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Screws or Fasteners for Heat Transfer Plates

RodHotRodHot Member Posts: 9
What screw or fastener have others used to secure heat transfer plates to the underside of the subfloor?

We are using a heavy 0.06" thick aluminum heat transfer plate with 1/2 PEX. Installed about 30 plates, cleaned up at the end of the day and everything looked good. Went home that night and come back to the job the next day and found two screw heads had broken off over the night. Now I am concerned that when we start heating the system more screws will break.

You can see on the box of screws the 2 broken heads we found on the floor the next morning when we came back. Strange that the screws would not have broken when we put them up. But they did break overnight and we found them the next morning on the floor below.

Looking for your suggestions for fastening the heat transfer plates.


  • pecmsgpecmsg Member Posts: 1,450
    Your using a impact gun and driving them in too hard or fast!
  • HomerJSmithHomerJSmith Member Posts: 929
    Underfloor heat transfer plates don't rely on tight connection to the sub flr to provide conduction like metal to metal connections with say, thermodiscs. There will always be an air gap between the plate and the wood flr, no matter how strenuous the fastening.

    I have always used a pneumatic stapler to fasten the plate to the sub flr. I rely upon convection in the joist bay, radiation, and conduction with good insulation to prevent backflow. I keep the insulation 1-2" below the subfloor so that the heat moves across the whole joist bay.
    STEVEusaPAGroundUpAlan (California Radiant) ForbesRich_49
  • heatheadheathead Member Posts: 101
    Those look like the screws I used. I haven't applied heat to system yet. Some did break on installation but not many. Good luck.
  • hot_rodhot_rod Member Posts: 13,493
    Conduction is by far the most powerful way to transfer. Do the best you can to get solid contact. I suspect a bit too much torque combined with low quality screws :)

    With a plank floor you may need more screws? The better the connection the lower the SWT to gets the job done. You paid for that aluminum use it to the best of your ability.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Jamie HallJamie Hall Member Posts: 12,947
    edited March 30
    Those screws are probably OK -- but if you are using a power driver or impact wrench (I'd use a regular power driver, or even a drill, rather than an impact wrench), set the torque to the lowest possible value that will drive the screw into the wood at all. That will give you decent contact and avoid stressing the screw head any more than you have to.

    I've managed to break those screws just driving them into harder wood. Not that difficult!
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • hcpatel78hcpatel78 Member Posts: 56
    edited April 1
    I just started to install uponor joist track plates. I am using zipscrews #7 x 1/2" long. Also used 12v Milwaukee drill driver with torque set at #9. I don't have any screw strip problem at all. Use made in USA(malco brand) screw. I bought from supply please see attached pics.
    Thank you,
    Hiren Patel
  • RodHotRodHot Member Posts: 9
    Thanks everyone for the feedback and comments. We ordered some different screws, and will watch the torque. Using an old Ryobi 18 volt clutch set to lower 1/3 torque setting (7-9), but will try and dial it back a bit to lower 1/4 setting (5-8). I think I will also be putting holes in between the existing holes. This will serve dual purpose, 1. if more heads break after install, at least there will still be some holding after the drywall goes up and 2. I agree with Hot Rod keep the surface of the aluminum against the surface of the wood.

    Thanks for the feedback.
  • hot_rodhot_rod Member Posts: 13,493
    when I was doing these type of installations for a living I invested in a Superdrive system. A self feed cordless screw gun with autofeed. I found a very substantial, engineered top quality US made 3/4" screw with a drill point. So it would pre-drill then drive the screw.
    It used the LOX drive which has 8 or 10 contact points so no cam out, and the bits lasts for thousands of drives.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • RodHotRodHot Member Posts: 9
    I can see where having the self feed cordless screw gun would be very nice!
  • RodHotRodHot Member Posts: 9
    Here are the screws I switched to, and more than a month later no issues with the screw heads popping off. A much better screw, and holds the aluminum plate tight. Thank you all for the comments/feedback.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,088
    Could be US screws versus China!!
  • hot_rodhot_rod Member Posts: 13,493

    Could be US screws versus China!!

    Good point @EBEBRATT-Ed I started buying bolts, nuts and screws from local or online Bolt and Nut companies. While they could still be manufactured off shore, they tend to be better quality.
    For bolt and nut stuff for the mowers and farm equipment I go with SAE grade 8.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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