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  1. #1
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    Default Roof HVAC miswiring

    Here's an interesting case a local inspector called me about over the weekend.

    A flat-roofed structure had an HVAC compressor on the roof. They were wired using a liquidtight flexible conduit method, around 2012. About 50 ft of it lay on the roof. Violation.

    My colleague was concerned about the conductor size, and whether the wiring should have been derated further. I believe he was unaware of the research-supported change in maybe the 2017 NEC permitting wiring over a roof to be derated just for ambient temperature so long as it's raised 3/4 inch. However, this was installed before that liberalization, and besides, it was not raised--not even supported as required.

    I had a few itty bitty concerns. With this observation, what speculations might be reasonable regarding other aspects of the installation? More specifically, what was inside that raceway? If the conductors or cable in it weren't wet-location rated, fuggedaboudid. What can we say about conductors that we can anticipate were overheated periodically for a dozen years?

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  2. #2
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    Default Re: Roof HVAC miswiring

    The answer depends on the reason the local inspector was there.

    Also, residential or non-residential building and the applicable code (Building Code (ICC?), Residential Code (IRC?), NEC, etc?

    Presuming the condenser unit was installed at the time of the wiring?

    Location of condenser unit related to edge of roof.

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

  3. #3
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    Default Re: Roof HVAC miswiring

    Fascinating. Jerry. I don't know the answers to most of your questions, but I imagine that after I've given you what responses I can, you'll pull those coins out of my ear.

    It is a residential high-rise, number of stories unknown to me.

    I strongly suspect IBC. (Direct NEC adoption by jurisdiction, probably 2008 at the time.)

    I imagine this was a condo pre-purchase.

    Condenser did not look near the edge of the roof, but no certainly and for sure no metrics. (And not my photos to share.)

    Yes, his presumption was that this went in before the unit was first sold.


  4. #4
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    Default Re: Roof HVAC miswiring

    Quote Originally Posted by david shapiro View Post
    It is a residential high-rise, number of stories unknown to me.

    I strongly suspect IBC.
    If the jurisdiction uses ICC codes, or codes based on the ICC codes, then the IBC would be the applicable code, with any local amendments, of course.

    High-rise would be at least 7 stories as a typical 7 story building will be greater that 75 feet above the lowest fire department access to an occupied floor. And some jurisdictions consider a roof as a 'occupied floor' as the roof is 'occupied when servicing equipment on the roof', and the roof also requires egress for that same reason, less that storys and a ladder from the 6th floor typically serves as roof access, 7 stories and above typically have a stair going to the roof. I did have some 7 story buildings which were initially designed with ladders from the 6th floors up to the roofs as the roofs were 72 feet above grade (intentionally for that reason), but grade was around the building, and the ground sloped away from the building with the driveway and "lowest fire department access" being "more than 75 feet above lowest fire department access - major can of worms was opened there, with the end result being that a stair went up to a roof door instead of a ladder and a roof hatch

    (Direct NEC adoption by jurisdiction, probably 2008 at the time.)


    I imagine this was a condo pre-purchase.
    Okay, local home inspector, not a local code inspector. He should have looked at either the conductors in disconnect (when he looked to see if it was fused - for ratings - or a molded case switch), or at the panel for overcurrent protection and conductor size to see if it matched the label for 'minimum ampacity' and 'maximum breaker/fuse size', and if the label said 'maximum fuse size' that would open the debate for "fuses and not breaker?", but a unit that new would address both.

    Condenser did not look near the edge of the roof, but no certainly and for sure no metrics. (And not my photos to share.)
    Equipment within 10 feet of roof edge should have guards along the edge, with guards long enough to protect the edge of the roof for at least that 10 foot distance from the equipment.

    Yes, his presumption was that this went in before the unit was first sold.
    So the age of the building is 2012?

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

  5. #5
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    Default Re: Roof HVAC miswiring

    Yes, 2012 or so.
    He did look at the conductors, but didn't tell me what they were. CB matched equipment, conductors at CB were suitable size. He thought they transitioned to the sealtite, but hadn't examined that point. I don't think that he checked what was in the sealtite--wet-location rated? cross-linked?.

    The reason I posted it here was that I wondered how far HIs are expected to go in examining it such equipment, besides matching nameplate and OC device. Of course, you being you, I learned other neat stuff about rooftop equipment and high rises.


  6. #6
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    Default Re: Roof HVAC miswiring

    Quote Originally Posted by david shapiro View Post
    The reason I posted it here was that I wondered how far HIs are expected to go in examining it such equipment, besides matching nameplate and OC device.
    Opening disconnect should be done, yes.

    Looking at disconnect rating and type is it is fuses or actual breakers, that should do. If molded case switch or infused pullout, need to check panel end. Also check panel if fuses or actual breaker is too high rating.

    Looking at circuit conductors for size. Not sure most would check insulation type for the "W" for wet location rated. Doubt any would check for raceway type, support, derating over roof, etc., as that's not really their job. That's the contractor's job and the code inspector's job.

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

  7. #7
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    Default Re: Roof HVAC miswiring

    Makes sense, given everything a HI has to cover.

    At the same time, it shows the arbitrariness of some lines we draw. I'm not talking about Code inspection versus safety inspection, but about table ampacity versus as-installed ampacity for conductors. As for suitability of conductors to the location, I'd hope that HIs call out NM in wet and UV-exposed locations for the same reason, and multiconductor SE underground, . . .
    .


  8. #8
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    Default Re: Roof HVAC miswiring

    When home inspection fees go from $500 to $5,000 ... I would hope that home inspector knowledge and reporting what reach the goals you are looking for.

    As my knowledge and prices went in the direction and then higher, my reporting also did. Which lead to 300 to 500 page reports.

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

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