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Protecting pex pulled through covered joist bays

rjwinzrjwinz Posts: 17Member
All, I used to post here in the early 2000's about my steam system. Now buying a house with electric heat and wish to install panel rads and a boiler, at least on the main floor of a split level. Some of the pex will have to be snaked through joist bays covered with drywall ceilings. Is there a way to protect the pex from nails? I am considering sliding pvc electrical tubing over the pex. Thanks for any help.
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Comments

  • SuperJSuperJ Posts: 475Member
    Consider using 3/8' pex if it will handle your loads. At high temp deltas you can get quite a bit of capacity out of small tubing and panel rads. And it's easier to snake it thru tight stuff.
  • rjwinzrjwinz Posts: 17Member
    edited March 19
    Thanks. I will get a design person to spec the system and hire someone to install the boiler and near boiler piping. I did electrical work for years and think I can snake the pex and set the rads. Just unsure how to protect it.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,460Member
    Pvc won't protect it against nails.

    I would suggest "Greenfield" or as the electrical code calls it 'flexible metallic conduit" it's fairly cheap and size wise it goes from 3/8" to 4" I think. 1/2" or 3/4" would probably be right
  • rjwinzrjwinz Posts: 17Member
    edited March 19
    Thanks. Might work well as long as I protect the pex from the end cuts. Thinking maybe one inch with connectors for 1/2 " pex. I could tape it to my fishtape and pull it and then run the pex thru. Good idea.
  • Jamie HallJamie Hall Posts: 10,138Member
    rjwinz said:

    Thanks. Might work well as long as I protect the pex from the end cuts. Thinking maybe one inch with connectors for 1/2 " pex. I could tape it to my fishtape and pull it and then run the pex thru. Good idea.

    Try using the end protectors used on BX cable. Should do it.
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,460Member
    @rjwinz

    Just put greenfield connectors on the end and put the threaded plastic electrical bushings on the connectors. U may have to go up a size to do this
  • clammyclammy Posts: 2,204Member
    Just use plumbing nails plates to protect pipes ,plus should drill your holes through the joists hi enough that screws and nails should not be a issue .when I do what ur proposing I switch my pex al pex to copper stubs up through the floor to copper it will take more abuse then the pex.when doing a job like your I usually use pex al pex instead of regular heat pex .i feel at hi temps that pex al pex has a better oxygen barrier then most heat rated pex .itmaybe a little harder to not kink and run but requires less hanger and expanses less the standard he pex . Get a nice uponor manifold to balance it out without much guess work .whenusing panel rads i always use the by valves isolation valves but that’s just me and I have my reasons ,I also try and use a variable speed pump usually a pressure differential type had good luck w wilo stratos eco .if your using a mod con u should try and run them at a lower temp you ll pay more now but less later .i have this set up at my own home and I heat w 135 de free water at about 10 outside temp my gas bills are very low even w the recent cold spell I was under 125 on my gas .good luck w your project peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • clammyclammy Posts: 2,204Member
    Usually for 1/2 pex I drill 1 3/8 holes and use pipe insulators Sioux chief has them they work quite well .peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • rjwinzrjwinz Posts: 17Member
    Thanks. We hit -30F a few nights this winter. Not sure what water temps we will need. I'm used to steam so I wouldn't mind 160-180 water.
  • clammyclammy Posts: 2,204Member
    The nice thing about those valves w the built in by pass is that if your lines run through unconditioned spaces as long as your system pump is running (constant circulation based on outdoor temp) you will have flow which should limit freezing if your worried plus at colder temps your system should be running anyway right. Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,460Member
    I believe he is pulling the pex over a sheet rock ceiling parallel to the joists not running through the joists
  • rjwinzrjwinz Posts: 17Member
    edited March 20
    That is correct Ed. Fishing it just like romex or mc or bx. I think the greenfield will work the best as long as i can get the pex thru it. The greenfield will stay below the holes in the floor. Since its just protection and not electrical it doesn't need to terminate in any sort of box. Thanks all for your comments.
  • JUGHNEJUGHNE Posts: 5,537Member
    IIRC, Greenfield flex has a internal "grain" to it.
    That is that it is easier to push/feed from one end than the other.
    We put a lot of flex in apartments and pushed all the wires thru.
    If one end was difficult we would go to the other end, the difference was obvious.
  • rjwinzrjwinz Posts: 17Member
    Good to know. The new stuff is mostly aluminum I think. Will have to test it .
  • Solid_Fuel_ManSolid_Fuel_Man Posts: 1,431Member
    What nails are you worried about? Like ones which protrude from the subfloor? Are you worried about future remodeling? Or just pulling the tubing freely over drywall and up a hole to a panel radiator?

    I agree with Clammy, size the rads for 120 degree water, you will pay more for the rads now, but the fuel you will save will pay for that in a few years!
    Master electrician specialising in boiler and burner controls, multiple fuel systems, radiant system controls, building controls, and universal refrigeration tech.
  • rjwinzrjwinz Posts: 17Member
    edited March 21
    Yes, typical nails one finds thru the subfloor. Also around any X bracing and sheetrock nails. Bays are full of foil faced fiberglass so we can't tell. Best to protect the pex IMO. My house and I want to do a good install. Thx.
  • Solid_Fuel_ManSolid_Fuel_Man Posts: 1,431Member
    I'm not there so I dont know, but I'm not sure you have that much to worry about.

    I'd likely use smurf tube (electrical non-metallic tubing) for that application. Carflex (non-metallic flexible conduit) is not conducive for pulling things through in long runs, really better for sleeving.
    Master electrician specialising in boiler and burner controls, multiple fuel systems, radiant system controls, building controls, and universal refrigeration tech.
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