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Transfer plates - C vs inverted U

Polycarp Member Posts: 135
I am in the planning and scoping phase of an in-joist radiant floor retrofit project for my own house.  For reasons of lower water temperature, greater responsiveness and more flexibility with floor coverings, we know that we want to go with heat transfer plates.  And if you're using plates, bearing our starting principles in mind, it seems like thick extruded plates are the way to go.  So, after doing some research I have a fundamental question:

Is there any important difference between the C and inverted U profile for the tube snap-in?

C profile:  <a href="http://www.houseneeds.com/shop/heatingproducts/radiantheating/ctrak_transfer_plates_main.asp">http://www.houseneeds.com/shop/heatingproducts/radiantheating/ctrak_transfer_plates_main.asp</a>

Inverted U:  <a href="http://www.pexsupply.com/Wirsbo-Uponor-A5080500-Wirsbo-Joist-Trak-1-2-Heat-Transfer-Panel-2111000-p">http://www.pexsupply.com/Wirsbo-Uponor-A5080500-Wirsbo-Joist-Trak-1-2-Heat-Transfer-Panel-2111000-p</a>

On a related topic, our sub-floor is 60 year-old tongue and groove.  This means that the underside is nothing resembling smooth.  Not only is the surface rough and somewhat uneven, each plank has a groove down the middle.  I'm worried that putting transfer plates on this would offer only limited contact conduction.  Is there a remedy for this situation?  Some kind of heat transfer goop like you put on a computer heat-sink?  Does this mean we might as well do bare staple-up or one of the convector fins?

I'm sure I'll have more questions.  The steam forum has been a life-saver for me, so thanks in advance.


  • Charlie from wmass
    Charlie from wmass Member Posts: 4,314
    WHy have you forsaken us in steam?

    on a serious note the profile is 6 versus 1/2 dozen. There is heat transfer sealent, look on Viega's installation guides they list it for holding the tubing in the grooves of their system. Even with limited contact the plates will stilll be better then plain staple up as the transfer area is still more than without. I am assuming you will be doing this yourself so the cursing of the old floors will not be paid for by the hour so do it as you planned. Make sure to grid off all the nails before pulling any tubing.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Polycarp
    Polycarp Member Posts: 135
    steam to hw

    Not forsaken.  I still own the house with the steam heat.  Don't take it the wrong way, but I hope to never have to ask another steam question because I *believe* that I am done with my steam upgrade.  :)

    This is for the house we just bought.  I will be doing some work myself, and some contracted out.  The level of sophistication we desire in the controls pushes just beyond my competency.  Also, we're looking at combi boilers, and we're seen enough reports of varying finickiness that we want an installer's warranty behind the boiler and controls.    We see the work that we plan to do as paying for better controls and better materials.

    I was hoping that there might be some kind of filler that I could put between the plates and the floor to fill the gaps.
  • Gordy
    Gordy Member Posts: 9,546
    C vs U

    Omega style plate which is best. IIt encompasses more of the tubing for better heat transfer, and holding power to keep it in place.

    Yes extruded plates transfer more heat, and are quieter.

    I question your thoughts on more flexibility in floor coverings though. You still have to think low r value floor covering especially in an underfloor verses a sandwich type install. Plates help transfer heat better than no plates, but do not dismiss the fact that floor coverings are going to be what ever you want. The higher the r value of such decreases output, and responsiveness.
  • hot_rod
    hot_rod Member Posts: 21,846
    edited December 2012
    I have tried

    a few different methods, spray adhesive double sided tape, silicone. The key is a good solid connection to the floor, any bump, nail point, splinter prevents good contact. One nail point can keep quite a bit of the contact area away from the flooring contact.

    You might look at the flexible graphite transfer system from Watts Radiant. It a great heat transfer medium. I played around with graphite years ago, it conforms to un-even surfaces better, but takes more fasteners to keep it in contact. A small short finish stapler is plenty, to install them.

    It takes a pretty powerful pneumatic driver to attach the heavy aluminum plates. A coil roofing nail gun was my tool of choice. A screwgun with drill point screws works well also, but is a slow go.

