Design

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stewart

Hi. I have written in before but can't remember or find my old username ... but hey! no matter, I'm a born-again Competent person :)

I've got my part p and have just completed the 17th Edition wiring regulations course ... and I learned a few things while doing the 17th Regs.

I found out that to satisfy the 17th Edition, a consumer unit has to have at least 2 rcds. I cannot find where the regs say this so could someone enlighten me to the relevent section please. I ask cause I have just fitted a 4 way consumer unit in a domestic dwelling TN-S and it was agreed that 1 rcd to protect the supply would be sufficient.

I realise from 314.1 that installations are to be divided into circuits to avoid hazards but as the intention is to keep to the existing provision of 1 lighting + 1 power + I kitchen + i cooker just assumed that providing all testing was as per regulations, that a nice new fully protected consumer unit with single rcd and 4 ways was more than sufficient. IF I have to, I'll buy another CU as the new one is not capable of splitting up.

Thanks,

Stewart
 
The short answer is that the Regulations do not require you to have more than one RCD. In fact, the Regulations do not state that every installation necessarily must have any RCDs dependant on a number of factors.

The reference is to minimising inconvenience in the event of a fault, which to me suggests a risk assessment based approach. If your risk assessment suggests that one RCCB would be appropriate then so be it. But you need to consider what would happen if it were to operate.
 
If there's only 4 ways I would just have a main switch and RCBO's protecting circuits, as this shouldn't be too expensive in comparison to buying a 5+5 dual RCD CU.
 
Thanks for the replies.

I got raised eyebrows when suggesting the use of 2 rcd's. You can imagine the response when I suggested rcbo's! :eek:
 
Gsxr was simply pointing out that rcbo's are your best option as they offer both short circuit and overcurrent protection. I can't see how he was advertising or being offensive by this.

However if you actually WERE competent you wouldn't need us to tell you this, after you had completed the install and possibly fitted the wrong board......would you.

Did you complete the full tests, a EIC and notify??

We all have to learn and if you are building your experience and competence then this is a fantastic resource but please listen to what your being told and don't have a go at people who reply
 
TPES said:
You being serious?

I think it's you. You alright?
Click to expand...


Sure, I'm fine thanks ......Actually, I've just realised! so it's ok to whack in 4 lines of advertising a product? the stuff under the dotted lines is advertising. Ah well.... sorry, I mean I thought the reply was meant to provide an answer and not to provide an excuse to stick in 4 lines of 'come to me' ......... lol, I think it must be me :mad:
 
Thats his signature. Which is posted on every single post he makes. His reply to you was:

RCBO's are your friend here...


Which is ontopic and correct.
 
stewart said:
Sure, I'm fine thanks ......Actually, I've just realised! so it's ok to whack in 4 lines of advertising a product? the stuff under the dotted lines is advertising. Ah well.... sorry, I mean I thought the reply was meant to provide an answer and not to provide an excuse to stick in 4 lines of 'come to me' ......... lol, I think it must be me :mad:
Click to expand...

It is actually just my standard footer that appears after every post i make....

And if you stick around, you may even find i am a pretty helpful poster.
 
Hmmm, not a good start

I seem to have caused offence. Ok, I'll apologise for my initial response but I hadn't realised the 4 lines after your single rcbo's are your friend was NOT part of your reply. It actually annoyed me, so again I apologise


I am perfectly well aware of what is a 'proper' installation, I just wanted to know if there is a distinct requirement' as in "2 rcd's HAVE to be used" ....

Now, please ..... I have apologised TWICE ............ :o
 
GStueyXR said:
It is actually just my standard footer that appears after every post i make....

And if you stick around, you may even find i am a pretty helpful poster.
Click to expand...

Lol sounds like Thomas the tank engine lol .........gsxr is a very very usefull engine......... He he

Sorry just talking dribble now
 
stewart said:
Hmmm, not a good start


I am perfectly well aware of what is a 'proper' installation, I just wanted to know if there is a distinct requirement' as in "2 rcd's HAVE to be used" ....

:o
Click to expand...


2 RCDs are not a requirement. 17th edition is non-stat. But, I guarantee that the NIC would reject your present installation on the grounds of non-compliance.

I refer you to my original answer 'RCBOs are your friend'.
 
Now you are possibly going to have to stand in front of your customer and explain why you are going to have to replace the guts of their shiny new board probably at your own cost because you didn't design the installation properly to start with.
 
