No RCD protection for socket outlets rated 32A or greater

[spud1]

Hi Guys,

Can somebody shed any light on why socket outlets rated at 32Amps or greater do not require RCD protection under BS7671?

Presumably theres some maths behind it?

And presumably the only exception is in a TT earthing System?

Cheers chaps

 

[telectrix]

presumably, socket outlets rated 32A or over are used by skilled/instructed persons.

 

[ringer]

That was my thinking too. And isn't the disconnection time for such sockets 5 seconds rather than 0.4 seconds? Does not answer the original question, but probably has some relevance.

 

[spud1]

Is that the only reasoning behind it ?

And am I correct to say TT is an exception?

 

[telectrix]

not sure of the answer to that, so will not risk giving you the wrong advice.

 

[spud1]

OK no worries thanks tele. Hopefully someone else might have an idea??

 

[ringer]

It's all to do with reg 411.3.x which is about as clear as mud. It's one of those regulations that gives specific guidance for a particular application (sockets less than 32A) without being clear about how to go about installing anything other than that. Suggest you try posing your query in the IET forums - you may get a full answer from the bods on there (or you may not )

 

[Deleted member 26818]

Generally, equipment rated at 32A and greater is not mobile/portable.

 

[ringer]

411.3.3
In AC systems, additional protection by means of an RCD in accordance with Regulation 415.1 shall be provided for:
(i) socket outlets with a rated current not exceeding 20A ......
(ii) mobile equipment with a current rating not exceeding 32A for use outdoors

though quite what kind of mobile equipment exists that is rated at over 32A is beyond me

 

[Rampage]

Welder.

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