How many sockets have I fitted incorrectly?

[ericmark]

I was looking at SentrySocket an MK product and noted these should not be used with a TT system. Before 2008 I am sure I have fitted a few of these sockets for where it was likely to be used to power items used outside and sure some of the houses were TT supplies.

OK likely there was a 100ma S type as well but I had never realised these were for TN-S systems only.

Also question use of double filtered sockets I have used on rings yet note now only rated at 13A for pair so really should be supplied from a FCU.

All would have been done pre-2008 and now no records of work and all done while employed cards in.

So two questions should I worry about the errors and second have RCD sockets always been like this or is it something new?

 

[ban-all-sheds]

I was looking at SentrySocket an MK product and noted these should not be used with a TT system.

Any idea why?

 

[stillp]

MK state "Suitable for use with TN-S, TN-C-S and TT systems".
See http://www.mkelectric.com/Documents...ifications/T27 SENTRY+SOCKET Tech 661-689.pdf

[Edit - whoops, sorry, no they don't! ]

 

[Lectrician]

Does seem odd - I think they mean a TN system (TN-C-S and TN-S). Does make you wonder though if a TT is OK and the confusion is caused the centre tapped type supply mentioned? I know these will fail if polarity is reversed.

 

[JohnW2]

How about this - seemingly more bizarre ....

Untitled

• JohnW2
• 24 Jul 2013
• 1

... it would seem that it's only single-socket SentrySockets that are 'only suitable' for use with TN-S, the implication presumably being that this restriction doesn't apply to double-socket ones! What's all this about?!

Lond Regards, John

 

[Spark123]

Odd.
A 127v line to neutral is basically a 230v 3 phase system. I can understand why is isn't suitable for this as a functional earth which is 127v above neutral is going to send it doolally!
Saying that, I wouldn't fit a normal BS1363 socket to a supply like this as you then have issues with plugtop fuses only being in one line anyway.

 

[JohnW2]

It's surely just plain daft. An RCD, certainly in a single-phase system, will do 'what it says on the tin' (operate in response to an L-N imbalance) regardless of the earthing system - indeed, even in the absence of an earthing system if some of the current can find a way back to the transformer other than through the supply conductors (hence RCD)?

Kind Regards, John

 

[ban-all-sheds]

Odd.
A 127v line to neutral is basically a 230v 3 phase system.

Could be 2-phase 3-wire.

Maybe they don't recommend it for TT because it only disconnects the line when it trips?

Somebody should ask them - MK have (or used to have) a pretty good technical help team. Could ask at the same time about the idea of N & E being connected together in a TN-S system.

 

[JohnW2]

Somebody should ask them - MK have (or used to have) a pretty good technical help team. Could ask at the same time about the idea of N & E being connected together in a TN-S system.

... and maybe also why single-socket ones are apparently different from double-socket ones in this respect!

Kind Regards, John

 

[JohnW2]

Odd. A 127v line to neutral is basically a 230v 3 phase system.

220V 3-phase, to be more precise.

Could be 2-phase 3-wire.

(ignoring the terminology issue!) ... 254V between phases? - that would be a little odd, too, wouldn't it?

Kind Regards, John

 

[ban-all-sheds]

It would yes - I didn't even think about bothering to multiply 127 x 2...

 

[JohnW2]

It is apparent that there is some difference between the single-socket and double-socket ones ...

Untitled

• JohnW2
• 24 Jul 2013
• 1

Who knows about BS EN 61543: 1966? What is it about the single-socket ones that doesn't comply with that standard, I wonder? It is, perhaps, as BAS suggested, 2-pole RCD operation (it does say 'double-pole switching', but that might apply just to the switches, not the RCD!).

Kind Regards, John

 

[mfarrow]

Somebody should ask them - MK have (or used to have) a pretty good technical help team. Could ask at the same time about the idea of N & E being connected together in a TN-S system.

... and maybe also why single-socket ones are apparently different from double-socket ones in this respect!

John, I don't see where you are reading any difference (apart from the BS compliance spec). Both statements posted about "only TN-S" to me say the same thing, only we yours states single sockets only, and we don't know where you got yours from. Would you mind clarifying?

 

[mfarrow]

Who knows about BS EN 61543: 1996?

From the standard:

This International Standard includes definitions, standard electromagnetic conditions, conditions of
operation in service and electromagnetic tests necessary for devices providing residual current protection.

It applies when required in a product standard and in conjunction with it, at present for:

— IEC 61008-series for RCCBs;
— IEC 61009-series for RCBOs.

It is intended to apply also for the same purpose, in conjunction with future IEC standards, for portable
residual current devices without integral overcurrent protection for household and similar uses (PRCDs),
to residual current devices without integral overcurrent protection incorporated in or to be associated with
fixed socket-outlets (SRCDs) — now under consideration — and to other RCDs incorporating overcurrent
protection.

The EMC characteristics of a product are generally influenced by the design and not by the
manufacturing process, therefore the tests of this standard are to be made for design verification and will
be repeated only in the case of modifications influencing the EMC behaviour.

I guess MK must have seen a market to get these certified as compliant, but not the single-socket ones!

 

[stillp]

It is apparent that there is some difference between the single-socket and double-socket ones ...

Untitled

• JohnW2
• 24 Jul 2013
• 1

Who knows about BS EN 61543: 1966? What is it about the single-socket ones that doesn't comply with that standard, I wonder? It is, perhaps, as BAS suggested, 2-pole RCD operation (it does say 'double-pole switching', but that might apply just to the switches, not the RCD!).

Kind Regards, John

Seems I'm needed here!
EN 61543 is titled "•Residual current-operated protective devices (RCDs) for household and similar use - Electromagnetic compatibility". I can't see why that would apply to double SRCDs and not single.