what kind of tubing for a radiant floor

Discussion in 'HVAC Heating & Cooling' started by wallyworld, Jan 10, 2009.

  1. wallyworld

    wallyworld New Member

    Messages:
    21
    Hi
    I'm planning on building a shop, 30 by 34, slab on grade. I want to install tubing for a radiant heat in the slab. What do you guys recommend for the tubing? I see all kind of different kinds of Pex tubing, so I'm not sure what kind?
  2. Paso One

    Paso One New Member

    Messages:
    10
    I used Oxy pex 2 zones as per attached pic

    Attached Files:

  3. wallyworld

    wallyworld New Member

    Messages:
    21
    Thanks for the reply
    I heard a rule of thumb, one foot of pex per square foot of slab, sound correct? What size tubing should I use?
  4. frenchie

    frenchie Jack of all trades

    Whoah... there's no rules of thumb for this. It depends on the amount of insulation you have, how many windows, how well air-sealed the building is... a whole bunch of things.

    You start off with a heat-load calculation, and go from there.

    Worst thing in the world would be to get alll your tubing in, then discover there wasn't enough tube for your heat load, or the loops were too long to circulate, or something else was so wrong you had to do it over.

    A couple of good places for basic info:

    http://www.healthyheating.com/

    http://www.warmair.com/html/radiant_floor.htm

    http://radnet.groupee.net/eve/ubb.x/a/cfrm/f/2771065301

    http://www.radiantpanelassociation.org/i4a/store/category.cfm?category_id=1

    http://forums.invision.net/index.cf...a-944e-48d9-a5f5-ce92a3b15927&CFApp=2&reset=Y

    http://hvac-talk.com/vbb/index.php?

    Heat-loss calculations - general info and online calculators:

    http://www.hvaccomputer.com/hvac/hlhg2.asp

    http://www.diydata.com/planning/ch_design/example1_imperial.php

    http://www.heatload.com/html/heatload_workshop.html

    http://www.hvacloadcalculations.com/

    http://www.slantfin.com/heat-loss-software-calculation.html

    http://www.trademate.co.uk/Services/HeatLoss/default.asp?_brand=CP

    http://www.bgmsupply.com/calculateheatloss.asp

    You might need these tables:

    http://www.hvac-toolbox.com/us-outdoor-design-temperature-humidity-d_296.html
  5. wallyworld

    wallyworld New Member

    Messages:
    21
    Thanks again
    What I'm trying to do is build a shop. Its going to be slab on grade, 34 by 30, one 10 by 10 insulated overhead door. A few windows, not many though for security reasons, one 3 ft entry door. It will be well insulated, 12 foot walls. R 33 walls and R 44 ceiling. I'll probably put a woodstove in it so the radiant won't carry the load. What I'm thinking of is homemade solar collectors covering the south facing wall. Here is the site I'm using for the collectors
    www.builditsolar.com

    I have a friend who can help with some of the design, I'm just trying to get general ideas. I have no illusion that the solar will heat this building but it would be nice if it kept it above 32.
  6. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Jeezus Frenchy, did you miss any links there :D
  7. frenchie

    frenchie Jack of all trades

    Yeah, I need to thin out the bookmark folders on this computer. Last time I transferred my bookmarks to a different computer, the file was 2.10MB.

    I probably just gave him a half-dozen different calculators... oops? Pick & choose at will, I guess.
  8. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    You missed the most important thing.

    You need 2 to 4 inches of insulation under the slab.

    More zones and/or larger pex will reduce pumping costs.
    More pex will improve heat transfer.
  9. wallyworld

    wallyworld New Member

    Messages:
    21
    2 inches under the slab and 2 inches on the perimeter of the slab is the plan so far.

    With multiple zones do I need a pump for each zone?
  10. alternety

    alternety Like an engineer

    Messages:
    651
    Location:
    Washington
    No you can use a manifold (just a feed pipe with places for the valves) and electrically driven valves. The thermostats will need to drive the valves so external power is probably required for the circuits. Usually thermostats only switch power, not supply it. If the loops are not going to be controlled independently, just a manifold to get them in parallel.

    You will already have some power source in there to control the pump.
  11. frostnip

    frostnip New Member

    Messages:
    18
    there is a manufacturer called wirsbo that makes the tubing as well. I worked as a helper at an HVAC place one summer and saw some cool things done with it. One home had the driveway as a zone to keep snow and ice off.

    I'd love to set up radiant floor heat here but I would need to save and the house needs a lot of other things first.
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