ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades New laws for U.K. Domestic wiring?

I'm glad to see that there are others who agree that the RCD is not the magic panacea to all ills that some believe it to be.

Loop impedance and the speed with which an OCPD will break the circuit is a primary consideration in the British IEE Regs. as well. On a direct phase-to-earth short the protective device must open the circuit within 0.4 sec. for normal outlets.

One indirectly associated problem is in the many rural homes here which use TT earthing, thus necessitating the use of a single main RCD. A ground fault on any circuit trips out the main and plunges the whole house into darkness. I wonder how many accidents that has caused? Personally, I would like to see the TT installations abandoned as soon as possible in favor of TN-C-S (PME/MEN system) in rural areas. It seems unlikely, however, as our Regs. are gradually moving closer to a common European standard, and TT seems to be favored heavily in much of Europe.

On permits, I don't see requiring them for simple repairs and replacements as a viable scheme. People would just ignore the law as they already do for gas. And if you prevent them from buying the appropriate parts from a store, they'll probably try to "get by" with salvaged second-hand materials.

Paul,
What is the required trip time (in uS) in the UK, at 30mA, for an RCD?.
What brands of RCD are most prevalent in the UK?.
You were saying about a single RCD knocking out all of the house, this is why I would not put an installation on the same RCD, a minimum of 3 RCD's is my way of working, two lighting and one 3 pole 230V for the Socket-Outlets.
Paul, how does TT differ from TN-C-S?.
As soon as you have a law, there will be some one out there that will circumvent it, just have a qualified person at each point where these things are purchased.

{Edited to remove misinformation }

On the matter of RCD's, trip times and TT systems:

The legal requirement in Sweden for an RCD that is intended as a life saving device breaking the current within 200 ms. Modern technology has long surpassed this and the RCD's you can buy trip in about 40 ms. I think the Brits have upgraded their regs to require 40 ms.

Improved technology has opened a window for short time delay (or perhaps they should be called ultra short time delay) which waits 10 ms to see if the fault goes away. (Reduces nuisance tripping)

The RCD on a TT system is not intended to save your life directly, therefore it can be allowed to take longer to trip. As Paul indicated, if a fuse or MCB is used as protection in case of a earth fault it only needs to trip in 400 ms for 200-277V systems and 800 ms for 120V systems. I think the RCD has a 200ms requirement, though.

Note the logic: If the MCB is used as protection, the voltage to earth at the fault will only be half of the nominal voltage: The rest is lost in voltage drop in the line conductor. (Assuming same resistance in earth and line conductors) In case of a TT system, the voltage a the fault can be close to the full nominal voltage as the current is much lower. This means the more current will flow through anyone being in contact with the protective earth.

The manufactures have begun making RCD's time delay. (I think I've seen values from 50 to 300 ms)

This means that you can put two RCD's in series, where the "main" RCD only trips in case the other RCD fails. This in turn means that a house on a TT system no longer need to plummit into darkness, unless the fault is on a circuit which is protected only by the "main" RCD.

There are long time delay RCDs too, which means that you can have several "layers" of protection, just like with fuses or breakers.

The world is getting better each day!

Some good information on RCDs on TLC's website: http://www.tlc-direct.co.uk/Technical/Distribution/RCD.htm

[This message has been edited by C-H (edited 04-25-2003).]

Another thread worth reviving.......

How has part P progressed? Anybody know? I've heard nothing more about it recently (although admittedly I haven't been looking! )

Paul I believe its doing very nicely, you wil be pleased to know its all systems go for Jan 2005.
I am sure I have had the list of runners and riders but cant find it! From memory its NICEIC, ECA, ZURICH Insurance Group, BSI, IEE, and another I cant remember the last one not many suprises realy. All good charitable organisations with sound pension funds. Will continue the search amongst the crap on my desk and confirm with a post late. The only certainty is its going to cost us money and business in the short and long term.
I have placed an on going order for paper to be delivered by the trailer load once a month, feel sure thats about the only extra I will need to cope with it all. Oh and a geezers comming round every half year with a trailer to shift the Bull S@!:.
I will sign off now and go and take my anti- cynicism tablets before retiring to the pit.

Found it! ELECSA is the other administering organisation for Part P more info on the Voltium webb site. Sorry I dont have the techy to do links.
Alan

Ah..... Thanks Alan. This looks like the site:

http://www.elecsa.org.uk/

I still say this is just not going to work, except for new buildings and really major renovation projects.

People in this country simply will not go running to their local council, begging permission to add a socket in their own home. They can introduce all the legislation and all the schemes they like, but the majority of DIY homeowners will simply ignore them, even if they are aware of their existence. The motto will just be "Don't tell them."

Tend to agree with you Paul, but its a big bucks fine if they get caught, and I the lecky will also face a hefty fine. It could finish up with quite a little industry snitching on your neighbour, ya know what I mean!!!

Just had a butchers at the Elecsa site they look well versed to look after the electrical industry, two years wxprience looking after double glazing association scheme. And we all know what double glazing does for you dont we!! Ah well only four more years to go....

No idea what the fines for not being good little boys and girls and telling the council will be, but how exactly do they propose to enforce it against the DIY homeowner?

Now if somebody decides to built a 400 sq. ft. extension without the council's permission, it's noticeable, and if somebody reports it within the required time period (is it 3 years?) then legal problems could follow.

But wiring is different. It doesn't show on the outside of the house (well, most of it doesn't!). There are no official records of what electrical systems are installed in homes. So at least in the early stages, even if some council pen-pusher did try to query something, the homeowner just says "Oh that as done back in 2004." How does the council prove otherwise, unless every new device is going to be date coded?

But proof is really beside the point. How is the council going to know that somebody has added a socket, or changed a light switch in his own house to even query whether some "illegal" work has been carried out in the first place?

As far as I can see, for the average DIYer the new regulations will be totally unenforceable.