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Thread: EMT on roof - water tight and drain?

  1. #1
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    EMT on roof - water tight and drain?

    I have read that the NEC requires EMT on the roof in a solar install to be "water tight", but also to drain. Can I run a section of EMT over the peak (up the 5/12 roof and down the other side) with no breaks, and leave the ends open (obviously with bushings to create a smooth opening and allow for bonding the EGC). This section of EMT would then be water tight (solid tube) and drained (open ends). Logically (to me that is) that would satisfy the NEC. Similarly I have another section of EMT tubes bound together with compression fittings ("water tight") and with open ends (both sloped so that they would drain).

    A related question - what do people put in the openings to keep critters out?

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    I've seen lots of EMT on a roof. I've never seen it not terminated into a box or enclosure of some type. I don't understand what you mean by this drainage requirement. Sounds like we need to see the wording of what you've heard so it can be verified and/or corrected.

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    What you're describing is done all the time in the solar world, but only with wiring (e.g. PV wire) that is allowed to be run exposed on arrays. You are basically just using it as support and protection. I've never had an issue with inspection with this method.

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    Reply

    Quote Originally Posted by MAC702 View Post
    I've seen lots of EMT on a roof. I've never seen it not terminated into a box or enclosure of some type. I don't understand what you mean by this drainage requirement. Sounds like we need to see the wording of what you've heard so it can be verified and/or corrected.
    Here is a FAQ from the Mike Holt Forum with examples of the wording:
    https://www.mikeholt.com/mojonewsarc...!~20030611.htm


    • Article 100 defines "Raintight" as "Constructed or protected so that exposure to a beating rain will not result in the entrance of water under specified test conditions."
    • 225.22 Raceways on Exterior Surfaces of Buildings or Other Structures. Raceways on exterior surfaces of buildings or other structures shall be raintight and arranged to drain.
    • 230.53 Raceways to Drain. Where exposed to the weather, raceways enclosing service-entrance conductors shall be raintight and arranged to drain. Where embedded in masonry, raceways shall be arranged to drain.
    • 358.42 Couplings and Connectors. Couplings and connectors used with EMT shall be made up tight. Where buried in masonry or concrete, they shall be concretetight type. Where installed in wet locations, they shall be of the raintight type.

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    I have had this discussion on jobs before. As has been noted, its pretty common to use EMT as a "sleeve" where PV wires need to cross walkways and such, or jump between sections of array. I am not sure off hand how to back it up with code articles, but it seems like the since the EMT is just a sleeve/protection and not a complete raceway system, and the conductors going through it are ok to be used without a raceway at all, then rain tight fittings would not be required and would be silly. I guess the "raceways to drain" requirement too? Its analogous to saying you can run direct bury wire through plumbing pipe, garden hose, or whatever you want because the pipe doesnt need to be there in the first place.

    We were doing a bunch of large rooftop system (~300 KW) and using EMT sleeves to pass between array sections and across walkways. We were trying to find an easier way that didnt involve pulling potentially long conductors through these pipe sections. Splicing them with MC4's could have been done, but we were trying to avoid unnecessary connectors. I had the idea of just using deep strut and laying the conductors in it.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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    yeah sure a jumper conduit.
    that is what i do all the time,
    as long as it is PV Wire or Engage Cable (Enphase)
    AND you use GROUNDING bushings on the ends of the EMT......that you have replaced the cheap lay in lugs on them with direct burial lay in lugs. (the steel set screw, aluminum lug body and copper wire will corrode into an unrecognizable mass within years otherwise)

    or if you terminate in a box, just drill weep holes.

    (Water will condense on inner walls of EMT and may fill up any down-stream box over time

    I have heard of a solaredge inverter filling up with water because the conduit entered it from roof and it had no weep holes.)

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    Quote Originally Posted by Zee View Post
    yeah sure a jumper conduit.
    that is what i do all the time,
    as long as it is PV Wire or Engage Cable (Enphase)
    AND you use GROUNDING bushings on the ends of the EMT......that you have replaced the cheap lay in lugs on them with direct burial lay in lugs. (the steel set screw, aluminum lug body and copper wire will corrode into an unrecognizable mass within years otherwise)

    or if you terminate in a box, just drill weep holes.

    (Water will condense on inner walls of EMT and may fill up any down-stream box over time

    I have heard of a solaredge inverter filling up with water because the conduit entered it from roof and it had no weep holes.)
    There's a reason Solaredge disco come with drains these days.

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    Quote Originally Posted by jaggedben View Post
    There's a reason Solaredge disco come with drains these days.
    ya noticed

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    I often think there should be "uphill" and "downhill" LB's. The latter with leetle weep holes.
    Recently, I have started removing gasket from bottom ones. Frankly, it will probably still hold water in.

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    Well since you got us started on this...

    You finally got me googling an idle thought I've had for a while. Which is: Where you come down from the roof and enter a building with an LB, to instead use a T with a drain in the bottom knockout.

    Thing is, you need the T to have the cover on the opposite side from the T hub, or wire pull is ...not gonna do it. Never seen one, but it turns out some companies apparently do make this. See TB option.

    And then, apparently there are ton of drain plugs to choose from.
    The trick will be finding suppliers that do this without adding any significant $$ to the project. I mean, I'm willing to spend about $3 extra.

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