Ernie Wisner wrote:I try to make sure the burn tunnel is as short as possible. if i could get it on all the systems the burn tunnel would not be more than a third of the heat riser height. if you have no problem with a barrel column in the house. by all means make the heat riser a but taller I think ours at the moment is 44 inches. burns like a champ. the other thing i would suggest is that instead of pipe you use brick for the heat riser. steel pipe will burn out and while thats not a bad thing if you have your perlite and clay mix right it is annoying to clean out flakes of burned steel. Sides i found out you can get 1/2 fire bricks and they work a treat.
Ernie Wisner wrote:nope wont melt the barrel. the book was written several years ago its about 17 years on the barrel now and still no problem. taller means more pull however; it also means your flame path will not in most cases reach the top of the heat riser. the perfect combo is for the flame path to be two thirds to three quarters the heat riser height.
Roger Merry wrote:What do you want the heat for ? The barrel will have to be way too high to boil a kettle !!
Len Ovens wrote:What you are looking for is constant CSA (cross sectional area) through the system. Generally the squarer the better. If one part will be smaller than others, it should be the riser, but not by much. So size the riser first. 6inch seems to be the minimum size that works well. That is 6inch diameter for a round riser at 28sqin CSA. I do not know if 5.3 inchs square would be fine in a square configuration or if it should still be 6*6. Generally all of us have built a massless setup to test what we have outside before installing it inside. So figure out the CSA of your riser first then go through all of your runs and calculate them to make sure they are the same or slightly larger. Then look at each transition from one run to the next and make sure they are ok. From what I have seen, most people who have problems have had a bad transition (barrel to mass pipe mostly because it has to be hand formed of cob and is therefore hard to judge the CSA. In that case oversize is better. My core is steel and so was easier to make sure of.