17th Edition - RCD requirements and concealled cables

[equitum]

"are you really going to carry out a high current earth leakage test on every piece of earthed conduit"

I know you said you had no more to say, but we would all really be grateful if you could answer B.A.S and tell us why this is necessary, how to conduct such a test, and where this test is required in "our" bs7671 regulations.

"delighter": could you also elaborate on why safe zones are borrocks, and care to mention if you have always used RCBO's for all final circuits (...in fact, are you actually JohnD??)

 

[oharaf]

I think we should put this stuff over every hidden conductor just so everyone knows exactly where they are

http://www.tlc-direct.co.uk/Main_Index/Cable_Accessories_Index/Electric_Cable_Below_Tape/

 

[securespark]

maybe the european style switching (auto alimentation???) with elv switch drops will become more common?
or pull cords?

Suprisingly ELV doesn't appear to have been considered when writing the regulation on concealled cables.

A good few years ago, I stayed in my sister's house in Brittany. Her place there has many multi-switched lights, with ptm switches & relays using this very system.

As you say, the local sparks call it auto-alimentation.

I have used this very system at home to switch the kid's bed-side lamps.

Each kid's bedroom has a din-rail enclosure fitted with a 24V selv supply & a relay.

There is a ptm switch by the door (MK "push" switch) and a Friedland "floating" bell push on a cord by the bed.

Like the auto-alimentation relays, each "pulse" (ie each press of a ptm switch) operates the relay.

So, push one to switch the light on, push again, the light turns off. Brilliant!

The only downside is the "clunk!" as the relay kicks in & out. Maybe they should be in the loft, but that was not practical at the time...

In fact, if the noise problem could be addressed, I could be tempted to use the system elsewhere in the house.

The one downside is cost. Each relay was round the £30 mark.

As for the "high-current earth leakage test", I think someone has the knickers in a twist.

In the good old days (15th) when I used to install b/e and galv. conduit, where the conduit formed the cpc, we had to use a high current tester to ensure perfect continuity between joints.

But that's not a leakage test and in any case, you only need to do that if you are NOT installing a cpc in the conduit.

 

[RF Lighting]

You ought to get with the times Simon.

Have a look at GET wireless switching. It will do everything your setup does, and also dimming and scene setting too.

One controller can control ceiling lights and table lamps independantly. Seperate remotes are available too, and as it is RF, you don't even need to be in the same room.

As much as I dislike all things wireless, I am really impressed with this gear.

 

[securespark]

Maybe I am a bit of an old-fashioned GIT...I just like the relative simplicity and reliability of something hard-wired.

In the same way I like hard-wired alarm systems & don't like wireless alarms.

Having said that, I'll give it a look.

EDIT: !"$££^^%*&*))*__+

Seen the prices????

 

[RF Lighting]

Yeah

I've got it in my bathroom. >£100 for a glorified dimmer. It is good stuff though

 

[holmslaw]

..

 

[GaryMo]

So, Holmslaw, back to safe zones, useful or nonsense?
Opinions don't count, purely BS7671:2008.

 

[holmslaw]

..

 

[ban-all-sheds]

You may not "give a stuff" what recognized bodies such as the NICEIC suggest is their interpretation of the regs (for which they have a significant contribution to creating) . However my point is that such organisations have a wealth of experience, expertise and qualified employees, which, dare I say, carries more weight in my opinion than your own far fetched drivel.

1) I was a little intemperate in my reply, but I think that "far fetched drivel" is equally, if not more, intemperate. And inaccurate.

2) You must admit that NICIEC do have a propensity for self-aggrandisement. I am by default disinclined to take any notice of their interpretation of regulations.

3) I am competent to interpret the regulations myself, and in my particular situation I am quite comfortable with my decision that I can design my installation on the basis of it being intended to be under the supervision of a skilled person.

 

[ban-all-sheds]

So, Holmslaw, back to safe zones, useful or nonsense?
Opinions don't count, purely BS7671:2008.

Of course opinions count. BS7671 says that unless they are deep. or protected or sheathed they've got to be in "safe" zones. The reason is that even when RCD protected, drilling into them is still going to be Bad News™. The RCD will stop it being directly dangerous, but it doesn't stop the cable being b******d, or help with the disruption of putting right the damage, and unless on an individual RCBO it could widen the effects of drilling into it to other circuits.

