OK! please accept my apologies for the delay. A few RL challenges to deal with.
That aside, Kristy I appreciate your lurking and glad you have learned. I read SO MANY posts and "the book" before starting this project and knew I had to pass on any and all that I gain from this.
Colin; oh, have I got a trick or two up my sleeve for an update (coming soon). "Rocky" performed so well last season that he cut our previous fuel consumption of almost 2000 gallons of heating oil in a year down to just over 700gal!!! with only burning about 1 cord of wood. So a 65% cut in our "slaves to pollution" budget equates to about $4500 not wasted on making our masters richer! My wife also got well accustomed to feeding our hot headed pet and managed to keep him burning many a cold day while my frigid bones were out wage slaving. The most impressive part to me was how many tons of rock, clay and dirt in my basement stayed well above typical ground temps and acted as a huge thermal battery (many times up to 78deg) and kept the vast majority of heat in our house instead of the usual 45-50 deg basement we used to have. This heating of our basement has changed/added to the thermal dynamics of our house's chimney effect as the basement drafts are warmed greatly before rising into the living areas and also helping to keep the boiler from cooling down as much as it had previously between cycles.
Oh, and Wolaver's Organic Oatmeal Stout is the best brain fuel for all your RMH needs!
Type of Wood Heat Output Easy to Burn Easy to Split Heavy Smoke Sparks BTUs per Cord Rating
Ash Black Medium Yes Yes No No 19.1 Mil Excellent
Ash Green High Yes Yes No No 20.0 Excellent
Ash White High Yes Medium Np No 23.6 Excellent
Red Oak High Yes Yes No No 21.7 Excellent
White Oak High Yes Yes No No 26.5 Excellent
Live Oak High Yes Yes No No 25.0 Excellent
Beech High Yes Yes No No 21.8 Excellent
Beech Blue High Yes Yes No No 26.8 Excellent
Birch Black High Yes Yes No Medium 26.8 Excellent
Birch Grey High Yes Yes No Medium 20.3 Good
Birch Paper High Medium Medium Medium No 20.8 Fair
Birch White High Medium Medium Medium Medium 20.3 Good
Birch Yellow High Yes Yes No Medium 23.6 Excellant
Box Elder Medium Medium No Medium No 18.3 Fair
Buckeye Ohio Low Medium Medium No No 13.8 Fair
Butternut Low Medium Yes Medium No 14.5 Fair
Catalpa Low Medium No Medium No 15.5 Fair
Cedar Eastern Red Medium Medium Medium Medium Yes 17.1 Fair
Coffeetree Kentucky High Medium Medium No No 21.6 Good
Hickory Bitternut High Yes Yes No No 26.7 Excellent
Hickory Shagbark High Yes Medium No No 27.5 Excellent
Hard Maple High Yes Yes No No 29.7 Excellent
Pecan High Yes Yes No No Excellent
Dogwood High Yes Yes No No 24.3 Excellent
Soft Maple Medium Yes Yes No No 19.1 Good
Cherry Medium Yes Yes No No 18.5 Good
Black Cherry Medium Yes Yes No No 18.6 Good
Walnut Medium Yes Yes No No 20.3 Good
Elm American High Medium No Medium No 20.00 Fair
Elm Red High Medium Yes Medium No 21.6 Good
Elm Rock High Medium No Medium No 23.5 Good
Elm Siberian High Medium No Medium No 20.9 Fair
Hackberry High Yes Yes No No 21.2 Excellent
Sycamore Medium Medium No Medium No 18.5 Fair
Gum Black Medium Medium No Medium No 18.1 Fair
Gum Sweet Medium Medium Medium Medium Medium 18.7 Good
Mesquite High Medium No Medium No Good
Aspen Low Yes Yes Medium No 14.5 Fair
Basswood Low Yes Yes Medium No 12.6 Fair
Cottonwood Low Yes Yes Medium No 12.2 Fair
Chestnut Low Yes Yes Medium Yes Poor
Yellow Poplar Low Yes Yes Medium Yes 16.0 Poor
Southern Yellow Pine High Yes Yes Yes Yes Good
Douglas Fir High Yes Yes Yes Yes 21.4 Good
Cypress Medium Medium Yes Medium No Fair
