All-RCBO CUs - because we can?

[JohnW2]

Yes, they may be different causes with the same effect - that doesn't mean we have to treat them identically.

Agreed, as a generalisation.

However, in this case, if one can implement a (potentially very cheap) measure which addresses both/all possible causes, why spend more to address only one of them?

If the risk is a true danger, then yes - treat them the same....

Some people seem to be basing their views in the fact that there is a potential 'true danger' (albeit only very rarely). If one doesn't believe that there is a true danger, then all we're left with is 'convenience' (and how much that is worth in £££, given the infrequency of the inconveniences).

But now we're talking about it, I'm thinking that an emergency light where each of our smoke detectors is (and maybe powered from the alarm circuit) wouldn't go amiss. Then it's whether to make them standalone or use maintained fittings and replace the ceiling rose with them.

Providing enough emergency lighting to avoid any dangers resulting from 'being plunged into total darkness' need not cost much. I have a few things like the one in the photo below dotted around my house in strategic places. They probably don't cost much more than a tenner apiece these days (and have no installation costs) and mine (which have replaceable rechargeable batteries) have been in service for years. In the event of lost power, they come on at full brilliance and can, of course, be lifted out and used as a torch, and they glow dimly when there is power, to reassure that they are 'working' - also flash if the battery is dying.

Kind Regards, John

 

[JohnW2]

... there's an RCD used as the main switch so the whole of the original house is on one RCD. The extension is the same, so in effect we have a split board arrangement as far as circuits go - original house (lights, sockets, smoke alarms, boiler) on one RCD, extension (kitchen sockets, lounge sockets, cooker, lights, shed & greenhouse) on another. My intention is to combine everything into one board using RCBOs (it would be a struggle to get the width for two RCDs anyway) - eventually !

In the meantime (given that 'eventually' might be slow in coming!), since the two boards are seemingly close enough for you to be combining them one day, I suppose you could consider making make the 'separation of circuits' more like what one usually sees in a dual-RCD CU by, say, 'swapping' the lighting circuits (and maybe also moving one of the extension's sockets circuits onto other board, if their were any spare capacity)?

 

[SimonH2]

Close is relative - only about 7m as the cable runs. The "new" board is in the extension running off a submain as it was easier for them to run one cable to a sub-board. I won't have any problem hacking into the plaster (to run additional circuits upwards from the main board) so extending the circuits to the main board won't be too much effort - when I get to that stage, "eventually"

However, there's only one spare way in the main board - so it will need replacing with a bigger one. I might just replace the innards for the time being and make both boards RCBO.

 

[JohnW2]

Close is relative - only about 7m as the cable runs. The "new" board is in the extension running off a submain as it was easier for them to run one cable to a sub-board. I won't have any problem hacking into the plaster (to run additional circuits upwards from the main board) so extending the circuits to the main board won't be too much effort - when I get to that stage, "eventually"

Fair enough.

However, there's only one spare way in the main board - so it will need replacing with a bigger one. I might just replace the innards for the time being and make both boards RCBO.

Again, fair enough - but making both boards RCBO does to some extent re-invoke the title of this thread [although if you do it to gain spaces in the CU(s) that would be an additional 'reason' ]!

Kind Regards, John

 

[SimonH2]

Well, one thing I can do is to replace the RCD in the main board with just a switch, and fit RCBOs to the existing circuits - plus an MCB for the submain. Then I can do away with the Henleys and associated wiring. There isn't room (only one spare way) for an RCD.
The second board will then need RCD protection, either by replacing everything with RCBOs or replacing the main switch with an RCD.

Mind you, the case itself (for the main board) does have a fair bit of space in it (including spare length on the DIN rail) - so I had thought of applying the nibblers to the front to add a few extra ways

Going somewhat off topic now, and into territory that's already been covered I think ...
As I read the regs - keeping the existing box and replacing the parts inside it would not be installing a new CU. If I later replaced the box with a larger one but kept the innards - then that would not be installing a new CU. And moving a circuit from one CU to another would not be installing a new circuit. Perhaps not what the legislators intended, but I end up with a larger main CU without anything being notifiable. Though when I build the garage, I could lump in a CU upgrade with BRs for that.