High Tower said:
Now you are possibly going to have to stand in front of your customer and explain why you are going to have to replace the guts of their shiny new board probably at your own cost because you didn't design the installation properly to start with.
Click to expand...


And for gods sake, if they have any leaflets laying around, dont acuse them of spamming advertisements.




:D:D:D
 
GStueyXR said:
2 RCDs are not a requirement. 17th edition is non-stat. But, I guarantee that the NIC would reject your present installation on the grounds of non-compliance.

I refer you to my original answer 'RCBOs are your friend'.
Click to expand...

Now, we getting somewhere lol. I happen to agree but in a fit of going along with client I chose to acquiesce and simply fit a single rcd controlled CU. I have regretted it but thought it complied.

So, I have 2 choices, either change it for a new CU , OR argue that it actually does comply.

I have decided that I will change the CU for one with 2 rcds, but I want to know is WHY my installation would be considered non-compliant? We are not talking new installation, just a new CU, so 4 mcb's and the only only one that could cause a hazard problem is if the lighting clicks the whole lot off..... so, just sticking the lighting on itw own separate rcbo doesn't remove the hazard ..... it might reduce the nuisance factor from a possible tripping of the freezer, but then, it not on a protected circuit so it difficult to be too concerned

So, reasons for non-compliance if you please:)
 
stewart said:
So, reasons for non-compliance if you please:)
Click to expand...


Would you agree that changing the OPD on a circuit is modifying that circuit?

Now go read about modifying a circuit and the requirement to ensure compliance.

5.1. Replacing a consumer unit in an existing installation
is an addition or alteration to that installation. The
work must therefore be designed, erected and
verified in accordance with the requirements of the
current edition of BS 7671, and must not impair the
safety of the existing installation. (Regulations​
110.1(xx) and 610.4 refer.)


 
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Would it be an inconvenience or cause a hazard in the event of a fault?

Most likely in a domestic property this would.. So I would be fitting a dual RCD CU to comply to regs.

But if this was a garage with a 16a & 6a circuit with a RCD main incomer this wouldn't be much of an inconvenience.
 
I agree that fitting a new consumer unit comes within the Scope (110.1xx) and also it improves (assuming replacing like for like) that 610.4 is indeed verified as the installation is bound to be safer.

Interestingly, it is section 314.1 that is the nuisance factor :)

Fitting an RCBO should be mandatory! As soon as you go along the path of not fitting an RCBO you are effectively reducing the effectiveness of the installation. So, the path I have chosen, and that the one most preferred by Clients, is one of cheapness and necessarily not the best .

I maintain that I am fulfilling ALL requirements of 314.1 - as necessary - and that section (iv) is not statuary so much as guidance. Therefore, if following on with discussions with client it is agreed that a single RCD is acceptable I assume I can fulfil my obligations by sticking a label on the CU stating "Warning It only has ONE RCD" with an accompanying note in the certificate in the relevant box that draws attention to any deviation ...... mind you, as far as I can see, there is no argument, no deviation ..... only a lack of proper guidance over what has to be a 'compromise' as per normal occurrence in Domestic Installations

Mind you, I'm still going to replace the CU, I'm just annoyed I fitted it in the first place

(and I would fit RCBO's if they let me lol)

...............................................................

:DNo adverts were harmed in the making of this space :D
 
wouldnt it of been better to do the research prior to the change? or gain a working knowledge of the regulations?

and i agree that GStueyXR Must stop with his constant advertising campaing ;)
 
Sticking a sticker on the CU won't decrease the percieved risk that would arise in the event of a fault tripping the RCD, i.e. someone falling down the stairs or stubbing their toe in the dark, will it?

That said, I'm not sure how much of an issue this really is. Most people know their way around their own house in the dark, but even that's not the point. I am concerned about somebody touching a live part and being electrocuted, decent earthing and an RCD will go some way to prevent that. Once the RCD has done it's job, I'm not particularly concerned; I use dual RCD boards because they DO minimise convenience and because the happy clapper clubs want us to, and to be honest they are normally just as cheap and just as easy to put in. But where should our conern end, we put in a new lighting pendant and the customer may get an energy saving bulb and they may drop it and they may get mercury poisoning from it..... where does it end?
 
rocker said:
..... where does it end?
Click to expand...

its simple - it ends with you, thats where the buck stops regardless of what regulations you follow, i install all my work to the best of my ability and comply fully to my interpritation of the regulations - and that would always be my defence in court
 
ezzzekiel said:
its simple - it ends with you, thats where the buck stops regardless of what regulations you follow, i install all my work to the best of my ability and comply fully to my interpritation of the regulations - and that would always be my defence in court
Click to expand...

