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AC Disconnect: Visible to Firefighter or Visible to Solar Tech? California.

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  • Sunking
    replied
    Originally posted by RShackleford View Post
    I also frequently read about "your local building code" or "the Building Code in your area". This confuses me. My area is my county, and they simply go by the NEC. Do other localities have local modifications ?
    Absolutely. A local jurisdiction can accept or amend any part of the NEC they want. Example in Chicago local code requires residential systems to be plumbed. That mean everything in conduit just to make sure Joe Home Owner has to use a union electrician to do any work. Several large cities have extra requirements, and can even make them up if the inspector does not like you for any reason. Since you have no experience, here are the two Golden Rules for a happy marriage and passing Inspections. Folloow these two rules to the letter.

    1. Inspector and Wifey are always correct.
    2. When Inspector and Wifey are in error, refer to rule 1.

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  • Ampster
    replied
    Originally posted by brycenesbitt View Post
    .....

    So that the fire crew, should that ever be an issue. won't feel a need to do more than pull the meter.
    That will most likely reduce the chance that they will go up on your roof and take an axe to your panels.


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  • brycenesbitt
    replied
    The "International Association of Fire Fighters" has an online training course on solar:
    https://www.iaff.org/solar-pv-safety/
    Have a view to get the same training as an actual fire fighter, to better understand what's done.
    With more and more solar houses, more and more crews have actual experience with solar.


    I've decided to add an extra sticker to this install, at the service entrance, that specifies two things:
    The location of inverter (on the other side of the wall)
    The fact that the unit has "rapid shutdown".


    So that the fire crew, should that ever be an issue. won't feel a need to do more than pull the meter.
    Last edited by brycenesbitt; 05-26-2020, 12:54 PM.

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  • Mike90250
    replied
    Originally posted by Sunking View Post
    Kind of a stupid silly question. First thing the FD does when they pull up to a house fire with solar on the roof is pull the DISCONNECT disconnect and SMASH ALL THE PANELS WITH A FIRE AXE. . Who gives a crap about the Technician. Follow the codes.
    I thought they just used a hose and rinsed them off the roof !

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  • Sunking
    replied
    Kind of a stupid silly question. First thing the FD does when they pull up to a house fire with solar on the roof is pull the DISCONNECT disconnect and SMASH ALL THE PANELS WITH A FIRE AXE. . Who gives a crap about the Technician. Follow the codes.

    Leave a comment:


  • Ampster
    replied
    Originally posted by bcroe View Post
    I do not know how the disconnect question applies to a ground mount array. My boxes are 230 feet from
    the array and 270 feet from the house meter. Certainly not visible from the house, but pulling the house
    meter will shut all AC down. Bruce Roe
    Hopefully if you have a fire there is sufficient separation that your wooden ground mount arrays would not burn down. ​​​​​​​

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  • bcroe
    replied
    Originally posted by bob-n View Post
    If you pull the meter, then your array can't feed the grid. But assuming that the rapid shutdown isn't there, can't your array still feed the house? Could a fireman swinging an axe into a wall of the house hit a live wire? Assuming that your array is treated like a backup generator, the output would still be live after the meter is pulled. That's not the way solar works, but that's the way the rules are written.
    The contract specifies my inverters, which will quit producing AC if the house meter is removed, guess
    that covers it. The installer thought so (if he did think about it), I had previously worried about running
    several hundred feet of AC underground wire to place the AC disconnects near the meter.

    I doubt there would be any axes through my brick walls. Bruce Roe

    Leave a comment:


  • nwdiver
    replied
    Originally posted by bob-n View Post
    If you pull the meter, then your array can't feed the grid. But assuming that the rapid shutdown isn't there, can't your array still feed the house? Could a fireman swinging an axe into a wall of the house hit a live wire? Assuming that your array is treated like a backup generator, the output would still be live after the meter is pulled. That's not the way solar works, but that's the way the rules are written.
    Not under UL1741. If a grid-tie inverter doesn't get AC then it can't make AC, pulling the meter has the same effect as opening the AC disconnect. Even if that were the case the are circumstances where the line from the inverter to the AC disconnect could run a fair distance (with micro inverters for example). IIRC there's no requirement that the AC disconnect be located near the inverter.... just accessible from the exterior of the home.

