Ground floor RCD protection

[gezo39]

Hi everyone,

I am having some work done in my kitchen which are additions and alterations to the existing ring main. The house installation has a Wylex rewirable type consumer unit with a sperate downstairs and upstair ring main, the main earth to the water stop cock and gas valve is in 6mm. The sparky states that any ground floor socket that may be used to take an extension lead outside needs to be RCD protected. He does not want to change the CU but says he will add an inline RCD. Firstly can this be done as you would have (as i see it) a rewirable fuse carrier feeding an RCD. Would it not be better to run new tails from a phase block to the mini RCD board and then have the output off that. It all sounds a bit confusing thank god i only work in Millivolts.

 

[Taylortwocities]

Can be done either way. I expect he'll be upgrading your main bonding to 10mm at the same time????

TTC

 

[Lectrician]

Bite the bullet and get the CU changed - it will be more, but if you think you will get it done in the future, the RCD he fits now will become redundant and a waste of money.

6mm bonding should really be upgraded, but *can* be left as acceptable. If it is a PME supply, the quote is something like "It is up to the designer to decide if the 6mm bonding is adequately sized".

Need to get the book out to double check!

If it is easy to change, change!

 

[gezo39]

Thank you gentlemen.

I would be happy to have the CU changed but he doesn't seem that up for it.

If he goes for the separate RCD fed from the fuse holder way of doing it what shall i look out for? should it be done in tails or T&E, my guess is it would not be 2.5 but say 4mm as the feed?

I like this forum at least you get answers, thank you to all

 

[Lectrician]

4mm T+E feeding RCD, 2.5mm ring ends out the RCD.

 

[Taylortwocities]

Or 6mm if you dont have 4mm to hand

TTC

 

[securespark]

That is not the correct way to do it.

See here:

http://www.theiet.org/forums/forum/...d=13458&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear

 

[Lectrician]

What makes you think it isnt correct from that link? It's just someones say so.

I wouldn't use a three phase RCD in that situation - it simply isn't designed for it.

As for coding a code 2 on a PIR - that guy is taking the ****. If he deems it against BS7671, which is a close to the edge call if you ask me, then a code 4 is appropriate, never a code 2.

Better go and rip out the ones installed in MOST science labs in schools then......the ones the council guys specced.

 

[ample]

Strictly speaking, it may just not be the ground floor sockets that feed equipment outdoors. I know it's not very likely that the upstairs will be used for outdoors but a possibility. The NICEIC area engineer told me a story about someone using an extension from upstairs, when I put the same argument to him.

 

[Lectrician]

The NIC tell plenty of stories.

I heard one about a school that was recently built, with a socket outlet with RCD protection provided in the garden quadrangle.

The NIC insector was looking at the install and noticed an extension lead from the corridoor to the garden via a metal framed window. The corridoor had no RCD protection.

Whats the call??






The official call of the NIC is that if a written risk assesment is in place for the premises stating which sockets CAN be used outdoors is in place, then other sockets can be excempt.

This was brought about due to a PIR we did at a site where there doors everywhere, and installing RCD protecting to all sockets that could be used outdoors would be vastly expensive. A risk assessment was adopted, and a few RCD sockets installed.

 

[securespark]

As I interpret the regulations, it is within regulation to fit an RCD socket adjacent to each external door, as long as you label all others as unsuitable for supplying equipment outdoors, but how impractical is that?

Just like the safety inspection I did at a domestic property which had a 3P board with adjacent accessories on different phases: It is not aesthetic(although it should be done, of course) to label accessories in a domestic situation.

But as for the single cable feeding a ring scenario, the ring does not terminate at the protective device. That is wrong, isn't it?

 

[RF Lighting]

But as for the single cable feeding a ring scenario, the ring does not terminate at the protective device. That is wrong, isn't it?

I'm not sure. The RCD is effectively a 1 way sub main fed from the wylex board.

It is not wrong to feed a ring from a submain board.

 

[securespark]

I shall bell my technical officer on Monday. I'm sure he objected to me doing this on a job, but can't remember what those objections were.