Redwood Medium Medium Yes Medium No Fair
White Cedar Medium Yes Yes Medium Yes 17.5 Good
Western Red Cedar Medium Yes Yes Medium Yes 17.5 Good
Mulberry High Yes Yes Medium No 25.8 Excellent
Eastern Red Cedar Medium Yes Yes Medium Yes 17.5 Good
Juniper Medium Yes Yes Medium Yes Good
Piinon Medium Yes Yes Medium Yes Good
Eastern White Pine Low Medium Yes Medium No 15.8 Fair
Western White Pine Low Medium Yes Medium No 15.8 Fair
Sugar Pine Low Medium Yes Medium No 15.8 Fair
Ponderosa Pine Low Medium Yes Medium No 17.0 Fair
True Firs Low Medium Yes Medium No 19.5 Fair
Tamarack Medium Yes Yes Medium Yes 20.8 Fair
Larch Medium Yes Yes Medium Yes 20.8 Fair
Spruce Low Yes Yes Medium Yes 15.9 Poor
Alder Medium Fair Yes Medium Yes 17.6 Fair
Apple Medium No No Medium Few 17.6 Fair
Ironwood (Hornbeam) Very High Yes No No Few 24.7 Excellent
Black Locust Very High Yes No No No 26.5 Excellent
Honey Locust High Yes Medium No No 25.8 Excellent
Magnolia Medium Yes Yes No No 18.0 Fair
Madrone High No No No No 30.0 Excellent
Willow Low No Yes Fair Fair 14.5 Fair
Ratings are variable, moisture content effects results firewood should be well seasoned and dry for its optimum
BTU rating. Firewood is easier to split while it is still green.
Firewood with High or Very high heat output 1 cord = 21,000,000 - 24,000,000 BTU = 200-250 gal. of fuel oil or
250-300 cu. ft. of natural gas.
Firewood with Medium heat output 1 cord = 17,000,000 - 20,000,000 BTU = 150-200 gal. of fuel oil or 200-250 cu.
ft. of natural gas.
Firewood with Low heat output 1 cord = 12,000,000-17,000,000 BTU = 100-150 gal. of fuel oil or 200-250 cu. ft. of
Consider the cost of 1 cord of firewood vs the cost of fuel oil or the cu. ft. of natural gas. The cost of firewood is
usually more stable than the cost of fuel oils or gas and should prove to be a huge savings on your heating bill.Firewood Measurements1 cord measures 8 feet long, 4 feet high and 4 feet wide or 128 cubic feet
I think I'm going to go for some black locust on my next wood run
Wow Dave if you only knew how I could have used that knowledge 2-3 months ago. lol
I digress. These calculations should be of some good use in the future though. I must admit, I prefer the sound of maintaining CSA as opposed to having steady ED.
lol Lord, forgive me for that there, Im sorry.
Good stuff. I look forward to seeing who chooses to discuss this thoroughly instead of humorously.
Peter Berg wrote:Martin,
I've come to understand you've got a p-channel in the feed. You mention in the vid the plate is hanging 1/4" into the tunnel. Have you thought about the 1/4" gap behind the plate as well? Thus the cooling of the first brick will be very much efficient and there's always some preheated air injected at that very important spot. The stove should be running cleaner with it, but it doesn't enhance the draft much.
Yes Peter, thanks for noting that. I have placed it 1/4" away from the tunnel brick and it hangs 1/4" lower than the tunnel ceiling. I do believe it runs cleaner now as I actually opened the "dummy" pipe for a second and had no smoke or stink. I will be getting a laser temp gun soon to get hard numbers on the subject.
james beam wrote:Hey Martin, Congratulations for the 'smog free' conversion of your old chimney/stove. Just think of the valuable environmental impact you're contributing, ~no petro fuel, ~very little wasted heat pollution, ~recycling scrap wood material, ~very little visible smoke pollution, ~no annoying fumes at ground level (your neighbors garage is now happy), ~enduring stove work (once you iron out all the kinks), ~high safety value in practice.
