Off grid NEC disconnect rules?

Do all the disconnects (CB's) need to be contained within only one box? The NEC code book doesn't seem to make specific sense on this for off grid.
I want to keep the wiring inputs from the charge controllers to the batteries separate from the wiring outputs from the batteries to the loads and their disconnects to help with avoiding EMI issues ,hence two separate conduits and two separate disconnect boxes. The combiner box would obviously need to be separate from the charge controller box anyway. Also having a knife blade disconnect is not so practical as it allows access to vandals to shut the system down. But having the disconnects locked within a box seems like it won't gel with the inspectors or allow access in case of emergency?

This is solely outdoors on a remote site with no building. Array, ground mount and loads all within the same footprint.

Comments

  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Off grid NEC disconnect rules?

    you may absolutely keep them separate in separate boxes. label them though.
  • solarabcdsolarabcd Solar Expert Posts: 38
    Re: Off grid NEC disconnect rules?

    Thanks for the reply Neil. What is your take on the disconnects being under lock and key within the box?
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Off grid NEC disconnect rules?

    consult your inspector as to what would be acceptable to do in his opinion. you could look it up on the nec rules, but ask all of this of him and he'll be impressed that you think that much of his opinion and he should be understanding of your concerns with vandals. he has the last word anyway on what you can or cannot do.
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Off grid NEC disconnect rules?

    From the 2005 NEC
    all cases this disconnect must be “readily accessible,” 
    which means it must not be in locked compartments, 
    no ladders are required to access it, and 
    no building material must be removed to get to it
     [690.14, 100-readily accessible].
    
  • solarabcdsolarabcd Solar Expert Posts: 38
    Re: Off grid NEC disconnect rules?

    The 2008 online version of the code reads a little different to that. I can't cut and paste as it is a locked version.

    2008 Vers 690.14 Para (1) indicates that they need to be at a readily accessible location and not in bathrooms (NA as the only thing crapping at this location will be a squirrel):D.
    Para (4) indicates the disconnecting means can consist of no more than 6 switches/CB's mounted in a single enclosure or group of enclosures (someone please ensure I am interpreting that correctly.)

    So in my case there will be 10 strings in the combiner box so the disconnect would have to be the 2 x CB between the combiner box breakers and the Charge controllers....... except they will be locked up. So I guess an external DC disconnect on these 2 separate array lines will be the solution? Plus one to disconnect from the Battery bank to the Loads.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Off grid NEC disconnect rules?
    solarabcd wrote: »
    So I guess an external DC disconnect on these 2 separate array lines will be the solution?

    Probably,

    "Since Section 690.31(E) allows the PV source or output conductors to penetrate the building surface on the roof (if they are routed in a metal raceway inside the building), it appears that the PV disconnect can be mounted inside the building in any readily accessible location. However, this NEC allowance may not be the safest option or even very clearly defined in the Code."

    http://www.nmsu.edu/~tdi/pdf-resources/CC130.pdf

    But of course,

    "When in doubt, consult with the authority having jurisdiction."
  • solarabcdsolarabcd Solar Expert Posts: 38
    Re: Off grid NEC disconnect rules?

    Thanks for the link dwh. I found that last week in my searches and at the end of the day it seems like liaising with Mr AHJ will be the way to finalize things to the their liking and interpretations.

    Thanks for your info and time.
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: Off grid NEC disconnect rules?

    In the end--decide what your needs are--and see if you can get the code/inspector to see your point of view--plus agree that the results is "safe".

    Also, figure out who needs access to the system (local fire, police, a local electrician/helpful neighbor) and see what kind of access would work best.

    Give a key to the local fire department--put a lock box with fire department master key/combination--or combination lock box with combination on file with those that need access--or "call me" numbers so you can supply the combination if needed, etc.

    In the end, many buildings in major cities have fire department lock boxes to save a guy with an axe causing thousands of dollars in damage to front doors.

    And, there have been issues now after 1/2 the city has these lock boxes and nobody can find 1/2 the keys. Now they are worried that thieves are getting into buildings.

    And requirements differ with applications... Office equipment I would design in over-temperature shutdown. For telephone central offices--they wanted the phone gear to run until destruction (service was more important than equipment costs).

    We had one piece of equipment that had a capacitor fail near the temperature sensor in a central office... Set off the fire alarm and the engine crew took a long time and a lot of work breaking through the security door (where was that lock box?)--Only to find that our system had shut down automatically long before they broke in--and they were ticked that there was no fire to put out. :roll:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 3,328 ✭✭✭✭
    Re: Off grid NEC disconnect rules?

