RMH smoke back-please help!!

Hello all, in my basement I am building a rocket Mass heater exactly to the specs of Ernie and Erica. The Brickplant and all the piping and are exact... everything is very proper. I Used firebricks in the Burntunnle and first portion of the heat riser and topped it off with 8 inch round terra-cotta fire pipe riser. Covered the whole thing with galvanized steel piping and filled with Pirma lite and fireclay slip. Put the barrel on top and somewhere in our packing and setting up of the perrmalite around the riser and everything the exhaust pipe pushed out about an inch to an inch and a half. So it's no longer perfectly under the barrel. We toyed with the idea of cutting out some of the Pirma lite Clay and pushing it back into place but we were not sure if that would be a good idea. So instead we covered it with a brick and packed clay/ sand around it. Once we lit the rocket it was not rocketing at all.... In fact the flame was coming straight up at us and tons of Smoke back. we did place a small fan over the feed tube and it's got it to draft in the proper direction however as soon as we remove the fan it came right back to us. We never really got a good fire. And fact the best read we got on our barrel was 200°F. A lot of the Clay is still wet and cold not sure if that affects anything I did read that somewhere. Please advise. Our exhaust on the outside of the house is at 1 ft above ground level. There is only about 1 inch gap between the wall of the house and the cap--- as we pushed it in to avoid rain getting in. Is that my problem possibly ? I also noticed that my barrel is slightly off level. Front to back it's perfect- left to right it's about a half of an inch off. Guessing with the buildup of the Pirma light and such I got a little extra caked on the bottom some how.... Where do I begin Thanks so much for all your feed back.

Kevin, simple answer, put a chimney on that blady thing. It can't work without a height diferential between feed and exhaust.

Sorry,I forgot to edit my post. ( now edited) the RMH is located in the basement and the exhaust is about 5ft above the base of the heater. Do you still believe this to be the problem?

Yep.

Tho, pictures would be good, as i haven't understood well how you did your heat riser. As well, imho, your top gap is too small.

I'm not sure I understand your description of the riser insulating and exhaust pipe area problem. Pics possible? Are you using 8" pipe for exhaust? Length of horizontal pipe?
A couple basic points. Any spot from the top of the riser to horizontal exhaust pipe needs to be smooth gentle curves. Riser to edge of surrounding insulating pipe, and transition area/manifold at bottom of barrel where it exits to pipe.
Second, as Satamax said you likely need a higher chimney stack.

Kevin Shay : After Ianto Evans' discovered the Secret to the parts of the Rocket Mass Heater RMH, (the Rocket Stove Came 1st !) He set out to find a location for
his intentional community Cob Cottage cobcottage.com.

The location he found has a very stable micro-climte with steady prevailing winds year round His first buildings were all One Story and less than 15' tall shaped
like large mushrooms or watermelons on the ground, By placing his horizontally exhausting vents on the lee side of the structures he was very successful in not
needing Vertical chimneys (Generally)

Today people are trying to retro-fit RMHs into existing structures, even trying to place them in basements, and exiting out of the house without regard to prevailing
winds ! It is no wonder that you are having trouble !

As a minimum you should plan to install a Vertical chimney that is 4-5' taller than the peak of your roof ! The storm of the decade, may come out of a totally
different direction, and without a good Vertical chimney you may not be able to use Your RMH for several days, as part of your plans, you should also plan that
there will be no electricity for running fans !

You will also need to consider that you have not allowed enough space to guarantee your Constant Cross Sectional Area at some point, or that a Gob of Cob
slumped out of place after you put the barrel on and is causing a restriction ! Your barrel will have to come off to Check ! For the Craft ! Big AL

Hi guys here are the pics.

Some more pic

I'm not an expert on rocket stoves in general, my own 6 inch drafted well first time so i need a few failures on that end to understand it better maybe,, but it looks like having a secondary cleanout in the vertical exhaust just before it goes outside, and using it to drop lighted paper in first would help get your draft going the right direction,,

and my instinct goes with yours that if you have a lot of wet cold cob around those pipes now there's a whole lot of resistance to getting anything at all outside

I've read posts about running 8 inch systems 50 feet or so in straight lines, i thought i remembered the specs at around 30 feet for an 8 inch system but from your pics if each elbow is worth 5 feet, seems like you've used up every bit and then some of what the stove should be able to push

that's all i can think of, everybody else covered the other possible probs.

Way too many elbows, that's right.

No insulation on the feed tube, and burn tunel. As far as i can see. Lots of mass in there.


You could try to insulate the last vertical bit going out the wall too. This might help. But it's more like 5 yards of insulated chimney outside or more to go above the apex could help a bit with the draw.

Actually there is some insulation and mass around the heat riser and burn tunnel. For some reason that photo did not come up- i'll repost it. I just wanted to show you some of the raw photos so that you have an idea of how it actually looks inside .