Thanks JB. It is almost euphoric to think about deeply. Especially knowing this is just the beginning of much more.
james beam wrote:Would you consider stuffing some new 7" or 6" duct pipe down the chimney from the top? The reason I want a duct pipe flue liner is because the old chimney is possibly 100 YEAR OLD MORTAR, ~if it can leak, it will leak~ (you have said it is seal tested or safe, but that chimney is really old, structurally sound is great, but still might eventually leak wet creosote fumes or steam). I would want a chimney liner secured with screws at each joint & sealed with foil. A chimney liner doesn't have to be installed immediately, while testing, but moisture + old brickwork + freezing outside temps = chimney liner. I'm not sure you can deform a 7" duct pipe into an oval shape, to fit within your existing chimney, I would prefer 7" over the 6"...if possible. You might try asking your local 'heating & air conditioning business' if they have, or can make, an affordable rectangular metal lining that would fit your chimney. Since ya got a dead bird in your cleanout tray, you could make a course screen for your rain cap. ~~Just a thought.
Yes, when finances permit, I would like to line the chimney. Rest assured, it is much newer than the rest of the house and the mortar is strong and holding well. As for the screen cap, I will when I feel balzy enough to toss a rope over the roof and climb up there.
james beam wrote:Now that your temporarily plumbed into the chimney, do you eventually expect to bury your 30+ feet of duct pipe in mass, as you know the idea is to retain as much heat into the mass, and waste to the chimney what is left over. Do you eventually expect to move the stove into the other room, or perhaps you like the stove where it is under the 'new' part of the house, which I totally understand. I once had an old house with an addition, the addition was always the coldest part of that house. From your diagram, I would be very careful of the stone walls, they support the house, in many ways.
Yes, I do plan on replacing the flex duct with 8" pipe buried level to the chimney once I remove some stone wall(s). I have been studying the house supports for some time as I plan to replace/rebuild several in attempt to level floors and create more basement space. This will be when I can bury a direct pipe to the chimney, effectively making the floor a very large thermal battery through the center of my house.
james beam wrote:As for heating water, I'm thinking 'double J, double barrel'...hehehe, that is because YOU are doing all the work, so well! :)
Nice! but I think I'll start with a coil of 3/4" copper tubing wrapped around my heat riser in a loop to my boiler (open loop)
james beam wrote:Heyyyyyyyyyyy hows that peterchannel T you made working out? Can you confirm that with the peterchannel T, the fire doesn't burn vertical on your feed stock, or is it the proper draft of the chimney? Obviously your using the peterchannel T, so I'm guessing it is doing the trick! Now that you got your chimney working, how is your 'coals hole' working? With the peterchannel T in place, will you try rebuilding the insulation brick around the feed tube?, yanno just for kicks.
I have yet to do comparison burns w/ and w/out the peter channel T so I really can't say just yet. I would bet the strong draft is the main fix here though. The ash pit seems to be working quite well with a proper draft and burns down to super fine ash but does hold hot coals longer; which is an added bonus to helping re-light another burn ;) If I do rebuild my feed, I am leaning towards a system like Rob has on his: http://www.permies.com/t/18515/stoves/Burning-Pellets-Rocket-Mass-Heater
Well, I do believe we have gone done figured this thing out! I have never had such a good draft with no smoke back naturally aspirated. Definitely was a issue of negative pressure plane and it would only be overcome by a roof peak height chimney.
A SUPER HUGE THANKS TO ALL WHO POSTED FEEDBACK! I would have probably given up without your support.
Now, brass tacks...
hey martin, did you know I'm not an engineer! but I can recognize a beer bubble when I see one, hahaha, so....some pixs or diagram of the basic basement & chimney location & RMH location might help. As for the chimney, is it a straight shot up?, or maybe cuz ya had multiple stoves, on various floors there are some turns in the chimney? I'm alittle curious why ya didn't go for the chimney in the first place, would it be easier for you to use in the long run, to simply rebuild your RMH in the room with the chimney? Even tho you have built a nice stove as it is now, I would definitely go for more draft that the chimney offers. The thing about an already built chimney there is noncombustible air chamber around the outside of the existing flue pipe, so you probably won't realize any mass warming from the chimney exterior itself...I may be wrong about this. Back in the old days they may have used fire brick up against the liner for the whole thing, and didn't need that air space, way back when, definitely would be good to know if it will warm up as usable mass. I'm thinking lets say your exh. temp. as it enters the bottom of your chimney, if it was 120 degrees & steamy, it must rise IF connected to a 30' vertical chimney. Yanno most of your clay joint cement and other parts, like your baffles should be reclaimable into a new setup.
