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Topic Title: Dual RCD plus RCBO consumer unit
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Created On: 27 July 2015 11:11 AM
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 30 July 2015 08:24 AM
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phantom9

Posts: 1757
Joined: 16 December 2002

Oops. Oh dear. Egg on face. So its a high integrity dual RCD with three sections. Great!

@OMS. I am not a great believer in following the Regulations more that I tend to see certain of the Regulations, shall we say, a little differently to others. When you read my posts I am currently seeing the, what I call, reverse psychology aspect of what people see in a requirement to do something and actually doing too much more or seeing imaginary things that just aren't asked for at all. I am interested to know why people do this. The best example so far I have cited is the 'escape route' Regulation where instead of accepting it people looked for all manner of escape routes to apply. It is very interesting and if I could use it to my advantage I could be a millionaire.
 30 July 2015 09:04 AM
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AJJewsbury

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When you read my posts I am currently seeing the, what I call, reverse psychology aspect of what people see in a requirement to do something and actually doing too much more or seeing imaginary things that just aren't asked for at all.

I think it's just a matter of being able to imagine yourself in somebody else's shoes.

The escape route one for example - many people might think something along the lines of "if I was sat on the toilet when the smoke alarms all went off, what would be my route out of the building to safety? - that entire path would therefore be one example of an escape route - as there'd be no point having an escape route starting in a corridor if access from the toilet to the corridor was blocked". You need to be able to spot the flaws in their point of view (if any), as well as being confident in your own point of view, to be able to debate the relative merits of each.

But that's just my point of view...

- Andy.
 30 July 2015 09:08 AM
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AJJewsbury

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So its a high integrity dual RCD with three sections

Just for clarification - there's an example on page 273 of MK's catalogue - http://www.mkelectric.com/Docu...0Catalogue/Sentry.pdf
- Andy.
 30 July 2015 11:10 AM
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mapj1

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I'm sure I keep saying it, but opinions on this forum are always just that - as I see it, there are two reasons why large pinches of salt are needed,
Firstly there is no particular guarantee that the image I construct in my head, based on the description of any poster's query or response , not just this one, accurately represents the situation that was intended to be described.
Secondly, the whole point about the informal 'rag chew' nature of the discussions on here is that it allows us to drop the " without prejudice or commitment" guarded type of dot and comma precision that would be required if for example I was charging for my observations - but the benefit is that I (or anyone else) can say things in rapid response mode that may turn out to be irrelevant or incorrect, but serve to provoke another line of thinking.
The downside of course is that it has little more legal status than " a man I was chatting to in the pub said..." But with a lot more moderation because usually someone pops up and says " aha but you have forgotten the XYZ effect"
- I find I learn a lot from other folks perspectives on why stuff is the way it is - more than I would from a dry quoting of reg numbers.

-------------------------
regards Mike
 30 July 2015 02:17 PM
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WiredScience

Posts: 323
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Originally posted by: phantom9

What about testing the RCBOs and RCD on the same side of the CU? Right messy set up to do it.


Why? Connect the test probes across incoming N and outgoing L, press the button, and write down the number on the display. It requires the same level of difficulty as testing any other RCD.

You only need to unbalance the sensing coil. That doesn't mean the test current has to return to earth.
 30 July 2015 05:10 PM
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phantom9

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Can't be bothered with all that faff tbh wired it adds to hassle and I like it simple.
 30 July 2015 05:54 PM
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phantom9

Posts: 1757
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Originally posted by: AJJewsbury

When you read my posts I am currently seeing the, what I call, reverse psychology aspect of what people see in a requirement to do something and actually doing too much more or seeing imaginary things that just aren't asked for at all.


I think it's just a matter of being able to imagine yourself in somebody else's shoes.

The escape route one for example - many people might think something along the lines of "if I was sat on the toilet when the smoke alarms all went off, what would be my route out of the building to safety? - that entire path would therefore be one example of an escape route - as there'd be no point having an escape route starting in a corridor if access from the toilet to the corridor was blocked". You need to be able to spot the flaws in their point of view (if any), as well as being confident in your own point of view, to be able to debate the relative merits of each.

But that's just my point of view...
- Andy.


It is more complex than that, Andy. You are sort of doing what I said people do and imagining an escape route rather than the purpose of the Reg. I am sorry it is just how my brain works, Andy. I used the 'escape route' scenario as an example of what I was trying to explain. There are other examples, the non-combustible CU fiasco is another where imaginations took hold and all sorts of added requirements arose from nowhere. It is very very difficult to make something so crystal clear as to obtain unanimity. I believe I could do it but whether I'll ever get chance I don't know. I spent a few years writing technical briefs for the MoD and tbh it was something I was rather good at. How the hell I have ended up as a bloody sparky I'll never ever know. It is poles apart from where I started my career at 16. Anyway, I digress.
 30 July 2015 09:07 PM
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AJJewsbury

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It is very very difficult to make something so crystal clear as to obtain unanimity.

Absolutely. And not just written words either. Several times I've been in meetings where two other people have been using the same words and seemingly agreeing, but it then becomes apparent that they've attached slightly different meanings to those words and actually disagree on some small but significant point. It's then a challenge to come up with a form of words that exposes the difference without introducing extra confusion or complexity.

