radiant floor manifold question

[SDPrairie]

Folks

I am building a new house in SD and wish to install pex in the basement floor and garage slab for future OWB. We will just put the pex in this summer and will complete the OWB project next summer. I have a few questions if someone wouldn't mind...
In looking at the online radiant heat companies they all recommend putting a manifold flush in the cement floor to avoid damaging the pex as it comes out of the cement. They have you surround the manifold with a wood box to keep the cement off and pull the box after the cement is dry. You then hook up to this manifold. My question is why don't you just run the pex up out out of the cement using some pvc pipe and put the manifold on the wall along with all the other gadgetry? Menard's sells NIBCO and they are not recommending the in-floor manifold but I have to think the companies that do this for a living know more than the Menard's guy - but I've been wrong before.
What size pex did you use? The basement slab is 1800 ft sq and the garage is 30 x 34. Menards is pushing 1/2 inch, onlines vary from 1/2 to 5/8 to 3/4. The basement will be one zone and the garage one zone. Thanks much, Steve

 

[Gavman]

Manifold is more difficult to work on in the floor system, I would mount it in a wall, there are sleeves to protect and help form the bend as it leaves the floor...
I have been around radiant heat systems for over 20 years and have never seen one in the floor....

 

[tmlkenney]

A Schedule 80 Long Ell 90 works like a charm to sleeve the bends in the slab/floor. You can leave them sticking up a couple of inches above finished grade and pour right up to them. You can then mount a 2x4 horizontally about 12" above the finished grade and mount the ends of the PEX vertically to that via the clip/anchor of your choice. Copper plumbing clips work well. Cap the ends so that no junk gets into them until you're ready to install the manifold and test the runs.

 

[SDPrairie]

Thanks for your help!

Thanks for your help!

 

[Highbeam]

No, do not put manifolds in the floor. My shop floor is 1800 SF and I used 1/2" pipe at 12" spacing.

Here's a pic or two. View attachment 306664View attachment 306665View attachment 306666View attachment 306668

I used 1/2" conduit ells. Note that I didn't want the inspector to know about the floor heat so I buried them, finished the concrete over the hole and then brought it up later.

 

[Gavman]

Hey and just a heads up re radiant heat, we always run the infloor pipe on 6" centres and no more than 200' per loop, its amazing how even the heat is, no cold spots fro the customer to complain about and on the grand scheme of things it doesn't increase the cost very much to do so...

 

[SDPrairie]

Highbeam

What kind of crazy regs do you have to deal with in NY that it was worth it to hide your in floor heat?!!

Thanks G for the 200 ft advice. I had read articles saying 250 ft, then it seems like every site was saying 300ft so I purchased manifolds based on that. I'll lkeep that in mind for the farm shop.

 

[Gavman]

Highbeam

What kind of crazy regs do you have to deal with in NY that it was worth it to hide your in floor heat?!!

Thanks G for the 200 ft advice. I had read articles saying 250 ft, then it seems like every site was saying 300ft so I purchased manifolds based on that. I'll lkeep that in mind for the farm shop.

Yeah 200 is ideal, 250 max and another tip, if you keep all your loops the same length (even if it means burying a bit more pipe in the floor) your system will be almost if not perfectly balanced IE all the areas will be the same temperature.... That helps if you want to do it yourself to save $$$

 

[ChoppyChoppy]

My floor is 12" spacing in my garage and house. The slab is 6" and the pex is maybe 1.5" down from the service. I can't tell where the pex is by temp.

With it 6" spacing, I'd guess you can put more BTU into the slab and get it to heat quicker? My slabs take about 24hrs to warm up the house/garage. Like if I set the garage at 45* and would like it to be 65*, it would take roughly a day.
I ended up putting in a water to air Modine heater right off the 190* boiler output for the garage to help out with that.

In the house, I don't really use the floor heat as I have the Blaze King in the living room. It might come on once in a while if no one put wood in the stove, but I don't depend on it for heat.

 

[tla100]

We used 90 degree bends in 3/4" grey electric conduit coming out of cocnrete at dads shop. Mine i went in basement from garage. Good thing i can get to it cause i lost pressure after frost came out so i have to put shutoffs on each loop and isolate it. Not sure how it happened, was virgin ground and had a good packed base of pitrun. Good luck

 

[kljahnz]

Just a couple pics. I am under the impression that with the manifolds and a pre calculated ' loop' plan. You can place the pex closer together around the perimeter's and spaced farther apart for the rest of the floor. I guess more btu's are needed for the parameters, for a more evenly heated slab.