2nd pic is for you, a quick basement diagram. Chimney is a straight shot up basement, 2 floors and an attic. It has a capped off port on each floor as it used to be active for two kitchens. It is a semi difficult reach, thus my avoidance. It has NO LINER. It is just a rectangular indoor single wall brick chimney, thus the extra mass idea. It drafts quite well as the new vid shows.
BTW: her name is Hippie Heater
Next up will be a water heater to assist boiler temps.
I am interested in requests for pic, vids, experiments, whatever. Y'all have given me so much, I'd be happy to tickle yer fancy.
Okay, I read the 'house is a chimney' article and I'm with you on the draft thing with the NPP and the size of your house... but your 5.5x8.5 chimney CSA (46.75) is smaller than your feed (49), and especially with such a long run-- although I suppose your NPP draft at the basement tap is the strongest and may overcome this difference.
So here's a suggestion: What if, after you tap into your basement chimney and you get such an amazing draft increase that your barrel temps jump 100 degrees, you then turn your old basement wall exhaust into your new sub-NPP cold air intake-- but don't duct it to the feed box; that would mess with your burn temps.. and don't just duct it into the basement; that would cool off your basement too much-- instead, duct it to blow across the barrel to increase the delta in your difference engine and heat the air as it enters the basement... you could put in a damper to control the flow. This may give your system the boost it needs to overcome the extra work of getting all the way across the basement.
I mean, since ya got the dang hole in the wall already... wot da heck, ya know?
Lol, Chris, yea what the heck, right? I was thinking something of the sort. As far as the CSA, if people can exhaust an 8" heater with a 6" pipe just based on the right amount cooling, condensing and shrinking of the gasses then I think my reduction of 3"CSA after a 35' run (including 25' of 10" duct) should be pretty safe. Based on the chart and my exhaust temps between 100-200deg F, I expect between 20-35 Pa drawing up the chimney. That should be noteworthy.
james beam wrote:hey martin, what a nice surprise you have a chimney already! I can't think of any reason not to at least hook on to that thing, temporarily for testing if nothing else. Can you run your duct pipe near the 55g barrel, to pick-up some heat on the way to the chimney? Is the access to the chimney far away, or thru the floor? Is this the same chimney that is presently on your house furnace? I'd say 'go for it'.
Chimney is against the opposite wall from my RMH, i need to make a 30' run through another stone wall in place of my current 15' run from mass to foundation wall, so an added 15' of length before entering my 30' chimney. But hey, it already drafts so Im believing it will do the trick. It is not in use. My house has 3 chimneys, only 1 currently in use by the furnace, all structurally sound, leak free and self drafting. This one is roughly 6"x8" ID, indoors and made of brick, no flue/liner but has only ever been used by wood stoves; more specifically there used to be 2 kitchen wood stoves/ovens, one on the first floor and another on the second floor as back then this house had 2 kitchens. It used to be a boarding house when the Erie RR was king in town. The 2nd floor kitchen was private for the owner and the 1st floor kitchen was shared by boarders. Originally, the house had the same steam heat as it does now but with no boiler as it was fed by a main steam line that came from the boiler shops downtown, must have been quite the perk!
OK, I would like some feedback/opinions on this. I have come to strongly believe today that my largest problem is with my exhaust draft, i.e. my chimney, or lack there of. Up until now I have not truly considered my house's specific needs to properly maximize draft. After reading the post "Is my barrel to small?" and the link that Peter mentions in the post:
Peter Berg wrote:
danny zeigler wrote:Are you saying that I have to build a vertical stack on the outside of the house up to the roof like with a wood stove?
Yes that's the picture. Read this artcle about the neutral pressure plain and other relatively unknown phenomenons. Especially the part after the header "Is Your House a Better Chimney Than Your Chimney?" That might be the problem in your situation.
RMH's burn tunnel sits 5 ft below ground. There are 2 stories and a full walk up attic above it with many upper story leaks. My house IS a better chimney than my chimney.
I now intend to tie into the basement base of a 5.5"x8.5" ID unused indoor brick chimney that exits my roof to peak height. This chimney drafts constantly as I have flame tested it on all 3 floors. This as opposed to my current configuration that back drafts excessive cold air when not being forced out by blower. I believe my NPP to be well up into my 1st floor and my basement negative pressure to be quite strong, more so than my RMH can overcome. Added bonus is that being that the brick chimney is indoors, it acts as more mass to be heated and radiate.
