My Second Bench

[Prescott]

Greetings fellow rocketeers!

Here's my second bench. I needed more heat transfer to water so added 50' of 5/8" copper tubing (I paid full price, an investment! 5/8's because that is what the original heating element had in it, that was what was kicking around...)

The bench needed to be bigger too, so this is what it looks like, as well as some circulator pump images etc













The tile surround is a lovely addition, the new pump was pricey (3 Hun with shipping) but is a great tool to heat the pre existing radiant floor setup. The last shot from afar has the workings of the pump, plumbing and wiring for the floor on the left, that's how far the water travels. (I was so stoked, there was enough room between my left and right zones to run the pipes along the floor once I ripped out the wooden divider. Certainly there is some heat loss, but it's going into the floor and that's the idea...)

I have since tweaked the plenum, opened it up some and smoothed things out. It feels like more heat is moving through the bench, the draft is better at the feed tube but I'm still getting creep up. Temps on the barrel seem about a hundred higher near the top of the sides, but there is a variety of temps based on types of wood and level of dryness, it's not an exact science... I play around with fire bricks to help, stacking one up on any wood sticking out so that when then the wood burns down it "shuts off the draft". I have all sorts of carbon and burns on my fingers and hands, it's a riot...

I am gone for 10-12-14 hours sometimes and there is more heat in the house than before I had thermal mass! I have some leveling to, adding mostly sand on top to make it flat and level, a little extension for the plenum clean out, but it's working nicely.

It was good taking out the insulation and just going for a bigger thermal mass, and incorporating rock and such from the yard. I love the stonewall feel, the granite chunk is a cool step up, foot rest. I am going to run this through the winter, maybe see if there is more room to open up the plenum any more, but I am likely going to build an 8 inch system, I would more heat faster since I have so many places to put it. I am looking for more heat to get into the water, but heating water is just so dang hard!

I'm contemplating putting some tile on the barrel, slowing the heat loss from the barrel so it gets into the bench/water, anyone have any experience/thoughts on that? The barrel gives the immediate heat, but after a couple of hours it gets hot in the house, I'd rather the floor be getting that heat...

It ain't perfect, but it's working and eats so much less wood than my cookstove and costed so much less than my fancy propane heater... Winning for sure! Hope this helps and/inspires. Thanks so much for all that I have gotten from you all...

More to come, stay tuned and keep it rockety~p

[Prescott]

Feel free to follow the links to my photobucket, for some reason the landscaped photos get cropped to square and it steals part of the view... surely you're getting the gist, but there's more if you want!

[pa_friendly_guy]

I am pleased to hear that it is working for you, that's great news. To gain more heat for the water I was wondering if coiling the water pipe tight around the exhaust pipe would work. Now you gain the heat from the bench through your rock and sand, but would there be more heat captured in the water if the pipe was closer to the flue? I am asking, not trying to tell you. Just thinking out loud.

https://www.youtube.com/watch?v=AbDMITAMLio

Here is a video of a guy doing just that. His unit goes on the stove pipe of a regular wood stove, but I can't see why it would not work inside your bench. I think a steam pop off valve would be a good idea with this set up because of the potential of building up too much heat. I do not know what effect this would have on your bench, I am sure it would lower the temps somewhat in the mass. There is only going to be so much heat, so I guess the question to ask your self is where do I want it, in the mass, or in the water?

[mannytheseacow]

Lookin good, there Prescott! Is it heating pretty well?

It sounds like you've already got pipes in the floor- I can't tell from the picture, is it cement or underlaying wood? Also curious what size space you're heating and what your climate is like out there in Maine.

So it looks like you have two heat loops? Is that a heat exchanger wrapped around the flue under the outlet and then a second one with the 5/8" pipe? That's pretty awesome if you're getting some serious water heating out of it!

[Prescott]

In reply, and thank you for the comments and questions!

Yes, it would be better if the second round of copper was wrapped around the flues, but I wasn't going to that length of undoing what I had already done! As for that fellow that did the wrapping, I believe I've seen that one (that's a but load of copper!) and having done some research and conversation etc, believe that having them that close might be counter productive, and having some aluminum flashing or something would help spread the heat into the copper. I will also, when I likely upgrade to an 8", imbed all the tubing in a cob like structure.

