A RMH fail

I really believed in the rocket mass heater. I really believed in it!! I read and researched all about it.  I had it fabricated in Ohio and sent here. The concept is genius.  And I worked so fucking hard on the hearth and the chimney and making it all come together.  

The rocket mass heater worked ok when the fire was lit, although it didn’t seem to be having the “rocket” draw or rocket noise from “the suck” at all, but the smoke was going up the chimney.  But then the fire went out and the smoke reversed and began to POUR into the house.  There was smoke everywhere and I couldn’t see, it was burning my eyes.  

I called Hopper, he lives close and is a fireman.  He came right over.  He said it would be good to have the whole fire department come because they could remove the smoke, and they did! But I was resistant to the idea at first because I was picturing toxic foam sprayed on everything, and not being allowed to go back into the house.  

But they came and they didn’t use anything toxic, and they got rid of the smoke, and they put out the smoking remains.  And they went up on the roof and checked out my chimney with a infrared heat camera and said all looked good! I am so very thankful…to Hopper and the entire crew…there were SO MANY!!!

I am heartbroken and disillusioned about the rocket mass heater.  And also it wasn’t cheap and now I’ll need to buy a “regular” wood stove.  I guess I’m just really sad, not just for wasting money on it, but because I really wanted it to work.  But I’ve lived with a normal wood stove for the last 30 years, so it’ll be fine.

I’m thankful that everything is ok.  I smell like a fucking pit barbecue.

I am a single mom with a full time job and two little kids.  I listen to a lot of the podcasts, so I know that often times, people go to a jamboree and tweak and fine tune RMH’s for days. That is not the kind of time that single working moms have.  It also could be user error, but I don’t have anyone here to ask that even knows WTF a RMH is…the firemen were mystified…never seen one. I will upload all video and pics that I have if you guys want to look.

I am just sitting here crying because it cost me a lot of time and money. And I REALLY wanted it to work.

Nevermind, it won’t let me upload any video.

Sorry to hear of the negative experience, Brooke. From what I see in the photos, you've got the rocket part but no mass. This should make it easier to troubleshoot. How much wood was in the feed tube when it started running backwards? How dry was the wood? How hot was the top of the barrel? The sides? Are all of your dimensions within the recommended ranges for the system (burn tunnel -> heat riser -> manifold -> flue all equal in cross section)?

I'm especially curious about that transition where the flue exits the barrel...is that a reducing elbow? That would be the first thing I change, as it appears to be a restriction at a critical point in the whole shebang. Try swapping that out for an oblong fitting that starts out bigger and narrows down to meet the pipe.

Don't lose hope...there might be one simple thing that needs to change and make this thing work smoothly. I've had some wicked smokeback events and learned from them, mostly lessons about needing dry fuel, stack height and outdoor chimney insulation.

Wow that is an interesting design, it looks well built but not a standard design, I really like the look of it!
The most obvious thing to do would be to contact the builder, the chimney outlet looks like a weak  link but the photos are not that bright or clear to comment much further …..
However I am sure all is not lost and a resolve is possible …..

Hi Brooke;
Bummer your new stove smoked your house out.

Who built that stove?   Are they an accomplished rocket builder?  Or was this their first rocket build?
It is a very nice looking unit, however...
A metal case rocket stove  using heavy bricks inside  seems like not such a good idea.
Heat would build in the metal skin and create a draft up the feed tube rather than up the chimney.
Ceramic fiber board like they used on the riser would be better.
The outlet to the chimney defiantly looks to small.
With no mass that stove should have worked fine... I can only suggest that a flaw was made during construction.

After your experience I doubt we can talk you thru fixing your rocket.
That would be too bad as RMH'S really do work just as stated, they just need to be properly built .

If it makes you feel any better my dislike for rocket mass stoves is the same as any fire that needs to be tended. I live in a very cold mountainous area where the heaters are going 24 hours a day for months, maybe a few breaks here and there. In general I find the less that people need to run their heaters the more likely they are to enjoy wood burning.

Hi guys and thank you all for your responses.  I’m going to try to answer everything. The wood was super dry, so dry for so many years that it was almost feather light.  I think this was the guy who built it’s first time with this design. It is lovely craftsmanship, but maybe there is a design flaw as suggested. He has built them before but as pellet stoves so the design was very different. The hole out the side of the 55 gallon drum is 5”, and I needed to connect it to 6” pipe, so the connector that comes out goes from 5” to 6”, so it’s going from smaller to bigger.  I wish you guys could see the videos but I can’t post them on here but they are on my Facebook if you have it, mine is Brooke Dryden, you can find me if you want to see the smoke video it’s crazy 😂.