Im up in Susquehanna PA just a stone's throw from the NY border with rt81 and Binghamton about 45min drive from Scranton. I am in the process of finishing up building my rocket mass heater http://www.permies.com/t/17748/stoves/st-RMH-build I am, along with my wife and 4 children (5th on the way), looking for some property to begin building an earthship and small produce farm.
Martin Seidel wrote:Question is, why do I still have smoke/flame back even after complete bypass of the baffles?
Maybe, just maybe, you need to cool the feed. The theory is this: when the whole feed tube is insulated, it could be that the self-combustion temperature of the fuel is reached at some point in time. To tackle that problem, try to confine the insulation to the lower portion of the feed, the level of the burn tunnel. As another measure, place a piece of a smaller drum on top of the feed tube. This will dissipate heat into the room, keeping the content of the feed cooler. Also, by adding this the combustion air will come in from above almost exclusively. This will help as well to cool the feed more efficiently.
Thank you Peter, I agree and have already removed the insulation around the feed tube's fire bricks (see pic below) and have been contemplating replacing the bricks entirely with a formed pearlite/refractory mud but I believe I will build one of those slide dampers as described in the post JB linked to earlier. I will be shielding the feed tube from the radiant heat off the barrel seeing as it is so close and throws a substantial amount of heat at and into the feed.
JB: Funny you linked that post. I have read and re-read that one so many times. I am also listening to Paul's podcast 104 yet again. I wouldnt say Im addicted to the blower, I just prefer not to smoke out my whole house Yes, I will be screwing the duct together when I know they will not be moved again. Thats the same reason I am using the duct tape, it is temporary, I used 1/2 the roll of aluminum tape just to tear it off to rearrange the duct. Backfill the whole floor laid duct? Yes, I was going to wait until the unit performed well but it seems I should at least semi cover that section to help with the draft. I plan on having stone on each side and top of that run enough to support itself and anyone who steps on it to avoid collapsing.
Chris: WOO HOO is right! I am so thrilled to be seeing my heater begin life. I did fill in about 1/3 of the baffled mass from the ends. I intend on opening the lid and filling the rest with my densest materials. Do you think raising the exposed duct back to where I had it would be better than cobbing over it? Glad you enjoy the pics. I committed early on that I would document every detail I could in attempt to share and help as many others as possible as these forums have helped me generously and I know there are plenty who just love to follow these builds and see/read every little detail.
In summary: I will build a feed damper insert, finish filling my mass and cover over the floor laid duct.
John: Yes, that was the plan from the start. To see if heating the basement with an 8" system set to burn several hours, 1-2Xs/day could surpass the need for or replace my 280K btu oil fired steam boiler. I believe this to be a big YES! Just have to fix a few bugs and install floor vents as needed.
JB: So glad you saw that right away. As soon as I opened the cavity, pulled the back slab and saw the soot patterns, I knew it was pic worthy evidence. It seems that the surface area prior to complete stagnation can be calculated as a maximum not to be approached? Question is, why do I still have smoke/flame back even after complete bypass of the baffles? As far as leaks, chamber to chamber, yes, but nothing into the basement. Fire extinguisher, yes, 10lb ABC with another just 15' away upstairs, garden hose in next basement room, Co2 detector 6' from mass on floor and smoke detector on floor joist at ceiling.
You will see the "chip chunks" burning in the feed tube. These burned great and do so anytime I have them piled in there. Problem is that any other form of wood fuel I put in ends up smoking back and flaming back, even if the feed tube is choked back. I slowly burned the mass dry and continued to burn for over 48 hours, feeding the fire hourly around the clock. 30 deg outside, furnace turned off and she kept my 4000 sq' home at 65 deg! I have SO much belief in this system, just need to work a few more bugs out.
Next, I will be removing the outer brick and perlite from around the feed tube in hopes of keeping them from getting so hot as to allow early combustion of fuel as previously mentioned.
OK folks, we are still at it. Thank you all for such excellent advise! Please keep it coming.
