plan for a future outdoor wood burner

[Carpenter]

     Hi all,

I am in the planning stages to build a wood working shop.  Eventually I would like to get an outdoor wood boiler, like a central broiler or other brand.  The shop will be located close to the sawmill and my solar kiln, and if it has enough heat left over I could potentially pump some to the house.  I would like to be able to throw slabs into it off the mill, (not green off the mill, they could have time to dry), but that should keep some of the moving around to a minimum.  I think I could retrofit the kiln for some additional heat in the winter.  The house is approximately 200' from where I plan to put the outdoor wood burner, I don't know if I can actually pump heat from one that far, but if not, we have been heating entirely with just a wood stove for several years anyway. 

My main question is for the shop, I plan to pour the concrete and would like to put a heated floor in it.  But, I probably won't have an outdoor wood burner for a few years.  How do I leave allowances to hook this thing up at a later date?  I understand that a radiant floor system should be done in loops of a certain length max, and that then there can be zones.  For the floor itself should I just run pex in loops to start and end at a certain point sort of like electricity is run from and back to a breaker box?  That question really seams self answering.  But, it will leave me for a few years with pex tubes just sticking out of the concrete.  I would assume that under normal circumstances these tubes could be hidden inside a wall, not so in this case, this will be a timber framed shop with planked walls, 1 1/2" tongue and groove with some foam over that, then sheeting and siding.  So, the electrical will have to run in conduit or a chase in some cases, and I can build a chase for the pex tubes.  Also, why do people use pex for a radiant floor?  I would think that flexible copper tubing would transfer more heat.  My main concern is the actual main hook up from the wood boiler to the control panel.  I have no idea what I need there.  I am assuming that the water line needs to be buried below the frost level and come up through the concrete.  My idea is to bury a piece of pvc tubing below the frost level that comes up in the building, and eventually run the supply lines from the outdoor wood boiler through that.  I just really don't know what size of pvc I need to run. 

Thanks guys, I know these questions are a little vague.  I just want to rough the system in for now.  By the way, the shop will be 44'x56' with a 32'x56' loft, and in the future I may add another 12'x56' wing to it, it will look like a barn.  I don't really need it super hot in there either, just a comfortable working temperature, I don't mind wearing a jacket, but occasionally it does get to 30 below here, and those are the days that I would really like to be working in the shop.

[thecfarm]

Lines do not need to to buried below frost line unless you want too. My lines I dug out with a shovel,about 18 inches deep with some red danger tape about a foot down to warn of electric wires and piping. The circulators run steady,so they can not freeze. I run conduit piping for my wires. I have no idea how that pex piping would do out in the weather with the sun. Any piping would need a cap on it,to keep out the weather,dirt and bugs and small animals.
I would start researching OWB. I looked for years before I decided on Heatmor. I even would stop at someone's home,if I saw them out at thier OWB and ask them questions about it.

[Roger2561]

I have a Central Boiler OWB.  If you go to the Central site, they have diagrams that show you how to hook up an OWB to the radiant system as well as other ways to heat a house, shop, domestic hot-water, etc...  But, agree with what said; do your homework before settling on one.  Ask questions, seek out those who have one and see how it works.  Good luck in search.  Roger

[Ford_man]

I used 5/8 pex in my floor (40*60 16ft high) . Use lots of insulation it is your friend./ I used 2 in hi-den under the cement and 3 ft down inside the foundation walls. doing it over I might use 3 in under the floor. the walls have 8 in bats and the ceiling has 18 In blowed in.

[Don_Papenburg]

Copper and wet concrete do not mix. It tends to destroy the copper . Pex last a lot longer than copper in heating .  it also has more give incase of cracking .  But make sure you reinforce the slab so it does not shift if/when it cracks.   Use the largest pvc that you can find  like 6" for the incoming tubes , gives a lot of room for push/pull tubing and add insulation at a later date.  Any more I would not go smaller than 4"  and do not use 90* elbows.   Use 22.5s or 45s with a short length of pipe to connect.   put a nylon or poly rope in the conduit when you install it and tie it off on each end .  Give Radiant tech a look on the net . they have a lot of good solutions ,plans and products that you can use copy or purchase.

[WmFritz]

Carpenter,

                    200' to the house is not far. Just make sure to use quality insulated underground lines so your not wasting btu's.
 
The length of your loops are determined by the diameter of the pex you use, i.e... for 1/2" the max loop length is 300';  250' is better. The bigger the diameter of the tubes you install, the more advantages there are. You can extend the loop lengths, space the tubing farther apart and run smaller (lower wattage) pumps.

One example of a pex layout with 1/2" tubing, 12" on center in a 2500 sq. ft. slab... would equal 10 loops total.

[KamHillbilly]

My boiler is 250' from house , like previous post use well insulated lines

[Hackermatack]

I have done a half dozen radiant slabs. Standard procedure is to insulate the slab with 2" or more of foamboard. Efficiency experts are now encouraging 4". The 1/2" radiant pex comes in 300' rolls which is about rite for a loop, most plumbing supply houses will have a stapler made special for stapling the pex to the foamboard that they will rent to you. You will want to start and end each loop in the same location where the manifold will be installed. Short 1" pvc conduit sweeps work well to protect the pex where it exits the slab, just slide them on over the pex to form a nice neat 90 degree bend. It is a good idea to hook the loops to your manifold before pouring the slab and pressurize the system with 50-80 psi air pressure, this will help prevent the tubing from being crushed while pouring and will tell you immediately if you have ruptured the pipe. Twelve inches is about the rite spacing for the radiant pex, I like to start with the portion of the slab furthest from the manifold, run my pex back and forth across the building and when the roll is nearly gone make the home run for the manifold, this helps make the manifold area less cluttered and helps eliminate the need to cross pipes (no harm in crossing them if necessary. You can find all kinds of piping and layout ideas online, I will try to answer any questions you might have.