The top of the barrel was hot, and the sides weren’t hot.

There were about two sticks of wood in the wood area. Very small pieces, split.

Here are some screen shots off the video, before and after the reversal.

And if anyone wants to come get it, I paid a good bit of money for it and it is very well made, and I don’t want it to go to waste… you are welcome to come get it.  But it weighs 350 lbs.  I had it made by a guy in Ohio and I’m in Colorado, so it’s not getting sent back. So if you know what you’re doing and you’re willing to work with it’s design and fix it, you are welcome to it.  I am sad and I don’t want it to go to waste.

Ok i found you video, it looks like you have placed the wood in through the front door and laid it flat down on the bricks?
The flame are simple going up because you have lit  a fire underneath the loading port?
Did the stove come with instructions because it looks to me like you have  lit it the wrong way around ?
In my mind the fire should be loaded with long sticks of wood though the top loading port and the front viewing door should be closed?

For a fan forced draft in a pellet stove, 5” would work just fine. For a passive draft RMH, no way. This manifold area needs to be quite large as it is the transition area where the exhaust gasses are switching directions. Too much friction in this area will definitely slow or even stall the stove.
A 10” (or 8” min) diameter pipe outlet reduced down to your 6” would work much better.

I am sorry, Brooke that this happened with your first stove.  Have you contacted the stove builder to see if they have any advice?

My question for experienced stove people, can this stove be reworked so it is useable? Maybe it is something simple that a local welder or blacksmith could do?

It would be such as share that this stove is not useable.

Brooke, all will not be lost, although at the moment I guess anger and frustration will be overpowering.
When you have settled down, the comments by others may lead you to a better place.
I found this film that talks about the starting procedure which surprised myself, since I plan to get one soon.
RMH use of
He explains why there is a specific starting procedure to ensure the 'chimney' is warmer than the firebox at the start. It ensures draft up the chimney occurs.I noticed others think this may be your problem.
But starting with the obvious, have you spoken to the builder and asked for help, I manufacture machinery for homesteaders and I would want to know if something was not working.

In fact when I started in 1972, I offered a lifetime guarantee on a compressed earth block machine I developed and I learnt a lot in the first few months.
Since then I have not had a single issue with them

I am confident if you explain your issues and frustration he will help.
So think again before giving it away.
regards

Thank you so much everyone. I definitely did not load it from the front, I loaded the sticks from the top of the J box, but there was very little “suck” at the flames and so the flames were burning straight up towards my living room ceiling like an indoor campfire, sparks and all.  So I shoved the sticks down flat at that point and into the bottom of the J.

It seems the starting method involves;
- putting some crunched up newspaper into the fire box
- lighting it
- push that paper back inside the firebox a bit closer to the chimney
- waiting a minute or so until you see the fire heading up the chimney
- adding very small kindling [ 1/2 handfull ]
- as draft draws the flames up the chimney add bigger material.

What is happening is that the paper starts to heat the flue so it starts to draw, as it draws the heavier material adds to that function
until its burning and drawing properly.

Good luck

Brooke,

I want to further elaborate on that starting procedure.  I think you almost had it, but missed the mark by just enough that it resulted in the unfortunate situation you experienced.

If you are game for trying again, Take some newspaper and crumple it up loosely into a ball of a size that will easily fit into the throat of your feed tube.  You'll light this and drop it into the tube.  Now what's critical here is that it then needs to be pushed back further into the throat of the burn tube so it is closer to the barrel.  This way the heat from the flames can begin to work their way up into the barrel and contribute to getting the heat flow going in the right direction.  I think what happened before is your fire never got far enough back into the throat, and the fire took the path of least resistance and climbed right back up out of the feed tube.  If I'm not mistaken, it looks like you have a front door opening to the feed area.
That would make a nice place to start the fire, and enable you to push it back further into the throat, just be certain to keep the top feed opening closed until you have a good draft going.  Be sure to use small kindling.  Work it up slowly and experiment to see how much wood you can load in it safely.  Keep a spray bottle of water handy if things start going south again.  

Key point.  You can't have both feed openings open at the same time.  

I think you have a lovely stove and it's too early to give up on it yet.

Good luck!

I found this by accident on this site
I am looking for plans for a small RMH

OOps!

Gerry Parent wrote:For a fan forced draft in a pellet stove, 5” would work just fine. For a passive draft RMH, no way. This manifold area needs to be quite large as it is the transition area where the exhaust gasses are switching directions. Too much friction in this area will definitely slow or even stall the stove.
A 10” (or 8” min) diameter pipe outlet reduced down to your 6” would work much better.

