Recommendation about new CU please

[Vicario]

I'm having an EICR this week and the electrician will then proceed to fit a new CU (no RCDs in the one I have) plus any other remedial work we agree on. My question is about the CU. I have read that they come with RCD protection for each individual circuit rather than a general one covering everything.

We have a very simple setup with just 7 circuits - two rings, central heating, two lighting, a larder light which is a wire that comes straight from the CU to the light switch next to it, and a socket on a 15A breaker that originally fed an old boiler (used now for a radio). There is also a shower circuit from Henley blocks (9KW shower).

What CU would you recommend, assuming I'd like each circuit protected by a dedicated RCD?
Presumably the sparkie will have his favourites so should I let him decide?

While I'm here.....I have a 2.99KW oven plugged into a socket at the moment. How disruptive would it be to ask him to fit a dedicated circuit for the oven? About 3 metres from the larder where the CU is, but flooring between boarded and covered.

 

[flameport]

Main switch, surge protection and RCBOs for each circuit.

Although only 7 circuits, you want a CU with substantially more space in it, such as 12 way at least.
That allows for any future alterations or additions, and also to have higher loaded RCBOs spaced apart from others.

 

[Taylortwocities]

How disruptive would it be to ask him to fit a dedicated circuit for the oven? About 3 metres from the larder where the CU is, but flooring between boarded and covered.

Only someone on site can determine that. Your electrician is the person to ask.

 

[EFLImpudence]

How disruptive would it be to ask him to fit a dedicated circuit for the oven?

Are you positive you don't already have one?

 

[ericmark]

Consider if you will ever have an electric car or solar panels, since a special RCD is required for some types, it could change what is the best selection.

But as already said, best person to talk to is the electrician doing the work, even as an electrician I made a mistake.

I lost two freezers full of food due to being away from home when the RCD tripped, I considered how much that had cost me, and having all RCBO CU unit makes economic sense. But some makes have double pole RCBO's and some (the cheaper makes) only single pole, which you need depends on earth type.

The selection of type AC or type A even electricians can't make up their mind on, most solar panels and EV charging points need type A, but depends on where you read as to other items. If the earthing system is TT then no real argument type A double pole, but with a TN system the RCD protection is secondary, so not quite so important.

Had I realised my RCBO's were type AC when placed on the counter I would have asked for type A, however it was marked type B (should have said curve B) so I missed it, and now I have 14 type AC fitted I am not going to change them, and on reflection with TN supply not really worried.

But cost between cheap single pole type AC RCBO's and SPD to more expensive type A double pole RCBO's and SPD is nearly double. Main jump is price of the SPD cheap one around £35 and more expensive makes can be over £100.

 

[JohnW2]

... Had I realised my RCBO's were type AC when placed on the counter I would have asked for type A, however it was marked type B (should have said curve B) ...

I'm not so sure about that - for decades, "Type B", "Type C" and "Type D" have been used to refer to 'the curve' of an MCB or RCBO, in the days when no-one thought about (and few probably even knew about) the AC, A, B & F variants of RCDs and RCBOs.

Hence, I would personally say that the original meaning of "Type X" (to describe 'the curve') should remain as it always has been, and the idiot who decided to use "Type" (for RCDs and RCBOs)(and, particularly, "Type B") to refer to something different really should be shot

Of course, it is only "Type B" which is ambiguous, since there are no devices (at least, of which I am aware) which have AC, A or F 'curves' - however, in my opinion, the responsible he/she still deserves to be shot for just that one ambiguity they have created!

Kind Regards, John

 

[ericmark]

I agree with @JohnW2, but to be fair when the RCD had the label type AC, A, F, and B the RCBO was rare. And had they kept the original type 1,2,3 and 4 for MCB's there would have been no problem, so maybe the guy who decided to move from 1 to 4 and use B to D should be the one shot?

However my point is very easy to make errors, I recount my error in the hope it will stop some one else doing the same.

It does not matter what we are talking about we tend to draw on our own experience and in this case home, and it is very easy to look at ones own home and forget not all homes have a TN-C-S supply, or a garden long enough to have a independent TT earthing system for the likes of electric car charging.

I have over the years been asked in work for advice, and then latter visited the guy's house and been shown how he has followed the advice, and then realised how some thing has been missed, and my advice was flawed. In some cases introducing danger as was the case with a static caravan when asked about connecting an earth, I had not even considered he might be fed from an ELCB-v and the result of following my advice had rendered the ELCB-v useless.

 

[JohnW2]

I agree with @JohnW2, but to be fair when the RCD had the label type AC, A, F, and B the RCBO was rare. And had they kept the original type 1,2,3 and 4 for MCB's there would have been no problem, so maybe the guy who decided to move from 1 to 4 and use B to D should be the one shot?

Maybe, but I still think that I probably correctly identified the person who most needs to be shot

As far as almost everyone was concerned "Types 1, 2, 3 & 4" were 'history', and had been replaced by "Types B, C & D", long before hardly anyone (at least, in the UK) had given any thought to the different variants of RCDs/RCBOs (AC, A, B & F). Just a few years of go, if you talked of a "Type B RCBO", I doubt that hardly anyone would have thought that meant anything other than "a B curve device".

Kind Regards, John