RMH quest...any suggestions, please ???

[smallhagrid]

Hi Folks.
I am delighted to join here so I can ask some questions, there's just not too many places where folks discuss RMHs !!!

After reading, watching and asking around about RMHs for over a year I am finally in a place where I need to set up something better for the winter's heating.

It is an old house and the chimney is quite far from the center of the house where the wet walls are and that is where the heat is very much needed.

Presently attached to that chimney in a distant & closed off room is an older, no-name box stove.

One of the thoughts I'm having was stimulated by the hybrid stove + rocket video made by Ernie and Erica - but I've found almost no other info along those lines...I wonder if there even is any more info to be found about that idea ??

Two ideas are rolling around in my mind, both involving using a small central room with no chimney for the heating location:

1. Make some sort of brick & barrel 100% home-made rocket mass heater.

2. Make the old stove into a hybrid for this season so as to more easily use the prepared cord of wood that is already on hand without needing to split it into slivers.

The problems I need to solve are...:
A. The room is quite small so any mass needs to be very compact.

B. Getting the exhaust as cool as possible so it can easily/safely be vented out.

Besides the old stove I have 30 & 55 gallon metal barrels, some stovepipes, a big bag of perlite and a length of that accordion stuff I was going to use for the exhaust at my previous place where I had better space for a thermal mass.
There's also lots of odd rocks around here too so I could also use those as part of a thermal mass.

I'm assuming that no matter what else I'll likely have to buy some bricks, mortar and other smallish stuff.

One other pertinent fact is that my situation is one of being a caretaker with no income presently due to previous long-term illness, so I am trying to be as frugal as possible here.

Thanks for any help & pointers.

[mannytheseacow]

I'm no expert, but here's my thoughts:

Could you run your flue into adjacent rooms horizontally through your mass? I would think that you would want to maximize the size of your mass to reduce exit temps and keep as much heat in the house.

A few particulars about my RMH and info- 6" system, 23' of duct, 3.6 ton mass, exit flue temps when pushed as hard as I can are 110*F.

[matt walker]

Welcome SH, glad to have you here. I read your similar post on Donkey's board, but frankly, it's so general it is hard to give you much pertinent advice. I think you will need to make some decisions and start heading down a path before you will find what's going to work best for you. That said, a couple thoughts. Forget modifying the old stove. I know the RMH's seem daunting, but once you get into building one you'll find that there's really not much to it, and they really do burn amazingly clean, which is why it's possible to do so much with the heat. You've got bricks and barrels, I say get a big fire going outdoors, burn off the paint on those barrels, and stack up some bricks and make yourself a little test RMH outdoors. Once you get that far, you'll be a lot more comfortable and will probably have a lot better idea on how it might fit in your space. There are a lot of ways to get the heat in the house, horizontal flue run through mass, barrel/bell radiators, brick bells, and so on. We can certainly talk you through any of those, and all will result in cool exhaust and the majority of heat in the house. So, I guess my answer is, just do it. What "it" is, we'll figure out along the way.

[smallhagrid]

Thanks Folks !!!
Unfortunately 1/2 of the problem(s) I face with this desired deployment is that the target room is only about 10' x 10' and has doors diagonally placed - and both are needed; worse still, the refrigerator is in there as there is no other place for it in the house (refrigerators belong in kitchens - really ?? Surely you must be joking !!!).

My main thought is to emplace -whatever- this project becomes right in the center of the room with exhaust/mass/etc. in between it and the window - as there is no other direction available for it to go except UP - so I could run something upwards, and then run that same something back down to the window for exhaust ???
(I'd have to use an electric fan to suck the heat out of that room - but that would be OK too.)

Boiling it down to a question then:
Would something like a small mass followed by a sort of ring of tubing above it which then goes back down to exhaust seem possible ???

As mentioned before - there is already a cord of dry cut/split stove-sized hardwood on hand, and making that into slivers small enough to burn in a typical RMH burn tunnel seems like ALOT of extra noisy work to annoy the downstairs neighbors with - that alone was my basis for considering re-using the nasty old stove for this season only.

Thanks.

[matt walker]

Hagrid, I didn't mean you should abandon the old stove, just use it as is until you get farther along on this project. I would say don't bother trying to modify it. You can also build a batch loading RMH which will take the larger fuel. They are a bit more complicated to build than a J-tube, but nothing too tough.

So, let's get you started on something that might work in your small space. Given what you've told us about the materials you have on hand and the space available, I suggest you consider a combustion unit of whatever you can manage, cast insulated is better, but if you have bricks to stack, that's a start. Enclose that combustion unit in a barrel and a half stack or so, exhaust out from there into another barrel or barrel and a half stack configured as a bell. I have a similar set up in my bedroom right now, and while it doesn't provide the long heating cycle that a large mass does, it does put a whole ton of heat into the room and the exhaust flue never has gotten higher than 150°F on the outside of the pipe. Easy to route that through a temporary window pass through. I stacked bricks inside the second barrel bell and that gives me about 400lbs. of mass for a small thermal storage battery. It's dead simple, has a small footprint, and puts a ton of heat into the space. So, there's a starting point for you, just one way you could go, but it could go together in a few hours and you could see how it works for you.

[matt walker]

Like so.....

[smallhagrid]

Thanks Matt.
The old stove is in a bit of an impossible situation as it puts zero heat where heat is needed - so it equals using a great deal of fuel as inefficiently as possible to create waste heat that is needed elsewhere - but that isn't going to get the heat.
(It's really rather silly.)

Thank you so much for posting that wonderful diagram of what you're using !!!

I was drawing a blank even after reading your description several times...it sounds wonderfully simple, but I just could not picture how all that went together AND fit into a small space - but now it makes sense, thanks.

Questions=>
Is there any perlite, mortar or other additional material used in your design ??
What have you used to seal joints and such, please ??

Edit:
Do you think that for the 2nd barrel in such a setup a 30 gallon one would be OK ??

Thanks.

[matt walker]

Well, as for perlite and mortar, ideally yes. I really don't think bricks make a good core at all, but if you've got them they might get you up and running quickly to get a feel for how things work. Ideally, this design would have no bricks and be a cast insulated core and riser. You can find my videos on how to do that here on the forum, and we've got some great examples of builds from other members. I would rather not go too far into the details here of how to build a good burning core, there are lots of options, but the gist is insulated and no leaks, from the feed to the top of the riser. As for seals everywhere else, well the first barrel would have to be cut to let in the core. You could then use cob to seal around the core where it interfaces with the barrel. The other junctions would all be flue pipe to barrels, so foil tape would do it, although I might be inclined to bed the whole lower sections in cob just to make the joints tight and to seal everything up. In that way you could have open bottom barrels set and sealed in cob. Makes things pretty easy.

[matt walker]

Oh, yeah, the 30 gallon would probably be a better place to start actually. The one I use with the large barrel is maybe radiating too much heat which puts a bit of a load on the system since the exhaust is so cool it doesn't have as much stack effect as it might otherwise.

[smallhagrid]