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Long time to get max heat output?

Posts: 126
Location: Springfield, mo
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Well I am finally nearing a satisfactory operational state with my rocket mass heater in the greenhouse. If you were following my other thread Autopsy and redesign I haven't done any more changes since the last post there. I have easy startup, am getting pretty good draw (though not especially rockety sounding), no smoke back and relatively high barrel temps (up to 800+ with 2" barrel/riser gap).
However it seems to take somewhere around 3+ hours to get there, which is about all I can take of continually tending a fire > . I don't know if it would get any hotter if I burned longer, but I suspect it might. I can get barrel top temps of 500 in less than 30 min, and about every 45-50min it'll go up another 100deg. It doesn't really matter what the outside temp is (5 or 45) so I don't think it's a cold plug in the inground exhaust duct.
It takes the extended burn time to get the mass up to 120-130deg (at least the first few feet of it) from an average daily start temp of 65-70. The vertical stack temps were it comes out of the ground outside are maybe 110-120.
If I could get higher temps quicker I could get the mass hotter sooner and not have to spend sooo much time tending the RMH fire. I have to keep the fire going in the house as well, and some times the shop too! 3 fires at once is quite a chore. Doesn't leave much time for anything else productive. Between collecting, cutting, splitting and burning wood I'm about worn to a frazzle I suppose having the coldest, snowiest winter on record for SW Missouri doesn't help either.
Posts: 4154
Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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John Adamz : I Think you are doing o.k. considering, with the incredibly larger Heat Sink that is your Thermal Mass, 4 Hours - 5 Hours, to get 19 - 20 hours
of heat is really not that bad! I think you should be measuring how long your system holds its temperature, rather than your units speediness ! You are not
dealing with high moisture content of the surrounding soils are you?!

Your Barrel temps do seem low, you are still running it on inside air correct ?

Wow, I stared at this screen for about 1/2 an hour and nothing else came to me except how much better prepared you will be for next year after this one ! Thats a lotta
help, HUH ! For the Craft ! Big AL !
John Adamz
Posts: 126
Location: Springfield, mo
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Allen Lumley-
The floor/ground in the greenhouse is fairly dry with the exception of maybe a foot of the perimeter when the snow melts (or just plain rain in the future).
I'll be modifying the perimeter drainage when weather permits to hopefully eliminate any water inside the dome.
When I ck'd the mass temps it went from 125 to 100 after around 5+ hours.
Yes I'm using inside air for combustion intake. I was reading the thread about cooling the feed tube since I have zero cob in that area now (just the firebrick) but I don't really have a problem given the type of small oak chunks for fuel I'm using.
I was just thinking that the barrel temps should peak out relatively quick regardless of what the temp is in the mass. I say that since I don't really notice any increase in draft flow at the feed tube (rocketiness) or watching the steam exit the chimney stack shortly after startup or hours later.
I need a new interior decorator. This tiny ad just painted every room in my house purple.
Rocket Mass Heater Manual - now free for a while
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