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

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

    Setup:
    Underground utilities
    Outside meter
    Outside main breaker leading to inside subpanels.

    A new inverter will be inside of the basement, about 1 meter away.

    Where must the AC and DC disconnect be?
    Standing right in front of either the main panel or the inverter, you can't see the other, without leaning over and looking out a window.

    AC Disconnect Inside Basement.jpg

    --
    It seems that the fire department will want the disconnect at the main panel.
    It seems a future solar tech will want the ac disconnect next to the inverter.
    Section 690.15 says "an ac disconnecting means shall be mounted within sight or in each inverter.".

    --
    The 2020 code adds a safety requirement. Installing the AC disconnect indoors would increase the chance
    of a child trying to open or operate it:

    2020 NEC Significant Code Changes Part 4 690 – Solar Photovoltaic (PV) Systems 690.15"
    "Where disconnecting means of equipment operating above 30 volts are readily accessible to unqualified persons, any enclosure door or hinged cover that exposes live parts when open shall be locked or require a tool to open."

    --
    The 2020 code adds:
    "An equipment disconnecting means shall be permitted to be remote from the equipment where the equipment disconnecting means can be remotely operated from within 3 m (10 ft) of the equipment."



    So does that mean the AC disconnect can be outside, as that's less than 3 meters away? What does "remotely operated" mean?
    Last edited by brycenesbitt; 05-12-2020, 02:52 AM. Reason: 2020 code change "An equipment disconnecting means shall be permitted to be remote from the equipmen"

  • #2
    Code is good, but the local inspector is the one who matters. This is a question for your local inspector.
    7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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    • #3
      Originally posted by bob-n View Post
      Code is good, but the local inspector is the one who matters. This is a question for your local inspector.
      Local inspector basically said "let's ask around". Probably will end up with dual AC disconnects here, on opposite sides of that wall.

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      • #4
        Originally posted by brycenesbitt View Post

        Local inspector basically said "let's ask around". Probably will end up with dual AC disconnects here, on opposite sides of that wall.
        In my county they let the circuit breaker be the disconnect with lots of labels. My inverter is inside the same wall as the meter and main panel which has the labels and breaker for the solar system. The installer who works in many jurisdictions made a call and got clarification from the building department, when I asked that the inverter be installed inside, instead of as originally detailed on the outside.
        Last edited by Ampster; 05-12-2020, 03:52 PM.
        9 kW solar. Driving EVs since 2012

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        • #5
          Originally posted by Ampster View Post

          In my county they let the circuit breaker be the disconnect with lots of labels. My inverter is inside the same wall as the meter and main panel which has the labels and breaker for the solar system. The installer who works in many jurisdictions made a call and got clarification from the building department, when I asked that the inverter be installed inside, instead of as originally detailed on the outside.
          Here the solar installer nixed the main breaker idea, they wanted a shutoff within reach of the inverter, so nobody else could flip it closed while they are working.

          So we get TWO disconnects: one on each side of the basement wall.
          Last edited by brycenesbitt; 05-17-2020, 03:49 AM.

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          • #6
            Originally posted by brycenesbitt View Post

            Here the solar installer nixed the main breaker idea, they wanted a shutoff within reach of the inverter, so nobody else could flip it closed while they are working.
            Here, the POCO seems to be the main driver of the requirement for an AC disconnect. They want to be able to easily and visibly perform a complete disconnect of a grid-tie installation from the grid.

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            • #7
              I'm trying to buy my AC disconnect (to between my GTI and the grid connection) - needs to be fused, I believe, since I'm doing a line-side tap. Simple AC disconnects, usually noted as being for air conditioners, are very cheap. "Solar" disconnects, on the other hand, seem to be very expensive: https://www.zoro.com/search?q=solar%20disconnect. I assume that's because they are also suitable for DC disconnect, with arc protection. Can I use the inexpensive AC-only disconnect ?
              Last edited by RShackleford; 05-16-2020, 02:04 PM.

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              • #8
                The whole AC disconnect thing has always amused me. There's a 0.000001% chance it's ever going to be used. The utility isn't going to go around opening AC discos on homes and if there's a fire the fire department is going to pull your meter to turn off the power. No one really has any use for the AC disconnect.

