plenum rated pex tubing

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by isolatae, May 3, 2008.

  1. isolatae

    isolatae New Member

    I need to run a 1/2" water line to feed a water cooler above a suspended ceiling in a comercial building. The ceiling is plenum rated. Do I have to use copper or is there a plenum rated pex available
  2. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona

    Ask the design engineer or the building department.
  3. I just have to ask....

    For my own general education ,, I must ask what the

    heck is plheum rated mean????

    thank you in advance...
  4. Gary Swart

    Gary Swart In the Trades

    Yakima WA
    I wondered the same thing, so I Googled it. Here's the what I found.

    Plenums in buildings are enclosed spaces that are not for human occupancy, but are often used for heating, ventilating, and/or air-conditioning equipment and airflow, and for other equipment such as cables, piping, and luminaires. 'Plenum boxes' or sections are portions of HVAC air handlers or terminal units.

    That doesn't really answer the original question, but at least Master Plumber Mark and I know what plenum means.
  5. Yeah but when you spell it like MPM did, plheum....

    It means that when you cough up some grumblings and go to spit.......? and it lands on yer shirt........?

    That's plheum! :eek: :D
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    A plenum is often also an air duct, so a fire there can spread toxic combustion byproducts throughout the building. As a result, there are special rules about what can be put into them - they must not outgas poisonous compounds. No idea if pex does...but it should be in the materials data sheet.
  7. now I know

    Most likely the pex is not allowed in
    a Phluem air duct....

    becasue when it burns it will let off toxic smoke throughout the building....

    I would check with the inspector, my guess is it would have to be copper to make them happy
    Last edited: May 4, 2008
  8. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Central Florida
    If anybody's got a PEX MSDS handy, it might be mentioned in there. I see that UPONOR (manufacturer of WIRSBO PEX) sells a complete fire-suppression system, presumably plumbed with PEX, strongly implying it can be used in a plenum, but none of the PEX information sites I've visited mention plenum installation at all. I've sent a few inquiries off to manufacturers and the pexinfo site, but they've all knocked off for Sunday.
    Last edited: May 4, 2008
  9. jimbo

    jimbo Plumber

    San Diego
    You can buy plenum-rated Cat. 5 phone/ethernet wire. Special jacket material. Costs about 4 times as much. Anxious to hear if there is a plenum-rated PEX.
  10. Spaceman Spiff

    Spaceman Spiff Architect

    Salt Lake City, Utah
    There is no plenum rated pipe other than copper and cast iron that i know of. sorry...
    and y'all are correct... a plenum (plenum rated stuff) is is the space above a ceiling and it is basically a huge return air duct. The idea is to not have anything that would give off toxic smoke when it burns. hth
  11. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Central Florida
    Wirsbo PEX OK in a plenum... sort of

    I just got a copy of Uponor's plenum rating to run from 0.50" to 2" PEX tubing within the plenum. You can't just throw it up there, unfortunately.

    Oops. It's a 174KB .pdf file, too big to upload. If anybody would like a copy, I'll e-mail it to you.

    The product description is "Cross-linked polyethylene tubing, identified as Insulated AquaPEX or hePEX, manufatured with a maximum outer diameter of 2" NPS, encased in fibreglass pipe insulation."

    The tubing must be encased in fiberglass pipe insulation with a wall thickness of 1/2" to 1" and specific fire ratings. Insulated tubing runs shall be located at 0" minimum spacing for a maximum of 3 adjacent pipes with an additional 18" spacing to the next pipe run. There shall be no exposed tubing.

    Practically speaking, it looks like Spiff's judgement is correct, although if you're willing to conform to the spec, you can run the PEX. You can probably run just about anything if you insulate it enough.
  12. gt1040b

    gt1040b New Member

    Plenum rated piping

    For information - Plenum Rated specifically means that it meets ASTM E84 standard for Flame Spread Index of less than 25 and Smoke Developed values of less than 50. This doesn't mean that the substance won't burn, and it doesn't mean that the fumes aren't toxic, it just means that it spreads an gives off smoke within a certain rate.
    If you have to use non-plenum rated materials in a return air plenum, you just need to cover it appropriately - you can meet code by wrapping the piping with insulation that meets the plenum rating (which most HVAC duct insulation does).
    Basically check the HVAC system, if the air handler has 2 ducts coming out of it, and one of them is just open above the ceiling, that's called an open plenum return system and you have to meet the ESTM E84 requirements. If both the supply duct and the return duct go directly to grilles/diffusers then you are in the clear and there are no special requirements.

    Much to my surprise, the Plastic Pipe & Fittings Assoc. (PPFA) have published information that BOTH PVC and ABS meet plenum rating requirements:

    BUT, Charlotte Pipe (and every other resource i've ever seen on the subject) says that PVC and CPVC do NOT meet the requirements for plenum rating:

    I've been designing plumbing an HVAC systems for over 10 years, and I have avoided the use of any sort of plastic piping in plenum systems, but moreover, I avoid using open return plenum systems when ever possible - they have way more drawbacks than benefits, IMHO.

    It's probably more info than you needed, but it's important to avoid getting turned down by a code official!
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