Screws or Fasteners for Heat Transfer Plates

RodHot

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.

pecmsg

Your using a impact gun and driving them in too hard or fast!

HomerJSmith

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.

heathead

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_rod

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.

Jamie Hall

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!

hcpatel78

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 house.com please see attached pics.

RodHot

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_rod

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.

RodHot

I can see where having the self feed cordless screw gun would be very nice!

RodHot

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-Ed

Could be US screws versus China!!

hot_rod

EBEBRATT-Ed said:

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.

JUGHNE

Just a hair brained thought: as hot as those get when quickly driven, could they expand when drilling in and then a little contraction as they cooled off and the head goes "Ping".

Shoot one into hard wood and remove right away catching it in your hand.

RodHot

Jughne, I think your correct. I know they did get warm when driving them into 100 year old subfloor. BTW, a year later now and the new screws are still working fine.

Rich_49

HomerJSmith said:

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.

CONDUCTION is KING