal burning appliance you should be fine.

Simply put, sounds like you have a hole bigger than you need. Assuming you have proper masonry surround, which you say you do, then yes, you can use either metal or clay thimble. Just make sure you have the thing sealed properly when you install it. That's why I stated to mortar an 8 inch clay thimble in there, then a 6 inch inside it, then a plain metal pipe through the 6 inch. I am not familiar with sizes of metal double wall thimbles, and if you can do it with them. I know it can be done with the clay thimble because that is exactly what I have in my home, an 8 inch clay, with a 6 inch clay mortared inside it, and then a metal pipe through the 6 inch. That metal pipe sticks out far enough into the room to connect the double wall pipe off the stove to it.

If you use a double wall metal thimble you still must seal the exterior of that thimble as it sits in your pass through hole. As far as nesting a 6 inch metal double wall thimble into an 8 inch I am unsure as I don't know the sizes etc.

Maybe you should ask your sweep his opinion on the matter too, never can be too safe when it comes to solid fuel burning devices.

 

[Dark Jedi]

I agree that you can never be too safe, hence my passion for using the double wall pipe even though I don't "need" it for clearance. The hole is bigger than I need because I am replacing the old Franklin that had 8" pipe with my new stoker with 6' pipe. The clay liner is actually 8.5" to accommodate an 8" thimble. I could use an adapter at the end of the double wall where it attaches to the thimble and still use any regular 8" thimble. My thought was that perhaps 2 thimbles (making a double thimble) are better than one and that then I might not need a reducer. I'll end up working with what's available in the end, however, and while this week is supposed to be pretty nice during the day with chilly nights, I can still get away with running the oil cash drainer once or twice a day to take the chill off. Those days will be over soon enough and hopefully the oil will become the supplemental heat only when it's super cold out.