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Thread: Surge arrestors

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    Surge arrestors

    If you install a T2 surge arrestor in a domestic property, do you connect it directly after the main switch, using a 16 mm wire and no fuse or,

    do you install a 32 amp mcb and wire it with 4 mm wire?

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    Quote Originally Posted by Isetech View Post
    If you install a T2 surge arrestor in a domestic property, do you connect it directly after the main switch, using a 16 mm wire and no fuse or,

    do you install a 32 amp mcb and wire it with 4 mm wire?
    Normally a surge arrestor has 125Amp protection rating requirement .Some are different.

    If it was 125Amp rating and my main switch is 80Amp protection , I would leave it at full rating.

    If you stick a 32 Amp C/Breaker in it may trip on a surge that it is trying to clamp and then letting the rest of the surges through which kind of defeats the object.
    I would rather let the surge arrestor take the surge to earth and if it is a big surge trip the 80Amp supply - That way I ensure the client is disconnected from any further surges .

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    Quote Originally Posted by GCE View Post
    Normally a surge arrestor has 125Amp protection rating requirement .Some are different.

    If it was 125Amp rating and my main switch is 80Amp protection , I would leave it at full rating.

    If you stick a 32 Amp C/Breaker in it may trip on a surge that it is trying to clamp and then letting the rest of the surges through which kind of defeats the object.
    I would rather let the surge arrestor take the surge to earth and if it is a big surge trip the 80Amp supply - That way I ensure the client is disconnected from any further surges .
    The big unit we install in the factories have 125 amp fuses and wired accordingly.

    I have decided to mount the unit next to the main switch and using the busbar at the top to feed the L of the surge arrestor which will have a 16 mm supply cable, which reminds me I must check the main switch is not identified line and load, because the line will be in the bottom. I will also fit a tag on the main cable identifying line and load.

    I am using a little T2 10 ka CBI unit.

    I am told the surge arrestor will not carry any load it is a transient over voltage protective device.

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    This is another topic which we should discuss in a lot more detail. I normally contact the specialist in JHB, but he has retired and only works as a consultant now.

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    The manufacturer indicated that no circuit breaker is required and a 16 mm wire connected to the top of the surge arrester and a smaller wire for the earth (no size indicated , so we will use a 6mm) would be the preferable way to wire it. Than k goodness I have a busbar on the top of the breakers which are not on earth leakage, so installing a 10 or 16 mm bridge across the top should be fine. The supply breaker is 60 amps.

    I think it might be batter to get it in writing.

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    Quote Originally Posted by Isetech View Post
    The manufacturer indicated that no circuit breaker is required and a 16 mm wire connected to the top of the surge arrester and a smaller wire for the earth (no size indicated , so we will use a 6mm) would be the preferable way to wire it. Than k goodness I have a busbar on the top of the breakers which are not on earth leakage, so installing a 10 or 16 mm bridge across the top should be fine. The supply breaker is 60 amps.

    I think it might be batter to get it in writing.
    What qualifications does the person have who passed this information to you?
    The earth wire is one of the key elements in the operation of a surge arrester.
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    Quote Originally Posted by Justloadit View Post
    What qualifications does the person have who passed this information to you?
    The earth wire is one of the key elements in the operation of a surge arrester.
    I suppose it is like asking the counter salesman at the wholesaler what size wire you need to connect a 7.5 kw motor.
    Last edited by Isetech; 18-Jun-22 at 08:37 AM.

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