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.
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.
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
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.
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.
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
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?
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
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 !
Many thanks !
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?
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
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 !
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 ?
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.
permaculture is a more symbiotic relationship with nature so I can be even lazier. Read tiny ad:
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