C.U. Conversion and 17th ed

[DJM]

This may be a silly question, but please bear with me.

As some will remember I had numerous CUs and with advice have had one replaced with a 19 way populated with RCBOs where appropriate. The intention was that it meant I can get the other CUs moved into the new 19way one by one reducing the disruption to the house, and I chose RCBOs because JohnD told me to (sorry I mean because it was the best route and with a view to ease of 17th ed compliance).

The question I have is, when I want to get the next CU transferred (which will almost certainly be after 17th ed starts) will I have lots of remedial work? For example, will I have to have lighting drops ripped out and metal conduit or some other protection included to comply? Beacause if that's the case then I will end up with a very under used new CU, and I think it will seriously put off people making their electrical installation safer. Or will it just have a massively long list of non-compliances making the installation safer, but practically unsalable?

 

[nozspark]

All hidden/burried cables less that 50mm deep must either be mechanically protected OR RCD protected.

NOTE:- Smoke alarms must not be on the same RCD as any socket circuit!

 

[DJM]

So for the lighting circuits if I have RCBOs rather than MCBs, then (assuming the rest of the circuit tests out correctly) they will be compliant?

 

[Adam_151]

So for the lighting circuits if I have RCBOs rather than MCBs, then (assuming the rest of the circuit tests out correctly) they will be compliant?

Yes, cables are allowed un-protected in prescribed zones as they always were, its just that in a domestic environment they need to be RCD protected now

(this is why we are seeing consumer units like this http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Contactum_17_Consumer_Units/index.html

A straight board populated with RCBOs is still the more elegant solution, just more expensive!

 

[GaryMo]

NOTE:- Smoke alarms must not be on the same RCD as any socket circuit!

Is that straight out of the 17th? I've still not received mine from the ECA so can't check.
Seems strange considering the new breed of consumer units will come with twin RCD's. The sensible way to connect would be to put the downstairs ring final on one and the upstairs ring final on the other.
Where would the smoke alarm circuit go?

Personally I would prefer a board full of RCBO's but it depends if the customer will stand the extra cost.

 

[Adam_151]

NOTE:- Smoke alarms must not be on the same RCD as any socket circuit!

Is that straight out of the 17th?

No, BS5839

According to BS 5839, circuits supplying fire or smoke alarms in
dwellings can be protected by an RCD provided that either:
i. The RCD serves only that circuit. For example with the use of an
RCBO
ii. The RCD should operate independently of any RCD feeding
socket outlets or portable equipment

I've still not received mine from the ECA so can't check.
Seems strange considering the new breed of consumer units will come with twin RCD's. The sensible way to connect would be to put the downstairs ring final on one and the upstairs ring final on the other.
Where would the smoke alarm circuit go?

On a third section thats either

non-rcd and cabled in a suitable way
non-rcd and contains an RCBO for the circuit
on a third RCD

(have a look at the hager pdf of the options they make)

 

[GaryMo]

On a third section thats either

non-rcd and cabled in a suitable way
non-rcd and contains an RCBO for the circuit
on a third RCD

(have a look at the hager pdf of the options they make)

Fair comment on the twin RCD boards with extra unprotected ways.

 

[Adam_151]

I suppose you'd have to put the sokcet outlets on one, and the lighting and smokes on the other, perhaps falls fowl of the inconvience regulation, though

I think perphaps the two RCD splits and nothing else were what came up after initial thinking, but the solutions put forward by the big names are the refined version of that

 

[GaryMo]

Looking at a new Wylex catalogue it seems they're making both

 

[GaryMo]

I suppose you'd have to put the sokcet outlets on one, and the lighting and smokes on the other, perhaps falls fowl of the inconvience regulation, though

Has a split load board ever actually complied? We've been putting all circuits supplying socket outlets on a single RCD for some time now.
Are we guilty of turning a blind eye?

 

[ban-all-sheds]

Yes.

But more importantly:

All hidden/burried cables less that 50mm deep must either be mechanically protected OR RCD protected.!

If you're replacing a CU why do you have to bring the rest of the installation up to 17th Edition levels?

 

[securespark]

Surely you only have to make your work (ie the board change) to the 17th, not the entire installation?

 

[ricicle]

Surely you only have to make your work (ie the board change) to the 17th, not the entire installation?

But the board contains the part(s) which would bring the buried circuits up to the 17th ie the RCDs/RCBOs - and would you not want to attempt to bring the installation as close to complying with latest regs as was reasonably practicable?

 

[GaryMo]

Surely you only have to make your work (ie the board change) to the 17th, not the entire installation?

If that's the case then can we carry on changing old consumer units to the popular split load type we currently use?
What you're saying is that most existing circuits wouldn't need to be RCD protected as they were designed and installed earlier than BS7671:2008.

Not the right way in my mind though.