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RMH for Dummies! Please help guide me through my first build!  RSS feed

 
pollinator
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Caleb Mayfield wrote:My feeling is weather, and possibly wind, is the primary culprit.
If I load it up with larger stuff off the bat, or less fat wood it takes longer to get warm and I struggle to get it up to 500 F. It gets warm and gives off the heat we need, and looking at the chimney it's burning clean, just not as well as a good hot start.

Just a thought.

Good luck!



Hi Caleb,
 Thank you for the suggestions!
Maddening enough, there was NO wind! Crazy.  They issued the burn ban due to the stagnant air.  I could understand high winds being a factor, but none..? Weird.
I appreciate the comment on using the smaller wood straight off.  I have noticed that too, when I am impatient to not want to babysit with smaller pieces, and instead add thick pieces... impatience does not pay off in best heating results.
Staci
 
Staci Kopcha
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thomas rubino wrote:Staci; If it is weather, then you might try making your chimney taller outside.  I know the costs involved with that, to do it right.  If needed, you might just try and stick a piece of plain stove pipe on top and see if it has an effect. (remember it will not be insulated ) If it seems to work and you can't afford a new piece of insulated pipe, then insulate your own. Ugly but wrap it with insulation and slide a larger pipe over top.   Later if that solves your problem you can save up for a shiny new metalbestos pipe.



Thanks, Thomas.
I have some extra single wall I could try, just to see, for when it happens again.
 
Staci Kopcha
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Graham Chiu wrote:Do you have weather data for your immediate region? In particular wind speeds? If not, can you measure it?



I will try a link:

https://www.wunderground.com/history/weekly/us/wa/tacoma/KPLU/date/2019-1-17?cm_ven=localwx_history

 
gardener
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How big is the gap between riser and barrel? A normal burn with typical gap should be getting barrel top temps several hundred degrees hotter than 475 I think. Also don’t forget that normally it takes heat about one hour to travel through one inch of cob. So if you have say 5 inches on top of the bench those temps will take some time to increase. Wouldn’t a taller chimney cause even more trouble, if the issue is too strong of a draft pulling the exhaust through the mass too fast for full heat transfer?
 
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500-600 is very common for a 6" J tube.    800-1000 for an 8" .  Of course there are exceptions.    The taller chimney may change things hopefully for the better but … its worth a try.
 
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Staci Kopcha wrote:

Hi Caleb,
 Thank you for the suggestions!
Maddening enough, there was NO wind! Crazy.  They issued the burn ban due to the stagnant air.  I could understand high winds being a factor, but none..? Weird.
I appreciate the comment on using the smaller wood straight off.  I have noticed that too, when I am impatient to not want to babysit with smaller pieces, and instead add thick pieces... impatience does not pay off in best heating results.
Staci



That makes sense. Sounds like a significant inversion layer which would hold in the smoke from less efficient fires and would keep warm air from rising. Depending on how low it was it could create drafting issues.

Hope it starts burning well for you!
 
Staci Kopcha
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Mark Tudor wrote:How big is the gap between riser and barrel? A normal burn with typical gap should be getting barrel top temps several hundred degrees hotter than 475 I think. Also don’t forget that normally it takes heat about one hour to travel through one inch of cob. So if you have say 5 inches on top of the bench those temps will take some time to increase. Wouldn’t a taller chimney cause even more trouble, if the issue is too strong of a draft pulling the exhaust through the mass too fast for full heat transfer?


Hi Mark,
 Can't remember it off of the top of my head, but I know it is adequate... Just over  2", I have it written down w/ my building notes somewhere.
I know it is well above 475, my temp reader just doesn't go higher than that.
Thank you for the stats: one hour/for one inch.  Patience is a virtue I am working on.
S.
 
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Hi Staci, what's the topography surrounding your house?  Are you in a basin or something?
 
Staci Kopcha
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Hi Graham,
 It is hilly terrain in my immediate area.  House is just nearing the top of a rise.
Got this from an on-line topo map:
Lng:-122.35285329999999
Lat:47.1702279
Elevation: 136m / 446feet
 
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Hi Staci.

I've been following your build with much interest.  In regards to your RMH troubles, I just wanted to weigh in with my two cents.  First, I find it odd that you have trouble with the draft not being strong enough to keep the fire from creeping up the feed tube, but then we are entertaining the idea that draft is so strong it's preventing your mass from heating up.

From what I have seen I would surmise that you need more space between the top of the riser and the barrel lid.  While two inches of clearance should be enough, I just have a hunch this area is the point of restriction that is keeping your dragon from performing to it's fullest.  Maybe others can weigh in on this?

Good luck to you in resolving this issue.  I'm very much impressed with your accomplishment thus far.
 
