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RMH Smoke Output

 
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Hello! Built a RMH and I have a question regarding the smoke output. There is something coming out of the chimney- not sure if it's smoke or vapor and I'm also not sure what is normal with a RMH. its white color and is flowing out of the chimney and it clears away in about twenty feet or so. it doesnt smell like smoke in the yard at all unless i go directly upwind from it and then its just a wiff of wood smoke smell on and off. is this normal? i wasnt sure if other people had the same output or if it was normaly less visible.

also curious about barrel temps, whats the norm for a rmh? i am seeing about 550f at top of barrel on average. i got an infrared thermometer that reads up to 1400f and it maxes out at bottom of feed tube. is that th hottest point of it or is the other end of the bridge much hotter?    

thanks
 
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Hi Katy;
The white vapor sounds like its steam.  
If your rmh is completely dry and heated up. Then the steam is from your wood not being dry.
If your rmh is new this season , it could still be drying.
It is normal and should go away.

Top of barrel temps vary between 6" and 8" , also depends on top gap between the riser and barrel top.
On average a 6" J tube runs around 600 F  an 8" 800 F.
Hottest part in a rmh is part way up the riser.  They have measured it above 1500 F.  
 
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Katy,  To add to Thomas, at the beginning of the burn there will often be some smoke as things get going and heated up. Any blue or grey colour is a definite giveaway to it being smoke. I find there will always be a light wiff of a smoke smell even when its burning 'clean' as there is other byproducts and vapours that are associated with burning wood that just don't get burned up. If it was pure steam it would smell like a kettle boiling or a dryer vent (with no fabric softener). It is often said that smoke is unburned fuel.
I find it also depends on the temperature of the exhaust gasses and air temperature for it to condense, the relative humidity of the air and any wind to dissipate the chimney outputs.
 
Katy Tee
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this is my first rmh so im still new to it all. the core is mostly dry and i havent added the mass yet. its a 6" j tube with a 3 1/2 inch gap at top of riser. i thinks the wood is not as dry as i had hoped, i dont have a moisture meter but ill try some other wood and see how that works. if the ice gets off the roof this weekend i can get up to the chimney to check exhaust temps
 
thomas rubino
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Katy;   Please don't go up on your roof. Its icy and you will not get a good reading.
Instead, acquire a candy thermometer.   Drill a hole in the exhaust after it leaves the mass and insert the thermometer.  
We jokingly call this the Tom & Gerry Dragon breath monitor.  
It is an innovation that is not in the builders guide and a foolproof way to know how well your rocket is burning.
Surface temperature on the pipe is misleading, and trying to get a reading on the roof all you will get is external pipe temps and that will be effected by the outside temps.

If your still adding mass then you are still drying cob. This moisture will condense inside your pipes and cause steam.
Have you gotten any black goo seeping from the joints in your exhaust after it leaves the mass ?  You may, it is very common and to be expected.

We like pictures... would love to see your build!
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Tom & Gerry's Dragon breath monitor
 
thomas rubino
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Katy;
As an example, my photo shows the stove running around 140F  . If I had checked the external pipe temps it would have been 70-80 F at the most ... probably less.
That particular meter is on my shop stove. An 8" brick bell system.  When I run it all day it is not uncommon to see that temp gauge over 250 F !   When I check pipe surface temps at that time, I'm getting 130 F... I can still lay my hand on the pipe... Big difference!  Its all good, these internal gas temps were not monitored in the early days of rmh pioneering... they are now!
 
Katy Tee
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ok that makes sense with the thermometer. is there a temp you aim for?
i can take some pics tomorow
 
thomas rubino
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Hi Katy;
No there isn't a perfect temp.
In our greenhouse I have had over 300 F easy, but its a greenhouse / artist studio , so we run the J tube  10-12 hrs a day.
My shop stove, brick bell takes its time 6-8 hrs but it has been over 350 F. This is also in an uninsulated building.
It all depends on your building , how well it is insulated, how tall are your ceilings  and the size of your mass.
Looking forward to your photo's!
 
Katy Tee
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Pictures of unit
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Katy Tee
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it's a work in progress.. i had a different mass configuration before but I took it apart. I had used dirt and filled it up above the exhaust pipes but it wasn't drying and I hadn't insulated underneath it so it was just staying cold. Not sure what I used - got it from a local mine/gravel place. They called it silt but it was their washstone byproduct that they said was basically clay. Easy to form and work with but had barely started to dry after a month. where it did dry was around the core. seems very insulative. I took it out and figured I'd try a mass that is mostly rubble and stone with just enough mortar and mud to hold it together. I also added a second barrel for fun. I was going to wrap it in stone as well. It's in my unfinished basement and I was trying to experiment with a few things before possibly building a permanent one next year.

