radiant concrete floor heating

[Dan_Shade]

Planning to put up a building, want two zones, (864 and 1185 sq ft.), heating with a Central Boiler stove.

Does anyone have suggestions for supply sources for manifolds, pumps, pipe, etc...?

[doc henderson]

I will have to go to the shop and look.  factory for the pec 30 miles from here.  did 4500 sq. feet int eh shop with 4 zones but all jumped to the same thermostat with no issues.  basement, dirty car welding shop and wood shop.  left at 60 most of the time.  summer set to 50.  run forced air in the summer.  I used 1/2-inch pex.  34 x 34 garage has 4 circuits the same length.  shop is 34 x 50 with 6 circuits all same total length.  i.e. for the circuits farther away, you have to account for this to make the resistance/length the same.  you have a max length in a line based on diameter, so the overall resistance is not too high.  the lines by the walls were every 6 inches x 3 lines then 1 foot apart.

[Dan_Shade]

thanks, i'm trying to sort out everything that I need.

manifolds
tubing
mixing valve
pump(s)
thermostat
expansion tank
breather/whatever to non-pressurize the system
heat exchanger (floor will be a closed circuit)

[sprucebunny]

I put radiant heat in a house 2 years ago. Here's some of the products I used.
4-Branch Stainless Steel Complete Radiant Heat Manifold Set - PexUniverse

https://www.supplyhouse.com/Bluefin-T050-1000-OXY-1-2-Oxygen-Barrier-PEX-b-Tubing-1000-ft-Coil
I got 500' rolls. Don't see them now. This is a better price.

Taco 5002-T3, 1/2" Threaded Mixing Valve (Lead-Free) - PexUniverse

[Dan_Shade]

Do either of you have any info on how to determine flow requirements for the pump?

Edit:

I found a pump article at How to size a Circulator Pump. Taco pump curves..

[sprucebunny]

I installed all the pex and manifolds and paid a professional to plumb the boiler and copper distribution. He preferred to install a 3 speed Taco pump. I can get the number for you today.

[doc henderson]

I just replaced one and got the pump on amazon.  we have a controller in the house that prioritizes domestic hot water via water-to-water heat exchanger.  the pumps are three speed I think, and there is a high-pressure bypass as well.

https://www.amazon.com/Honeywell-PC3F1558IUF00-Speed-Circulation-Pump/dp/B006T9G9X8?pd_rd_w=QXTa8&content-id=amzn1.sym.80b2efcb-1985-4e3a-b8e5-050c8b58b7cf&pf_rd_p=80b2efcb-1985-4e3a-b8e5-050c8b58b7cf&pf_rd_r=39PKW21JSGNGR95NNXA1&pd_rd_wg=NNJXA&pd_rd_r=ff5709b6-0ca9-4e4c-909f-59ed5dcbb80f&pd_rd_i=B006T9G9X8&psc=1&ref_=pd_bap_d_grid_rp_0_58_i

[scsmith42]

Dan, when I designed the in-floor heating for my shop, Radiantec had the best information online that I could find.

Experience, Energy Efficient Technology & Low Prices - Radiantec

There is a plethora of information on their site, and I benefitted greatly from studying it.  They have online manuals that will walk you through just about everything.

Good online sources include Supplyhouse.com, ebay and amazon.  The Radiantec information will help you to decide what to buy

[Corley5]

Google Dan Holohan. He has written at least three books on the topics. "Pumping Away" "The Lost Art of Steam Heating", and "Classic Hydronics"
I  bought them before I installed my in floor heat. Mine isn't in concrete. Good books. Pex Universe, Pex Supply, and Supply House are where I sourced my materials.

[sprucebunny]

 Pumps are Taco 015-MSF3-ICF. They have a built in flow check.

[Dan_Shade]

Thanks all,

@scsmith42, did you put insulation under you slab?

[sprucebunny]

I have 2" of sheet foam and a vapor barrier under my 6" slab poured 20+ years ago. Holds heat well.

[doc henderson]

I put down a vapor barrier and 10 inches of sand.  after it dried out, dry sand is a good insulator.

[Dan_Shade]

@sprucebunny, is the sheet foam the blue or pink stuff that comes in 4x8 sheets?

is yours in a shop/garage or a basement?

[doc henderson]

we used the blue around the stem walls for a thermal break.  some say the foam under concrete may cause uneven water absorption and cause cracks.

[Dan_Shade]

Did you install it against the wall (beside the slab), or on the ground (under the slab)?

[scsmith42]

Thanks all,

@scsmith42, did you put insulation under you slab?

Yes I did.  It's best if you can isolate the footer under your walls from the main slab too. 

[sprucebunny]

Yes, I used blue or pink. There is also a 6" high band of the 2" foam between the slab and the foundation wall which is 5' deep and 2' higher than the slab. It's a garage at ground level with 12' ceiling and living space on the second level that also has radiant heat. 28' x 38' with four loops = about a foot of tubing per square foot.

One thing I failed to do was plan for cracks in a large slab. I think there is supposed to be some kind of "break" thing every 12'. Mine just cracked where it wanted and hasn't been a problem but if I'd known to plan for it, I would have.

[doc henderson]

to cut joints, you can do it as you finish the concrete with a trowel.  big slabs, we often cut with a saw, but have to be careful with pex in the slab.  We have also done blind joints by using a straight edge and a trowel.  you follow the line or edge and jab along the line and separate the sand in a line and can finish back over the top.  on the second floor of my shop, we did 1.5-inch sleepers to screed off of at 8.5 foot intervals.  we fastened the pex to the plywood with clips.  poured fiber reinforced concrete over the top.  very little cracking.  One on a dog leg that gets narrow along a stairway opening.  to find the pex later, you mop the floor, turn on the heat, and l ook for the pattern of the fist places to dry.

[nopoint]

Few bits of advise. Don't over complicate things. I have four loops of 1/2" pipe in a 40x50 shed. At concrete cuts/joints I put a short piece of pipe insulation on pex pipe to allow a bit more flex room. Have a a basic manifold from supply house and one pump that circulates. Floor has antifreeze and wood boiler does not. Use a simple plate exchanger. I didn't really understand the ins and outs of a pressurized system so I simply have a piece of copper pipe with a loose fitting cover that acts as a stand pipe. This allows for expansion and contraction of antifreeze in floor loop. Pump is controlled by simple 120v thermostat on wall. I have no zone valves or other electronics involved. I have 3 speed pumps but I believe they are all on high... Not saying any of its "correct" but its been working problem free for 10 years or so.....