Gerry, i'm sorry to contradict you. But, in this case, there is plenty of space between heat riser and wall of the barrel. It is narrow, but should function.

What i see,

https://permies.com/t/171374/a/163438/9EA5294B-727C-4CCC-899F-8989D7B95A4D.jpeg


In  this pic, a short stubby chimney on the right, with smoke coming out.

That chimney is uninsulated and way too short.

Two more meters of insulated chimney would be better.

The OP said on her facebook thread that there is 4' of chimney above the nearly flat roof. It is not tall, but would be adequate in otherwise good conditions.
She also said that the wood (a few sticks) burned fine for ten minutes, then finished burning, went to coals, and started reversing and smoking back.

I think there was insufficient fuel to heat up the system, and when the flames making the draft went away, the heat from the coals took the easy way straight up out of the feed.

Glenn Herbert wrote:The OP said on her facebook thread that there is 4' of chimney above the nearly flat roof. It is not tall, but would be adequate in otherwise good conditions.
She also said that the wood (a few sticks) burned fine for ten minutes, then finished burning, went to coals, and started reversing and smoking back.

I think there was insufficient fuel to heat up the system, and when the flames making the draft went away, the heat from the coals took the easy way straight up out of the feed.

That's quite à possibility.  What other cause i could see, with such a short chimney. Opening a door, where hot air escapes by the door as well as the chimney. The csa of the door being bigger, it might reverse the draft, with that stubby tube out of the roof.

Lack of mass or insulation in the chimney might make the system more prone to reverting too. If it can't sustain it's own draft, because the chimney is cooling too rapidly.

Learning from the "failures” or what went wrong to me is just as important as if everything went right.
I sure hope the OP decides to stick with it so that we can all grow from her experience.

If it helps to clarify anything, the chimney is 4’ and is triple wall insulated. It just looks short because it’s at the back of the roof, and the other one for the furnace is at the front of the roof. Maybe this pic is better. My roof is flat.

That chimney looks totally fit for purpose to me. Concentrate on the points mentioned earlier in the thread...I'm confident we can sort this out if the burn tunnel is not a complete dog.

It looks like you have tried a "one and done" approach to the stove. While I fully appreciate the WHY of this, please note some of the very best builders have had problems fixed with the slightness of change. Yours may need but one of the changes recommended.  You mentioned you researched for a very long time and in depth, so I presume you have gone to the web site of  https://donkey32.proboards.com/   Trust me, there is over a years of reading just going over all the variations, AND YES PROBLEMS folks have had often fixed by little things.

For example, did you know if the outside temp and the inside temp of your house, are nearly the same,(Like a test run in the fall) A draft is really had to establish, and harder still if you don't have a good stove design. True of many wood stoves.    So many  little things.

There is a fellow on the above site, that has experimented more than almost everyone else put together in the world. He has found many things that DON'T work and the many things that DO.  But I am willing to bet, he would ask for dimensions, and many other details before any summation of answers. He is fantastic in rooting out the problem, and sometimes they are simple. Some as simple as having internal riser to close to the barrel top, (easy fix)  I could never through out a fix suggestion without knowing exactly  the dimension details. If you choose to go forward, those details may require some digging on your part.

The end result is probably worth it, but might take just a bit to get there.

After having another look at the setup, I have to wonder if the transition plenum from the bottom of the barrel to the stovepipe is too small.  It seems to me that the system should work well enough if not over-fueled but I have my doubts it is adequate for a full throated burn.  What do ya'll think?  I'm very hopeful we can come to a positive outcome here.

Brooke,  have you at least been curious about giving it another go?  But perhaps just burning balls of newsprint to see what happens.

I agree with an earlier observer. The 90° elbow at the exhaust point forms an effective 180° bend. The chimney simply isn't hot enough to counter the back-rush of cold air here as the process began.

..IN A SIMILAR CASE, I have a friend who observed that radiated heat via distributed hot water is far more efficient than tapping heat from air.  He's installed a 3/4" copper coiled pipe inside his barrel which effectively withdraws far too much heat OUT of the re-burning chamber. As a result, lots of creosote builds up in the chimney and started a fire, TWICE.

To wit, I am preoccupied with other physical heat-transfer principals that could contribute to building ideal small residential installations. I'm especially enamored with the notion of keeping the firebox outdoors, in partly conditioned 'greenhouse-like' spaces.  This space serves like a "BBQ pit"; a very pleasant casual dining room, safe for pets, spills, wood supplies and organic residue.