Heat riser questions

Rocket Mass Heaters, Rocket Ovens, Cold boxes, Solar collectors, etc..
Talk about your projects

Moderator: matt walker

Heat riser questions

Postby rjdudley » Fri Jul 05, 2013 3:41 pm

So I'm now moving on to creating the heat riser and I have some questions for the experts:
1) Can I use 8" galv. pipe inside a 10" galv. pipe (this would replace the 17 gal. barrel in Matts video) with two inches of insulation?
2) Matt, your heat riser video has you using fireclay and perlite. I still have some HeatStop 50 refractory left over. Would this work with the perlite replacing the fireclay?
3) Matt, again in your video you said the pipe was 31" long. Was this because the 55 gal drum is approx 34" tall?
4) Is it ok to build this heat riser outside and then move it into the house later or does it need to be build right on the burn chamber after the burn chamber has been installed? I guess I'm asking if it will be portable/stable enough to move around. I'd like to set up the burn chamber outdoors, fire it up several times. That would entail remove the heat riser day to day. Too fragile you think?
4) Will the 8" galv. pipe burn away? In other words do I have to worry about replacing it periodically? I thought I read on here somewhere that it should last for years, but, can't recall where I read that. And I don't recall reading about the pipes lifetime in Ianto's book.
Thanks everyone, I'm loving this Permsteading site. The amount of info/feedback/back and forth is priceless.
Ray
rjdudley
 
Posts: 84
Joined: Fri Jun 14, 2013 7:10 pm
Location: New Hampshire

Re: Heat riser questions

Postby matt walker » Fri Jul 05, 2013 5:48 pm

So glad you are liking our little spot here Ray, we're glad to have you here. We move pretty slow compared to the bigger boards, but I created this space so we can all share in a friendly environment free of some of the baggage of larger sites and I can't tell you how pleased I am with how we are evolving. We do have a great crew here!

On to your questions....
1) I don't believe that a 10" outer will give you sufficient wall thickness here. This is a crucial area as far as insulation goes, the more the better. If you are having a hard time sourcing the small barrel you could take the 10" flue pipe and open it up and screw sections together to create a larger diameter outer shell. It will be awkward filling it though since it won't want to be round.

2) Oh man, that's a tough one. My gut says it will work fine, probably even better than the fireclay, but I haven't tried it. The fireclay has the benefit of being basically immune to really high temps, even if you get it hot enough to start to vitrify you are basically just firing the riser. I couldn't say that the heatstop will react the same way, it might though. Whatever you use, make sure you really get the mix as light as possible, as much perlite as it will hold and still stick together. That's the key to having a high insulation value which again is crucial in the riser.

3) Yep, the 31" should give you the right height inside a regular drum, and you set the drum in a cob seal so if anything the top gap will grow on install which is fine. The key here is that you want as much riser as you can fit in the build, and 31" is probably the minimum you would want to go to ensure a strong draft in the feed.

4) I set up mine outdoors and fired it off, then carried it in in the two sections, core and riser. That said, if you can avoid doing that you guarantee success. Once these things are drying out they get very fragile, although your materials will alleviate that some. Don't forget what I said about cracks though, you will have them, so you will want to be very careful moving a fired core. Using the little drum as the riser outer also adds a ton of support while you carry in the riser, without that, I'm not sure I'd want to try to lift it.

5) If your stove works as well as I expect that inner pipe will be gone in a matter of a few firings, amazingly enough. That's why the mix in the riser is important, it's got to fire hard enough to stay in place once the inner liner is gone. My home system is made of just fireclay and perlite, and I'm sure if I took off my barrel and tapped on the riser it would collapse, but it's well protected in there and without any major shocks I imagine it will last a lifetime. I've played with enough of these outdoors to see them in all states, and it's pretty amazing how stable they are once fired. So yeah, your pipe will burn out and you'll pull out the pieces when you clean the burn tunnel. It's a little unsettling but it's totally normal and expected.
User avatar
matt walker
Site Admin
 
Posts: 1806
Joined: Tue Jan 03, 2012 5:50 pm
Location: North Olympic Peninsula

Re: Heat riser questions

Postby rjdudley » Sat Jul 06, 2013 1:01 am

Thanks for taking the time to answer those questions Matt. Of course they just lead to more:
1) If I can't source the 17 gal. barrel, but, I CAN get a 14" galv. duct do you believe that would work? It would give me the 3" of insulation all the way around.
2) As far as moving it indoors, wouldn't I have to fire it up outside to make sure it's functional? Or are you saying to just assume it'll be fine and build it indoors? I would hate to have it fall apart on me outdoors and then have to start from scratch.

Ray
rjdudley
 
Posts: 84
Joined: Fri Jun 14, 2013 7:10 pm
Location: New Hampshire

Re: Heat riser questions

Postby matt walker » Sat Jul 06, 2013 4:10 pm

Yep, a 14" pipe would work great. As for firing it first outdoors, it is a good idea, but I'm confident your core will burn beautifully. It also doesn't need the long dry out that my clay mix needs. I dunno, it's hard to say without seeing where you are installing it, but I might be inclined to just build it in place, myself. That said, it's pretty fun to light these things off outside with a temporary chimney in place on top of the riser and watch 'em rip! I suspect it will be just fine which ever you decide.
User avatar
matt walker
Site Admin
 
Posts: 1806
Joined: Tue Jan 03, 2012 5:50 pm
Location: North Olympic Peninsula


Return to Heating and Cooling

Who is online

Users browsing this forum: Google [Bot] and 16 guests

cron