So I managed to run the pipe up on about a 35 deg angle to meet the gasses up high coming right out of the large barrel opening across the ash pit. I filled in behind the pipe into the mass with clay and rock mostly but capped it with cement before closing it all up. Now the exhaust runs this 35deg angle, 4' straight through the mass, 90deg Tee, 15' straight, 90deg, up 3', 90deg and straight out through cinder block wall. This seems like a pretty short, smooth run and should eliminate the "baffled mass" as a cause for any future problems.
The following shows the widening (yet again) of the mass' cavity to fit in an 8"x4' section of pipe. I dug out another cubic foot of dirt and rock and had to drill and chisel another hole in the end cap stone to align with said pipe.
The last burn video was the best burn so far. I have seen this RMH make huge progress towards overtaking my oil fired steam boiler as primary heating source for my 4 story (basement included) home. Just a few more hurttles and she will be there. In my last vid, the fuel was thick hardwood chips split from waste 6x6 blocks. It was the only burn configuration I could get to burn without fan assist or smoke/flame back. Even the fine split (1") bone dry, 10yr seasoned ash, as hot as it burns, flamed back hard without my 7" fan pushing air down into the feed tube.
So here it is. Taking the advise mentioned, I have undertaken more modifications in hopes of natural aspiration. These 3 pics show the opening up of my barrel side cleanout and the "steps" down into the mass chamber that was previously "bypassed" with a piece of sheet metal.
JB: I installed a piece of sheet metal to block off the baffles and immediately saw an increase in air flow! See today's vid for the full 4 hr burn. As far as basement wide air flow, I have a 4" pvc pipe with that cruddy inline fan bringing in outside air. I have a floor grate to install in upstairs floor to feed "cold air return" close to feed tube also. I also considered the height of my feed tube off the floor (16") and the blower inlet height of my furnace, both "bottom feed" air from floor level. I have a CO detector mounted 18" off the floor at mid room. I did (re)upright my outside chimney. Whats your take on running the duct up above roof level?
Colin: Ash pit; look at my early pics of the base bricks. I built the bottom of the feed tube 1 upright brick deeper that the burn tunnel floor. No missing bricks but yes, that pile of coals really pushes heat up the feed. I need to install a "table" style grate to only allow ash to fall into the pit.
Chris: WOW! Thank you! your honesty is much appreciated. And your humor is just what I needed. Thank you sir. Your explanations are spot on, man. You are right, I get it now. It would be nice if I read your comment before I got to work on her tonight. Ehh. Seeing the results from blocking off the baffles has me tossed up between your #2 & 3 ideas. To start, Im ganna tackle that first drop next to my barrel side clean out stone. I figure, with the Heisenberg's molecular death march already semi blocked and the draw getting much better, if that first drop can be fixed to increase draw also, then I'm that much closer to my victory cigar
Ok, James / Andor, I am reluctant to, in a way, bypass this menagerie of my hops infused cranial creation. lol After several beer burps, I can't help but think that the individual chambers need an upper release channel, i.e. Im ganna peel the lid off her and cut a 1" deep x 12" wide channel into each baffle. That will add an additional 12sq" to the CSA between each chamber and allow for the upper (pressurized) gasses in each chamber to have a vent to flow into the next chamber without "burping" backwards and fighting the flow.
Thanks again! *buuuuuurp*
I received a great comment/suggestion on my youtube vid:
it'll be smoky for a few minutes,but you should try unhooking the flue the first place you can,after the mass to see if it picks up any draft.if it helps maybe you should move that last upward 90 closer to the mass then go out of your dwelling with the flue at level. more of your heated exhaust will flow upwards sooner that way.as it is now that last 10 or so feet before your 90 might be the problem
krowebmf76 30 minutes ago
This looks to be a good diagnostic tool prior to opening my mass again
Also there has been some RMH threads talking about using house temp. air, is better than cold air...I think you said it was 20's in the basement, so that cold source air may have something to do with it.
james beam wrote:hey martin, real nice work, I like the little flower flange you cut on the end of your heat riser inner pipe...real pretty. LOL
Ok what about trying this, find a piece of sheet metal or flashing, an put it on the underside of your baffles. I think it is your baffles that are disrupting your exh. flow, and causing 'back pressure bubbles' much like beer bubbles in your belly...that makes you burp back. So if you found a length of sheet metal to temporarily block off your baffles, & promote flow straight thru to your first Tee. It might be about 10" wide and about 4 or 5' long, fit it in there to block off your baffles, an yet still might transfer some heat to your baffled radiator thing, but mainly to get uninterrupted exh. flow for testing, its temporary, see if that will improve natural draft.