I didn't completely cover the feed tube and the burn tunnel because I was afraid if I needed to dismantle it I didn't want to have to undo everything.. I saw many other designs with just as many turns. Is that young to be a problem? the book said 20-40 feet and the only way for us to do it that way would be with turns.

The photo with the bed is our second cleanout. Wondering if we should light a paper fire in there as was suggested that for an upper clean out on the vertical pipe? And I'm actually going to take another photo of the burn tunnel feed tube area because I have more mass on it then in the photo I sent

every elbow creates extra friction over a straight run,, they estimate that friction as if it was 5 feet of linear space, so every 90 degree turn subtract 5 feet from the 40' total

and yes that does give less contact with the cob as the actual distance decreases and the number of turns increases


in a smaller space like that adjusting the riser height clearance with the top of the barrel can throw more radiant heat into the room, less down into the cob

and i have seen some of the multiple turns and wonder how anything ever makes it through the maze in those sort of systems, and god bless them when it works

like i alluded to earlier, your system pushes it to the limit, and the mass of cold air residing in the cob may just be making your system difficult to get going and once the clay is hard and warm it will be one of those systems that needs a push now and again to get it going but ultimately will work

it looked to me like you might be able to cut out that lower loop if it became necessary just by some simple rerouting at the first cleanout, sending it to the upper loop at that point,, maybe you could even have some sort of switch system that allows it to go straight into the lower loop or be turned for easier starting to go to the upper loop

just some idle thoughts,, hope it gives you some ideas

Well, now that it's all cobbed, before dismantling, you should try to make it work. So,


First of all, get rid of that outside cap, and put a real chimney there. Insulated tube. Otherwise, it will never work. Go above the apex of the roof.

Then prime your chimney with that last cleanout. People use newspaper, i use denatured alcohol or meths. It gives a longer burn.

Then when you have primed your chimney, close the cleanout cap, and check with incence, if you have draft at the feed tube. If you have draft, light the fire. If you haven't, prime again. If it never draws, use forced air with a fan at one end or the other. This will draw the air the right way, and let you dry that load of cob. Once all dry, it it still doesn't want to draw, dismantling time it gonna be.

Just to explain, you have the equivalent of 40ft, just in elbows. Why haven't you tried it without the mass before?

if it was me at this point with all the frustration i'd get a plumbers propane torch drill a 1/2-3/4 " hole in the vertical exhaust , slap a gob of cob around it to seal it and just let it burn for a while and see if i could get something moving just as it is

the incense idea at the burn tunnel is a good idea, i'll have to use that next time

if you could get it rockin and rollin without doing too many alterations, that might provide the drying and warming you need to determine what else you might want to add to your permanent installation

It looks like it is set up against the brick wall which is against the outside this will make it vary hard to get dried out much less up to temp. The cold ground will fight you and make it harder for things to dry. Try using a plummets tourch or a heat gun to push the hot air as you are lighting the fire and raise your chimney above the roof line this will create vertical draft. Stay away from fans as the system show be self correcting and a fan distorts that Good luck

Boy my spelling and grammar suck! One mor thing putting ant galvanized or tape is a bad idea and will smoke and off gas I notice your inner burn tower is covered in tape that will have to burn off first.

Kevin Shay : While you have multiple problems with your design (Too many elbows as one ), we will make you a successful Rocketeer if you hang in there
with us !

Right now you have two (2) problems, the least of which is draft ! Which is primarily due to insufficient Vertical Chimney ! Plus very wet Cob, which takes a LOT
of heat energy to dry it out!

Erect a decent Vertical Chimney, at least 4' above the peak of your roof, and temporarily insulate all other heated objects from the heat escaping from the Cob
Thermal Mass Until you have dried out that Mass and we are at a good start !

Unfortunately, you will also have to deal with the 'other problems' of basement installation of A Rocket Mass Heater RMH, It is your job to research and understand
" Stack Effect ' and '' whole house Stack effect ''!, This can make it impossible to 'Run' a Clothes drier, a Hooded fan over a Kitchen stove , a gas water
heater, or a Bathroom vent, AND use a RMH! (especially within a Basement location !

Please understand this is all part of the (sometimes painful ) education process you have set for yourself, If you are willing to work towards your original goal, we
will make this work !!! For the good of the Crafts ! BIG AL !

Nice disco ball

Wow man you're scaring me Big Al! So basically it sounds like I need to run 30 feet of vertical pipe outside my house… Now does it have to be the insulated stuff that cost a small fortune or can I do 7 inch and 8 inch and insulate it myself? Or does it even have to be insulated at all? I have a fireplace in the living room and hardwood floors throughout so the basement was really my only option to place the RMH and it seemed perfect because the previous owner had a stove sitting there and closed off the 8 inch terra-cotta exit… So to me it was providential... Sounds like not so much anymore. But I'm willing to put in the blood, sweat and tears as long as you guys can be patient with my zillion questions and problems

Many thanks !