I would like to create some turbulence in the tubing, so it tumbles so as to increase the surface area, increasing the heat transfer potential. The 5/8s copper isn't huge though so I am reluctant to bang it all up (ever so gently of course) before I know it's final resting place.

As for the heating element, I took a couple of pieces OS stove pipe, wrapped the tubing as tightly as possible around it and then made some flashing (see homemade solar panel construction if it doesn't make sense, I'm not going to explain it all here), spacing the copper a couple/few inches apart. The flashing needed to be snipped periodically in order to bend and then riveted it down, wrapped it on Roxul and then wrapped that in flashing. It works okay, again, turbulence would be a good thing, and after the fact I guess I wouldn't insulate. I was tinkering with something I saw on the RSMH videos (boom squish was the most disappointing video for me as that was the one I was most excited to learn from)

The water comes out a couple few degrees warmer, it's not hot (unless I turn off the circulator) and I made an insulated tank to hold more heat. I am thinking about pulling the tank and just sending the heat straight to the floor, the tank isn't really heating up, and just sapping heat from the floor...

I can heat the floor up 15-20 degrees in a few hours, but the house is almost too hot by then with so much heat coming off the barrel. A 62 degree floor beats a 40 degree floor! The tubing is in 2 inches of cement insulated with two inches of foil backed polyisocyanurate insulation. The floor is 600 square feet, I forget how much tubing is in there but could dig up that info. Our weather is, well, it can get heavy duty butt cold. A serious freeze means 10-20 below zero and can stay below freezing (daytime highs) for a week or two... Winter is long and dark and I am not going to live with cold feet!

I am going to have some time over the holiday break to get things heated up BIGTIME. I have cheated and assisted the heating of the water on propane AND rocket stove and with electric kettles. Over thanksgiving I was gone for 5 days and things cooled down to 45, floor and air temps. In a handful of hours the cabin was in the 70's and the floor was creeping towards 60. It took a lot of work, siphoning water and shuffling the hot in, moving cold to pots etc, but it was a fun experiment, and it felt good to chase the cold.

Ultimately I would rather be doing,that with with wood, a rocket stove, so going to see what kind of optimization I can do with the existing six inches, but feel an 8 would give those extra BTU's. time will tell, and I will tell you about it here!

Hope this helps, or at least creates dialogue, inspires and/or better rocket science~onward!

[matt walker]

Good stuff Prescott, very cool project. It's great to have you and Manny here discussing what you are learning with these systems. it's so hard to find solid discussion based on actual experience of radiant floors being driven by rocket stoves. I'm learning tons following along with you two. Overall I'd say your experience so far is fairly encouraging, 60° floors is for sure better than 40° floors!

[pa_friendly_guy]

I have another question about wrapping the copper around something. Could it be wrapped around the outside of the Barrel . You indicated that there is plenty of heat coming off the barrel, too much at times. Could the barrel heat your water and put that heat in the floor? Again, I am asking, I like thinking out load.

[Oddmar]

Check out this build...about 2/3 down there is a pic of a pretty lady taking a bath next to the RMH drum wrapped with copper tubing. http://www.flickr.com/photos/fishermans ... 122351115/

Bet no one has seen a RMH quite this large!

[pa_friendly_guy]

I had seen their build before. It is lovely and really suits their needs. They live in a tiny cabin with out running water that is heated by their kitchen cook stove. The Yurt gave them so much more space and made their lives way better. She said that being able to take a Bath in the winter was truly wonderful. The rocket stove heats the floor and keeps the Yurt nice and warm. Keeping fire in it does not seem to be a problem they said because they are either going out to fetch another beer, or they are going to the out house to leave one there. . They had many comments about their build but they were surprised that no one commented on the fact that they changed the fire box to run horizontal instead of vertical. They seem to feel that it works fine and allows them to load more wood at a time. I believe they would run more copper line around the barrel if they had it to do over again, the water does get hot, but more Hot water would be nice. All in all it was a wonderful build that truly did fit their needs.