Going rate for CU change

[Aragorn84]

Because IMO its bad design to introduce spurs from a ring final where they could have been avoided.

Are you suggesting that if you were to add some sockets to an existing ring final, you'd take a spur as a first option, rather than looking to see if its possible to split the ring and incorporate the new outlet(s) into the ring?

 

[JohnW2]

Because IMO its bad design to introduce spurs from a ring final where they could have been avoided.

I suspect that it's only really 'bad design' because people have been brought up to think that it is.

If you think about it in a literal/pedantic fashion, then every socket on a ring final is actually 'a spur from the ring'. The actual 'ring' is formed by the cables and their connections to the terminals at the back of sockets or other accessories. In the case of a socket 'on the ring', there is then a (very short) set of conductors from those terminals to the actual contacts of the socket which mate with the pins of a plug. The socket is therefore a 'mini-spur from the ring'. Whether it really makes much difference whether the 'spur' is, say, 1cm/2cm long or 1 metre (or more) long, I'm by no means sure.

Kind Regards, John

 

[EFLImpudence]

Because IMO its bad design to introduce spurs from a ring final where they could have been avoided.

I disagree as well.
If it complies it is not bad design.

Are you suggesting that if you were to add some sockets to an existing ring final, you'd take a spur as a first option, rather than looking to see if its possible to split the ring and incorporate the new outlet(s) into the ring?

It makes absolutely no difference.

 

[ebee]

If I`m designing/installing a ring from scratch then like you I consider it good practice to install all on the ring proper. Although I can`t actually fault anyone who does add spurs at this stage. I ticks all the boxes of "a better practice" against minimum compliance for a number of reasons.

However, at the origin (on a short length that is) it is usually easy for anyone after to trace it, and make provision for altering if adding another.

(Actually, having more than one spur at the fuseway is no detriment providing of course that they could be secured correctly from an electrical and mechanical viewpoint - although it would probably be non compliant).

Once the ring is installed, anyone after could either spur off any point or the ring could be extended and the particular method used depends upon causing least damage to decor mainly. Obviously reducing the risk of future combatants spurring off spurs might also be considered when making this decision. Purely electrically though, spurs done correctly have no disadvantages

 

[Aragorn84]

I fully agree, theres nothing technical wrong with it, i just didnt like it.

Obviously some of the other issues WERE against regs, other stuff was perfectly fine, but was just sloppy, and added up to a whole picture of bad workmanship, and not what i'd call a "good electrician"

For instance he mounted the CU sideways as it wouldnt fit the proper way round. I suggested he simply remove the side of the boxing-in that enclosed it and put a new board on the wall, and even offered to do it for him but he couldnt be arsed and insisted on squeezing it into the small space left by the old 4 way rewireable board.

We're splitting hairs here anyway on one small point, my point was that had any "normal" uninterested member of the public have had that work done, and paid the money for it, they'd probably have been quite happy with the guy and highly recommended him to their friends and family as being a "good electrician".

 

[JohnW2]

If I`m designing/installing a ring from scratch then like you I consider it good practice to install all on the ring proper. Although I can`t actually fault anyone who does add spurs at this stage. I ticks all the boxes of "a better practice" against minimum compliance for a number of reasons.

I'm sure that's a common view, but, as I've said, I don't think it has got much, if anything, to do with electrical (or regulatory) considerations. Yes, most people designing a circuit from scratch would probably put all sockets/accessories 'on the ring' - but that's probably more about convenience (a little less work!) than anything else.

The only electrical downside of a spur I can think of is that (in one sense) it could be said to involve one more cable termination, but that's pretty trivial - indeed, although it involves 'terminations in one more set of terminals', the number of conductors terminated is no different). It also, as you say, makes it a little more difficult for someone to 'spur off spurs', but I'm not sure that a designed is really expected to attempt to make a circuit 'future idiot-proof' . Indeed, if a designer really did want to make it impossible for some incompetent person to install a spur off an unfused spur, then (s)he should avoid the use of ring final circuits altogether!

(Actually, having more than one spur at the fuseway is no detriment providing of course that they could be secured correctly from an electrical and mechanical viewpoint - although it would probably be non compliant).

