Need help, wood-burning furnace problem! (long)

[JSUnlimited]

I have noted of the past several years a slight crack in the clay thimble that passes through my poured basement wall leading out into the chimney.

The wall was core drilled and the thimble was placed through that. It then extends past the outside of the wall goes through the chimney block and butts against a coresponding hole in the flue liner. It is mortared in place where it meets the flue liner. The thimble stuck out inside the basement wall aproximately 10-12 inches or so. A 6" single wall pipe exits the furnace and passes through the thimble. The pipe is inserted as far as it can go and ends at about the edge of the flue liner inside the chimney.

When I was removing the old single wall pipe to replace it with new, the thimble cracked and several large pieces fell to the floor. Once the pipe was removed, I noticed no cracks much past were it goes through the basement wall heading out.

Here are some pictures...hopefully you guys get what I'm talking about.

I would like to be able to cut whats left of the thimble flush with the basement wall and use something to seal around both the wall/thimble and pipe/thimble. Then perhaps put a trim collar around the pipe where it meets the wall.

Any suggestions?

 

[JSUnlimited]

Couple more pics.

 

[ToadHill]

Other than making it look better I don't think you need to do anything. Since you are cgoing through a cement wall, the thimble was redundant anyway.

 

[arrow]

Toad is right. Basically if the flue ajoins the cement opening and there are no gaps there, you could just shove a stove pipe all the way through. Anything else you do would be cosmetic. Nice furnace set up. the way to go if you want to heat an entire house with wood. Much more efficient than a wood boiler.

 

[scott_vt]

Good Evenin MegaMe,
As the other guys have noted allready, you probably dont really need to do anything ! But in case you want to patch it just the same, they do make a fireproof cement that can be trowled into the flue liner to repair any cracks or breaks. For the life of me I cant think of the name of the stuff, but it works and its also expensive !

Wish I could offer more help than that !

 

[CurlyDave]

I think you want to replace/repair/substitute for the thimble.

Enough heat will deteriorate or even destroy concrete.

 

[arrow]

Concrete is a pretty stable entity as far as heat resistance. If concrete is subjected to 1000* or more problems can ensue. I measure the heat output at my exit at 123*. This is with stove pipe going through the concrete hole. It has been there for 35 years. My main concern was the creosote which can get pretty caustic and why the liner should remain in his cellar outlet. A clay liner will convect heat all the way to the surrounding concrete which will be only a little cooler than the liner itself. Any real concern here is best addressed by an insulated stainless insert going out to the vertical flue.

 

[jpm]

i had the same problem and solve it with a metalbetos thimble. the cause of the cracking is heat diff. vs the mass of the concrete

 

[JSUnlimited]

Other than making it look better I don't think you need to do anything. Since you are cgoing through a cement wall, the thimble was redundant anyway.

A brother firefighter that works for a neighboring city to the one I work for inspects and relines chimneys on his days off. He came over and inspected everthing (flue, thimble, crown, etc). He said the same thing as Toadhill and others. Other than doing some things for cosmetics and sealing the voids from cold air coming in when not in use....to not worry about it.

So, what I did was to first take a diamond disk for my 90 deg. grinder and cut the jagged edges off of the thimble flush with the wall. Then I used 1200 deg. sealer to seal up where the thimble meets the flue liner. Instead of sticking the single wall pipe into the thimble until it stops (the thimble and flue liner do not meet perfectly), I put a male to male connector on the end. This allowed me to have the end of the pipe to pass thru where the thimble and flue liner meet. The end of the pipe now sticks out into the flue about an inch. This bridges any gap that might be present where the thimble and liner meet. I replaced the old single wall with new and using the same 1200 deg. sealer I sealed all of the gaps between the pipe/thimble and thimble/basement wall. I also put a trim collar on the pipe (see pics).

Now, the only problem is that after everything was put together and sealed I noticed that the horizontal piece runs toward the chimney instead of back towards the furnace. I have read where things should run back toward the woodburning appliance in case of creosote. I did make sure that the male portions of the pipe were running towards the furnace. In order to get enough space all around the single wall pipe I had to do this as it was noticed that the thimble is not exactly level.

Any concerns? I guess being OCD and a firefighter, I am putting too much thought and worries into this!

 

[arrow]

Mega

Even if the horizontal pipe is leaning toward the chimney, you should still be ok as if it stays liquid enough , it will fall toward the clean out. Worst that will happen if your chimney is not capped is it will stink to high heaven when it rains after a few years build-up. The rest looks real nice and neat.