Wood-Fired Radiant Floor Heat

We have a wood fired hot water heater, built by Amish. This is a heavy iron double barrel that you feed a fire to heat water:
http://www.lehmans.com/store/Stoves___Cook_Stoves___Hot_Water_From_Your_Stove___Hot_Water___x2D__System_Two___26845?Args=&customField1=W9
It has a pressure gauge, vent pipe and is operated outdoors, with the hot water moved indoors via a garden hose. It is very effective, we have had ours since 1999.
My question is; can we utilize this unit for a radiant heated floor? We would install PEX tubing under the floor boards. I've seen this application done using an on-demand water heater very successfully.

My neighbor uses his indoor wood stove to heat up water for his radiant floor heating. I'll see if I can't get some pictures of his set up and pex manifold.
We put inan on demand water heater when we built our house to take advantage of the radiant floor heating application farther down the road.

Two things to be aware of. PEX can't take temps over 130, but I'd run it no higher than 125. This means you'll want a mixing valve to control the temp going into your piping. Second, you want to make sure there is no air in the lines or your pumps won't move the water. Most heating systems are closed loop and use a special valve to take air out of the lines.

I agree always err on the side of caution with any thing hot and under pressure. The pex-al-pex I purchased is rated 180 degrees @ 125psi well above any radiant floor system requirements.

I installed radiant floor heat in our kitchen using a "kit" from http://www.radiantec.com a few years ago. I'm fairly handy and it was easy for me. Okay working in a 2' crawlspace wasn't, but... I found the product good, but the instructions lacking. I was glad to have a plumber friend give me advice in how to best hook into the boiler. The instructions they gave me on that part was very weak.

Most boilers for hot water heat run at 180F so your wood boiler should do just fine in creating hot enough water.

Thanks for that link, Silver!
That worries me about the connection, too.

We have a combination of shallow crawl space under part of the house and a slab for larger portion. We are placing a sub floor over the slab and want to install the system at that time.
The crawl space is only 12" deep so I've been slowly excavating with a cement hoe and 1 gal bucket to deepen the space for access.
I'm not sure if something extra is needed in order for the system to transition from slab to crawl space.

Robert Ray wrote:
My neighbor uses his indoor wood stove to heat up water for his radiant floor heating. I'll see if I can't get some pictures of his set up and pex manifold.
We put inan on demand water heater when we built our house to take advantage of the radiant floor heating application farther down the road.

I would love to see his set up!
What would he do in case his wood stove goes out? For instance, if an emergency came up and the wood stove was allowed to completely cool down? I assume it would continue looping with cool water.

His house has a monolithic slab floor so the pex was looped into the concrete during construction. Once the slab is warmed up it retains heat for some time.  He should be back next week and I'll post pics. I think he has construction photos still.
He constructed a stainless heat exchanger that bolts to the side of his wood stove so it is something he could remove and place on another stove should the current one fail.

Another place to get PEX supplies is http://www.pexsupply.com. In the past I've found their site much easier to locate parts I want than the manufacturer website. The prices seem reasonable. But going here, you will have to know exactly what you want. I don't think they help you, but it would be worth asking. They are fairly interactive via twitter.

Amadou wrote:
That worries me about the connection, too.

It wasn't hard, they just didn't give any details. Had I not had a really good plumber as a friend, I'd have probably asked for more details. If you get to that point of needing help, let me know and I can try to explain what we did.

The crawl space is only 12" deep so I've been slowly excavating with a cement hoe and 1 gal bucket to deepen the space for access.

I don't envy that job! Make sure you have enough room to roll over well. It was easier to work in there before I put up the insulation. After that the space felt a lot smaller! I was in fairly good shape at the time and I was glad. It took a lot of physical scooting on your back to feed the pipe. My helper struggled quite a bit.

I'm not sure if something extra is needed in order for the system to transition from slab to crawl space.

You will probably want a separate zone for each. The max space you can heat on a single loop is 200-300sq ft. They will also have different heating characteristics.
Best of luck
Jim

Amadou wrote:
Thanks for that link, Silver!
That worries me about the connection, too.

We have a combination of shallow crawl space under part of the house and a slab for larger portion. We are placing a sub floor over the slab and want to install the system at that time.
The crawl space is only 12" deep so I've been slowly excavating with a cement hoe and 1 gal bucket to deepen the space for access.
I'm not sure if something extra is needed in order for the system to transition from slab to crawl space.

We're considering something similar, but solar heated. 

We're planning to put ours in over top of the existing slab - it will take a few inches of height, but it's really the only way to do it and I hate walking on the slab-on-grade all day. 
We're doing a poured earthen floor (I know we said we'd never pump water through earthen masonry, but warm mud would be almost an improvement in this particular situation).  So jointless pipes will be a priority, and we may create a "box" for the connections that's easy to access for repairs.  (We've had good results with decorative tile or slate set into earthen surfaces, with one tile hiding the maintenance area).

Wish you luck, and hope it goes well!

-Erica Wisner
http://www.ErnieAndErica.info

Erica Wisner wrote:
We're doing a poured earthen floor (I know we said we'd never pump water through earthen masonry, but warm mud would be almost an improvement in this particular situation).

I'm familiar with rammed earth floors on slab using a small amount of cement as a binder but not "poured earth".  Can you describe how this works, perhaps in the alternative building section, please.  I'd think in drying you would get cracks and it would flake.  Love to learn something new.