Fixing wires - How tight is too tight for PEX?

As HR said, not so tight that the tubing can't move, but tight enough to do the job.

I have had occasions to open up a slab after the fact that an electrician had "Discovered" our tubing for us. It was a slab ob grade pour. The tubing was distorted from the ties. The barrier hadn't been violated, but there were obvious pinch marks on the exterior of the tubing. I do not believe that the Europeans allow the tubing to be tied to metal with metal.

I am not aware of any massive failures associated with this method of tube fixing.

Although a pain in the thumbs, I prefer the use of cable ties. In fact, when I did my daughters sidewalk (curved) I used some of that "Snow Fence" for the mesh, and nylon ties. NO metal in contact with the tubing. I affixed the mesh to the ground using landscaping stakes (plastic, Ortho) and from what I hear, it held quite well during the pour. I intentionally wanted the tubing as deep as possible, because this is also a reversing system that can take advantage of the solar and ambient energy to be harvested for use as a DHW pre heat.

ME

Ron asked:

to use solar energy for DHW preheat, why should the pex tubing be as deep as possible? If you could provide links to the technical reasons for that i'd be interested in learning about it. thanks.

Ron, unless the tubing is on some seriously substantial support system, it's going to end up on the bottom in most cases anyway. No real scientific reason, just a gut feeling and mimicing real world experience. You will note the sensor well in one photo near the manifold box. It will contain the slab sensor used to dictate operation of the SIM and energy recovery programs. I will not allow it to be drawn below dew point, which here in Colorado is fairly low. I could "make" water, but am worried about the accumulation of condensate slime. If I'd have thought about it sooner, I could have had the cement plant throw some copper sulphate into the mix, and then I could have generated enough water to maintain plant life for the Xeriscape plants along side of the sidewalk for free I don't think the landscaping would have appreciated the copper sulphate tho.... Trade offs in every corner...

Extraction will be a 2 stage process. Direct off the slab, through a plate heat exchanger when differential is adequate, and 2nd stage is a vapor compression heat pump. Heating is done direct via modcon through plate heat exchanger to the slab. The whole shebang will be controlled via an ENV PC based control system. (Google Climate Automation Systems for more information).

My ultimate hope is to show that we can harvest more energy than the SIM system uses for keeping the sidewalk clear, and create more SIM sales for our manufacturers. There will be times during the seasons that we can actually harvest the night time ambient energy from the slab as well. Having the tubing at the bottom of the slab will lessen short cycling of equipment due to mass storage tendencies of concrete.

Mechanicals begin in earnest this fall. Would have started sooner, except that we had to establish a baseline for consumption (brand new home) to have something to compare to.

I am soliciting participation by hydronic equipment manufacturers, including Caleffi, Grundfos, Taco, and others. ENV is donating the programming. I donated the insulation, tubing, mesh and S&R lines between the slab and mechanical room. All participants will be named in the final executive report of findings. The Environmental Defense Fund is also interested in our findings.

ME