New build questions

[matt walker]

You are still going to need the chimney at the end, so I'd do that first, but for sure you should get in there and redo that area as well. You want it BIG, like bigger than CSA by as much as you can. 6" ducting squished or not is usually not enough space there.

[abarlow]

Oh man. That sucks. But isn't there 6 inch ducting leaving that area? You are saying that the CSA of the beginning of the exhaust needs to be bigger than the CSA of the exhaust in general? Keep in mind this is a 6 inch system...

[matt walker]

The pinch happens due to all the other constriction going on right there. It's possible you have enough space for the gasses to make the turn and not be pinched, but if there isn't the same distance between the opening and whatever part of the core/riser assembly is behind that opening then it's pinched in that axis too, if that makes sense. So, it's not the CSA of the "port" but rather the whole volume of space that makes an invisible 90° turn there. Man, this seems clear as mud. I can picture it though!

[abarlow]

Interesting. Well i do have quite a bit of space on that side of the heat riser... I wonder how i could tell if it's sufficient or not before digging into it. i wish there were ways to test individual components.

[mannytheseacow]

Can you get at it from the clean out there to chunk it out? There's the beauty of cob. Nothing a screwdriver in a tight space can't fix!

[abarlow]

No, it's all pipe. I wanted to do it in cob, but my father-in-law thought that it would be quicker and easier to do in pipe. So there are two 6-inch Ts connected to another like this:



The top of the first t (the one under the big barrel) is squished a bit to fit. But there are quite a few inches on that side. Like 8 inches i think.

You can see the opening before the top went on in this large version of this photo the barrel went just to the left edge of the hole:


That photo should show you the area. Would love to leave it... oh how i would love to leave it

[mannytheseacow]

hmmm. Well, you know you have to do the chimney, and you know you gotta rough in the bench. I might be inclined to do that and then come back to the barrel exhaust plenum possibility once you've determined it's an issue. It's not as big a chore as you might expect to take the barrel off and bust that opening up a bit.

I was thinking about your clay issue- I'm sure whatever dirt you've got on your property will work. If you're absolutely sure there is zero clay in it then you could always buy a bag or two of bentonite and crush it up in there with your dirt.

[matt walker]

Yeah, I agree with Manny. That hole does look small, but the way you made the connection negates what I said above, so it just may be that it's fine. Don't be scared though, it's really a simple task to break out the barrel, and for sure don't cob around that area until you are sure you are satisfied with performance. If I were you though, I'd save yourself the headache of wondering if it's having an effect and just get in there and open that up as much as possible.

[abarlow]

So guys, if I am going to break in there and make some changes, what exactly am I trying to achieve? How do you guy's make that transition?

Also, do I just break the cob away from there and set it aside, then wet it again and reuse it?

[matt walker]

You should be able to reuse the material, I usually do. As for the how, well, your transition is different than mine, but I like what you have done there. I would just shape that opening to be a funnel type shape, with the smallest part being the flue pipe that it joins. Just make it all as big as possible and you'll be fine.