New thimble question

[Coyoterun]

To recap my situation, I'm in the process of installing a new WS IS this winter. I'll be dropping a pre-insulated Olympia SS liner down a existing interior brick chimney and installing an insulated wall thimble into a sheetrock wall that runs just in front of the chimney. I have not yet purchased the liner or other supplies. I've been visiting with a salesman at Woodlanddirect who seemed to be quite helpful in assembling the correct list of supplies so that everything fits together.
The attached picture shows the existing area. The red circle is where the thimble will go. There is a opening in the chimney just behind there. This (broken link removed to https://www.rockfordchimneysupply.com/PDF/insulated-wall-thimble-instructions.pdf) seems to say that for a 6 inch thimble I only need about a 14X14" square.

Here's the question: The salesman says I need a thimble that will require a wall opening about 19"X19" and that will cost about $323. Does that sound correct? It sounds as if he's looking at a bigger thimble than I need.


Oh, and the professional installers in my area don't think I need an insulated liner at all so I'm not very confident in them. It's an interior brick chimney with only the 4" of brick and mortar separating the liner from the floor joists.

 

[begreen]

I did a quick search on their site for thimbles and didn't see an insulated thimble listed. Not sure what the salesperson is proposing. Did he give you a part name and number? There are good insulated thimbles made by Saf-T-Thimble (heat fab) and (broken link removed)(Dalsin Mfg). These are different from wall thimbles designed for passing class A chimney pipe thru a wall.

This article goes into some of the options for passing through a combustible wall. It discusses insulated thimbles too.
https://www.hearth.com/talk/threads/chimney-passing-a-chimney-through-the-wall.147754/#post-1987049

 

[CenterTree]

It seems that the opening need only be 13.75" x 13.75" rough. (as you said 14x14).
Not sure what type thimble would use a 19"sq hole??

Did he tell or show you his style/brand thimble that needs 19"?

And. yes, thimbles can be expensive, but they are a very crucial part of the flu system and should never be skimped on just due to price.

 

[begreen]

If Woodland is supplying the Olympia liner ask them about the Olympia insulated wall thimble.
(broken link removed)

 

[Coyoterun]

I just have my scribbled notes from the phone call. I was going through them now before calling them back later this week. It pretty much all seemed in line and made sense until I got to the thimble.
The salesman said several items aren't on their website as they don't do a lot of Olympia volume. He did say the liner and thimble would be drop shipped direct from Olympia. I'll ask him to review that thimble, get part number, etc. If I'm not satisfied I don't have to order from there. I just wanted to get everything from one place so that everything matched up and I got everything that was needed without ordering a lot of things I didn't need.

And I don't want to cut any safety corners on this install, but I don't need to dump an extra $100 on something that's bigger than I need. Also, a 14" square wouldn't need to cut any wall studs. A 19" would.

Thanks for the assurance that I need to do a recheck on that thimble.

 

[WayneN]

This is the kit I used but it comes with a lot more than you need. That price doesn't seem right since this kit included wall thimble, wall supports, vent cap, etc. Also I only needed a 10 inch diameter with 6 inch pipe. Inner diameter 6, outer was 8, and triple wall needs only 2 inches of clearance for combustibles. The thimble is round so a circular hole was cut through the wall. The through wall pipe is triple wall then steps into either a double or single adapter. I went single with my install.














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[webby3650]

This is the kit I used but it comes with a lot more than you need. That price doesn't seem right since this kit included wall thimble, wall supports, vent cap, etc. Also I only needed a 10 inch diameter with 6 inch pipe. Inner diameter 6, outer was 8, and triple wall needs only 2 inches of clearance for combustibles. The thimble is round so a circular hole was cut through the wall. The through wall pipe is triple wall then steps into either a double or single adapter. I went single with my install.


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Hopefully you ended up with a 12" hole rather than 10".
The OP is looking at a liner kit with an insulated wall thimble, totally different system than you installed. Nice job on yours, doesn't look like a real fun one!

 

[WayneN]

I think it was close to 10.5 inches. The black round plate is about 3.5 inches. It's not that bad to install but I think clearances should be the same wall thimble wise right? 3 wall class a going through the wall only needs 2 inches clearance total. The outer diameter of the pipe was 10 inches. It's all prefabricated by supervent so there's no way to make the clearance more or the thimble would fall through. Note the exterior part is square but the interior is round. Any bigger hole and you can't mount it. There's a good 2.5 to 3 inch clearance inside the thimble box the way it's designed.

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[webby3650]

I think it was close to 10.5 inches. The black round plate is about 3.5 inches. It's not that bad to install but I think clearances should be the same wall thimble wise right? 3 wall class a going through the wall only needs 2 inches clearance total. The outer diameter of the pipe was 10 inches. It's all prefabricated by supervent so there's no way to make the clearance more or the thimble would fall through. Note the exterior part is square but the interior is round. Any bigger hole and you can't mount it. There's a good 2.5 to 3 inch clearance inside the thimble box the way it's designed.

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2" clearance on a 10" pipe requires a 12" circle or square.

 

[Highbeam]

2" clearance on a 10" pipe requires a 12" circle or square.

Don't you need that 2" clearance on both sides of the pipe. So 10+2+2=14.

 

[begreen]

Don't you need that 2" clearance on both sides of the pipe. So 10+2+2=14.

Correct. For example, triple-wall DuraPlus is 10" OD and needs a 14" hole. Double-wall insulated chimney is 8" OD and needs a 12" hole.

This does not apply to the OP's installation which is with a liner in a masonry chimney and requires an insulated thimble or 12" of brick in all directions around the thimble.

 

[webby3650]

Don't you need that 2" clearance on both sides of the pipe. So 10+2+2=14.

I meant to say 8" OD pipe.