Additionally before placing the drum back on, I put 2x4s over the riser and measured the gap between the two drum sections. I got 1.25 inches. Since the 2x4s are 1.5x3.5 that would give me 2.25 inches of space between the riser and the top of the drum.
This time during the burn I had to close off 50% of the feed tube to get any draft and when the drum hit 400 degrees it flamed out and I got smoke blow back and fire out the feed tube.
I sealed off the feed tube with bricks and let it die out.
About this time, it occurred to me that maybe my mass duct really didn't have enough rise, so I tore that apart and reinstalled it with a 3 inch rise in each 10 foot section with a 1 inch rise between the end elbows for a total of 7 inches of rise before it hits the chimney. And I had the same issue as before: at 350-400 smoke blow back made its appearance.
In the meantime I met a young gentleman at one of the local fireplace shops who had attended one of Paul's RMH Seminars, and explained to him the problems I was having and showed him my photos. He offered his opinion that the CSA of the exit duct going to the Mass was probably not enough. So, back to the books and sure enough there is a 3 inch CSA requirement there I had totally overlooked (much to my chagrin).
I tore out the back of the support bricks and again cut them to the size I needed and also considered since the surfaces of the ceramic board, the tiles and the firebricks that support the riser were not perfectly smooth, I would put a thin (1/2 inch) layer of cob between the riser and the core to make sure everything was sealed up tight.
This having been about the fourth time I had torn things apart, another thing became apparent. While the silicone is wonderfully easy to apply and does seal things up, its a real pain in the rear to get off and clean up. So, this time since I was cobbing things up, I decided to use cob for the resealing of the drum.
see 15-sealed by cob
16-exit duct csa
With the new duct gap in place and everything rebuilt, the final burn was more dismal than any of the others such that even a small fire to start came back through the feed tube.
So this is where I currently sit. There has to be a choke point somewhere, and having just read the post on how to make your RMH rockier, the only other think I can think of is to lower the riser, or move the whole thing back the the three inches I moved it forward.
While I'm not freezing, as the propane back up is in place, my pocket book is hemorrhaging to keep the propane flowing. So the sooner I can fix this the sooner my pocketbook will love me again lol.
Thanks in advance for your posts and constructive comments.
the chimney which consists of 3, 4 foot runs , 1, 90 degree elbow and 2, 45 degree elbows to get outside.
Satamax Antone wrote:We have heard here, of several semi failures, where people burned, with bare pipes. And the heat extraction was too much, so the stove stalled. I think you are in the same kind of case.
Gerry Parent wrote:
Re-looking at your photos, hooking up your pipe directly to the manifold barrel IMHO is not a very good way to go. I would almost guarantee that this is the bottleneck area that is killing your draw.
Gerry, Jim has a fair bit of space. And i don't think this is much of a problem.
Matthew Goheen wrote:It may be working fine, but let me mention that that “aluminum insulation” is basically plastic bubble wrap with an aluminzed layer or two of plastic in there.
About as fire resistant as plastic shopping bags. If either of you ever has someone run your rocket continuously to where the mass gets really hot, that stuff will melt onto the pipe in the 300F-350F range, and begin to really smoke and combust in the 400-500F range.
Easier to install, but makes me think of burning plastic army men as a kid, watching flaming drops of plastic fall off and make a flitting sound as the tiny drop of “kiddie napalm” fell from the army man to the ground.
There may not be enough mass of plastic for a real fire there, but certainly a toxic, stinky mess of plastic combustion products.
I would be inclined to keep a close eye on that any time the stove is running, especially while you are troubleshooting and not operating in a static and “fully dried out” state.