RCDs are like fire rated downlighters. Too many people just put them in everywhere because they don't actually understand the regulations which mandate their use, or allow their omission.
Kitchen electrics question
- Thread starter rjb2001
- Start date
Sponsored Links
Yes, but you're talking about regulations now. If, which you clearly don't (and, as I said, I sympathise with your view), you believed that RCDs provide significant improvements in safety, you presumably would be advising customers that the best ('safest') course for them (if they could afford it) would be to have RCDs beyond what was 'mandated' by regulations.
Kind Regards, John
I thought metal CUs were banned (or difficult to configure compliantly) on TT supplies? What are we supposed to install - unobtanium?
I suspect a lot of 5WWs will have difficulty in doing the metalwork necessary to install a metal CU (as well as putting the L and N tails through separate knockouts...)
It would be better to improve the specification and quality of CUs in particular terminal screws. The terminals on the 40 yo Wylex I ripped out (with 2 screws per way) were in way better condition than the BG replacement I put in.
Indeed. I think that those Wylex CUs were one of the best-engineered bits of domestic electrical kit which have ever been produced - then or since.
Kind Regards, John
Sponsored Links
@ Rob
This potential move away from insulated enclosures... is it from the DPC of AMD2?
I seem to remember the DPC for the original 17th suggesting the use of an RCD would permit ignoring the safe cabling zones but you would still be allowed to conceal non-rcd protected circuits in safe zones as per 16th. How that got changed about before final publication!
Not sure I 100% agree with your stance on RCDs, I don't like to see general sockets not on RCD in a domestic property because you don't know what some muppet is going to do, or what dodgy appliances they are going to plug in.
This potential move away from insulated enclosures... is it from the DPC of AMD2?
I seem to remember the DPC for the original 17th suggesting the use of an RCD would permit ignoring the safe cabling zones but you would still be allowed to conceal non-rcd protected circuits in safe zones as per 16th. How that got changed about before final publication!
Not sure I 100% agree with your stance on RCDs, I don't like to see general sockets not on RCD in a domestic property because you don't know what some muppet is going to do, or what dodgy appliances they are going to plug in.
I presume you mean AMD3 (due for implementation early next year) (AMD2 was the one which most people didn't even notice - essentially an 'Addendum', rather than an amendment, relating just to electric car charging). If so, AFAIAA there was no proposals regarding metal CUs in that - but I may, of course, have missed it!
That presumably puts you in the opposite camp from RF - i.e. believing that RCDs do have a significant impact on safety?
Kind Regards, John
It was in the DPC for amd. 3 which Simon linked to a couple of months ago.
I do RCD protect general sockets in domestic properties as like you say there is not enough control over how the circuit will be used, but like to keep circuits where you can reliably use earthing to provide ADS such as lighting or fixed appliances off RCD.
Again in the real world, cost and time comes into this, and despite not liking it a dual RCD board and PVC/PVC cables is often the order of the day.
http://www.flameport.com/electric_museum/old_equipment/wylex_multi_rate_metal_fusebox.cs4
apart from the proximity of bare earths to busbars (I never considered that while I was taking it out)
That's more a case of poor installation, than a manufacturing defect!
I can only recall maybe three old wylex's I've been to which have burnt out and every time it was due to them being abused.
Shame modern wylex stuff isn't made to the same standards...
I can only recall maybe three old wylex's I've been to which have burnt out and every time it was due to them being abused.
Shame modern wylex stuff isn't made to the same standards...
Oh So the holes fir cables in the back were close to the bus bar
Ah - you mean the new proposed 421.1.200? As you are aware, that doesn't specifically call for metal encloses - only 'non-combustible' (of which it gives ferrous metals as an example) OR 'not-readily combustible' materials - a note to which indicates:
I had assumed/suspected (I know!!) that many plastics (maybe even including some currently used for enclosures) would meet this requirement (or other acceptable specs - this is only given as 'an exampe'), and that we would therefore probably be seeing a change in the plastics used, rather than a widespread change to metal - but, as always, maybe I was/am wrong!
Kind Regards, John
The ones I knew didn't really have 'backs' as such - just a 'loose' thin sheet of paxolin (or suchlike) between the 'backless' enclosure and the wall behind (cables entered top and bottom)
Kind Regards, John
I tink sleeving was optional at the time; none of the other earths were sleeved anywhere.
Yeah I agree with that with the exception that never really liked to see shower units without RCDs on 16th edition installs, but cookers and immersion heaters etc are best kept off RCD.
How true. But when the dual RCD boards start cropping up in commercial environments, its a step too far
Interesting views. It does sound as if you are one of the 'RCD-sceptics' (as, I suppose am I - even though my TT installations renders many of my views rather moot)! As for your statement, presumably it is only pretty exceptionally that you would have a circuit (in a TN installation) for which you could not "reliably use earthing to provide ADS [I presume you mean via an OPD]" - in the exceptional cases (as with all circuits in TT installations) you would normally be obliged to use an RCD to achieve the ADS.
Whatever, you seem to be thinking primarily in terms of ADS (in response to L-E faults), whereas the RCD-enthusiasts would assume that effective ADS was already in place, but would be thinking additionally/primarily about people touching live severed cables, touching nails/screws which have penetrated cables (as per the 'one in a billion' tragedy which beset the MP's daughter) or the DIYer (or inquisitive youngster!) was was tinkering with an improperly isolated circuit etc. etc. - in none of which situations would OPD-mediated ADS usually be of any help.
I suppose that one 'upside' of RCD protection, even for those of us who are 'RCD-sceptics', is that they afford a second line of defence, ADS-wise - which some might think is a good idea since we really don't have a clue about (and cannot test) the in-service reliability of MCBs.
It sounds as if you, too, are probably 'in the camp'. A question for both of you ... you both seem to feel that most non-sockets circuits (with the possible exception of showers) 'are best kept off RCD', and I wonder why that is? Is it simply because you want to avoid 'inconvenience' due to tripping of multi-circuit RCDs (in which case you would presumably be happy with individual circuit RCBOs?)? ... OR is it because you are worried about 'nuisance trips' ... OR ... do you see some other specific downside of RCD (or RCBO) protection that I haven't thought of?
Of course, in practice, a combination of the requirement for virtually all domestic sockets to be RCD protected and the requirements in relation to buried PVC cables are, between them, likely to mean that a very high proportion of new domestic circuits actually do now have to have RCD protection - whatever 'camp' we happen to be in (intellectually/ philosophically)! Furthermore, there are still a substantial number, like me, who do not have any choice, since we have TT installations - I suppose one could be 'stubborn' and just use 100mA RCDs for those circuits you would not want to RCD protect ('just to make a point'!), but that would seem a little silly.
Kind Regards, John
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