    Watts added a stiffener to the graphite to make sure the tube keeps in contact with the graphite. I have not tried any with this upgrade.

    You might contact them for a sample

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Polycarp
    Polycarp Member Posts: 135

    They are both appear to be omega.  The only difference is where the opening is, side or bottom.

    For the floor coverings, our thought is that more R-Value in the floor coverings means higher water temperatures and less responsiveness.  We're a fairly mild climate and are planning an envelope upgrade, so we just *might* be in the realm where bare staple-up is actually reasonable.  (Still need the final heat loss calc.)  So, with the transfer plates, we should be able to have *some* flexibility on the floor coverings before driving the water temperature or responsiveness outside of our personal parameters.  Does that make more sense?  any sense at all?

  • SWEI
    SWEI Member Posts: 7,356
    heat transfer sealant

    Got a link to that manual?  Can't seem to find it on their site.

  • Gordan
    Gordan Member Posts: 891
    edited December 2012
    My limited experience

    I'm pretty much in the same boat as you, perhaps a bit worse. My desire was to heat the foyer slab from below. The slab (3", I think) was poured on top of a tongue-and-groove car deck and is tiled with terra cotta tiles. The deck boards run perpendicular to the joists (my guess is that yours are diagonal) and they exhibit an appreciable amount of cupping, so I had concerns about the quality of the contact between the boards and the plates as well as between the boards and the slab. It's a fairly small area, about 80 sf, so I bit the bullet and installed the plates and the tubing. I used a LOT of screws for each plate, sometimes two on each side of the grove for each deck board, and even with this there are many visible gaps. Still, without insulating from below (unheated basement, largely below-grade) the temperature of the slab gets into the mid seventies with 110 degree water, so it's not terrible. Given how cold the slab used to get, and my 18-month-old's tendency to rip her socks off, this is a vast improvement in comfort and I'm glad that I did it, but if I depended on it as a primary heat source and had a much larger area (read: expense), I might have had more trepidation getting into this.

    For reference, most of my house is heated with radiant ceilings and those floors are as warm as this slab, or nearly so. Something to consider. This floor has no carpet or furniture on it to interfere with output, but others do.
  • Polycarp
    Polycarp Member Posts: 135

    You're pretty right about the subfloor.  I'm actually considering bedding the plates in thinset or some other similar material to fill the gap.  I'd need to deal with the moisture issues with the application on wood, but it might be doable since I'd still be using mechanical fasteners to hold the plates in place.
  • Polycarp
    Polycarp Member Posts: 135

    Wow, and I thought extruded aluminum was expensive ..  $9.50 a plate.
  • Gordan
    Gordan Member Posts: 891
    Well, you could

    You could do a lot of that and not significantly improve the situation. I was considering using thermal mastic but it's not cheap. What turned me off of that idea was primarily the notion that there's nothing I can do to get rid of the air pockets on TOP of the deck. What's cupped on one side is cupped on the other.

    At some point, it makes sense to step back and assess your priorities and your plans for meeting them. You know more about the problem you're trying to solve than you did at the outset; does your original approach still make the most sense?
  • Polycarp
    Polycarp Member Posts: 135
    I think it does...

    but I think it means that this will end up being a bit of a hybrid system.  The plates are simply going to emit more to the air than normal plates would.  It seems to me, then that I should do a small air gap with radiant barrier, good insulation and sealing up the air gap to make the convective effects work best.
  • Gordan
    Gordan Member Posts: 891
    Sorry, but...

    Sounds like a terrible idea for a host of reasons. Stick with what a product was actually designed to do. Extruded plates are poor emitters of IR and look nothing like any convector that I've ever seen.
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    get a sample

    of any plate you want to buy.

    I'm not that impressed with the tubing groove in those C plates. not very solid contact from what I've seen so far. but I should be getting a full size plate soon to check out.

    contact is king. if the plate needs silicon or whatever it's not a very good plate.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • Polycarp
    Polycarp Member Posts: 135
    gotten that sample?

    Have you gotten that sample?  Any impressions?
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    not yet

    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
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