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16A sockets in domestic installation

Keir Stitt

I'm intending to use a small CNC at home. It needs a 16A single phase supply and preferably I'd just connect via an interlocked EN 60309 commando socket, but that would be a departure from 553.1.201 because commando sockets aren't shuttered.

Ironically I would be okay installing a European Schuko on a 16A radial - because they are shuttered but clearly not particularly robust for a workshop and not polarised either. Maybe get an IEC 60906-1 from South Africa.

Of course I can risk assess a departure from 553.1.201 given that interlocking offers a greater level of safety than shutters. 

I could use a 15A BS 546 but these days protective devices are harmonised at 6, 10, 16A etc. And BS 546 / BS 1363 haven't kept up, so a 15A wouldn't have sufficient protection and in any case i think an interlocked commando offers a greater level of protection.

I presume many electicians just put commandos in people's garages without even considering that they're departing from BS 7671.

I get the impression 553.1.201 is a old provision which when read today has unintended consequences. It is of course a national departure from HD 60664.

What are people's thoughts on using commando sockets in a dwelling? In terms of the departure risk assessment, are there circumstances in which an interlocked socket may offer less safety than a shuttered socket? 

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    Keir Stitt said:
    Of course I can risk assess a departure from 553.1.201 given that interlocking offers a greater level of safety than shutters. 

    Interlocked outlets may be provided with either an interlocked switch or an interlocked isolator.

    Interlocked isolator versions used to be quite rare and expensive, but now are more readily available as some special locations (e.g. Section 708) require them. Best to ensure they have the 'isolator' symbol on them.

    Another consideration, though, is that socket-outlets to BS EN 60309 series (including interlocked isolator types) I understand are Overvoltage Category II ... BS 1363-2 shuttered outlets are Overvoltage Category III ... so, do interlocked industrial socket-outlets (even with the isolation function) always offer 'equivalent safety' to a shuttered socket-outlet to BS 1363-2?

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  • 0
    Keir Stitt said:
    Of course I can risk assess a departure from 553.1.201 given that interlocking offers a greater level of safety than shutters. 

    Interlocked outlets may be provided with either an interlocked switch or an interlocked isolator.

    Interlocked isolator versions used to be quite rare and expensive, but now are more readily available as some special locations (e.g. Section 708) require them. Best to ensure they have the 'isolator' symbol on them.

    Another consideration, though, is that socket-outlets to BS EN 60309 series (including interlocked isolator types) I understand are Overvoltage Category II ... BS 1363-2 shuttered outlets are Overvoltage Category III ... so, do interlocked industrial socket-outlets (even with the isolation function) always offer 'equivalent safety' to a shuttered socket-outlet to BS 1363-2?

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