New fuse box?

[Iggifer]

My parents had a re-wire mid 1990s, must have been the earlier part as I don't remember it.

Split load MEMERA 2000, all sockets were RCD protected (3 circuits kitchen/up/down) and everything else was not.

Must have been a regional thing

I'd have one of these in my house (I'm totally keeping that when it comes out next week )

 

[securespark]

471-16-01 A socket-outlet rated at 32A or less which may reasonably be expected to supply portable equipment for use outdoors shall be provided with supplementary protection to reduce the risk associated with direct contact by means of a residual current device having the characteristics specified in Regulation 412-06-02(ii).

A lot of people I knew wanted to cover their arses and RCD-protect all the sockets when the 16th came out, then there was no slipping through the net, as it were.

A true-life case we heard about when I was doing my 16th update was a 3rd floor flat whose sockets could be argued not to be reasonably expected to supply equipment outdoors, therefore no RCD protection was required for the sockets. However the owner would run an extension lead out of a window to clean his car.

 

[deadshort]

I made 2 points.
To change that CU, we would have RCD protected the shower and any downstairs socket circuits. I don't recall protecting the upstairs socket circuits.

It was possible to wire up that extension without a board change. FYI some extensions have more than one story.

Yes, but they don't float in the air

DS

 

[deadshort]

My parents had a re-wire mid 1990s, must have been the earlier part as I don't remember it.

Split load MEMERA 2000, all sockets were RCD protected (3 circuits kitchen/up/down) and everything else was not.

Must have been a regional thing

I'd have one of these in my house (I'm totally keeping that when it comes out next week )
View attachment 107025

Bloody woodworm !

DS

 

[Risteard]

When I started my apprenticeship back in 1998, in domestic work, if we installed a new CU we generally fitted a split load board with RCD protection to all sockets and the shower.

Exactly my point - it was the done thing.

 

[Risteard]

Could you perhaps explain that a little? Are you saying that you don't think 'additional protection' is appropriate in a commercial or industrial setting?

Kind Regards, John

Generally appropriate design and installation methods will mean it is not needed. There are, of course, exceptions (e.g. socket outlets rated less than 32A (with certain exceptions); bathrooms etc.)

 

[JohnW2]

Generally appropriate design and installation methods will mean it is not needed. There are, of course, exceptions (e.g. socket outlets rated less than 32A (with certain exceptions); bathrooms etc.)

Do not those 'exceptions' cover much of most commercial installations (other than lighting)?

More generally (including industrial), do I take it that you share RF's view that one need not be concerned about faults which would trip an RCD but would not invoke ADS?

Kind Regards, John

 

[Risteard]

Do not those 'exceptions' cover much of most commercial installations (other than lighting)?

Not really, as earthed metallic conduit and trunking is generally used. Certainly socket circuits are liable to need RCD protection. It seems fairly common to use RCDs even where not actually required. But that may not always be desirable in my view.

More generally (including industrial), do I take it that you share RF's view that one need not be concerned about faults which would trip an RCD but would not invoke ADS?

What type of faults do you have in mind? Certainly neutral/earth faults must be avoided but I'm not sure that that's a great reason to install RCDs everywhere - proper selection and erection of wiring systems along with proper insulation testing etc. during erection and upon completion are the answer.

 

[scousespark]

Yes, but they don't float in the air

DS

Can you read?
The op said he had an extension wired in 2006. To comply an RCD SO near the door was enough. It was NOT a rewire or a board change. Is that clea now?

 

[JohnW2]

Not really, as earthed metallic conduit and trunking is generally used.

That's not really the point - as you've said yourself, if there are "socket outlets rated at less than 32A" at the end of those conduits or trunking, then there is likely to be a need for RCD protection.

What type of faults do you have in mind?

Well, for a start, L-E faults which are not quite zero impedance. Don't forget that many final circuits are designed to 'only just' satisfy the requirements for ADS. An L-E fault of even less than an ohm therefore might well be enough to raise the Zs of the fault loop to a level at which an OPD might not operate for a long time - certainly not within the required disconnection times.

Kind Regards, John

 

[deadshort]

Can you read?
The op said he had an extension wired in 2006. To comply an RCD SO near the door was enough. It was NOT a rewire or a board change. Is that clear now?

Yes, that's clear now.

DS

 

[stillp]

Don't forget that many final circuits are designed to 'only just' satisfy the requirements for ADS. An L-E fault of even less than an ohm therefore might well be enough to raise the Zs of the fault loop to a level at which an OPD might not operate for a long time - certainly not within the required disconnection times.

I had to deal with a case a few years ago in which an OCPD failed to operate, leading to a fire that put a large factory out of action. The fault was a damaged cable, probably a very low impedance fault, but it was on the end of a 100 metre extension lead...

 

[JohnW2]

I had to deal with a case a few years ago in which an OCPD failed to operate, leading to a fire that put a large factory out of action. The fault was a damaged cable, probably a very low impedance fault, but it was on the end of a 100 metre extension lead...

Interesting, but that shouldn't really happen, should it?

Whilst, as I said, a fault with an 'almost but not quite' zero impedance could result in delayed OPD operation (i.e. not satisfying disconnection time requirements), for it not to ever operate at a current which could result in a fire is not meant to be possible - since a cable is deemed to remain 'safe' with a current of 1.45In (of an MCB) for an hour, beyond which the OPD is required to operate. Although a long extension cable can obviously reduce the fault current appreciably, that doesn't alter the generality of what I've just said - whatever the current, the OPD should operate before the cable becomes damaged or dangerously hot.

In the case you describe, was there certainty that the OPD was not faulty (and I presume it was appropriate for the cable) ?

Kind Regards, John

 

[stillp]

was there certainty that the OPD was not faulty (and I presume it was appropriate for the cable) ?

Yes, the OPCD was well within spec and was suitable for the cable size. There were some other contributing factors though.

 

[JohnW2]

Yes, the OPCD was well within spec and was suitable for the cable size. There were some other contributing factors though.

Thanks. Do I take it that you are not able to share the nature of those 'contributing factors' with us?

On the face of it, if there are factors which would result in BS7671-compliant cable protection being inadequate to prevent fires, I think that we (and JPEL/64) would have reason to be very worried!

Kind Regards, John