DIY Hydronic Floor Heating

[MN Renovator]

Could having two pipes separated on a vertical plane cause the floor to crack from either differential expansion from more pipe and less mass or from more heat in one general area? I have yet to see a basement or garage floor without a long crack in it, I'd imagine tempting fate isn't the best idea.

[Mikesolar]

Originally Posted by Drake

I guess I can't see how letting pex cross itself constutes "Poor" planning if a valid reason for not having it cross is not presented(I haven't found one yet). THe illustrations on pg 16 clearly show what I consider poor planning in heat distribution from what I have read as by most the ideal. That of having the most heat along exterior walls and less in center.One pattern is clearly most heat to least across progression. The other two are fairly equal across loop with the return of loop much cooler(which must be a heating loss from adjacent hotter tubes). A better loop pattern I would think ought to hotter on the outsides and cooler in the middle. Don't see that from any of these plans. Varying the tube spacing could maybe do it but that isn't shown. Have planned out a few different patterns that better run hottest fluid along exterior but a concentric spiral to center is the shortest loop and has zero return bends(just 90's) that are more difficult with narrow tube spacing.

I did present one good one. No one coming after you will realize that it has been crossed and, because it is very unusual, it could cause issues. Plus, if you look at any manifold, the supply starts to the left of the return (depending which way the manifold is oriented) and this is continued for each loop. Crossing them will, at the very least, look odd.

[ecomodded]

Drake
Have you looked at changing the entry point so you can get the coverage you need without crossing a line.

[Drake]

I'm not sure I am getting a fully clear explanation of the question I'm asking except for MN Ren who I think speaks of a crossing of two tubes(one over the other) within the slab. Being over 4" thick I can't see two 1/2" tubes significantly weakening slab at A few single points especially when I plan to over reinforce it anyway There would be no difference that normal the positions of tubing at manifold. Yes, the layout within slab might not identifiable but I plan to include a record of layout in the construction log of the addtn build that I now keep for everything I build. Something I learned for my first major remodel. Any layout used would need this for future. And yes I have layed out a couple loops that do not cross that track along exterior walls first than work to center. They just have far more 180 bends. Maybe I have gotten it wrong that the desired is to supply more heat near exterior walls. If not, I don't see that any of the patterns illustrated are doing it. Most of the heat in two of them is in the center. Wish i was knew how to post some diagrams. I appreciate everyones input on my questioning SOP.

[ecomodded]

If you install it like the professionals do it will be a professional job.

Usually there is a reason why procedures are in place and rarely are they apparent , its best to follow them to avoid unforeseeable problems.

Although I foresee a expansion crack if you crossed them in that thin 4" slab.

[Drake]

I was only asking what might be the reason pex shouldn't cross to understand if it is valid in every situation. If one wishes to do exactly what what everyone else says we should do(professional or not) we would never have any alternative innovation nor would most of us ever gather enough understanding to be DIY'ers. I thought a lot of the spirit of this site was to question SOP to see what can be achieved. I have done custom remodeling for years and some of the best new things I have learned have often come from someone asking why I was doing a thing a certain way. Coping professionals doesn't guarantee you the best result possible. Most often it will be just what is currently accepted by an industry.

[ecomodded]

A few people mentioned their concern with cracking

Since you do not find that viable you may be able to find some literature on the subject.

Or just do it because you don't think there will be a problem

[Drake]

I have taken great consideration of comments shared and have searched all the sources I feel could provide objective information(which is why I have inquired here as well). 1" displacement(two 1/2 pieces of pex) within a 4" slab would be a lower ratio than the accepted single 1/2 pex in 1 1/2 thin slab and would be only in a few single point of conjunction(not long parallel runs). A ten degree potential difference in crossing tubes is not enough to thermal shock concrete, especially reinforced. As for a crossing pex layout not looking professional, who sees it once installed. Irreguardless, as the application of this discussion is all but irreversible once poured, and that I have been able to design a none crossing pex layout that feeds from exterior to interior as well as distribute solar gain throughout floor I will use it. It requires more tube and severe bends but not outside what is being done.

One of the major reasons I have become a DIY'er is to be able to get what I want, not what a professional wants, within building and safety codes.

[Mikesolar]

The question I have is......why is it so difficult to do it without crossing over? What are the special issues you have? Honestly, it is the first time I've come across it expressed like this and I'd like to know.

[Drake]

It's actual that it would be so much easier if crossing is OK and when that might be. But if we start with Heat to a space is best supplied to area of greatest heat loss, forced air, baseboard, hydronic all recommend this and it makes sense to me. This has been suggested to me to apply to radiant floor hydronics as well(and maybe this is incorrect) so when I look at standardly used layout patterns such as detailed on pg 16 of this post I don't see that being achieved. Clearly thermographics shows graduated heat distribution across loop or nearly equal across pattern to higher in center than exterior. No greater on exterior, less interior. A spiral pattern from exterior to center would supply hottest fluid to walls, coolest to interior but how to return to manifold? chasing itself back without crossing creates a near equally heated floor. Crossing under itself shortest way back to manifold does not. It might very well be that my small 16x36 slab(two loops) might be served fine by being heated equally a crossed it. I have since layed out a serpentine "U" pattern that doesn't cross which also runs hottest along walls working coolest to center and should also redistribute passive solar gain in half the area to the other half. I just know that accepted reasons to do/or not do things often don't get rethought as the application those things are used in change, advance or innovate so sometimes stepping back and asking why again is not a bad thing.