6" round to 6" oval - Implications

[Mike Wilson]

If we use a 6" round flex liner, and ovalize it for a foot or so where it passes through the damper, how badly will that impact draft? This is a project at a neighbor's house, he has an insert with a 6" round direct connect to the tile in the chimney right now, and we are replacing it with flex to the top. Will this 1-2' run of oval 6" ruin his draft, or will it be ok? Chimney height is 18' total.

-- MW

 

[webbie]

If we use a 6" round flex liner, and ovalize it for a foot or so where it passes through the damper, how badly will that impact draft? This is a project at a neighbor's house, he has an insert with a 6" round direct connect to the tile in the chimney right now, and we are replacing it with flex to the top. Will this 1-2' run of oval 6" ruin his draft, or will it be ok? Chimney height is 18' total.

-- MW

In my experience it does not ruin draft. Consider than many stoves have been built throughout the years with oval collar, including many Vermont Castings models.

The key is "oval" and not "squashed" - if it gets below about 4.5" then I think draft might start to become affected.

His chimney is not all that tall - and, of course, the taller the chimney the better the draft. In a shameless plug, let me suggest that he could purchase the external castings and cap for our CC88 Extendaflue (and run his liner up through it) and therefore add three feet of additional double wall liner to the top of his installation.

See: http://www.extendaflue.com/cast.html

On second thought, he should use the bigger one (CC1212) cause it fits better over the larger tile that he probably has!

 

[Mike Wilson]

In my experience it does not ruin draft. Consider than many stoves have been built throughout the years with oval collar, including many Vermont Castings models.

The key is "oval" and not "squashed" - if it gets below about 4.5" then I think draft might start to become affected.

Well, if I measured it correctly he'll be down to 4 to 4.5 inches just at the damper. Looks like a standard damper to me. The other option we are discussing is to use 8" oval all the way up. 6 inch oval has too small a cross section (we did this in the old forum), but 8 inch has about the same as 6 inch round does. But, the stove calls for 6 inch round, etc etc etc. Tile is 13 inch OD. Doing the project next weekend, and I am advising him on how to go, seeing as he's not the internet type. I don't want to screw the guy up.

-- MW

 

[Mike Wilson]

Well, the decision was made. He ordered a 20' flex kit, with the top and bottom plates, etc. I hope this works!

The plan is to ovalize the bottom 2' of the flex, and then lower it down the chimney to the insert. Once its through the damper we'll "re-round" the oval part on the bottom, and connect it. Once we connect it to the insert, we'll install the plates, etc. Hopefully it will help with his wind problem, and make it easier to clean.

-- MW

 

[Mo Heat]

What size flex? Ovalized?

On another topic I'll slide in here. IIRC you originally installed your Kennebec with only a short connection pipe/flex/etc to your existing clay liner. Is that correct? Yet, in a subsequent post you mentioned you had a full liner to the top of the chimney. If I've got this all correct, did you experience problems with your original setup and have to add a full liner? Wind maybe?

 

[saichele]

If you were really concerned, you could actually buy a length of the oval with the same cross section as 6"round. I think it's about 4x10, less the corners. This ups your cost, because you need that (40/ft), plus the oval to round and round to oval bits. Lower everything except the last oval to round from the top, and attach the last adaptor when it pops out of the damper.

That said, I suspect you're probably OK even with ovalizing a bit.

Steve

 

[Mike Wilson]

Mo,

Absolutely correct. The installers originally put 5' of flex into the tile and "sealed" it off. I then re-sealed it after I determined my draft wasn't so hot. They never siliconed the direct connect plates. That was late December or so. Worked absolutely fine for Jan and Feb, I loved it. In June I had a sweep come by and clean the chimney, and fix a cracked cap on top. He had to pull the insert and re-insert the insert ;-) to do the job. Pain in the neck for him, and not cheap for me. Then I learned that if I had flex to the top, all I would have to do is pop the secondary burn plate off the top of the Kennebec, and you can clean the whole flue from there, without pulling the insert out. So, I had him drop a liner in before he re-inserted the insert. He used some flex that came with the bottom few feet oval right out of the box, convenient. For me, it was more a matter of cleaning ease, and my dealer never told me how easy it would be to clean... never even mentioned popping the secondary plate off. That said, I think the insert does burn more consistently in winds now with the flex. I had to pay the guy to do this though, not completely cheap.
What I am up to now is with a neighbor's Quadrafire insert. He has plenty of working room on top of the insert in the firebox, and wants to do the job himself. He has a small inseret, the 2700, in a pretty large fireplace. And his flue is clean, which is good.

Okay all, I am off for the Turkey Day weekend, don't know if I'll be able to check in remotely, so enjoy the bird, and burn well!

-- MW

 

[iamquaker]

ok i know this is a really really old post that i am pulling back up. but i was bored and started reading old posts.

how easy is it to clean this "oval" section of pipe?