Extending Baseboard heat using PEX back to copper


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Old 12-06-11, 04:35 PM
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Extending Baseboard heat using PEX back to copper

I have baseboard heat in my home. There is a section in my rec room ( 40" below grade) that I would like to modify. There is a section that crosses a doorway. Currently the piping goes up over the doorway and then back down in the far corner to continue the loop back to the boiler.
I would like break into the concrete floor, extend the baseboard piping using PEX and then go back to copper to continue the loop.

This would eliminate about 48' of copper (22' in the ceiling + 16' vertical, + 10' horizontal which loops through a section of baseboard.) Also, it will eliminate the need for me to build soffits (or chases) to hide the vertical pipes in each corner.

My question is can I use PEX for this? It appears that PEX is used for Radiant heating application so I am thinking it is OK to bury it in concrete. I am thinking it doesn't need to be in a sleeve.

Also, can I use sharkbite adapters or should sweat on copper to PEX couplings? I haven't used sharkbites, however I know many speak positive about them

Thanks in advance for any comments or suggestions.

Larry
 
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Old 12-07-11, 03:54 PM
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Hi Larry, yes, you can use PEX. It doesn't NEED to be in a sleeve, but the slab will suck some heat out of it as it passes through, and 180 water shouldn't really be run in concrete... I would probably insulate it myself.

About the PEX you want to use... do NOT use the type that is for potable water supply. You MUST use PEX that is rated for heating systems because it has an oxygen barrier built in to it. I would use PEX-AL-PEX , which has a layer of aluminum encased in the tubing.

I have used Sharkbites a few times... in places that I was unable, or afraid, to use a torch. No problems yet. I think the most important thing in trouble free use is to make sure that you don't 'scar' the O-ring by not properly preparing the pipe/tubing beforehand. Remove all burrs and ream the pipe/tubing smooth. Make sure there is no 'tension' on the fitting. If you are only doing two fittings, and you can get the torch in without burning down the house, I would say to use sweat adapters...
 
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Old 12-07-11, 08:08 PM
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Thanks for your response.
I'm thinking I will likely sweat the fittings on.

So would you suggest insulating the PEX-AL-PEX with the foam pipe wrap or some PVC pipe?
I read somewhere that suggests using 1 1/4 Grey PVC elbow over the PEX (I guess electrical conduit elbows?)) where the PEX goes in and out of the concrete.

thanks again

Larry
 
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Old 12-07-11, 08:40 PM
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I'm not sure I see the need for the conduit... if you did use conduit, you would need to be careful that you didn't have to exceed the bending radius of the PEX going through elbows and such... or are you saying only to use the conduit where the PEX enters and exits the slab?

I would probably just use that cheap foam stuff... I dunno really, I'm just thinking out loud... never thought about this before...

I will say with some certainty that you don't want hi-temp water in the PEX in contact with the concrete. Whether or not that cheap foam stuff would be enough to prevent problems with the concrete possibly cracking... just don't know!

Let me understand the plan a bit more though... you are planning to jack a 'ditch' into the slab and run the pex in that ditch... ?

Hopefully you will get some other replies.
 
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Old 12-07-11, 09:00 PM
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Trooper, he posted the same question in the Plumbing forum where I responded with the suggestion of using a PVC or PE sleeve. I never mentioned any size. I think that having the possibility of 180 degree water running through a PEX pipe that is completely restrained from expanding and contracting with temperature changes (as it would be if encased in concrete) is a bad idea. Your idea of using foam pipe insulation IS a good one, just make sure that the longitudinal seam is secure and the foam is long enough to encase the PEX from point of entry to point of exit with no means for the concrete to enter.
 
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Old 12-08-11, 06:27 AM
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-I was originally thinking I would use the conduit only where the PEX enters and exits the slab (to give it some support)

Now I'm thinking to just use the PEX wrapped in foam and then somehow support the PEX to the walls after it exits the concrete

Good idea to bring the foam out above the concrete to isolate the PEX from the concrete. I guess an inch or so is good.

My plan is to break a ditch 3" x 72" in the concrete, place the PEX (wrapped in the foam )in the ditch, install all the fittings, test it for leaks (purge out the air), and fill the ditch with concrete.

How does that sound?

Thanks Furd and NJ Trooper for your help.
 
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Old 12-08-11, 10:02 AM
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Larry, one problem you might run into is being able to find a place to buy just ten feet or so of the PEX.

The more I think about it, the idea of using a 'sleeve' of plastic pipe where the tubing enters and exits the slab is a good idea.
 
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Old 12-08-11, 10:37 AM
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If you do not use a sleeve where tube enter and exit there is a risk of pipe shearing off. It has become a standard practice to do this.
 
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Old 12-09-11, 05:58 AM
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So if I am going to use a plastic sleeve, perhaps I should use
1 1/2" electrical PVC (which has one piece elbows) for the entire run?
However..........NJ Tropper has a Good question .."where will I get 10" of PEX-AL-PEX"........

Maybe I'll have to re-think this project.......and use copper wrapped in foam insulation?

Unless I can find a Radiant heat installer that will part with 10'.
Also, are the PEX-AL-PEX fittings different fom the normal PEX fittings?

A seemingly easy project gets complicated.......
Thoughts anyone?

thanks
 
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Old 12-09-11, 06:38 AM
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Most in floor heat installers have lots of short pieces of pex left over.
 
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Old 12-09-11, 03:12 PM
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If you can find a guy with 'remnants' in his truck he might just give you a piece... might be able to scam some fittings too!

Each manufacturer seems to specify their own fittings... which kinda makes it a pain.

But, copper is an alternative also. Just make sure to keep the concrete away from the pipe and allow for expansion space (the foam insulation should allow for that).
 
 

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