Indeed - and I can't see why it should be non-compliant ... and most MCBs are rated to take at least 4 x 2.5mm² conductors.

Purely electrically though, spurs done correctly have no disadvantages

Exactly - apart from the very minor issues I've mentioned above.

Kind Regards, John

 

[JohnW2]

I fully agree, theres nothing technical wrong with it, i just didnt like it.

Fair enough, and I'm sure that many others think like you - but I don't think that makes it 'bad design'.

We're splitting hairs here anyway on one small point, my point was that had any "normal" uninterested member of the public have had that work done, and paid the money for it, they'd probably have been quite happy with the guy and highly recommended him to their friends and family as being a "good electrician".

Indeed - and I, for one, have already totally agreed with you about that. I think we also agreed that (in the absence of proper regulation of electricians) there's very little that a 'normal member of the public' can do, either to select an electrician who will probably do good work or to tell whether work which has been done is actually 'good'.

Kind Regards, John

 

[ldoodle]

Are RCBO's so much better than MCBs?

Look at this hager CU, with 10 MCBs: http://www.tlc-direct.co.uk/Products/HGVC766H1X.html

Less than £75 with VAT.

3 RCBOs cost that, excluding a CU to put them in!

 

[JohnW2]

Are RCBO's so much better than MCBs? Look at this hager CU, with 10 MCBs: ... Less than £75 with VAT. ... 3 RCBOs cost that, excluding a CU to put them in!

I suppose it depends upon your viewpoint. All-RCBOs is obviously the ultimate in circuit separation, hence decreasing the 'inconvenience' caused by a fault on any one circuit. However, I guess you ask yourself how often you 'suffer inconvenience' as a result a a fault taking out all the circuits protected by one RCD - and then decide whether that difference justifies the cost differential.

On the other side of the coin, 'nuisance trips' of RCDs (and, indeed, reliability questions about RCDs) seem to be quite a common problem. If, as I would assume, much the same applies to the 'RCD part' of an RCBO, having lots of RCBOs presumably may increase the probability of experiencing such 'nuisances'.

As always, swings and roundabouts, I guess!

Kind Regards, John

 

[ekmdgrf]

Are RCBO's so much better than MCBs?

Look at this hager CU, with 10 MCBs: http://www.tlc-direct.co.uk/Products/HGVC766H1X.html

Less than £75 with VAT.

3 RCBOs cost that, excluding a CU to put them in!

Define "better".

The advantage of having RCBOs over separate RCDs covering multiple circuits is that if there's an earth leak on a circuit, it doesn't trip out half the circuits in the house. That's annoying. Also, if an RCD fails and can't be reset, you again loose half your circuits until you can get it fixed.

So the question is: does the inconvenience of the above justify the cost of using RCBOs? That's a question only you can answer but given the cost of a board full of RCBOs, it seems unlikely.

 

[EFLImpudence]

Define "better".

More to your liking.

 

[ekmdgrf]

Define "better".

More to your liking.

Why would the OP want to choose an installation that's more to my liking?

 

[EFLImpudence]

RCBOs have the disadvantage of not indicating if it was an overcurrent or earth leakage which caused the trip.

Perhaps three RCCBs would be even better or perhaps one RCCB and one MCB per circuit.

Where will it all end?
Perhaps there's no real need for RCD protection on other than sockets and showers.

 

[JohnW2]

Where will it all end? ... Perhaps there's no real need for RCD protection on other than sockets and showers.

... and there's scope for debate/discussion even there. If all ~25 million households in UK were equipped with two RCDs at, say a fairly modest average price estimate of £50 each (including fitting), that would amount to some £2.5 billion. Given that we appear to be very uncertain as to how many (if any!) deaths and serious injuries have been prevented by the gradual introduction of RCDs, it would not be difficult to speculate that spending the same £2.5b in some other safety-relevant field might well result in considerably more reduction of injuries and deaths.

Kind Regards, John

 

[diynoob]

Best CU is a can of worms.

I'm shocked and appalled that you recommend using a can of worms as a consumer unit, and even go so far as to say it's the best.