So whether the "safe" zones are a good idea or not is a valid discussion point, and opinions on where they are on the spectrum from nonsense to good idea are the only things that count, as we all know that the regs permit them.

I've always been dubious, as they only work if everybody knows about them, but in practice what's a realistic alternative? We have to have cables buried in walls, so we need to seek a balance between what's feasible, practical, and reasonably safe. People ought to have the nous to think that cables might run vertically or horizontally to accessories, but I'll bet they all don't, any more than they all have the nous to not smoke, but what can you reasonably do? RCDs mitigate some of the risks, but not all. They have at least abandoned the madness of the draft 17th which allowed cables to be run anywhere and at any depth as long as RCD protected.

Any designer is quite entitled to argue that concealed cables are not adequately protected by being in a "safe" zone and that he'll implement other methods to protect them.

What worries me about holmslaw's attitude is that he thinks all the ways to protect cables against damage are b******* - he won't accept "safe" zones, he won't accept mechanical protection, and he won't accept depth > 50mm. He seems to think (and this is my interpretation, but given his track record I'm not holding my breath waiting for a clarification) that as long as you remove the immediate danger of damaging a cable by using RCDs then as a responsible spark your job is done. But that ignores the consequences of damaged cables, such as broken ring finals which are now dangerous, the inconvenience of lost circuits, the inconvenience of the loss of other circuits via RCD action, the inconvenience and cost of repairing cables, and the possibility of unsafe repairs being done.

Try really hard and read and understand what I have previously said.

I have read it, and I understand it.

I still can't see in it though any answer to the question "have you always thought that all those things were b******?"

 

[GaryMo]

So, Holmslaw, back to safe zones, useful or nonsense?
Opinions don't count, purely BS7671:2008.

Of course opinions count. BS7671 says that unless they are deep. or protected or sheathed they've got to be in "safe" zones. The reason is that even when RCD protected, drilling into them is still going to be Bad News™. The RCD will stop it being directly dangerous, but it doesn't stop the cable being b******d, or help with the disruption of putting right the damage, and unless on an individual RCBO it could widen the effects of drilling into it to other circuits.

So whether the "safe" zones are a good idea or not is a valid discussion point, and opinions on where they are on the spectrum from nonsense to good idea are the only things that count, as we all know that the regs permit them.

'Opinions don't count, purely BS7671:2008' was a little tongue in cheek dig at Holmslaw who on many occasions says the same.
Seriously though, whether safe zones are a good or bad idea matters very little as they have to be complied with under certain circumstances. Those who think they're a bad idea or nonsense should adopt 522.6.6 (i), (ii), (iii) or (iv) with the bonus of not needing install RCD's on all circuits (apart from socket outlets under 20A and circuits in bathrooms).
I'm also fully aware of which circumstances require safe zones to be adopted.

You have to comply with any one of five options from 522.6.6 if cables are going to be concealed in walls or partitions at a depth of less than 50mm

(i) Cable with earthed metallic covering.....
(ii) Enclosed in earthed conduit.....
(iii) Enclosed in earthed trunking.....
(iv) mechanically protected against damage......
(v) Installed in safe zones.....

Now where 522.6.6 (above) applies and the installation is not intended to be under the supervision of a skilled or instructed person, a cable installed in accordance with 522.6.6(v) and not complying with 522.6.6 (i), (ii), (iii) or (iv) shall be provided with additional protection by means of an RCD (or RCBO ).

Safe zones are still very much alive in the 17th edition, unless you use (i), (ii), (iii) or (iv) from the above list.

 

[17thman]

yeah wilex make em too. i have just done 17th course and the take on it is that a domestic installation could not be deemed as leaving with the use of a skilled or instructed person. dual rcd board up power and down light with down power and up light on either side. pu hall/stairs and landing on its own rcbo before the two rcds, ie atfer main switch. this should satisfy old 314.1

 

[17thman]

yes but it is 522.6.7 that requires that insists on rcd's

 

[GaryMo]

yes but it is 522.6.7 that requires that insists on rcd's

Only if 522.6.6 (v) is employed and not 522.6.6 (i), (ii), (iii) or (iv) and the installation is not intended to be under the supervision of a skilled or instructed person.