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New to radiant heat.... HELP

I am new to radiant heat. I recently installed a radiant heat system to heat the downstairs of my home. I am attempting to heat roughly 900 square feet of floor space with 1/2 pex tubing 8" on center between the floor joists, with heat plates. I just started the system up the night before the temps dropped to 30 below (uncharacteristic for this area) and the house did not have heat before (its a remodel I am working on). My question is how long will it take from a cold start for the floors to start warming the lower level? My 99,000 BTU boiler has been running for two days straight.....HELP!


  • kcoppkcopp Member Posts: 2,744
    A few hours....

    Did you put insulation under the floor joists.?
  • Rookie123Rookie123 Member Posts: 5
    Cold house

    Yea, I insulated all the joist bays with R19. The house literally had no heat so it was very very cold inside when I started it up. I have the thermostat set to 60 right now and it has run the entire time and we have yet to reach 60 degrees.... not sure if this is normal for wood floors.
  • kcoppkcopp Member Posts: 2,744
    How long are the ....

    loop lengths? How many loops? What circulator? What temperature going out?
  • IronmanIronman Member Posts: 3,403
    Need a Lot More Info

    First, let me say that radiant takes a long time to bring a structure up to temp even in moderate cold weather. Waiting til record cold to turn it on was, well... not the best decision you've ever made.

    Now, we need some specifics:

    1. What is the heat loss for the structure? Was a scientific load calc done?

    2. How much tubing is in the floor? It should be around 1350' with 8" centers for 900 sq. ft.

    3. How many loops?

    4. What are the supply and return water temps?

    5. What type of floor coverings?

    6. What size circulator?

    7. Is there any other heat source?

    8. How is the boiler/system piped?

    9. What boiler?

    10. Why a 99k btu boiler on floor that can only emitt about 27k btu's at best?

    11. What's controlling the supply temp to the floor and what's it set at?

    12. Please post some pics or a diagram of the boiler, its near piping and the manifold(s).

    13. How much/type of insulation under the floor?
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • Rookie123Rookie123 Member Posts: 5
    cold house

    I have five 300ish feet long loops. I have steibel eltron circulating pumps and the outgoing water right now is 145ish and the return back to the boiler is reading 130. It seems like the water is plenty warm its just not heating up...seems like it should have warmed by now...
  • Rookie123Rookie123 Member Posts: 5
    don't beat me up too bad!

    I have about 1400 feet of tubing 8" on center with heat plates. I have 5 loops. supply is going in a 140ish and returning at 130ish. I have wood floors with scattered thin area rugs, no pad. No other heat source besides a wood stove in dining room that I am blasting to try to assist. Its a quiteside boiler with 3/4" supply lines that dump into a hydrosmart panel with 1" lines that run to manifold to supply my 1/2" pex tubing. My boiler has a control panel that I can set the water temp on and then the thermostat tells it when to cycle the pumps. R19 insulation under entire floor area......thanks for any input....
  • GordyGordy Member Posts: 7,109

    Iron mans questions need to be answered to be helpful.

    The big thing here is under floor radiant. You have plates that's a good move. Are they extruded or stamped? I think iron man is being generous with 30 btu sf output for underfloor depends as he says how much r value you are pushing through.
  • IronmanIronman Member Posts: 3,403
    No Beating

    Just need info to correctly advise you. What you've supplied so far sounds good, but the big thing is the heat loss calc. Without that, you're shooting at bats in the dark.

    A scientific heat loss calc is the foundation to all design; it's necessary for sizing and designing everything in the system.

    If you're experiencing -30* temps, I seriously doubt that there's a radiant floor anywhere that could keep up with that.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • kcoppkcopp Member Posts: 2,744
    are you...

    sure you have all the lines purged of air?
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