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Thread: 2 buildings one PV system

  1. #1
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    2 buildings one PV system

    2 buildings own by one entity.
    One building is 8 feet taller than the other.
    They abut on one side back to back so their entrance are on two diffrent streets.

    They both have their own utility laterals and each have their own service switch’s, main water pipe grounding electrode etc. By definition they are two distinct building with common ownership.

    Both roofs have modules but, only the taller one has all the inverters, disconnect switches and interconnection to the service.

    Sytem is 100% export.

    The conduits are only bonded to the taller building and they cross over to the shorter building never bonded to any grounds in the shorter building.

    Permanent signs and placards will be posted in the shorter building, both on the roof and at the service , advising first responders what address the disconnects are located in to initiate a shut down in the event of an emergency in the shorter building.

    1) Do these conduits pose a shock hazard as a result of being bonded to a seperate building?
    2) Is this PV system in compliance with 2014 NEC? If not why.

  2. #2
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    Quote Originally Posted by johnjohn View Post
    ...

    1) Do these conduits pose a shock hazard as a result of being bonded to a seperate building?
    No.

    2) Is this PV system in compliance with 2014 NEC? If not why.
    Probably compliant. The only possible issues I can think of involve the number of supplies to a building. See 230.2 and/or 225.30. However, your description, while a little lacking in detail, implies that there is no alternating current supply on the shorter building that could be used to supply loads. (You said all inverters are on the taller building.) In that case I don't see any of those sections being violated. Furthermore, there are allowances in those sections for parallel power production systems and different characteristics.
    Last edited by jaggedben; 02-04-18 at 11:50 PM.

  3. #3
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    Quote Originally Posted by johnjohn View Post
    2 buildings own by one entity.
    One building is 8 feet taller than the other.
    They abut on one side back to back so their entrance are on two diffrent streets.

    They both have their own utility laterals and each have their own service switch’s, main water pipe grounding electrode etc. By definition they are two distinct building with common ownership.

    Both roofs have modules but, only the taller one has all the inverters, disconnect switches and interconnection to the service.

    Sytem is 100% export.

    The conduits are only bonded to the taller building and they cross over to the shorter building never bonded to any grounds in the shorter building.

    Permanent signs and placards will be posted in the shorter building, both on the roof and at the service , advising first responders what address the disconnects are located in to initiate a shut down in the event of an emergency in the shorter building.

    1) Do these conduits pose a shock hazard as a result of being bonded to a seperate building?
    2) Is this PV system in compliance with 2014 NEC? If not why.
    IF that is the case than I think you are good. Even if the two buildings were electrically connected by their equipment grounding and bonding conductors, I don't see an explicit NEC violation, but I don't like it: you could have neutral current from one returning to the source through the other (of course would depend on utility system topology, whether fed by same transformer or not, and existence of low impedance paths like common metal water pipes). The stars could align and bad things could happen with a lost neutral or severe fault scenario. I have run into this a few times (not something bad, just the situation) with three way switching between two structures that each had their own service.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  4. #4
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    Quote Originally Posted by jaggedben View Post
    No.



    Probably compliant. The only possible issues I can think of involve the number of supplies to a building. See 230.2 and/or 225.30. However, your description, while a little lacking in detail, implies that there is no alternating current supply on the shorter building that could be used to supply loads. (You said all inverters are on the taller building.) In that case I don't see any of those sections being violated. Furthermore, there are allowances in those sections for parallel power production systems and different characteristics.
    The shorter building does have its own alternating current that supplies loads. That is one of my concerns. When you enter any building you should be able to shut all the power in that building including the PV. This will not be the case as it relates to the shorter building. Only signs in the shorter building will direct you to the taller building around the corner to shut the PV that will initiate the rapid shut down in the shorter building.

  5. #5
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    Quote Originally Posted by johnjohn View Post
    The shorter building does have its own alternating current that supplies loads. That is one of my concerns. When you enter any building you should be able to shut all the power in that building including the PV. This will not be the case as it relates to the shorter building. Only signs in the shorter building will direct you to the taller building around the corner to shut the PV that will initiate the rapid shut down in the shorter building.
    I wouldn't argue against the sensibility of requiring the shorter building to have rapid shutdown initiation on its own building. Under the 2017 I think that would be required. But the 2014 NEC is a lot more vauge about rapid shutdown and doesn't explicitly require it.

    What I meant about AC loads is that you are not violating 230.2 by having two different AC supplies on the same building.

  6. #6
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    You might find that the city or county AHJs don't like having stuff cross property lines and entangle separate properties unless there is an easement in place. Just because the owner owns both today does not mean they will own both in the future.

    The NEC does not really cover this situation, a generator on one building feeding another. A very flexible reading of the NEC can try to shoehorn something to fit this but it's really not covered. Overall I think it's a bad decision to install a PV system like this, but I can understand why someone would want to.

    As for grounding, If you touch the PV system on the roof and some other grounded conductive item you should not get a shock. If both those are not on the same equipment grounding system then you can't provide that protection. But you also don't want to interconnect the grounding system from two different services. So it's a catch 22.
    Last edited by pv_n00b; 02-06-18 at 01:41 PM.

  7. #7
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    Quote Originally Posted by pv_n00b View Post
    You might find that the city or county AHJs don't like having stuff cross property lines and entangle separate properties unless there is an easement in place. Just because the owner owns both today does not mean they will own both in the future.

    The NEC does not really cover this situation, a generator on one building feeding another. A very flexible reading of the NEC can try to shoehorn something to fit this but it's really not covered. Overall I think it's a bad decision to install a PV system like this, but I can understand why someone would want to.

    As for grounding, If you touch the PV system on the roof and some other grounded conductive item you should not get a shock. If both those are not on the same equipment grounding system then you can't provide that protection. But you also don't want to interconnect the grounding system from two different services. So it's a catch 22.
    You may make a valid point. This is how I see it. Under definition "Building" is a structure that stand alone or that is cut off from adjoining structures by fire walls...
    It would seem 690.13 mandates a disconnect for PV in a "Building". 230.7, although not related to PV because PV is not a service per definition, also mandates a disconnect for all conductors. To me, and I could be mistaken, NEC rules are applied to each building or structure individually. A roof is part of a building. So when first responders show up they expect to be able to shut all power in a given "building or structure" so they are not injured while trying to fight a fire rescue people etc. Signs, placard etc are meant to direct you to locate switches within that same building and NOT another address. In that sense the code, in a roundabout way, does not want to allow live conductors in a "building" without a means of disconnecting them within that same "building" even if under one management.

  8. #8
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    Another consideration

    Is it isolated DC output circuits passing from one building to the other or AC output from the rectifiers passing to the other building. Would it make a difference?

  9. #9
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    Quote Originally Posted by Codegui2 View Post
    Is it isolated DC output circuits passing from one building to the other or AC output from the rectifiers passing to the other building. Would it make a difference?
    Rectifiers?

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