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  • bob-n
    replied
    If you pull the meter, then your array can't feed the grid. But assuming that the rapid shutdown isn't there, can't your array still feed the house? Could a fireman swinging an axe into a wall of the house hit a live wire? Assuming that your array is treated like a backup generator, the output would still be live after the meter is pulled. That's not the way solar works, but that's the way the rules are written.

    Leave a comment:


  • bcroe
    replied
    I do not know how the disconnect question applies to a ground mount array. My boxes are 230 feet from
    the array and 270 feet from the house meter. Certainly not visible from the house, but pulling the house
    meter will shut all AC down. Bruce Roe

    Leave a comment:


  • bob-n
    replied
    Newer inverters shut down when the meter is pulled. Older inverters varied. Insisting on a safety disconnect means that they emergency crew (firefighter, etc.) doesn't have to think about the age of the system. Pull disconnect and the line is assuredly cut.

    That said, there's still hundreds of volts coming out of the panel string. Let's hope that the installation has the panel string floating so touching one wire and earth doesn't kill you. That has been a requirement for inverters for many years now.

    Leave a comment:


  • RShackleford
    replied
    Well, very little trouble to put in the AC disconnect; they cost $10-15 and are a good way to transition to the metal conduit that AHJ wants to see once going into the house. There is a stud wall perpendicular to the exterior wall of house, and the main panel is recessed into that stud wall, with its edge right up against the exterior wall. So I figure I'll mount the AC disconnect right there, slightly above the top height of the panel, and come out the rear of the disconnect with metal, into the side of the stud wall and down into a knockout in the main panel. Use PVC conduit to get from inverter into bottom of disconnect.

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  • nwdiver
    replied
    Originally posted by RShackleford View Post
    My impression was that it's more for if the POCO is having weirdness on the grid and wants to remove the PV from the equation.
    I've never heard that. It's a safety switch to protect line workers and fire fighters. Line workers are protected by the anti-islanding requirement and fire fighters are protected when they pull the meter and the anti-islanding requirement. Xcel has done work on the lines near my house before. I lost power and they never touched my AC Disconnect. I suspect it's they same everywhere. I doubt a utility is going to waste man-hours LOTOing residential AC disconnects then clearing them again when they're done.

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  • RShackleford
    replied
    My impression was that it's more for if the POCO is having weirdness on the grid and wants to remove the PV from the equation:

    "In order to comply with the Final Rule of the Rural Utilities Service regarding the Interconnection of Distributed Resources (IDR) as codified at 7 C.F.R. Part 1730, Subpart C, the Cooperative requires that the Interconnection Facilities shall include a lockable disconnect and visible open EDS that is readily accessible to and operable by authorized Cooperative personnel at all times. The EDS is a manual load break disconnect switch or safety switch with a clear visible indication of switch position between the Cooperative System and the Interconnection Member. The switch must have pad lock provisions for locking in the open position. The switch must be visible to, and accessible to, Cooperative personnel. The switch must be in close proximity to, and on the Interconnection Member’s side of the point of electrical interconnection with, the Cooperative's System. The switch must be labeled "Generator Disconnect Switch.” The switch may isolate the Interconnection Member and its associated load from the Cooperative 's System or disconnect only the Generator from the Cooperative 's System and shall be accessible to the Cooperative at all times. The Cooperative, in its sole discretion, determines if the switch is suitable and necessary."
    Last edited by RShackleford; 05-26-2020, 12:50 PM.

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  • nwdiver
    replied
    Originally posted by brycenesbitt View Post

    And just to be clear, when the fire department hits the main, or pulls the meter, the inverter shuts down.

    The only need for a "disconnect within reach of the equipment" is for electricians unfamiliar with
    circuit breaker lockouts ( e.g. https://www.garvinindustries.com/pan.../one-pole/ubl1 ).
    Yep; That's my point. None of the reasons for having an AC disconnect will ever actually be used. The fire department isn't going to go hunting for a disconnect switch when there's a fire. They're going to follow the lines to the meter remove it and carry on to the next task. Removing the meter has the same effect as opening the AC disconnect.

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