Exactomondo! As long as fixed wiring is installed safely and to regulations, that is and should be where our involvement ends.
 
ezzzekiel said:
wouldnt it of been better to do the research prior to the change? or gain a working knowledge of the regulations?

and i agree that GStueyXR Must stop with his constant advertising campaing ;)
Click to expand...


Yes, it is always better to be prepared, and I thought I was. Of course one has to be open minded and be prepared to accept that one can lag behind the regulations. Being complacent is not an excuse for poor workmanship. But when you are dealing with Clients sometimes the best approach is one of compromise and let's be honest, if I do my work properly it will definitely be an enhancement.

So, there I was complacently sitting and reviewing the IEE regs when I hear this innocent comment, "The IEE regs dictate that at least 2 rcd's have to be fitted for a CU to comply..." Well blow me down with a feather but upon querying it it was confirmed (though no proof was offered)

Now, I'm not exactly wet behind the ears nor am I ignorant of the regulations so I wants to find out where in the regs I am out of touch. Sadly there is no such proof, only a 'necessary' adjunct ............
 
The regs make reference to mimimising nuisance tripping and circuit segregation as well as safety (not sure of the reg nos now as late). On that basis a min of 2 RCD's is sensible since imagine if it is dark and a lamp 'blows' and trips out all power so that the person in the kitchen cant see and spills hot oil over them selves while someone else trips and falls while lookign for a torch to find the CU and restore light etc etc.
 
High Tower said:
I think your biggest sin was letting a penny pinching client dictate how a installation should be done
Click to expand...

Lol :) I think you spot on.

Mind you, the mamby pamby fuddy duddy wuzzyness of a certain publication didn't help ...

The BS7661 should take a leaf out of the cigarette packet ..... I mean to say, it likewise has all the 'warning labels' you can stick on the outside of the CU.

Why not go further:

Passive mcb's can be a danger to others

An rcd a way can keep the other's ok

how many times a year do you re-test your rcd? ...... quit the habit and die:eek:

......................................

:) here endeth the Sunday Sermon ..... those magic mushrooms are brill! :)
 
Last edited by a moderator:
stewart said:
Lol :) I think you spot on.

Mind you, the mamby pamby fuddy duddy wuzzyness of a certain publication didn't help ...

The BS7661 should take a leaf out of the cigarette packet ..... I mean to say, it likewise has all the 'warning labels' you can stick on the outside of the CU.

Why not go further:

Passive mcb's can be a danger to others

An rcd a way can keep the other's ok

how many times a year do you re-test your rcd? ...... quit the habit and die:eek:

......................................

:) here endeth the Sunday Sermon ..... those magic mushrooms are brill! :)
Click to expand...



I dont see what the standard for 'Specification for inflatable armbands worn as flotation aids' has to do with this thread LOL.



:D :D
 
Last edited by a moderator:
andekoch said:
e if it is dark and a lamp 'blows' and trips out all power so that the person in the kitchen cant see and spills hot oil over them selves while someone else trips and falls while lookign for a torch to find the CU and restore light etc etc.
Click to expand...

See, this is what I don't get. If it's dark and your kitchen lights go out, what use are the kitchen sockets and upstairs lights being on?? the only way to stop people being in the dark is to have two lights in each room on seperate RCDs, or maybe have the lights wired so that the kitchen, hall, bedroom one, bedroom three are on RCD1, and dining room, living room, landing, bedoom 2 and bathroom are on another, which would be absolute lunacy!
 
you could loop into a non-maintained bulkhead possibly

dunno if they have leakage

at least a few lighting rcbo's would minimize nuisance if you need 30ma protection
 
One day, there will be self-certifying CU's that will test and verify and self-test and even come with a handy remote control fob that will allow you wherever you be to reset that darn RCBO!

Naturally, each additional item of protection will come with a cost and the time will come whereby an improvement in safety will immediately be reflected in a set of Regulations that will be fluid rather than stagnant.

But, as things stand at the moment, if my customer can only afford a reduced level of electrical safety then I have to be aware of what is my bottom line of service. Maybe I have to choose between what they are prepared to pay against what I can offer and maybe I might have to quote for a lower standard but provide something that might reduce my profit but will be of a standard as would be expected by my peers ....

right then ..... single rcd it is lol :eek:
 

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