Nice idea JB! that would be a great way to diagnose if the baffles are causing the smoke back. As much as I dont want to open that big (270lb) end cap, it will be for good cause and that's why I put them cleanouts in, cause all the experts said you'd need to get back in for mods.
james beam wrote: how is that 'coals hole' thing working out? Is it catching & holding lots of coals like you expected, or are the coals getting blown up the burn tunnel? I also think your little fan on the exhaust to pull, might be a easy change you could try...yanno if you haven't burnt yours up yet. LOL
The ash pit works well even without a grate yet. The exhaust fan was the first thing I changed as it was a complete choke point and smoked back even with a fan in the feed. The lil fan def didnt push like the package said :(
james beam wrote: Can we get a pix of the outside stack & rain cap, is it upright or laying on the ground, and you also mentioned a 'damper'...but I don't think you put in a damper valve, so that is alittle unclear. Also you said 12' of steam cloud at the exh. port...but that's with a box fan forcing it right?
Also there has been some RMH threads talking about using house temp. air, is better than cold air...I think you said it was 20's in the basement, so that cold source air may have something to do with it.
Pics are as follows, although the outside has been mod'd as stated before with no changes to the lack of draw.
No damper in this duct. Yes, massive fog on first burn with this 8" exhaust. That was with pusher fan at feed tube. Subsequent burns have not produced nearly as much steam, a sign the mass is drying.
Jon, I am having similar problems with my 8" unit. Take a look, we may end up answering each others problems http://www.permies.com/t/17748/stoves/st-RMH-build Is your rmh in your basement? As far as a heat riser being to tall, I dont think that is possible (within reason). My unit has a riser height 3 times the length of the burn tunnel and 4 times the height of the feed tube. It should only make it draw harder relative to the exhaust exit and, as I am learning, the surrounding air pressure to exhaust gas density ratio.
Where is an Admin when you need a good formula? How about that, a numerical ratio of surrounding air pressure & density (@ feed tube) to flue gas density to outside air conditions? A solid set of parameters here to work backwards from could be quite groundbreaking!
Thank you Colin for your well explained idea. I was thinking the same as I know I have serious negative pressure in my basement being 75% underground and having 3 stories above. My exhaust pipe exiting the mason mass gets quite warm to the touch. I haven't taken a reading on it yet but it is almost scalding when she is in a full burn, my guess is in the 180-200 deg. My first burn produced a cloud of fog worthy enough to engulf my neighbors driveway and garage, lol. That was fun. On the last 2 burns, she has had moisture trailing 10-12 feet from my stack with outside temps in the upper 20s. I will try your idea to pipe exhaust lower than my riser by more of a syphon method as my pipe exits the foundation wall 4ft up inside and 1.5ft up outside. I will point the outside Tee in the steepest downhill slope I can with the 5ft pipe extending from that and a cap on the upper Tee opening. Hopefully this will allow enough "drop" to pull more exhaust out. Funny, I was trying to find as many relevant details on the "push/pull" picture chart in Ianto's book, it seems we were all of a like mind.
BTW, this is a pic of the back wall inside my mass that settled when tamping in all the backfill. I guess using a 20lb sledge like I was ramming earthship tires to achieve maximum density was, in hindsight, a bit excessive.
And here comes the challenge, I have serious draft/draw issues! I had opened my battery to inspect and found there was settling so I dug the channel out to ensure minimum CSA and ended up with 60-70" CSA inside. That didn't solve it so tonight I opened the drum to no answers. What I did find was that the drum lid concaves 1/4" from cold to hot but with a 2.5" gap atop heat riser, this shouldn't be the culprit. I have ideas but am looking for feedback as to why she only drafts by force (fan).
Made a vid of tonights burn:
So my whole rediculous idea of venting my 8" system through a 4" pipe powered by an inline fan flopped hard *cough*cough*cough* The fan was advertised as pushing 80cfm and I was under the impression my unit only needed 32-35cfm. Well, the dang fan was made (and rated) in china and I believe my required system cfm information was wrong. No need to dwell, just simplify back to the book.