Sleeving pex and pump size questions
Last Post 26 Sep 2018 03:50 PM by sailawayrb. 5 Replies.
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pdhntrUser is Offline
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23 Sep 2018 04:18 PM
I am building a 24 X 30 shop, poured concrete floor, in slab 1/2'' pex. The slab will be 4" in the center with thickened edges. Pex stapled to the insulation, rebar above, fiber in cement. I am having trouble understanding the "control joints" and sleeving thing. The cement guys are going to cut the concrete afterwards, do I need to sleeve the pex under these cuts? I am using three "lines" of pex, 300' each to lay out on the insulation. Can someone give me an idea of what size pump I should use to move the water/antifreeze solution at a proper rate? I am going to use my outdoor boiler as a source. I have a Taco 007 already. Would that work? Thank you. Jim
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23 Sep 2018 05:46 PM
You really should do a heat loss analysis (e.g., ACCA Manual J or equivalent) of the building that you be will heating with this HR system. Then you can properly determine the HR system supply temp and flow rates that are needed to accomplish this mission at the outdoor design temp for your location. One can’t really spec a pump until the flow rates and PEX circuit lengths have been determined. Nevertheless, I suspect your Taco 007 pump will likely be okay for three 300’ circuits. We have some free software on our website that would allow you to accomplish all this DIY if you are so inclined:

Borst Heat Loss Analysis Software

Borst Hydronic Radiant Floor Heating Design Software

If your PEX is toward the bottom of the slab with rebar above it, you are at much less risk of encountering control joint damage to the PEX during the actual cutting or subsequently when the concrete actually cracks/separates at the control joint locations and pulls/stretches the PEX. Nevertheless, it is still good practice to sleeve the PEX where a control joint passes perpendicular to the PEX. You can use a larger diameter section of 12” long PEX that is cut longitudinally to facilitate snapping over and protecting the operational PEX. This gives the operational PEX a 12" distance to freely stretch which can be safely accommodated by the PEX versus something much less if it were not sleeved.
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
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24 Sep 2018 03:11 PM
I am not concerned about the actual cutting. The cement guys cut only about 1/2 to 5/8 an inch deep, and the pex will be stapled to the foam 4" below.

But cuts every 8-9 feet realistically means I could have a hundred sleeves to buy, make and install. So do the ends of the sleeves have to be taped?

Thank you sailaway. Jim
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24 Sep 2018 03:29 PM
You would likely be just fine with not sleeving the PEX at all given that it is at the bottom of slab and your cuts are 8-9 feet as the PEX should not see much concrete stretching at any one location. However, we would still sleeve the PEX if it were our job. No, you don’t need to tape the ends as not much concrete will fill the sleeve. Please also be aware that some tapes are petroleum based and will slowly dissolve the PEX over time, so it is best to never tape PEX unless you are absolutely certain that the tape is compatible with PEX.
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
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26 Sep 2018 03:13 PM
Please also be aware that some tapes are petroleum based and will slowly dissolve the PEX over time, so it is best to never tape PEX unless you are absolutely certain that the tape is compatible with PEX.
. I was going to tape the joints of the insulation. What tape should I use? An internet search turned up nothing. Thanks. Jim
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26 Sep 2018 03:50 PM
I know that some duct tapes are petroleum based and these are best avoided. Any tape recommended for sealing EPS/XPS panel seams that does not first require a primer paint be applied should not be petroleum based as EPS/XPS are also not compatible with petroleum based products either. I believe it is the petroleum based adhesive on the back of tapes that is the potential issue here as opposed to the exposed tape surface. So as long as you use a tape recommended for your insulation panel (e.g., Siga Wigluv), you should be just fine.
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
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