I built my RMH using the Dragon Heater 6" Castle components and design. I followed the build exactly to specs yet after several burns, I am extremely disappointed with it's operation. I'm just not getting temperatures that were claimed by Dragon Heaters nor the draft, especially when it's windy outside. I've spent a lot of money on this and so far, I've found it to be a 3,000 lb pile of crap in my home. I really need to get this operating effectively and efficiently as I was planning on this being my only heat source. Any help would be appreciated and please go easy on me, this is my second build and I was hoping to rely on a proven design.
6" burn chamber: Dragon Heater shippable core lined with perlite and fire blanket, inside 13" x 18" clay flue pipes
1st bell: 18"x18" clay flue pipes lined with fire brick
2nd bell: 18"x18" clay flue pipes, no lining
3rd smaller bell for flue exhaust: 13"x13" clay flue pipe with 6" flue
6" steel flue pipe: exits vertically 9', 15 degrees for 4' through the 16" thick brick walls in my home, 4' vertically outside
After a 4-6 hour burn at night (burning primarily douglas fir), here are my temps (Fahrenheit):
Top of burn chamber inside: 230
Top of 1st bell inside: 200
Outside of 2nd bell: 105
In the morning, the unit is still giving off some heat but nothing that can be noticed. Most of the heat is still in the burn chamber and temps are around 90.
On a windy day, I get a lot of back draft, flue temps won't get over 100 and I have to use a flue fan to create draft (even that doesn't prevent backdraft)
Modifications that I've done:
Added 1"-1.5" faux stone, a concrete product
Flue fan to increase draft but may be sucking all the heat out of the RMH Damper to close off when the fire burns out
Hmmm... What strikes me in your story: the draft should be stronger when it's windy, not the other way around. The heater seems to be up to specs as long it isn't leaking seriously but how about the chimney stack?
A good chimney is straight up, insulated, inside the envelope of the house and extending above the highest point of any roof nearby. Yours is going up as a single steel pipe for 9 ft, an elbow, 4 ft nearly horizontal as I read it, another elbow and 4 ft up. You don't mention the height of it compared to the building, other buildings or high trees in the direct vicinity.
The question is now: is at least the part outside the house insulated? If not, this should be done at least, don't forget the elbow and the stack should be high enough to reach above the highest point of your roof. A chimney stack that stops under the eaves is only possible in very specific circumstances like a very constant wind direction and a one-storey house with absolutely no openings situated higher than the ending of the pipe.
See such a heater as a whole: the chain is as strong as the weakest link and I am inclined to think your chimney isn't up to specs and thereby the weakest link.
Thanks for the input. My chimney is not insulated once it goes outside. The highest point on the roof of my home is 45' and in order to save $$$, I've opted to have a shorter chimney. In order to run the flue inside the building, that would entail going through the first floor ceiling joists, second floor ceiling joists (which was the original flat roof covered in 4" of plaster and tin) and then through the attic and roof rafters. My first floor is 11' high, the second is 12' high and the attic another 5'. It would cost a fortune in insulated pipe. I think the best I can do is to extend the pipe through the second floor and exit horizontally as high as I can go on the second floor. So this may solve my draft problem on windy days. However, would this increase burn temperatures inside the RMH?
Does insulated pipe really make a difference? I would think that uninsulated would help release more heat into the room?
I used to have a 10" stainless steel insulated chimney that went through the eaves. It was for a diesel fired steam furnace in my basement. I tapped into it for a 6" wood stove and it worked well most of the time. However, strong winds would come down and affect the wood stove as well. I've since removed that chimney and entire setup.
Pic of the chimney and building. Yes, I know it's not all the way up to the roof. Yes, I know it's near a window (second floor is vacant). Yes, I know what building codes should be but I knew that I would be experimenting and things may change.
Without giving a reason why, your comment is not helpful. This setup works fine if there isn't any wind. I know I have to make modifications but would like constructive advice, not just "this won't work".
Location: Southern alps, on the French side of the french /italian border 5000ft elevation
Imagine a sail, what does make the boat go forward with the sail? Overpresure on one side, underpresure on the other. Imagine the overpresure given by the wind against a house wall. One thing which you have most certainly done in your life, left your hand outside the window, while driving. A hand is rather small, but sometimes, when you reach higher speeds, it's hard to push forward. Imagine, a slight overpresure, a few grams per square foot, of a huge wall. This has only three sides to escape, right side of the wall, left side of the wall, and along the eaves. Overpresure builds up against that wall, and counteracts the stack effect. https://en.wikipedia.org/wiki/Stack_effect
Hence my comment.
Solution 1 go through the floors, with a single layer tube. And making a little trimmer hole at each floor. Which can be insulated with vermiculite concrete. Clearance from the wall of the pipe, to the nearest piece of wood, in euroland, is usually 8 inches.
Solution 2, use a sucker fan, from a fridge. I use pabst brand, at the very end of the "chimney" where you have your cowl now. And leave this running when the wind is going the wrong direction. Carefull tho, this could kill you, if the wind turn direction, and the fan is not on. Blows the fire back in the house, smokes the house while you sleep, or something alike. Solution 1 is far safer.
Thank you for the descriptive reply. Very helpful.
I did install a fan about 3' above my flue after it exits the stove. However, it's not enough to combat the extreme wind that we are having today. Otherwise, it works well. I'm just concerned that I'm sucking all the heat out the chimney.
So...I'll reroute the chimney to create better draft. That problem is solved. Will this get me higher temps inside the stove?
Location: Southern alps, on the French side of the french /italian border 5000ft elevation
What bugs me, is that you have to come here for customer support.
Anyway, With 135/145F° flue temps, this is way too low an exhaust temp.
Do you have a pic of connection between heat riser's top and first bell? I mean, all the connections. We know your chimney is restricting some. That's for sure. But what about the other components?
I know i don't like J tubes anymore, due to their lack of power. This is my opinion thought. After a 6 hour burn, with a crappy Homemade 6 with no mass, my 330sqft workshop was up to a good 20C° from something like 8C°And the bells, metal ones made out of big gas bottles would keep heat for may be two more hours.
Mike Pop wrote:Does insulated pipe really make a difference? I would think that uninsulated would help release more heat into the room?
Yes, an insulated pipe would make a world of difference, start with the portion which is outside and the less of the pipe is outside the better it is. Uninsulated pipe will release more heat into the room, yes. But is the burn hotter because of that? No, rather the contrary. The temperature difference between the column of air inside the pipe and the outside air is causing the draft. Lower difference and the draft is weakened up to the point that the fire is creaping out of the feed. And you need strong draft to keep the fire down in the feed tube plus ramp up the temperature inside the burn tunnel. It is the same effect as the bellows blowing into a blacksmith's fire. No bellows and the iron won't get hot enough.
More draft means more air blowing into the fire thus mimicking the blacksmith's bellows and causing more turbulence in the same time so excellent mixing will occur. The fire is getting hotter up to the point that all the combustibles will be converted to heat, water and CO². Hence, when there's no visible smoke you're close to complete combustion. Black soot in the pipe means the fire wasn't hot enough to burn it all and a substantial portion of the fuel is lost as smoke. It is much easier to close the feed tube for 50% to restrict the draft as opposed to try to get the fire hot when draft isn't adequate in the first place.
Satamax explained the effect of overpressure caused by wind blowing against a closed wall. I'll second his opinion about this phenomenon.
The people from Dragon Heaters knows all this too well, and I find it hard to believe they didn't tell you so when you described the situation.
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