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Multi temp loops question

Hello. I am new to this site. I am a P&H contractor (sole proprietor) near Denver. I am doing a whole house remodel for a data systems contractor friend. This house has a in-slab radiant zone, a baseboard zone, and 2 separate staple up zones. Also have a side arm water heater, and using a Triangle Tube Prestige.

We decided to install the staple up (pex-al) tubing suspended 1-5/8"down below the sub floor by installing 2x4 backing on 4' intervals. My question is, since the tubing is not touching the floor and heating the joist cavity (insulation barrier below), can I run it with the 160*-180* baseboard loop off my manifold? The slab loop will be mixed down to 120 or so. Client is installing engineered hardwood flooring.



  • SWEISWEI Member Posts: 7,356
    Suspended tube

    is a really bad idea -- especially when you have an embedded tube slab in the same house.

    Has anyone done a room-by-room heat loss?  Where did you get the 120ºF number for the slab?
  • ZmanZman Member Posts: 3,476

    Swei is correct ( again)

    How far along are you?

    A heat loss should be done.

    Condensing boilers don't condense at high temps.

    High temps and dry climates are brutal on hardwood floors

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Reply

    Yes, we did a heat load calc. House is totally gutted so all new insulation, good windows, etc. Unfortunately, floor/ceiling height in it (1 story) is under 8' framing, so he did not want to pour a floor. Does not like baseboard either. I don't like staple-ups (suspended in this case) either, but that is what this is. Mis-typed, in slab zone will be set at around 130; common for this area. Doing a primary loop with secondary loops for the different temeratrure zones per TT's design manual.
  • IronmanIronman Member Posts: 3,408
    I Third

    The slab must be controlled by either a smart valve or variable speed mixing and outdoor reset or else it will over heat for hours after the thermostat is satisfied.

    The staple up should have been attached directly to the bottom of the floor with heat transfer plates. Doing it the way you're describing will greatly reduce the output of the floor (probably to where it can't carry the load) and waste energy by using the higher temp water.

    We'd like to help you get it right and I'm glad you came here asking. If you'll supply the info needed (heat loss, piping lengths, piping arrangements, etc.), there are several very good pro's on here that will give you the right info and advise to do it so it performs like it was intended.

    Do search for an article by John Seigenthaller entitled "Plateless in Radiantville" for more info by one of the best in this industry.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • Thanks

    Gentlemen, I need to run out with today's business, I will get back to this later. Thank you for the replies.
  • M LaneM Lane Member Posts: 123
    Plan so far

    Hey guys- here is a sketch of what I was planning. So far, we only have the backing blocks up (no tubing) in the staple up section and a 300' loop poured in slab at the garage area.. The drawings are only my plan, have not started to build yet.

    Radiant plates are out of this guy's budget, and the hardwood flooor (an Engineered floor btw.) is not in yet. Customer is going to insulate to the hilt, including spray foam in the exterior walls. Right now we have designed the system for 40 btu/square foot
  • SWEISWEI Member Posts: 7,356
    edited November 2013
    Radiant plates are out of this guy's budget

    is that due to lack of planning, or poor project management?  Whatever the cause, I would make the case for plates and then get the customer to sign a waiver refusing what we recommended.

    Then tear down those ridiculous blocks and staple the tubing directly to the subfloor.  Even cheesy homebrew aluminum sheetmetal is better than nothing.  Insulate right up to the tubing and you will reduce the required water temp significantly.  Watch out for spray foam as can have compatibility issues with tubing and/or fittings and has a nasty tendency to expand between them and the subfloor.

    I'd put the higher temp zone on the primary, direct piped from the boiler and then mix down to the slab from that.   Slab supply should also come after the high temp zone.
  • M LaneM Lane Member Posts: 123
    Thanks again

    Bad project mgt. by the client. No pre-planning budget.

    I do hydronic jobs all the time, but have managed to avoid staple-ups. My supplier has a guy who I really trust for system packages, he was the one who told me about the blocking method; insinuated that the joist cavity would get heated up.
  • SWEISWEI Member Posts: 7,356
    edited November 2013
    Hard data has two links to Sigenthaler articles that are worth the few minutes it will take to read them.

    Quote from the second link:

    Does Plateless Have Any Place?

    In the interest of fairness, yes it does. Tubing stapled at 8-inch centers directly to the bottom of a wood subfloor can provide limited heat output sufficient for floor warming, with the balance of the load handled by properly sized supplemental heating. I suggest limiting what you expect from such an installation to no more than 15 Btu/hr./sq. ft. with total floor resistances not exceeding 2.0 degrees F•hr.•sq. ft./Btu (including the subfloor). This limited output might be sufficient for a well-insulated home in a mild winter climate, but it’s not going to cut it for a ski chalet with 25-foot- high ceilings and a gable full of glass in Vermont.

    My candid advice to newbies in hydronic radiant heating is to avoid plateless staple-up installations altogether. The possibilities for underperformance and the ensuing costly corrections are just not worth it.
  • M LaneM Lane Member Posts: 123
    edited November 2013
    Change of plans

    OK. After the responses here, and reading the Siegenthaler article, I have decided to tell the client that at a minimum plates must be used. After reading the Watts tubing manual again (which mentions suspended installs but refers to much higher supply temps) I am going to push him into the SmartTrac system instead.

    You guys have been invaluable.

    I am going to have to add a pump for baseboard zone I see. Eventually that zone will be radiant too, so I don't want to go my usual route of building an injection system for the radiant off a high heat manifold. Hate relying on a manual mixing valve as well
  • IronmanIronman Member Posts: 3,408
    edited November 2013
    A Couple of Suggestions

    You designed a pri/sec series loop which is fine. Since the baseboard is the higher temp zone it should be the first in the series, not the floor. The temp is descending as it goes downstream, so should the zones as far as temp goes.

    I would also recommend that you use a Grunfos Alpha circ on the baseboard zone in lieu of a standard circ and a bypass differential valve.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • WeezboWeezbo Member Posts: 6,232
    is the heat loss so astronomical ,

    because of the covered patio being open to the outside air?

    if so close it in . thats the cheapest way to bring those heat loss numbers in line .

    Buderas and Runtal ,Myson and many others provide some very fine looking and preforming panels that would make their home also look very this century and take the heating systems input and maximize its potential to the radiant panels .

    Leave the radiant droop along heating for someone else ...when plates don't make it , then, droop along will surely miss the mark.
  • WeezboWeezbo Member Posts: 6,232
    Droop along ,...

    best place to use any of that is in like the entrance way to a master bedroom floor ,that way when someone is considering buying a home the floor is a bit warmer there than anywhere else in the room : )

    you can use some of the pex run out to your new DiaNorm panels or what ever you decide is within budget to create some small floor warming effect .
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