Installing RCBO Query

[JohnW2]

Flameport is absolutely correct. I doubt that he would ever reveal whether or not he would feel very slightly slightly happier for an appliance to have an AC RCD on rather than no RCD at all.

Yes, in terms of the regulations, he is absolutely correct.

However, he is a very intelligent man and,although you may be right that he would never reveal it, I feel sure that, regs aside, he would be (more than "vey slightly slightly") happier with a Type AC RCD than no RCD at all.

If not, the implication would be that he felt that a Type AC RCD offered absolutely no safety benefit over 'no RCD', which would mean that the £billions that have been spent on Type AC RCDs in the UK was all 'wasted money' (and I'm sure that he will have been advocating installation of RCDs at a time when Type AC ones were almost the only option in the UK).

Kind Regards, John

 

[Harry Bloomfield]

Utter tosh

You mean - your level of professionalism is so very low, you need to spend 'considerable amounts of time', just working out which circuit is the cause of a trip?

 

[veedee]

Not permitted, as the existing RCD is a Type AC, which is no longer permitted for anything other than fixed equipment which has no DC components - basically resistive heaters and nothing else.

So is the following correct? Either

1. Change the existing Type AC RCD for a 63Amp Type A 30mA RCD? Cost £47.74

Or

2. Replace all of the existing MCB's with RCBO's
Cost £43.20

Option 2 is the most cost effective and it would free up space on the consumer unit.

While I'm there, I might as well replace the plastic CU for a shiny metal one

 

[AndyPRK]

Your original idea it fine.
Change the lights to 6A rcbos.

Minimal work for a diyer. Cost effective.

I don’t think we would want a diyer replacing an RCD or messing around with the whole board.

 

[SUNRAY]

So is the following correct? Either

1. Change the existing Type AC RCD for a 63Amp Type A 30mA RCD? Cost £47.74

Or

2. Replace all of the existing MCB's with RCBO's
Cost £43.20

This was im my draft for post#22, however such work is I believe notifiable and A lot of effort,
I agree with:

I don’t think we would want a diyer replacing an RCD or messing around with the whole board.

Option 2 is the most cost effective and it would free up space on the consumer unit.

While I'm there, I might as well replace the plastic CU for a shiny metal one

And it's definitely notifiable.

Your original idea it fine.
Change the lights to 6A rcbos.

Minimal work for a diyer. Cost effective.

Something that hasn't been mentioned yet is borrowed neutral but the harmonised cable would generally indicate it should be ok.

 

[JohnW2]

Something that hasn't been mentioned yet is borrowed neutral but the harmonised cable would generally indicate it should be ok.

I'm not so sure that the colours of the cables (i.e. the age of the installation) means all that much in terms of the likelihood of a 'borrowed neutral' !

 

[JohnW2]

2. Replace all of the existing MCB's with RCBO's
Cost £43.20

Do you really mean 'all' (i.e. all 5) of the existing MCBs, or perhaps just the two for lighting circuits?

If you did mean what you wrote, where are you going to get 5 RCBOs of any brand (let alone MK) for £43.20 ?

Kind Regards, John

 

[ebee]

Without proper testing you can not always be sure that "borrowed N syndrome" will not rear its ugly head

 

[JohnW2]

Without proper testing you can not always be sure that "borrowed N syndrome" will not rear its ugly head

Indeed not - and, as I wrote, I don't think the fact that the wiring is in harmonised colours cables makes much difference to the likelihood of it "rearing its ugly head" !

Kind Regards, John

 

[AndyPRK]

Should they trip when a particular light is turned on, the op can put both circuits into the same rcbo, while they consider the best way forward

 

[SUNRAY]

I'm not so sure that the colours of the cables (i.e. the age of the installation) means all that much in terms of the likelihood of a 'borrowed neutral' !

My experience is that 2 way 'conventional' is quite uncommon since harmonisation, in fact I've found many young electricians haven't heard of it. Accordingly borrowed neutral is equally uncommon.

 

[JohnW2]

My experience is that 2 way 'conventional' is quite uncommon since harmonisation, in fact I've found many young electricians haven't heard of it. Accordingly borrowed neutral is equally uncommon.

It's undoubtedly the case that such becomes increasingly likely with the passage of time, but I feel sure that you will agree that the point in time at which wiring was installed (whether the 'time of harmonisation' or any other) offers no certainty.

It is probably wise in such situations to assume that a 'borrowed neutral' might be present (and decide what one will do if it is)!

 

[ebee]

Agreed, plan for it and by all means hope against (but do not assume) it.

 

[SUNRAY]

It's undoubtedly the case that such becomes increasingly likely with the passage of time, but I feel sure that you will agree that the point in time at which wiring was installed (whether the 'time of harmonisation' or any other) offers no certainty.

It is probably wise in such situations to assume that a 'borrowed neutral' might be present (and decide what one will do if it is)!

Yes I believe borrowed neutral is less likely in a fully harmoniosed installation and quite agree that it is by no means certain and should be considered.

Please note who it was that brought up the subject.

Agreed, plan for it and by all means hope against (but do not assume) it.

 

[JohnW2]

Agreed, plan for it and by all means hope against (but do not assume) it.

There are "assumes" and "assumes", and I don't think there was anything wrong or unwise about my suggestion that one probably should "assume that it might be present", is there?