Yes, you can insulate it yourself. Use perlite poured down into the space between your 2 different size stove pipes.

The way we did it was to build a square structure out of Unistrut and cover it with Hardie siding, but I'm not sure we saved a lot of money. The advantage is that we can move it around if we need to.

Kevin Shay wrote:Wow man you're scaring me Big Al! So basically it sounds like I need to run 30 feet of vertical pipe outside my house… Now does it have to be the insulated stuff that cost a small fortune or can I do 7 inch and 8 inch and insulate it myself? Or does it even have to be insulated at all? I have a fireplace in the living room and hardwood floors throughout so the basement was really my only option to place the RMH and it seemed perfect because the previous owner had a stove sitting there and closed off the 8 inch terra-cotta exit… So to me it was providential... Sounds like not so much anymore. But I'm willing to put in the blood, sweat and tears as long as you guys can be patient with my zillion questions and problems

Many thanks !

Yep, if you want draft, you need pipe 30feet. Tough. Two pipes one inside the other is good. Unlike Cindy, i wouldn't use perlite. But plain old rockwool, and have one inch each side. So 6 inside and 8 outside or 8 inside and 10 outside tube.

You should have asked about fitting it on your living floor. Basement rockets are crap. Rocket mass heaters nowadays are not all mass. There's the use of bells which has improved the weight, (a smidge) and you can always brace your old floor. The first prob with basement rockets is, are you ready to stay in the basement for three to four hours a day?

We spend a lot of time in our basement.

Jay Kepple : Welcome to the Discussion, one of the great benefits of Your carefully crafted Rocket Mass Heater RMH, is it's ability to Burn it's fuel at such very
freakily high Temperatures That The "Burn'' is nearly 100% efficient !

This Demands a generous unimpeded air supply. The combination of Time, Temperature, and Turbulence Allows the near perfect mixing and Combustion of
the wood gases. Creating the needed air flow for your RMH to work so efficiently is crafted into the over 100,000 RMHs already Built. While every RMH will be
different from its neighbor, the Ratios and Math for this process is petty much wrote in Stone.

Follow the Steps, and 'Bobs your Uncle'!, Designing out obstacles to efficient Rockets, and Skillful use of them requires pre-planing and attention to details.

There are a few good sources for written instruction, The best still appears to be the 3rd edition of Ianto Evans' " Rocket Mass Heaters ", Available as a
Download $18.oo PDF Copy from Rocketstoves.com ! Also a few good DVDs available here and at ernieanderica.info

For All the rest of your information you have your fellow members and these Forums and the privilege of unlimited '' Searches '' in our Permies Cloud of 100s
of Thousands of Forum Threads 24 / 7.

Mostly our job consists of discussing in these forums what will and won't work and what Might Work! A word of CAUTION > There is so much CRAP out there,
and Videos of 'Units of Flaming Death' Called RMHs, especially in U-Tube Land, that you should view every video of these Frankin-clones, indeed all videos
hypercritically !

Because of the promises of great Efficiencies, and Wood Savings, and the idea of longing around on a heated bed till noon everyday is so charming, it is easy
to convince your self to rush into building a Rocket Mass Heater, especially after you start gathering materials! As All Test Rockets should be erected out of
doors first, and tested there, you have time to learn from both the successes ,failures and near misses reported in these Forums !

For the Craft, Think like Fire! Flow like a Gas! Don't be the Marshmallow! Your comments,Questions are solicited and Welcome! PYRO - Logically BIG AL !

Hey gang! Good news... I installed one of the duct fans and had the RMH running for about an hour or two yesterday and for about 4 1/2 hours today.... The cob is starting too dry up a bit in spots .... Was steaming off loads! We are buried in snow - so once it clears and I can safely be on a ladder and my roof I plan to put a stack out there . But this seems to be working? The barrel had a temperature read of over 600°F and the exit pipe was reading at about 100°F. The mass was nice and warm but still very damp. I think I have at least 3 -5 more days of long fires before it's dried out.
As for being in the basemtnt - no problem for us as it is the only spot with a Tv and where we do most of our socializing .
I know the fan isn't optimal but how do you think it's doing with all thing considered ?

At what location are you using the duct fan? 600deg barrel temps (on top?) are at least decent enough to get the cob dried out. My 6" core system only gets to 7-800deg on top of the barrel (still room for improvement) and flows very well without a fan, although I did use one while tweaking the parameters of the system.
The good news is things will likely improve when the cob dries out, the bad news is if it doesn't you may have to bust up some cob and remove some of the duct in the bench. Or you might get it to flow with a high vertical chimney stack and eventually do away with the duct fan.

I have the fan right before the elbo that is heading out the building . The temp read was actually on the sides. . I'm hoping to do away with the fan.... Crossing fingers!