Masonry Chimney Thimble - What Does Correct Look Like?

[funbaker10]

Hello Everyone.

I have a wood burning central furnace that vents into a masonry chimney. The chimney was constructed out of concrete block with a clay/ceramic tile lining. The chimney has three separate clay tile lined flues of which one is being used for the wood furnace. The other two are for two separate open fireplaces.

When I installed the wood burning central furnace about eight years ago I vented it to an existing penetration into the chimney. It has been working OK but the existing penetration into the chimney is quite low relative to the outlet of the furnace. This results in a rather shallow pitch of the connecting pipe between the furnace exit and the chimney. To improve this situation I want to make a new penetration into the chimney about 32" higher than the original.

I have been gathering as much info as I can off the internet and watched as many videos I can find but still have some questions. I want to do this "right" and want to meet code, etc. My main questions are these:
1) Does a clay/ceramic thimble need to be mortared in through the chimney wall penetration?
2) if yes, what type of mortar is required?
3) Is modern practice to use a clay/ceramic thimble or have things changed (metal thimbles?)
4) Does the connecting pipe then go all the way through the thimble or does it simply connect to the thimble?
5) If the connecting pipe goes through the thimble is it OK for the connecting pipe to contact the thimble? Does it rest on the bottom of the thimble?
6) In my case the stove connecting pipe is 6" in size. What should the ID of the thimble be?

Any experience or info you might be able to share would be greatly appreciated.
Thanks.

 

[bholler]

Hello Everyone.

I have a wood burning central furnace that vents into a masonry chimney. The chimney was constructed out of concrete block with a clay/ceramic tile lining. The chimney has three separate clay tile lined flues of which one is being used for the wood furnace. The other two are for two separate open fireplaces.

When I installed the wood burning central furnace about eight years ago I vented it to an existing penetration into the chimney. It has been working OK but the existing penetration into the chimney is quite low relative to the outlet of the furnace. This results in a rather shallow pitch of the connecting pipe between the furnace exit and the chimney. To improve this situation I want to make a new penetration into the chimney about 32" higher than the original.

I have been gathering as much info as I can off the internet and watched as many videos I can find but still have some questions. I want to do this "right" and want to meet code, etc. My main questions are these:
1) Does a clay/ceramic thimble need to be mortared in through the chimney wall penetration?
2) if yes, what type of mortar is required?
3) Is modern practice to use a clay/ceramic thimble or have things changed (metal thimbles?)
4) Does the connecting pipe then go all the way through the thimble or does it simply connect to the thimble?
5) If the connecting pipe goes through the thimble is it OK for the connecting pipe to contact the thimble? Does it rest on the bottom of the thimble?
6) In my case the stove connecting pipe is 6" in size. What should the ID of the thimble be?

Any experience or info you might be able to share would be greatly appreciated.
Thanks.

Yes it gets mortared into the chimney. That mortar doesn't matter but it needs mortared to the liner with refractory mortar. You should use a 6" thimble and the pipe should slide in until it is flush with the face of the liner. The hardest part is cutting the hole in the liner without cracking it. I generally do that with an angle grinder. Probably one in 10 cracks anyway.

 

[funbaker10]

Yes it gets mortared into the chimney. That mortar doesn't matter but it needs mortared to the liner with refractory mortar. You should use a 6" thimble and the pipe should slide in until it is flush with the face of the liner. The hardest part is cutting the hole in the liner without cracking it. I generally do that with an angle grinder. Probably one in 10 cracks anyway.

I assume if you put in a 6" thimble a piece of 6" single wall stove connector pipe will fit with just the right amount of clearance? Also, as far as using refractory mortar to mortar the clay thimble to the chimney clay liner. Is refractory mortar just a special mortar that is mixed up in the same manner as regular brick mortar? And mortaring in the thimble to the chimney clay liner must be done reaching through the thimble and using some sort of 2 or 3 inch drywall knife type tool? Have you ever tried using a hole saw to get through the clay chimney liner?
Thanks for sharing your experience.

 

[bholler]

I assume if you put in a 6" thimble a piece of 6" single wall stove connector pipe will fit with just the right amount of clearance? Also, as far as using refractory mortar to mortar the clay thimble to the chimney clay liner. Is refractory mortar just a special mortar that is mixed up in the same manner as regular brick mortar? And mortaring in the thimble to the chimney clay liner must be done reaching through the thimble and using some sort of 2 or 3 inch drywall knife type tool? Have you ever tried using a hole saw to get through the clay chimney liner?
Thanks for sharing your experience.

Refractory mortar either comes premixed or dry and you usually butter the end of the crock before sliding it in. No I change never tried a hole saw you would probably need a wet core saw and drill to be able to do it. That makes a big mess.