Coalpail.com Forum

I am haveing a new 8 inch flue masoney chimmney put up this months, the stove calls for a 8 inch flue, but the inside diameater of the clay flue pipe is closer to six but it is called a 8 inch flue pipe does that sound right? The thimble going into the wall is a 8 in inside diameter.

I know kwystorker had said that you could order a 6 inch outlet on there stove if you need it.

I just put in a masonry flue thimble. I told the guy at the supply house I need to install an 8" flue. The ID is 8" the OD is 9 1/2". Is it to late to exchange your flue? I can't answer about the keystoker, I don't know anything about them.

http://superiorclay.com/flue-liners.php
Shows nominal inside diameter and effective flue area.
Make sure you have the correct size flue.
8x8 flue has 42 sq inches.
8 inch round has 50 sq inches.
-16 percent difference.
8.5x8.5 flue has 49 sq inches.
-2 percent difference.
8x12 flue has 67 sq inches.
+34 percent difference.
Your flue must meet the manufactures minimum size requirements.

8x8 flue tile is only suitable for a 6" flue coller on the appliance.... Many,many people make this same mistake,and if the flue is tall enough and the conditions are right the appliance will perform ok.

JOE.G, is your chimney flue square or round? How tall is it?
Square tiles are measured on the outside of the tile, round ones on the inside diameter

I would shrink that thimble to 6" and order your unit with a 6" collar.

My buddy got new Harman sf-260 I told him a 8x8 tile chimney is the way to go. the Harman has a 7" pipe. I thought 8x12 would be over sized. Whats the best size masonry chimney. It will be an inside chimney about 25' tall.

Square and about 30 feet high.

Being a chimney sweep let me say this square liners tend to crack in the corners if at all possible go with round for the long haul

Is your recommendation based on chimneys that have wood stoves attached to them? These flues can get much hotter than a coal chimney. I've never seen a clay lined Anthracite coal coal chimney crack at the corners. Cracks at the top yes, but there it was likely the freezing thawing action of rain and snow.

JOE.G wrote:Square and about 30 feet high.

Your fine, go with the 6" for the collar, stovepipe and thimble. You should be able to cement a 6" thimble in the 8" that is in there. Nothing should go beyond the chimney's interior wall into the flue.

Can I keep the 8 inch off the stove and into the 8 inch thimble?

I would check with Keystoker, it seems big with your flue but it may work as you have a fairly tall chimney.

I'm doing the same thing now Joe, I had the block and flue deliverd and noticed the clay flue was only 6 1/2" ID,8x8 is the OD.The pipe off the boiler is 8" into an 8" thimble. I called Keystoker and they said it will work, but you may have a problem durring warmer weather. I asked about using a 8x12 and he said that would be better, more draft area, and just adjust the baro. damper. I'm going with the 8 1/2x8 1/2 or the 8x12.

Dave

A tall 6.5" id chimney will draw better in warm weather than a short 8x8" or 8x12"... the draw is determined by not only the difference in the air temperatures of the exhaust air to the outside air, but also the velocity of the air rising.. a big chimney willhave a lot less velocity..

Personally I would stay with 6.5" or the 8x8" don't think about going larger.. it will be counter productive... there is not that much air going up the stoker's chimney... look at the size of the combustion fan air inlet... about 3" diameter...

Greg L

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Thanks for the info.Greg, I'll stick with the 8x8.

Dave