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Main switch rating

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  1. #1
    Apprentice (new member)
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    Default Main switch rating

    Gidday fellas, i was just wondering if you can help me. In my switchboard i have three power, and 2 lighting breakers. My main switch looks exactly like the breakers only it's rated at 40A, one of my mates reckons it should be 80A to cover the sum of all the breakers combined, is he right?

  2. #2
    Golden Member nev25's Avatar
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    No
    It depends on the Maximum Demand of youre house on the system.

  3. #3
    notanapprentice dan76's Avatar
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    depends on whether its a circuit breaker or an isolator, if its an isolation switch than i think its not the right size, but if it is a circuit breaker then it may be there to limit current and protect small consumers mains.
    either way call a local sparky to check it out for you

  4. #4
    Golden Member nev25's Avatar
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    Yeah its quite common to have a 40amp Mains switch on 6mm2 mains

  5. #5
    Slow but rough Uncle Bob's Avatar
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    Quote Originally Posted by nev25 View Post
    Yeah its quite common to have a 40amp Mains switch on 6mm2 mains
    Just adding to clear it up a bit.
    CB's are rated to the cable size their protecting. A mains switch rating covers what current it (the switch) can carry safely.

  6. #6
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    So on average, a household with 3 power and 2 light and an oven, what is the main breaker rating? I know it depends on the size of the mains cable but on average wouldnt the average household have 6mm2 mains?

  7. #7
    notanapprentice dan76's Avatar
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    mate there are too many variables for us to tell you what it should be with out looking at it ourselves.
    is your mate a sparky?
    unless you are trying to limit current flow on say 25mm or bigger mains then an 80 amp mcb is not going to do you any favours.but if it is an isolation switch 80 amp is a pretty standard size.
    if your overly worried about it get a sparkie to look at it
    as to the size of the mains, depends on the age of the house, the older it is the more likely for the mains to be smaller, would have to look at the cable to tell for sure

  8. #8
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    Quote Originally Posted by Craig W View Post
    So on average, a household with 3 power and 2 light and an oven, what is the main breaker rating? I know it depends on the size of the mains cable but on average wouldnt the average household have 6mm2 mains?
    Depends on the age and how the cable comes in (aerial or underground in conduit). There's too many variables because of all the changes over the years.

    I can't remember what size aerial we have from the pole to the house (10mm???) but it's slightly smaller then the 16mm that runs down to the switchboard and we have a 100amp main breaker. Our pole fuse is 100amps.

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