Graham Chiu
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Staci Kopcha wrote:Hi Graham,
 It is hilly terrain in my immediate area.  House is just nearing the top of a rise.
Got this from an on-line topo map:
Lng:-122.35285329999999
Lat:47.1702279
Elevation: 136m / 446feet



Hi Staci

Do you have any pictures of the terrain surrounding your house?  Are you surrounded by trees?

I think since your problems are intermittent we are positing an external weather event such as a cold inversion layer near the house.  A taller chimney may not solve this problem if you can't get above the inversion layer.
If you can make your chimney smoke that might help diagnosis.  With an inversion layer your smoke won't rise but will fall back onto your roof.
 
Staci Kopcha
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Thomas Tipton wrote:Hi Staci.

I've been following your build with much interest.  In regards to your RMH troubles, I just wanted to weigh in with my two cents.  First, I find it odd that you have trouble with the draft not being strong enough to keep the fire from creeping up the feed tube, but then we are entertaining the idea that draft is so strong it's preventing your mass from heating up.

From what I have seen I would surmise that you need more space between the top of the riser and the barrel lid.  While two inches of clearance should be enough, I just have a hunch this area is the point of restriction that is keeping your dragon from performing to it's fullest.  Maybe others can weigh in on this?

Good luck to you in resolving this issue.  I'm very much impressed with your accomplishment thus far.



Hi Thomas,
 Thank you for the kind words and insights.
I tried making the tower taller, but not shorter.  I am not sure of an easy way to do it, even for trial.  Otherwise it would involve either cutting bricks and redoing the tower top, or unseating the barrel, raising the rim higher on cob.
If I knew for sure, I could do it.
Thanks!
Staci
 
Staci Kopcha
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Hi Staci

Do you have any pictures of the terrain surrounding your house?  Are you surrounded by trees?

I think since your problems are intermittent we are positing an external weather event such as a cold inversion layer near the house.  A taller chimney may not solve this problem if you can't get above the inversion layer.
If you can make your chimney smoke that might help diagnosis.  With an inversion layer your smoke won't rise but will fall back onto your roof.


Hi Graham,
 I can take some pictures for you. House is pretty open. A willow out front. A few Maples in back.
Today smoke was moving off sideways, not up or down. I haven't spent much time observing smoke movement- thank you for the tip! I will make a point to make a study of it.
Staci
 
Staci Kopcha
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RMH frustration.
At this point, I want to smash the second bench (after the "L"), as it is never very warm or retaining much heat. I suppose it would mess up the system, because there would not be the ideal duct length, BUT, honestly it is pissing me off. (Pardon my phraseology) The temp of the outside corner of the "L" read at 64F, 70-87'F is what the rest of it runs.
Perhaps I am under a misapprehension in that the second portion of the bench is supposed to be warm...??  What is a typical temp?  I will see if I can find it anywhere.
Maybe my expectations are out of wack??

 Today it has been running for 4.5 hours.  I used a mix of fir and madrona wood , with odd bit of cherry, alder, and maple - all very dry.
Chimney pipe inside the house at the very top is at 107F. First portion of bench is slightly warm to sit on, second portion cool.
Temps today were cold, and now 32F, snow is predicted.
Wind is nearly zero. Pressure is "29.41 in"
 
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Staci Kopcha wrote:RMH frustration.
At this point, I want to smash the second bench (after the "L"), as it is never very warm or retaining much heat. I suppose it would mess up the system, because there would not be the ideal duct length, BUT, honestly it is pissing me off. (Pardon my phraseology) The temp of the outside corner of the "L" read at 64F, 70-87'F is what the rest of it runs.
Perhaps I am under a misapprehension in that the second portion of the bench is supposed to be warm...??  What is a typical temp?  I will see if I can find it anywhere.
Maybe my expectations are out of wack??



Staci,  You are now at where I was in 2016....tired of making compromises and wanting my stove to just work better!

Not suggesting that this is your path to go, just saying that this is the path I took and what it did for me...

Picture 1 is what my Dragon looked like at the time before I made changes....similar shape to yours....I just wasn't getting consistantly good draft nor was the far end of the bench warming up. I too was following what I was researching at the time and making some of it up as I went as well...as we all do.

Picture 2 is when I chopped off the L portion of the bench and made a small bell instead. I was inspired by Kirk Moberts video Rocket Bell Retrofit  This dramatically increased the draft by eliminating 4, 90's and about 10 feet of piping. Perhaps too much draft as I was getting a lot of the heat going up the chimney which spurred me to make another change after the season was over..

Picture 3 & 4 shows the piping being removed entirely and being replaced with a bell. Mucho better in both departments!...draft slowed down allowing the gasses to stratify and  thereby giving more time for the heat to be extracted. The bell is still small for the stove but I don't have the room to expand it any further but is still the best configuration to this day.




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Graham Chiu
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Staci Kopcha wrote:RMH frustration.


