The usual recommendation is a 1:2:4 proportional relationship, and if the riser is not at least 3 times the feed tube height, you may experience poor performance. (There are varying ideas on where to measure the lengths, which would result in different finished dimensions.)
A properly functioning RMH will be extracting enough heat from the flue gases that the chimney will not add much draft. The heat riser/barrel system drives the draft, and pushes the rest of the system.
thank you for your input.
Satamax Antone wrote:Well, if the system behind is well made, it should be the same, pretty much.
Glen, this is just a 4.5" toy i tossed together in the yard to play with. the feed and burn tunnel are brick pavers then the riser was cob perilite. the bricks, at tunnel, are covered with the insulated cob mix too. im not to the point of building an entire system yet. accept for that occasional poof it roars very good.
Glenn Herbert wrote:A properly functioning RMH will be extracting enough heat from the flue gases that the chimney will not add much draft. The heat riser/barrel system drives the draft, and pushes the rest of the system.
To me, that's an overly optimistic statement. Ho many people are there around, who have a system of proper lengh and design with no chimney? Who never experience smokeback.
Anyway, a good chimney is always a plus.
i thought that flue power was enhanced by it being next to the barrel? giving it a boost upward. i would think this could only help in drafting.
They weren't very bright, but they were very, very big. Ad contrast:
five days of natural building (wofati and cob) and rocket cooktop oct 8-12, 2018https://permies.com/t/92034/permaculture-projects/days-natural-building-wofati-cob