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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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  • 0

    If this CNC machine of yours is a non portable  thing then wouldn't it be easier to power it from a 20 or 25 amp double pole isolator? That would get round all the problems of which type of plug is best and you wouldn't lose any portability if it a big heavy lump if a machine. Also south African 15 amp plugs are now rated at 16 amp although the design is the same as when it was 15 amp.  I always thought those old plugs looked capable of carrying much  more than 15 amp the plug pins are very beefy 

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  • 0

    If this CNC machine of yours is a non portable  thing then wouldn't it be easier to power it from a 20 or 25 amp double pole isolator? That would get round all the problems of which type of plug is best and you wouldn't lose any portability if it a big heavy lump if a machine. Also south African 15 amp plugs are now rated at 16 amp although the design is the same as when it was 15 amp.  I always thought those old plugs looked capable of carrying much  more than 15 amp the plug pins are very beefy 

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  • 0 in reply to Kelly Marie Angel

    the plug pins are very beefy 

    Although it's usually the springy socket contacts rather than the c.s.a. of the pins that's the limiting factor ... it can be quite a challenge to get a decent reliable contact area, especially on a curved surface (and one where the radius of the curve may reduce slightly over time as the pins wear) - one of the design features of the 13A system was flat pins is that the flat contact areas provided better and more reliable contact.

       - Andy.

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