Underground line question

[goosegunner]

Extra security in case the foam ever become waterlogged? Maybe it's not worth the effort...

I am not sure but if it is water logged wouldn't it still lose heat to ground if the foam was holding water?

I will be doing mine in about 2 weeks. I just cut the garage floor today so I can come through the frost wall. I will be 4-6 feet down in very nice sand, but I still have the same concerns as you.

gg

 

[woodsmaster]

Since the PVC would not actually be carrying any fluid, I'm not worried about expansion and contraction.

I do wonder if I could bend my own 2" PVC conduit. That would be pretty cool. I bet I could make a heating blanket of sorts.



Just a curious wondering at this point...old 1-3/4" fire hose is free to come by. Is there any reason I couldn't sleeve the PEX inside of that? I can get 100' lengths of the stuff and it's obviously very flexible. It shouldn't degrade encased inside of the foam. The only benefit I'd lose is the ability to replace the PEX just by sliding the old out and the new in.

I've used a salamander heater to heat the conduit and it works pretty good.

 

[Tennman]

Ok... I understand why someone may want to insert the pex into some type of pipe if there is a concern regarding vehicle traffic, but look up the properties of PEX. Pex should have a lifetime in terms of 100+ years. Presuming no physical damage due to rock contact Pex has material properties to outlive our grandchildren. Do research on the properties of closed cell polyurethane. In general pex has better lifetime properties than PVC. AND, AND, from a pure thermodynamic efficiency, that air space in the PVC will be heated by the water in the pex. If you are heating anything between the boiler and HX energy is being wasted. Pex in PVC or anything with an air gap between the pex and insulation will be less efficient. That's just the law of thermo. No nothing really "sticks" to pex just like trying to bond to teflon but I don't care about a .0005"-.001" gap between the pex and the foam. That's definitely in the noise. Eventually the differential thermal expansion between the pex and foam will cause a disbond.... but the gap will be essentially nothing. Bottom line, putting the pex in a enclosure with an air gap is less efficient and the pex will out live all of us. My 2 cents. Seems like a lot of effort for little to no benefit. BTW. we drove the backhoe over our foam right after blowing the foam.