Inverter Battery - Fuse, Circuit Breaker?





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  1. #1
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    Default Inverter Battery - Fuse, Circuit Breaker?

    In talking to so-called solar system installers, many are installing AC circuit breakers as protection for the inverter batteries.

    Their utterances:
    - "we've installed them everywhere and have never had a problem [sic]"
    - "they work equally as well on DC as they do on AC"
    - "we don't use fuses because you don't want to be left in the dark when a fuse blows and you don't have a spare [sic]"

    Scary.

    Does anyone know where to get DC circuit breakers rated around 125A?
    I still prefer fuses though. Any preferred brand/type and availability, again around 125A.

    Thanks
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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    It's going to set you back a few thousand Rands but the electrical whole sales will have eg North and Robertson, Voltex etc.
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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by hunter26 View Post
    It's going to set you back a few thousand Rands but the electrical whole sales will have eg North and Robertson, Voltex etc.
    What's that for?
    If you make a noise or need music in the bush or on the beach, you’re missing the point.

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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by PRA View Post
    What's that for?
    125Amp, sorry a few hundred rand if single phase AC breaker
    Last edited by hunter26; 2020/02/17 at 09:27 AM.
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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    I bought Victron 125A fuse the other day.

    Can't help with breaker.
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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by hunter26 View Post
    125Amp, sorry a few hundred rand if single phase AC breaker
    Apologies - I'm not sure I understand.
    Are you saying that an AC breaker should be installed as an inverter battery protection device?
    If you make a noise or need music in the bush or on the beach, you’re missing the point.

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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by Prof View Post
    I bought Victron 125A fuse the other day.

    Thanks.
    Wow - the fuse cost a lot more than the holder.
    If you make a noise or need music in the bush or on the beach, you’re missing the point.

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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by PRA View Post
    Thanks.
    Wow - the fuse cost a lot more than the holder.
    You get cheaper fuses.
    But since all Victron, stuck to what I trust
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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    For your own protection you have to fuse the dc setup. I prefer the self extinguishing fuses but they are difficult to source and are expensive. R450 vs R75 for an anl type fuse.

    Use dc breakers for dc - I would not trust an ac breaker to do a disconnect when I really need it or to last. Dc and ac operate totally different, the internal parts are made out of different materials and sizes of contacts to cope with the loads. If there is a fault the ac breaker welds closed and/or melts so you will not be able to switch it off.

    Ballpark figure is about R250 for a dc breaker. Try any solar shop. The installers propably use the cheapest ac breakers which cost R45 - there's your reason.

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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    I paid R850 for a 80A DC Circuit breaker last year ( Local electrical shop)

    Im sure one of the electrical gurus will chip in but the reason why a DC breaker is so much more expensive than an equivalent AC breaker is because with AC you have a 100 zero volt crossings every second. With DC this never happens, so to extinguish the arc that is created by the current when the contacts open under a fault conditions requires some extra components.

    I prefer DC breakers above Fuses, because the end user doesn't always have the necessary skill or knowledge to change the fuse, to to replace a blown fuse with the correct rating. Whereas with a breaker, anyone can flip a breaker back up.

    2am on a Saturday morning the blown fuse is quickly replaced with a piece of copper wire

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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Somewhere someone is talking BS in order to get the price low as DC stuff are expensive.

    Easy if you have solar panels to test say a 5A AC breaker and see if it trips.

    I have done so and can say the ancient Fuchs breakers work just as well on AC as DC. A Samite just won't trip close to the current it should.

    You can get a 125A fuse for R250 or pay up to R1100.
    Last edited by ekkekan; 2020/02/17 at 01:31 PM.

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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by ekkekan View Post
    Somewhere someone is talking BS in order to get the price low as DC stuff are expensive.

    Easy if you have solar panels to test say a 5A AC breaker and see if it trips.

    I have done so and can say the ancient Fuchs breakers work just as well on AC as DC. A Samite just won't trip close to the current it should.

    .
    This is terrible advice ekkekan. No one is BS anyone, DC breakers are more expensive for a very good reason. The trip curve might still be valid but the contacts will fuse together on an AC breaker the day you really need them to open.

    DON`T USE AC BREAKERS IN DC APPLICATIONS
    Last edited by Family_Dog; 2020/03/10 at 06:49 AM.