 

[JohnW2]

Going somewhat off topic now, and into territory that's already been covered I think ... As I read the regs - keeping the existing box and replacing the parts inside it would not be installing a new CU. If I later replaced the box with a larger one but kept the innards - then that would not be installing a new CU. And moving a circuit from one CU to another would not be installing a new circuit. Perhaps not what the legislators intended, but ....

Yes, we've done that one before

One of the silly things about the literal drafting of the legislation is that "installing a CU" (which you say above, three times, you wouldn't be doing) could be said to NOT be notifiable, since the only thing that is notifiable is "replacing a CU"! That has led people to suggest that if you left an existing CU in place (maybe little, or not at all used) you could then install an additional new one, without having 'replaced' anything. The catch then is that many/most people would probably say that any circuits you connected to that new CU would be 'new circuits' - hence back to being notifiable again!

I'm not really sure why people expend effort in trying to find these 'workarounds' in relation to the law regarding notification, unless merely to ease their consciences. If they are going to undertake notifiable work without notifying it, then that's their business, and the chances of anyone in authority ever discovering are almost non-existent (and, even if they did discover, the chances of them doing anything about the non-notification, per se, even smaller) - so they do not really need to have arguments up their sleeve which attempt to justify the legality of what they have done!

Kind Regards, John

 

[EFLImpudence]

As I read the regs - keeping the existing box and replacing the parts inside it would not be installing a new CU. If I later replaced the box with a larger one but kept the innards - then that would not be installing a new CU.

Then you are misreading the regulation.

Notification is required for the replacement of a consumer unit; it does not mention installing a new one.

This might not make any difference to your argument but you will have to reword it.

"keeping the existing box and replacing the parts inside it would not be replacing a CU.
If I later replaced the box with a larger one but kept the innards - then that would not be replacing a CU."

 

[JohnW2]

Then you are misreading the regulation.....

Too slow

Kind Regards, John

 

[EFLImpudence]

D'oh.

 

[Notch7]

I would assume that changing rcds / rcbos / mcbs in a consumer unit would require testing.

from what Ive read these things are sometimes faulty when new, so without testing one wouldnt be very confident they provide the protection they should -thats aside from any regulations.

 

[EFLImpudence]

The RCD functions can and should be tested, but nothing is done to test MCBs or the MCB part of an RCBO.

There is very expensive equipment that can test MCBs - or inadvisable methods.

 

[JohnW2]

I would assume that changing rcds / rcbos / mcbs in a consumer unit would require testing.

As EFLI has said, residual-current functionality in RCDs/RCBOs can and should be tested, but, in practice, over-current functionality (or RCBOs or MCXBs) can't.

However, any electrical work, whether notifiable or not, should be properly tested (which few DIYs can or do do) - so that, in itself, does not influence notifiability. Since BS7671 requires that testing, and given that almost everyone relies on compliance with BS7671 to demonstrate compliance with Part P, it follows that it could be argued that a very high proportion of DIY work cannot be shown to be compliant with Part P - but that's how it is!

Kind Regards, John

 

[ban-all-sheds]

There used to be a P2.

 

[JohnW2]

There used to be a P2.

There was? What did it say, and when did it disappear?

 

[ban-all-sheds]

Ah.

There was. And it said:

P2. Sufficient information shall be provided so that
persons wishing to operate, maintain or alter an electrical
installation can do so with reasonable safety.

It disappeared in a very early amendment, in 2005, or early 2006.

And the only reason I mentioned it was because I misrememberified it. The issue of testing had been raised in this thread, and I thought that P2 had been the requirement to do testing, but of course it wasn't. That had been in P1, and was removed in the same amendment that deleted P2.

Originally P1 read

P1. Reasonable provision shall be made in the design,
installation, inspection and testing of electrical installations
in order to protect persons from fire or injury.