    My opinion is to always put an external disconnect for any roof mounted solar. I try not to use solar on a roof for the reason that if there is a building fire the roof is where firemen are going to most likely be. Iif they do not feel safe up there you will just be another insurance loss. I would also install an IPO (near the solar disconnect) on your inverter/charger to shut it down and not worry about access to the batteries other than what the inspector wants.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail offgridsolar@sti.net

  • mike95490mike95490 Solar Expert Posts: 7,307 ✭✭✭✭
    Re: Off grid NEC disconnect rules?
    .... I would also install an IPO (near the solar disconnect) on your inverter/charger to shut it down and not worry about access to the batteries other than what the inspector wants.


    Darned if I can't figure out what an IPO is. help me.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • solarabcdsolarabcd Solar Expert Posts: 38
    Re: Off grid NEC disconnect rules?

    This is at an off-grid remote site - no dwelling. Picture the array mounted to a large ground frame structure and communication equipment attached to the same structure, 2 x battery compartments under the frame and array all within a 30sq ft footprint. All loads are 48VDC - no inverters.
  • Dave AngeliniDave Angelini Solar Expert Posts: 3,328 ✭✭✭✭
    Re: Off grid NEC disconnect rules?
    mike90045 wrote: »
    Darned if I can't figure out what an IPO is. help me.

    Help me....When in doubt read the manual we use to say at HP. Inverter Power Off
    IPO It is a switch that turns off the inverter, even in search mode, no AC out. Works well with thunderstorms and being outside a neighbor can shut down the system without having inside access to your refrigerator.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail offgridsolar@sti.net

  • t00lst00ls Solar Expert Posts: 143 ✭✭✭
    Re: Off grid NEC disconnect rules?

    I will re-read the NEC book again.....but if you dont have any buildings and it's not connected to the grid.......you dont need NEC code....nonetheless you should follow some safety rules

    the NEC was put into place for fire safety.....no buildings to burn ..right?
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: Off grid NEC disconnect rules?

    At least history wise--UL (Underwriters Laboratories) was sort of started by insurance companies to examine .

    Wiki History of UL

    William H. Merrill:
    William Henry Merrill began his career as an electrical engineer in Boston, Massachusetts. At the age of 25, he was hired by insurers for the World's Columbian Exposition to examine the safety of the electrical wiring in the Palace of Electricity. This experience led him to found Underwriters Laboratories. In 1916, he served as the organization's first president. William Henry Merrill also served as the National Fire Protection Association's secretary-treasurer from 1903 to 1909 and its president from 1910 to 1912.

    And, looking around:

    NEC code history:
    The National Electrical Code (NEC), or NFPA 70, is a United States standard for the safe installation of electrical wiring and equipment. It is part of the National Fire Codes series published by the National Fire Protection Association (NFPA). "National Electrical Code" and "NEC" are registered trademarks of the NFPA. While the NEC is not itself a U.S. law, NEC use is commonly mandated by state or local law, as well as in many jurisdictions outside of the United States. [1] The NEC codifies the requirements for safe electrical installations into a single, standardized source.
    The "authority having jurisdiction" inspects for compliance with these minimum standards.

    So--if there is no insurance involved, does not affect any local government entities, and there is no liability issues (workers, burglars--yes for real, etc.), then no code requirement.

    If this is a contract site (say radio/telecommunications repeaters, weather station power, etc.)--they may have their own requirements for safety.

    In the end--Practical safety and following codes where applicable (insulation types, temperature ranges, conduit fill, etc.) is all good.

    An external emergency shut off--May not be needed. But if you put one in and a lock box or a small pad lock to cut by the fire department (if there is any) would probably make people happy (even if it does not make anything safer).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • t00lst00ls Solar Expert Posts: 143 ✭✭✭
    Re: Off grid NEC disconnect rules?

    bill....as I re-read the original post......I dont think there is even an inverter involved....if this is the case and there isnt any ac my only concern is when he said knife switch

    using a knife switch with high voltage dc can cause an arc that can kill and also the damage a knife switch to begin with

    any disconnect to dc voltage should be encased in a way to provide quenching

    I believe robin has said something about this somewhere along the line

    I seem to recall looking at damaged breakers

    maybe the OP can tell us a bit about the system again or what it is used for since there isnt a building
  • t00lst00ls Solar Expert Posts: 143 ✭✭✭
    Re: Off grid NEC disconnect rules?

    ahha found it...robins etl test

    http://www.midnitesolar.com/pdfs/MidNite_165vdc_ETLtest.pdf

    this opens a pdf document in your browser

    I found this very interesting
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