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Thread: Fused vs. Non-Fused

  1. #1
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    Fused vs. Non-Fused

    Here's a question I've always wanted to ask, and would like some clarity on:

    In PV systems, I've noticed that some disconnects are fusible and some are non-fusible.

    Can someone give me pros/cons of using each? What are some situations where you would want to use a particular type? Thanks!

    Regards,
    Andy

  2. #2
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    Quote Originally Posted by andrew.tkelly View Post
    Here's a question I've always wanted to ask, and would like some clarity on:

    In PV systems, I've noticed that some disconnects are fusible and some are non-fusible.

    Can someone give me pros/cons of using each? What are some situations where you would want to use a particular type? Thanks!

    Regards,
    Andy
    If you are connecting via a line side connection, you must use a fused disco within 10' of the point of interconnection. If you are connecting through a backfed breaker, fuses are redundant and unnecessary.

  3. #3
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    Quote Originally Posted by andrew.tkelly View Post
    Here's a question I've always wanted to ask, and would like some clarity on:

    In PV systems, I've noticed that some disconnects are fusible and some are non-fusible.

    Can someone give me pros/cons of using each? What are some situations where you would want to use a particular type? Thanks!

    Regards,
    Andy
    I made a list a while back about breakers vs fused switch vs non-fused switch but couldnt find it. I dont see non-fused as having much use unless it is a utility requirement or a disconnecting means is needed/wanted say at a separate structure. Note that Non fused switches have a relatively low SCCR of 10,000 amps (they do "series rate" with certain fuses), which further limits their use.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  4. #4
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    Quote Originally Posted by electrofelon View Post
    I made a list a while back about breakers vs fused switch vs non-fused switch but couldnt find it. I dont see non-fused as having much use unless it is a utility requirement or a disconnecting means is needed/wanted say at a separate structure. Note that Non fused switches have a relatively low SCCR of 10,000 amps (they do "series rate" with certain fuses), which further limits their use.
    Around here we must install a bladed disconnect near the point of interconnection or the utility meter for every PV system we install. Every utility in Texas I have dealt with (and that's most of them) have that requirement. Some AHJ's even require two of them for some systems.

  5. #5
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    Quote Originally Posted by ggunn View Post
    Around here we must install a bladed disconnect near the point of interconnection or the utility meter for every PV system we install. Every utility in Texas I have dealt with (and that's most of them) have that requirement. Some AHJ's even require two of them for some systems.
    Yes most utilities require that here in NY too. I am spacing out: do most fused disconnects have visible break or not? I definitely recall seeing ones where the mechanism was shielded....
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  6. #6
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    you may also find the requirement for 110.26 application become a different interpretation for a non fused disconnect.
    CircuitRyder --- Unfortunately not all good ideas are code enforceable.

  7. #7
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    Quote Originally Posted by electrofelon View Post
    Yes most utilities require that here in NY too. I am spacing out: do most fused disconnects have visible break or not? I definitely recall seeing ones where the mechanism was shielded....
    The ones we use have them.

  8. #8
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    Bear with me, but considering the SCCR limitation and that you need an OCPD somewhere anyway, I still see quite limited use for non fused switches. I guess if you make your interconnection inside the building with a a fused switch, and need to add a switch outside for the utility. That could be non fused. Interconnect with a circuit breaker and unless its a small service, you will likely need a fused switch.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  9. #9
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    Quote Originally Posted by electrofelon View Post
    Bear with me, but considering the SCCR limitation and that you need an OCPD somewhere anyway, I still see quite limited use for non fused switches. I guess if you make your interconnection inside the building with a a fused switch, and need to add a switch outside for the utility. That could be non fused. Interconnect with a circuit breaker and unless its a small service, you will likely need a fused switch.
    Au contraire. If you interconnect with a circuit breaker, fuses in the disco are redundant and unnecessary. We deploy far more unfused discos than fused ones.

  10. #10
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    Quote Originally Posted by ggunn View Post
    Au contraire. If you interconnect with a circuit breaker, fuses in the disco are redundant and unnecessary. We deploy far more unfused discos than fused ones.
    But I was speaking to the low sccr rating of non fused switches. What I was getting at is if you use a circuit breaker interconnection, a non fused switch does not series rate with it. Sure likely not an issue with a residential service, it doesn't take a very large service to get over 10k. Of course if one is ignoring the sccr rating, it's a moot point
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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