Writing is even harder as you get no immediate feedback - so you not only have to try and convey they idea you need to get across, but simultaneously dismiss any other preconceived similar but-not-quite-the-same ideas they might have. Hence my point of re-reading what I've written and asking myself how could this be mis-interpreted - or if you like trying to look at it from others' points of view.

(of course, all that is something I usually fail to do entirely when typing hurriedly for a forum...)

- Andy.
 31 July 2015 12:47 AM
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mapj1

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It is to do with how we "know" stuff, and is another side of being able to realise an alternate use for something to the one on the label. You may keep pens in a coffee mug or trim your nails with side cutters - I need coloured shapes on my otherwise identical drawers in the bedroom to identify which holds socks or pyjamas without opening all of them each morning to see. My long suffering wife knows but does not understand why I can't just use relative position in the chest of drawers as a guide - but then equally she can't read circuit diagrams, where position is irrelavent and connectivity is all, seeing only a tangled mess of lines.
It is quite likely the other person's world really is different, it just happens to be in the same place.

-------------------------
regards Mike
 31 July 2015 11:13 PM
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spinlondon

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To my mind, these so called 16th and 17th edition boards are mis labeled.
They are only any use for new builds and fail to comply with the requirement to minimise inconvenience when used to upgrade re-wireable and cartridge boards.
 01 August 2015 08:44 AM
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ebee

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Originally posted by: spinlondon

To my mind, these so called 16th and 17th edition boards are mis labeled.

They are only any use for new builds and fail to comply with the requirement to minimise inconvenience when used to upgrade re-wireable and cartridge boards.


Could you elaborate on that? Spin

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 02 August 2015 07:39 PM
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phantom9

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I have made my views known about dual RCD split boards and IMHO they do not comply with the 'minimizing inconvenience' clause, as Spin has stated. It is another manufacturers gambit to claim compliance with the reg and it has been accepted by the trade because it is a cost thing as usual.
 02 August 2015 08:00 PM
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Lieuwe

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Interesting thread! .. I found this image that looks like it is the same unit that we have in the BTL.

Link Removed
 02 August 2015 09:03 PM
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ebee

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I probably agree with the minimizing bit you two .
To me minimize actually means to take to its lowest common denominator ie one cpc per point and I am not aware of any but the tiniest installation fulfilling that one.
Reduce might be a better word than minimize perhaps.
Then of course we need to know what the IET committee intended its words to mean.

I was just interested as to what Spin was trying to convey when he mentions new builds and I was wanting elaboration of his actual thoughts.

Nowt wrong with asking for clarity

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 02 August 2015 11:00 PM
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potential

Posts: 1642
Joined: 01 February 2007

Originally posted by: Lieuwe

Interesting thread! .. I found this image that looks like it is the same unit that we have in the BTL.



Unit


your link

You ask in your original post why should the RCBOs be there.
I respond by asking why shouldn't they be there?

It would be perfectly acceptable, some would say better, to have ALL the 15 ways fitted with RCBOs and do away with the 2 RCDs.
They certainly don't make the CU unsafe and they comply with the regs.
 03 August 2015 09:13 AM
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phantom9

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I agree entirely, potential. I stopped fitting dual RCD CUs years ago and my default CU is the Denmans Curve fully loaded with RCBOs. Problem is its bloody plastic.
 03 August 2015 09:19 AM
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Lieuwe

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Originally posted by: potential

Link Removed



You ask in your original post why should the RCBOs be there.

I respond by asking why shouldn't they be there?



It would be perfectly acceptable, some would say better, to have ALL the 15 ways fitted with RCBOs and do away with the 2 RCDs.

They certainly don't make the CU unsafe and they comply with the regs.


Well because from a consumers point of view, these RCBO's cost what £30? .. that is £450 quid in RCBO's for a 15 way unit like that.

I wasn't questioning the safety of it, I was just wondering why they stuck in 5x£30 RCBO's rather than 5X£3 MCB's (there are no alarms and other items on the RCBO's that you would really want to keep running .... )
 03 August 2015 09:33 AM
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phantom9

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From an economics point of view if all RCBO CUs were made compulsory then said RCBO would reduce in price and we would not have this ridiculous dual RCD CU as the de facto choice for sparks. It is not ALL about price for some of us. It would stop the cowboys under quoting if they had to use the best stuff. Price is subjective as to expensive /cheap anyway. Lets face it electrical components are amongst the most expensive products on the market compared to builders, chippies and plasterers. Plumbers have a similar issue to us but they charge good rates and it is no longer argued. Plumbers have better business sense it would seem. Electricians should do the same and stop trying to get jobs based on the price of the components. Electricians prices look expensive when viewing the total figure but people don't seem to realise this. I have been paying £12 a pop for my RCBOs and they are good quality. Had zero comebacks on any of my CUs.
 03 August 2015 10:05 AM
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tomgunn

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As far as I know - using RCBO's you dont have to worry about 'supplementary' bonding to bathrooms etc.
Tom

-------------------------
Tom.... (The TERMINATOR).

handyTRADESMAN

Castle Builders
 03 August 2015 10:21 AM
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AJJewsbury

Posts: 16117
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As far as I know - using RCBO's you dont have to worry about 'supplementary' bonding to bathrooms etc.

It makes no difference to the bathroom bonding requirements if the circuits are protected group protected by RCCBs (RCD only devices) or individually by RCBOs - as long as there's 30mA RCD protection of some sort.
- Andy.
IET » Wiring and the regulations » Dual RCD plus RCBO consumer unit

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