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                • #9
                  Originally posted by nwdiver View Post
                  No one really has any use for the AC disconnect.
                  By installing a *fusible* AC disconnect, one has the option of doing a line-side tap (https://www.zoro.com/buchanan-displa...ctid=123572619) instead of connecting to a double-pole breaker in the main panel. This is what I am doing.

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                  • #10
                    Originally posted by RShackleford View Post
                    By installing a *fusible* AC disconnect, one has the option of doing a line-side tap (https://www.zoro.com/buchanan-displa...ctid=123572619) instead of connecting to a double-pole breaker in the main panel. This is what I am doing.
                    And you are doing that because of the calculations about your panel buss bar or because you are out of breaker space?
                    9 kW solar. Driving EVs since 2012

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                    • #11
                      Originally posted by Ampster View Post

                      And you are doing that because of the calculations about your panel buss bar or because you are out of breaker space?
                      The latter. Will probably add a critical loads subpanel at some point, which will free up a lot of space, but the line side tap seems more straightforward anyhow. I guess insulation-displacement is kinda kludgy, but its use is widespread around here, and the AHJ cast no shade upon it at all, when he came out to see my conduit trench.
                      Last edited by RShackleford; 05-16-2020, 11:42 PM.

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                      • #12
                        For what it's worth, I used a low-cost air conditioner disconnect, and both town inspector and power company approved.

                        Line-side taps have advocates and haters. They work. They are practical. They are relatively easy. They are relatively inexpensive. What's not to like?

                        They require making high-current connection to existing high-current cable that is often old aluminum. To me, that seems a bit risky, so before doing mine, I called the application engineer at one of the line-side-tap manufacturers and told him my plans. His response surprised me. He said that he does not recommend using his company's line-side-tap product like this. He said that it will make good connection, but if something does go wrong in that connection, there is nothing between there and the power pole to protect you. The tap is ahead of your main breaker, directly connected to the incoming mains. Between the tap and the power pole, there is no fuse, no circuit breaker. Your only protection is the huge fuse in series with the HV going into the transformer.

                        So what did he recommend? He said that you can buy a new meter box that has two connection points on eacn meter pole output. Why is that better? Because those connections are tested and rated for unprotected connection from a load center to the mains. But my power company doesn't allow me to change the meter box. So I went with a new circuit breaker in my load center.

                        Many people use line-side taps. I've never heard of one failing. You'll probably be fine. No matter what else, install it extremely carefully. Follow the manufacturer's torque, spacing, and all other instructions to the letter.

                        Please note that I am not an electrician. This is not professional advice, just me repeating what I've been told. If you have the slightest doubt, hire a qualified electrician. If you are an electrician or if anyone reading this is an electrician, please forgive me if these are ignorant comments.
                        7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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                        • #13
                          The post had been rapidly edited or something, and was locked into spam moderation. It's now out of quarantine.

                          And please note his last line:
                          Please note that I am not an electrician. This is not professional advice, just me repeating what I've been told. If you have the slightest doubt, hire a qualified electrician. If you are an electrician or if anyone reading this is an electrician, please forgive me if these are ignorant comments.
                          YOU are getting information from un-vetted voices on the keyboards of the internet. What matters is the Building Code in your area, and your ability to perform or contract to meet the code. Stray from the code and you will find if there is ever an incident, your insurance company is most likely not going to help you.

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                          • #14
                            Originally posted by nwdiver View Post
                            The whole AC disconnect thing has always amused me. There's a 0.000001% chance it's ever going to be used. The utility isn't going to go around opening AC discos on homes and if there's a fire the fire department is going to pull your meter to turn off the power. No one really has any use for the AC disconnect.
                            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 ).

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                            • #15
                              Mike is right. Follow the code.

                              That said, I also believe that there are better and worse code-compliant ways to implement a system. As proof, simply note that the code is constantly being updated.

                              Side story, perhaps with a bit of relevance. My friend's house burned to the ground. He and his wife got out unhurt, but lost everything. The insurance company paid to have the house rebuilt, but not without a hassle. He told me that they traced the cause to a bad power strip. I'm guessing that the MOVs in it absorbed one too many surges. He followed the code. Insurance covered it. But he was horribly inconvenienced for over a year and lost all irreplacable possessions.
                              7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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