I tried using some different wood and am still seeing steam coming out of the chimney but it seems to be burning better. Top of the barrel temps were around 670. I think some of the steam is from stuff around the ducting but I think some of it may still be coming from the wood. I have several different species of wood that I'm using in various stages of seasoning. Some of the stuff I thought was dry turned out not to be. Some of the stuff I thought wasn't dry turned out to be. I'm burning black locust, pignut hickory, white oak, red oak, rock maple, red maple...  If there's any moisture that comes out of the wood, is that just water or might some wood just have resins in it that might come out through the grain when burning?

Thanks.
 
thomas rubino
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Hi Katy;
Thank you for the photo's!
Things are looking good!,  I'm sure that as you cover your pipes with mass (and they dry) , your steam will disappear.

I would like to make a suggestion though. Its a change I wish I made to mine. But didn't!  Yet...  
Where your pipes make the 180 degree turn. You currently have exactly what is recommended in the builders guide.
I would remove that turn and build a small clay brick box ( not fire brick) .   Run both pipes in and add a cleanout access on the side.
This eliminates any restriction the turn back created. Your stove will love you for it ,and cleanout will be easy.

I suggest this as you have not gotten to that far end yet.  Nothing fancy , just used or new regular clay bricks  , that far from the core you could even use cement to build with.
You certainly do not need this but its something you will like in the long run.

Welcome to the wonderful world of rocket science!
 
thomas rubino
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Larger rock with just enough cob (mud) to fill any air spaces , is one of the better/ cheapest mass materials available.
Consider boxing that mass in with brick walls.  More mass and its easier to fill.
 
Gerry Parent
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thomas rubino wrote:Where your pipes make the 180 degree turn. You currently have exactly what is recommended in the builders guide.
I would remove that turn and build a small clay brick box ( not fire brick) .   Run both pipes in and add a cleanout access on the side.
This eliminates any restriction the turn back created. Your stove will love you for it ,and cleanout will be easy.


Hi Katy,    As Thomas suggested, this is what I did to mine in 2016. The pipes can be seen entering and exiting the box which can really be made in many ways. In fact, if you wanted, you could even move your inline "for fun" barrel down a bit to perform this function as well.
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Katy Tee
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thanks for the tip on the box at turnaround. ill try that next week.
 
Katy Tee
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Just out of curiosity- is it ok to throw in a handful of pellets (like for pellet stove)?
 
thomas rubino
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Yes you can. Just don't cover the burn tunnel or it will back draft on you.
 
Katy Tee
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Great! Thanks for all the helpful feedback.

Another question- I've had fires where I've left the feed tube uncovered and also, covering the feed tube partially with a brick, and I don't notice much of a difference (besides it sounding more "rockety"). Is it better/more efficient one way or the other?
 
thomas rubino
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I think some folks like the rockety sound.
For years now, I have not covered the feed tube at all.
 
Gerry Parent
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Katy,  I know you are referring to the burning phase, but I found that covering the feed tube (completely) after the fire is out helps to keep the heat in the mass rather than allowing the natural draft which can flow for a long time after the fire is out to carry away all that stored heat up and out the chimney.
 
Katy Tee
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so i covered half the mass in large stones then ran out of mud and mortar so i just covered the other half with pea stone for now. had a fire for the first time in a few days today and had a lot of oozing come from pipe. i guess cause new mass is still drying? i hear this is normal as the mass drys but what if the mass is dry and there is condensation? are the pipes likely to condensate from the mass being cold? so could this happen every time the system cools off? what temps are considered cold for a mass?  
 
thomas rubino
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The mass takes quite a while to dry. It took mine over a month  to totally dry out and heat the far end of my mass.
Your wood if not dry will provide moisture in the system as well.
Your mass once dry will stay warm for several days depending on conditions.
The pea gravel section is going to cool every day and need reheating. I would replace that as soon as I could.
The ooze will go away after a few weeks of steady burning.
There is no," too cold" for a dry mass. As soon as the dragon starts roaring the mass will heat up.
Its all normal for a new system.  

Good job!
 
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