Some Questions/Observations

[rjdudley]

We love our RMH. Really love it.
But, as we burn and heat up the mass how does everyone think it should be done?
Do you think: a) Burning hot, like 600-700˚, and really pouring heat into the bench or b) Do lower burns, like 400˚, and allow it to charge more slowly? I ask because if I burn it really hot then the thought of too much excess heat going out the stack makes me crazy, but, with the amount of mass we're charging it takes hours to hit about 130˚.
And that brings me to my next question: What is a decent bench temp. for all day radiating heat? My cathedral ceilings aside, my heater is also in an open room with dimensions of about 20 x30. When the bench is at 130˚ the radiant heat isn't really noticeable after the fire burns down unless you're inside 10 feet.
How hot can a bench get and still be usable to sit on, but, generate the 12-14 hour heating effect we hear about?

Next question: has anyone tried to burn newspaper logs? Would they generate too much ash or would the rockets intense heat diminish that? Newspaper is pretty cheap/free and newspaper logs burn fairly well.

Observation: we're noticing that we get alot more ash in the burn chamber than I thought we would. Certainly more than that woman that has a paper lunch bag that she hasn't even filled after one years burning! It's less than the wood stove used to put out and I'm not complaining, just observing.

[mannytheseacow]

I've had some similar observations, Ray. I get way more than a bag of ash per season, but what I'm getting is waaaaay less than what I was producing before. I'm burning pretty consistently from day to day at this point and I'm getting about 1/4 cup of ash per day, or a 16oz cup of ash a week. One thing I've noticed is that if I don't clean the ash out, it seems to go away! I don't want it blocking up my system but to some extent it does seem to combust if it drifts further down into the burn tunnel. Also, I've read in several places not to burn newspaper any more than you have to. I haven't tried to burn paper logs. I keep my burning limited to 1 or 2 sheets at startup and that's it. I should have prefaced all this with the fact that everyone's fuel is different, so that will be a major factor.

The major thing I have noticed is that my bench seems to have a sweet spot. Don't dwell too much on my bench temperatures because I have to monitor those at the cold spots.... My bench doesn't take much to get to 86*. It will get there fast and stay there for a long time. After that, I've noticed that I can burn really low (barrel at 250*-300*) or really hot (500*+) and I will see little change in my bench. Of course, the longer and hotter I burn the more instant heat is given off from the barrel, but it has little impact on the long term bench heat.

My goal is two fires a day. Once in the morning and once in the evening. We've had our coldest outdoor temp so far last night at 16* and I'm still doing okay with just the RMH for my whole house. So, the scientist in me is thinking.... there's got to be some golden ratio here!

Just for the sake of others that are planning on building RMHs, it would be great if everyone currently using RMHs could post their data here.

Here's my data and a brief explanation:

I'm guessing there is some key with how many cubic feet of space you're trying to heat, how many cubic feet of bench you have, the surface area of your heat tubes in your bench, and how many degrees you are trying change between the outside air temp and the inside air temp.

For me, I have 11,480 cubic feet of house to heat, 100 cubic feet of bench, 70 square feet of surface area in my tubes, and I'm trying to raise the temp in my house an average of 50* (20* outside, 70* inside).

So, my ratio is like: 100 : 0.9 : 0.6 For a 50* change.

I'd like things to be a little warmer, so if I were to do this all over again I think I would go for a little bigger bench and a little more surface area in my tubes to transfer that heat into the bench. So for my 6" system, and a 50* temperature change, I bet a ratio like 100 : 1 : 1 would have been closer to what I'm looking for. Anyone else care to share?

[mannytheseacow]

[hpmer]

Ash is the non-combustible part of the wood, so if you have less as the days go by if you don't clean it out, I suspect that's because the stove draft is blowing it further downstream.

That has to be what is happening to that woman's stove. Ash is just a fact of life when burning wood and, if it's not in the burn chamber, it had to go somewhere. Some may have made it up and out the chimney, but I'd bet most of what's missing is "stored" in the bench.

As for newspaper I can say from experience that papers do generate more ash. I think that's because they have some clay as part of their make-up. For me that's not necessarily a bad thing as I collect the stuff to use in future stove building projects, but it does present other challenges.

[rjdudley]

I'm really liking this thread.
As a recap of things I've read/learned/heard about RMH's: they can provide heat for many (12-24) hours after the burning, they burn very hot and therefore produce very little ash and also carbon dioxide & steam as by products, you can burn sticks and have great heat AND someone (Ianto Evans) once heated his house for a whole year just on junk mail.

Now having had mine for several months I've come to the following conclusions:

They DO in fact provide residual heat for many hours following the burn BUT the amount a room is heated is predicated on the size of the room needing to be heated. My bad. I'll be doing Mannys (aka the Steven Hawkings of our RMH thread) math shortly, but, I should have considering the impact of my vaulted ceilings in my equation.

The ash. Where to begin here. It would seem to me that much talk is given about the high internal burn chamber temps. This can be somewhat misleading in that if you're not constantly burning at temps where the barrel is say 700˚+ , but, actually doing much lower temp burns (say 300-400˚) then isn't more ash to be expected? Lower temps = less material that will completely burn. Some things take the higher temps for complete combustion. So REALLY dry wood with a REALLY hot burn in a REALLY small space would be optimal.

Forget the sticks, because unless you live in a phone booth (do they still have those?) it ain't gonna happen.

Ianto DID heat his office for a year with junk mail, but, my research says it was with a rocket heater not a rocket MASS heater. I could be mistaken.

The worse case scenario for us here is that we now have a much more efficient wood burner. I'm VERY happy with that.

[freedomlives]

I have both of Ianto's books, and the cob cottage he describes is small. We've actually used far less wood than neighbors around here, even with a really inneffecient/inapropriate repurposed old stove that was supposed to be burning coal, but we only heated our office and bedroom those winters. Right now (due to renovations) we are moved around and are in the guest bedroom next to the kitchen, and having added insulation to the attic, we keep warm without using tons of wood in the kitchen stove, but still just two rooms to heat-- we'll see how the rocket stove does once I install as part of the renovations...

I just wanted to highlight what someone else said-- ash is the portion of wood that is not combustible, which means that temperature of combustion doesn't really matter, the same mass of the same species of wood is going to produce the same amount of ash. Of course ash is very fine particle size, so maybe with a hot fast burn it does get blown out the chimney. Though, also, ash is the greyish stuff. Anything black in your ash is charcoal, which could still burn. I suppose a colder fire is more likely to have coals that burn down to small pieces and then go out before complete combustion leaving sand grain to BB sized specks of charcoal.