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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Ja. DC comes at a price.
    But I'm amazed that you are tripping your battery circuit..
    What amperage are you talking?
    If you fit an appropriate fuse it should only blow with a catastrophic failure in the inverter..
    Last edited by Richard Mackay; 2020/02/17 at 11:49 AM.

  16. #14
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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    When a fuse blows there's a problem.
    You don't simply 'put in another fuse' - you find the problem first.
    If you don't the replacement fuse will also blow.

    Using an AC circuit breaker in a DC application is irresponsible and negligent.
    There's a reason why they manufacture DC circuit breakers.
    If AC and DC breakers are 'simply the same' why do they bother to manufacture DC breakers?

    See the last sentence in post #12!
    If you make a noise or need music in the bush or on the beach, you’re missing the point.

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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by ekkekan View Post
    Somewhere someone is talking BS in order to get the price low as DC stuff are expensive.

    Easy if you have solar panels to test say a 5A AC breaker and see if it trips.

    I have done so and can say the ancient Fuchs breakers work just as well on AC as DC. A Samite just won't trip close to the current it should.

    You can get a 125A fuse for R250 or pay up to R1100.
    Oh dear.

    Looks like it is time again.

    https://www.youtube.com/watch?v=Zez2r1RPpWY

    Watch this and then please tell us again how safe your Fuchs breakers is on DC.

    A MUST WATCH FOR ANYBODY WITH DOUBTS ABOUT DC BREAKERS AND ISOLATORS/SWITCHES AND FUSES.
    Last edited by Family_Dog; 2020/03/10 at 06:49 AM.
    Cheers

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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by Tiaan Pot View Post
    This is terrible advice ekkekan. No one is BS anyone, DC breakers are more expensive for a very good reason. The trip curve might still be valid but the contacts will fuse together on an AC breaker the day you really need them to open.

    DON`T USE AC BREAKERS IN DC APPLICATIONS
    My be read the post. A person fitting AC breakers and saying it will work just as well on DC is BS the next person. Nowhere did I refer to the price of DC equipment being BS.

    Advice is when you pay me - all other comments are just an opinion.
    Last edited by ekkekan; 2020/02/17 at 01:30 PM.

  20. #17
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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by PRA View Post
    In talking to so-called solar system installers, many are installing AC circuit breakers as protection for the inverter batteries.

    Their utterances:
    - "we've installed them everywhere and have never had a problem [sic]"
    - "they work equally as well on DC as they do on AC"
    - "we don't use fuses because you don't want to be left in the dark when a fuse blows and you don't have a spare [sic]"

    Scary.

    Does anyone know where to get DC circuit breakers rated around 125A?
    I still prefer fuses though. Any preferred brand/type and availability, again around 125A.

    Thanks
    Phone Solar Advice, they have Keto switches and 125 A DC fuses. I paid R1k for the set. They assured me they are DC fuses but I have not actually checked..
    The next question is should you be using 125 A or 80 Amp There was a huge debate with graphs etc on the powerforum but nobody was prepared to definitively say which fuse is the correct one to get...

  21. #18
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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by NewLandy View Post
    The next question is should you be using 125 A or 80 Amp.
    Thanks for the information.
    I'm installing a Victron MultiPlus ll GX 3kVA and the product manual recommends a battery fuse rated at 125A.
    If you make a noise or need music in the bush or on the beach, you’re missing the point.

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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    @Fluffy - I was merely pointing out that unlike the Samite the Fuchs will actually trip. Further I have a Fuchs that has tripped DC about 30 times without problems. May be it is working fine as the current is low. This is a 5A Fuchs MCB. This breaker is used in a circuit where as soon as the battery went below a certain level and the current increased it would trip to protect the charger. It is in use since 2015 LS.

    While we on MCBs on the battery side. Bear in mind you are going to have a larger volt drop over a MCB current coil than using a fuse. This might not be on all MCBs but on the Siemens DC I used.

  23. #20
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    Default Re: Inverter Battery - Fuse, Circuit Breaker?

    Quote Originally Posted by PRA View Post
    Thanks for the information.
    I'm installing a Victron MultiPlus ll GX 3kVA and the product manual recommends a battery fuse rated at 125A.
    Is this fuse on a 24V or 48V battery?

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