Hang radiant tubing w/electrical clamps - Question

ianm

I designed and installed the radiant floor system in my new home in 2000. To fasten the PEX tubing under the wooden subfloor I first ran 4" strips of 1/2" sheetrock along the entire tubing run and then attached the tubing to the sheetrock strips using 1/2" electrical conduit clamps. I did this for three reasons: 1) To hold the tubing away from the underside of the subfloor where the hardwood flooring nails protruded, 2) Provide some extra heat dispersion since I opted not to use aluminum transfer plates, and 3) Allow the tubing to move more freely than staples would. The third point I actually read about after the fact in Dan Holohan's book 'Hydronic Radiant Heating'. All of this works beautifully except for one point. When the system comes on, especially from a cold start, we can hear the tubing 'popping' under the floor. Its not loud but sounds like some one making popcorn a floor below. It subsides as the tubing stops expanding. The strange thing is that when the system shuts off and the tubing starts to cool it is silent. What is causing this? Does this ever happen with tubing directly against wood? I want to use a similar installation in an expansion above my garage, but eliminate the noise. All suggestions welcome.

Weezbo

Hmmm.

It is the expansion thing going on:) you may be able to do something easy to help for a while by controlling water temps. you would want to have the system function at as constant a temp as possible,an as mizerly as possible...use only enough flow to deliver the btu.s set it and forget it.in other words dont keep freakin with the thermostat.outside reset would be a definite stroke in the right direction also.depending on Where you live diff set back might be kinda helpful.matching the room or floor sensor (sophisticated T-stat in DIY language) differential respondse time more closely to outside temp changes...all these things will help. you have difugalties however. whatever it is is what it is after that,or "The nature of all mechanical things ,is Decay"

Weezbo

Oh. try plastic \"clamps as they are a little more forgiving on

the pex pipe.the expansion thing will still be going on however. this temp water in the ceiling.. well....its going to be ..Diffrent, lets say.so.,if you got your heart set on the radiant ceiling idea at least consider this prior to begining the project.

DaveGateway

Hang radiant tubing w/electrical clamps

I did the same thing, based on Dans' book. I didn't put in any sheetrock though & it doesn't make a sound! The 1/2" PEX is free to slide in the PLASTIC ELECTRICAL clamps & droops down between the clamps, if it needs to when hot. The only insulation that I used under it is called reflectex, (from Home Depo) Its an aluminized mylar with air bubbles product. I used the 16" wide rolls, as my TJIs are 16"OC
I put it clear at the bottom of the TJIs, so I have a 8"-14" air space above it to the PEX. Seems to work great!
I have a well insulated basement (foam blocks filled with concrete) & insulated floor as well. The basement stays about 52deg. all winter, so some of my heat goes down, but is very comfortable for working out etc. Bill Patrick