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Thread: conduit on rooftop

  1. #1
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    conduit on rooftop

    Is there a change in the NEC about running EMT conduit on the roof of a residential condo bldg? The loads are for HVAC units and ex-fans. I was told that to re-work the conduit runs it has to be in RIGID conduit. Is this correct?

  2. #2
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    There seems to be an urban legend going around that EMT cannot be used outdoors. I think it might be because UL chanegd the rules on how they test the raintightness of EMT a while back.
    Bob

  3. #3
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    Thanks for the reply. A couple of years ago we only had "Raintite" fittings up to 1" approved by the city inspectors here in SD.
    The manufacturers have since complied with fittings up to 4" with a UL listing.
    It is a non-corrosive area I think the customer just got bad advice.

  4. #4
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    Quote Originally Posted by MGE
    Is there a change in the NEC about running EMT conduit on the roof of a residential condo bldg? The loads are for HVAC units and ex-fans. I was told that to re-work the conduit runs it has to be in RIGID conduit. Is this correct?
    Just be carefull to check if your crossing any expansion joints, roofs can generate a good amount of heat, I have seen EMT on roof tops pull apart at the couplings, IMO EMT is not the best choce for roof tops. I see no problem with short runs of EMT properly supported, something I would want an engineer to seal, before installing.
    Last edited by satcom; 07-09-07 at 07:31 PM.

  5. #5
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    Quote Originally Posted by satcom
    I see no problem with short runs of EMT properly supported, something I would want an engineer to seal, before installing.
    Okay, now you've got me scratching my head. Who the heck engineers conduit runs? Isn't that the electrician's job?

  6. #6
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    Quote Originally Posted by MGE
    The loads are for HVAC units and ex-fans. I was told that to re-work the conduit runs it has to be in RIGID conduit.
    Wouldn't you rather use RNC? The R stands for RIGID. As satcom said pay close attention to expansion joints. And add your own as per 352.44

  7. #7
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    You would almost have to put a gun to my head to use EMT on the roof. I think a lot has to do with the climate but in my area EMT outside will rot out.

    Most of our job specs require RMC on roofs.

  8. #8
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    Quote Originally Posted by mdshunk
    Okay, now you've got me scratching my head. Who the heck engineers conduit runs? Isn't that the electrician's job?
    Worked many years of commercial, and heavy industrial construction, and can recall only a few jobs that did not have a plan set for conduit layouts, today many EC's think they can do a design build, without the benifit of a professional design engineer, and of course the expense of plans. Is it done, you bet it is.

    We had a strip mall a few years back, where they did a design build, floor plans, and some sectional details, somehow it slipped by the review, winter snow load brought the roof down, did misplaced conduit runs, and mechinical equipment add to the failure?

  9. #9
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    Quote Originally Posted by satcom
    ....did misplaced conduit runs, and mechinical equipment add to the failure?
    I don't know. I give up. Did they?

    Did the engineer who sealed the truss plan contribute the failure, by not accounting for equipment that exists on every modern commercial rooftop?

  10. #10
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    Quote Originally Posted by mdshunk
    I don't know. I give up. Did they?

    Did the engineer who sealed the truss plan contribute the failure, by not accounting for equipment that exists on every modern commercial rooftop?
    The township cleaned out the entire construction department, after the hearing, my point is conduit runs are not something the electrician lays out on a project, he is not a structural engineer.

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