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Thread: Engineer VS. AHJ

  1. #1
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    Engineer VS. AHJ

    It's nice to know the NEC inside/Out. However, the majority of electrical projects have been designed by an engineer indicating wiring methods and sizing.
    My question is: if an engineer over designs an electrical system such as service / feeder conduits and wiring, and I do the install per code ( smaller conduit and wiring) can the AHJ reject my installation?
    Even though the installation met code, it's not what the engineer designed.

  2. #2
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    Quote Originally Posted by Unbridled View Post
    It's nice to know the NEC inside/Out. However, the majority of electrical projects have been designed by an engineer indicating wiring methods and sizing.
    My question is: if an engineer over designs an electrical system such as service / feeder conduits and wiring, and I do the install per code ( smaller conduit and wiring) can the AHJ reject my installation?
    Even though the installation met code, it's not what the engineer designed.
    The code is a minimum standard, not a design manual. An AHJ might very well be able to reject the installation because it failed to meet the design spec.

    Edit to add: You may also have electrical codes that reference the NEC, but put in plain English the requirement to follow engineered plans.
    Cheers and Stay Safe,

    Marky the Sparky

  3. #3
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    Depends on the contract. Usually, you have to install per 'approved for construction' plans. Any change requires a revision to said plans.
    I will have achieved my life's goal if I die with a smile on my face.

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    Quote Originally Posted by Unbridled View Post
    It's nice to know the NEC inside/Out. However, the majority of electrical projects have been designed by an engineer indicating wiring methods and sizing.
    My question is: if an engineer over designs an electrical system such as service / feeder conduits and wiring, and I do the install per code ( smaller conduit and wiring) can the AHJ reject my installation?
    Even though the installation met code, it's not what the engineer designed.
    I've had a discussion about his with an inspector, and his stance was that if it is an engineered job, he is inspecting it to the engineered drawings since that is what was approved for construction.

    I agree with him. I would not change from the drawings unless I had a written/approved change order.

  5. #5
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    Quote Originally Posted by Unbridled View Post
    It's nice to know the NEC inside/Out. However, the majority of electrical projects have been designed by an engineer indicating wiring methods and sizing.
    My question is: if an engineer over designs an electrical system such as service / feeder conduits and wiring, and I do the install per code ( smaller conduit and wiring) can the AHJ reject my installation?
    Even though the installation met code, it's not what the engineer designed.
    If the AHJ requires stamped engineering plans, its usually for a reason.

    It would be kind of pointless to have an engineer design something, and to have the City review and accept it, only to have something else installed in the end.

    Plans frequently have minor changes, and I don't think AHJ's should require every minor change to have an engineers approval. But service and feeder sizes I would expect to conform to the engineered drawings.

  6. #6
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    Quote Originally Posted by steve66 View Post

    It would be kind of pointless to have an engineer design something, and to have the City review and accept it, only to have something else installed in the end.
    Welcome to my world.
    The more they overthink the plumbing, the easier it is to stop up the drain

  7. #7
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    Quote Originally Posted by Unbridled View Post
    It's nice to know the NEC inside/Out. However, the majority of electrical projects have been designed by an engineer indicating wiring methods and sizing.
    My question is: if an engineer over designs an electrical system such as service / feeder conduits and wiring, and I do the install per code ( smaller conduit and wiring) can the AHJ reject my installation?
    Even though the installation met code, it's not what the engineer designed.
    Piling on here...

    If I were to design and stamp a set of plans, I expect the project to be installed the way I drew it. If you as the installer want to change it in the field, I expect you to contact me about it. I may or may not agree with you, but if I don't, you'd best build it to the plans as drawn because I won't be changing them. When the job is inspected, the AHJ will compare what's installed to what's in the plans, and if they don't match, the job will most likely fail the inspection.

  8. #8
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    I don't believe engineering plans anticipate wiring methods (raceway type), or derating requirements that affect Service, Feeder, or branch wire size.

    Conductor length also changes subtantially when avoiding plumbing & HVAC equipment that always block the intended raceway path for electrical.
    Roger Ramjet NoFixNoPay

  9. #9
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    Quote Originally Posted by ramsy View Post
    I don't believe engineering plans anticipate wiring methods (raceway type), or derating requirements that affect Service, Feeder, or branch wire size.

    Conductor length also changes subtantially when avoiding plumbing & HVAC equipment that always block the intended raceway path for electrical.
    If the engineer knows what he is doing, all the items in your first sentence should have been taken into consideration during the design process. If there are site conditions that compel a change for the reasons described in the second sentence, they need to go in an RFI for the engineer's review and comment. You can't wing it and expect everyone to be OK with that.

  10. #10
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    Quote Originally Posted by ggunn View Post
    Piling on here...

    If I were to design and stamp a set of plans, I expect the project to be installed the way I drew it. If you as the installer want to change it in the field, I expect you to contact me about it. I may or may not agree with you, but if I don't, you'd best build it to the plans as drawn because I won't be changing them. When the job is inspected, the AHJ will compare what's installed to what's in the plans, and if they don't match, the job will most likely fail the inspection.
    That's not the worst part. The OP is now facing two very unpalatable choices. First, rip out what doesn't conform and replace it with the required sizes of conduit and cable, or, assuming the engineer and owner will let it slide, prepare a nice fat change order to return the difference in value (value, NOT cost) between what was bid ('cause you know that the more expensive option was on the bid set) and what was supplied. Be prepared to have said change order audited within an inch of its life. I hope for the OP's sake that this was a small job.

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