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5A Junction box

JDW

Are 5amp junction boxes acceptable on a 6amp lighting circuit?

I personally wouldn’t use them as they are too small, but if they are already fitted are they acceptable? 

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  • 0

    Hello JDW.

    I think there's a bit of history involved in your initial question, which dates back to the rewireable fuse days, 5A, 15A, 20A & 30A (metric values?!) When we harmonised round about 1980 the main IEC MCB equivalents were 6A, 16A and 32A (i.e. not metric!), so those values were introduced in the UK to harmonise. Close enough for no existing hardware changes to be necessary. Where found, an existing 5 amp junction box on a 6 amp MCB will be fine, all other things being equal.  The small size makes cable sheathing enclosure a common failure with these - most guys installed 20 amp JBs for just that reason; the actual terminals themselves being similar in size.

    Regards,

               Colin Jenkins.

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  • 0

    Hello JDW.

    I think there's a bit of history involved in your initial question, which dates back to the rewireable fuse days, 5A, 15A, 20A & 30A (metric values?!) When we harmonised round about 1980 the main IEC MCB equivalents were 6A, 16A and 32A (i.e. not metric!), so those values were introduced in the UK to harmonise. Close enough for no existing hardware changes to be necessary. Where found, an existing 5 amp junction box on a 6 amp MCB will be fine, all other things being equal.  The small size makes cable sheathing enclosure a common failure with these - most guys installed 20 amp JBs for just that reason; the actual terminals themselves being similar in size.

    Regards,

               Colin Jenkins.

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