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Which RCD for Garage Consumer Unit, mains coming from house

Discussion in 'Electrics UK' started by Squiral1, 17 Sep 2020.

  1. Taylortwocities

    Taylortwocities

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    Discrimination between MCBs is quite hard to achieve. A ratio of 2:1 is often bandied about. There are proper tables provided by manufacturers of stuff.

    An easier way is to have a FUSE at the source end feeding the downstream MCB.

    But you are designing it, so you obviously know what you are doing. :LOL::LOL:
     
  2. JohnW2

    JohnW2

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    I wouldn't say that there is really any "must" about it. Unnecessarily having two OPDs in series which won't 'discriminate' is silly, and a potential inconvenience, but that would seem to be about all.

    If there were a "must", we would have somewhat of a problem, in that, as we all know, a 13A BS1362 fuse will often tonot discriminate from a B32 MCB (let alone a B20) and, perhaps 'worse', a 13A BS1362 fuse in a plug certainly will not, if plugged into a socket which is a 'fused spur', discriminate against the identical 13A BS1362 fuse in the FCU (not to mention 3A fuses for fans fed by B6 MCBs :) ) - so, if discrimination between OPDs were a "must", many of the common aspects of electrical installations would 'not be allowed' :)

    Kind Regards, John
    Edit: typo corrected
     
    Last edited: 19 Sep 2020
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  4. Squiral1

    Squiral1

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    I'll look at various options and decide which is best to go down. I could fuse switch it, that is an option.
    The cave CU is there if needed.
     
  5. Taylortwocities

    Taylortwocities

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