 Today it has been running for 4.5 hours.  I used a mix of fir and madrona wood , with odd bit of cherry, alder, and maple - all very dry.
Chimney pipe inside the house at the very top is at 107F. First portion of bench is slightly warm to sit on, second portion cool.
Temps today were cold, and now 32F, snow is predicted.
Wind is nearly zero. Pressure is "29.41 in"



I gather that the smoke from the top of your chimney is drifting sidewards with no wind.  So, there's a draft issue.  Can you crack open a window in the room where the stove is to see if it helps?
Is your stove making the expected rocket sound?
 
thomas rubino
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Good Morning Staci;
   How frustrating your dragon is not behaving... BAD DRAGON !  
Gerry's fix worked well for him and might be something to consider, next summer. If you have to...
But I know that after all your hard work, following the plans to the letter … asking advice … the dam thing should work like its supposed too ! Stomp foot loudly !

I suggest that for now, you put a candy thermometer in your chimney. Start monitoring your true gas temp rather than pipe temp.
I have been learning how different gas temperature's are from pipe surface temps.  And how rapidly that temp changes. It is a true indicator of rocket performance.

Lets find out how hot your exhaust is really getting.  


I paid $8 brand new , dollar store could have them, yard sale could have one.    


Simply drill a hole in the chimney as it is leaving the house and insert thermo.
DSCN0115.JPG
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Candy thermometer
 
Gerry Parent
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thomas rubino wrote:Good Morning Staci;
I suggest that for now, you put a candy thermometer in your chimney. Start monitoring your true gas temp rather than pipe temp.
I have been learning how different gas temperature's are from pipe surface temps.  And how rapidly that temp changes. It is a true indicator of rocket performance.


Hey Thomas,   If we keep convincing people of monitoring their flue temps with candy thermometers, maybe they'll be enough of a demand for manufacturers to produce an RMH Thermometer!
Instead of saying "Confection zone", "Deep Fry", "Hard/soft ball" etc... they could say "Dragon Roaring!",  "Efficient", or "Butt warming zone!".  ;)

Staci,   I know it was difficult for me to rip out all that finely crafted rock work I spent so much time on but I knew what I had to do and I don't regret it as I learned so much from the doing of it. Perhaps akin to those Buddhist Monks who spend a long time creating those intricate sand mandalas, only to sweep them away when they are finished.... a spiritual practice in letting go and impermanence.
The joy for me was in the doing of it but I certainly didn't do it just to knowingly rip it apart. I really tried my best to make it work (and I certainly hope you can train your Dragon too!) but I just got to a point where I knew I was getting frustrated which I didn't want.... so here I am sharing my experience for what its worth.
 
thomas rubino
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Thanks for sharing that Gerry!   I have every confidence that Stacie will follow thru and figure this out no matter what she has to do.

Now on to Tom & Gerrys excellent new business venture!
We buy a truck load of candy thermo's … relabel as RMH monitors and WALA !  We are filthy rich in days !!!  WHOO HOO …..
RIGHT … and then we start selling beach front land in the mangrove swamps...
 
Staci Kopcha
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I whine and stamp my foot and my dragon roars.
The irony.
With this recent change of weather (bitter cold- teens, snow and ice- pressure has increased to 30.36), my heater- bench and all- has been working beautifully.
Unfortunately, this weather is not the norm for our region and I presume troubleshooting will continue.
I will hold off on my plaster coat and finishing until I know if modifications need to be made. (Gerry Patent, I noticed your lovely rock work prior to your modifications- must have hurt.)
I will also look for a "Tom & Gerry's" dragon thermometer to help me on this journey. ;)

Staci
 
thomas rubino
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Ha Ha Staci;
That reminds me of my step daughter when little. Stamping her foot... Whining … sometimes it even worked ! Seems that still holds true!
Nice that your Dragon listened and behaved while the cold temps and snow were there.

Did you ever try adding the extra stove pipe ?  
Seems like this may be barometric pressure related.  So a taller chimney might very well do the trick. To bad your not closer. I have 6' of 6" metalbestos (Selkirk)  leaning against the shop wall , waiting for a new home!

Once you start using a Tom & Gerry "Dragon Breath Monitor" :)  You will start seeing how every little change at the feed tube, has a reaction at the chimney. Prolonged monitoring  should help pinpoint your problem.

Oh; Congratulation's on  "beeing"  a pollinator !
 
Staci Kopcha
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And, smoke is rising.
DSC_1377.JPG
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Graham Chiu
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So, with the colder weather you have a greater thermal gradient between your outside chimney and the inside of the house, so the thermosiphon starts working.
Sounds like the simplest thing to do to permanently fix this problem is put a fan on the chimney to increase the draw irrespective of the outside temperature.  The trouble is, those fans can be kind of expensive.
Or, you can try using your hair dryer to drive the fire where you feed the fuel when you start the fire.  That might increase the heat enough to establish a decent draft.
 
Graham Chiu
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As an aside, has anyone tried putting a heating element around the single skin chimney before it becomes double skin.  Heating the chimney might get the draft established.
 
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