When is a new circuit not a new circuit?

[oldbutnotdead]

Precis- house has been empty for many years. Was rewired around 2004/5 I'd guess (modern ish split load CU with MCBs and 1 RCD, brown/blue links internally but red/black T & E from every breaker) and whoever did the job couldn't be bothered (or was told not) to install a sensible number of sockets in each room (1 x double) or to remove the rubber sheathed T & E (from the 30s maybe) or the conduits full of fibre insulated (doesn't look like asbestos) singles from Lord knows when.

Anyway, renovating. There was a fair bit of damp in some of the walls so some of the sockets had gone a bit corroded- no dramas, easy replace.

BUT I am getting a low insulation resistance reading from the first leg of the downstairs 'ring' (why he bothered with only 4 sockets on I have no idea but there we go)- showing 15 MΩ L-E where everything else is 100 MΩ plus. So I'd like to replace this leg but that would mean a bit of blue/brown T & E in the CU- is that a new circuit (notifiable) or a repair (not notifiable)?

Future plan (of course) is to extend the hell out of the rings (which since April 1 2013 I'm allowed to apparently). Also I'll be sorting the lighting circuits- all in red/black T & E, all insulation resistances and continuity are fine but there are about 4 big stealth JBs under floorboards which I want to get rid of for obvious reasons.

TIA

 

[flameport]

Replacing a piece of cable is not a new circuit. Even if replacing all of the cables. Old/new wire colours makes no difference either and the presence of one or the other proves nothing.

There are many previous wranglings over what may or may not be a new circuit, but the reality is that no one knows and even fewer care.

 

[JohnW2]

Future plan (of course) is to extend the hell out of the rings (which since April 1 2013 I'm allowed to apparently).

When you talk about 'allowed', I presume you're talking about 'notifiability'. Even prior to April 2013, you could extend an existing circuit to whatever extent you wanted without notification.

Also I'll be sorting the lighting circuits- all in red/black T & E, all insulation resistances and continuity are fine but there are about 4 big stealth JBs under floorboards which I want to get rid of for obvious reasons.

As you are probably aware, since April 2013, the ONLY works which remain notifiable (in England - Wales is different) are replacing a CU, extensions/modifications of circuits in zones of a bathroom and addition of a 'new circuit'. As has been said, there will be debates about the precise meaning of 'new circuit', but I think most people would agree that if the rating of the OPD in the CU has not changed, and if the circuit still serves the same general purpose ('lighting', 'sockets' etc.) as it always did, then no work on, or extension of, that circuit constitutes 'creating a new circuit' - even if most/all of the cabling and accessories are replaced. Opinions might vary a bit more when an existing circuit has been 're-functioned' (e.g. if a previous immersion, shower or cooker circuit has been adapted for some different purpose) - but, even then, I think that many would say that is not a 'new circuit' (if the rating of the OPD has not changed).

Kind Regards, John

 

[oldbutnotdead]

Thanks both. flameport- that was my reading, wasn't sure whether working within the CU was classed as notifiable. JohnW2- yes 'allowed' should have read 'not notifiable' and that's a sensible point re not changing the OPD rating or type.

 

[JohnW2]

JohnW2- yes 'allowed' should have read 'not notifiable' and that's a sensible point re not changing the OPD rating or type.

In the absence of any official definition, that seems to be the criterion that many people apply - i.e. if a circuit is literally 'new' (wasn't there at all previously), or if the OPD rating has been changed (particularly 'upwards'), it probably should be regarded as a 'new circuit' (hence notifiable), since fundamental issues of 'design' then arise.

I'm personally far less convinced that one creates a 'new circuit' by "re-purposing" an existing circuit, provided that one does not increase the OPD rating - but others probably disagree with me about that.

Kind Regards, John

 

[PBC_1966]

In the absence of any official definition, that seems to be the criterion that many people apply - i.e. if a circuit is literally 'new' (wasn't there at all previously), or if the OPD rating has been changed (particularly 'upwards'), it probably should be regarded as a 'new circuit' (hence notifiable), since fundamental issues of 'design' then arise.

I'm not sure that merely changing the fuse or circuit-breaker for a different one while doing other work would really make it a new circuit, any more than adding extra cable and a dozen more sockets to a ring would make it a new circuit. The circuit was there already, and you've just made changes to it, including the protective device which was already there and already part of the circuit concerned.

I'm personally far less convinced that one creates a 'new circuit' by "re-purposing" an existing circuit, provided that one does not increase the OPD rating - but others probably disagree with me about that.

Again, there's the ambiguity in the regulations as to what "new circuit" actually means. But if you can extend a ring by adding cable and a dozen sockets or you can extend a lighting circuit to add a ceiling fan and none of that counts as a "new circuit," then I don't see how, for example, "re-purposing" a redundant feed to an immersion heater outlet, fitting an FCU and installing a smaller heater in the cupboard could be a "new circuit" either.

wasn't sure whether working within the CU was classed as notifiable.

Only "replacing" a consumer unit is notifiable. And that opens up the question of what "consumer unit" means in the regulations. It's also clear that if you fit a new consumer unit in place of something which was not a consumer unit, then it's not notifiable since you're merely fitting a new consumer unit, not replacing one.

There are many previous wranglings over what may or may not be a new circuit, but the reality is that no one knows and even fewer care.

Bingo! And even fewer will know what was already there before you changed it anyway.

 

[JohnW2]

I'm not sure that merely changing the fuse or circuit-breaker for a different one while doing other work would really make it a new circuit, any more than ....

I think you may have misunderstood me. I certainly would not regard replacing an OPD with one of the same rating created a 'new circuit'. Nor, as I went on to say, would I usually think of a 'new circuit' having been created if I replaced an OPD with one of lower rating.

However, the issue arises if one increases the rating of an OPD, which, in practice, will nearly always also mean replacing the cable with one of larger CSA. For example, if one had an unused immersion heater circuit, wired in 2.5mm² cable on a 16A or 20A MCB and then 'replaced' the MCB with a 40A or 45A one and then (necessarily) replaced the cable with 6mm² or 10mm², to supply a shower, I cannot see that one could reasonably deny that it was a 'new circuit'!! In fact, the only sense in which the circuit had any relationship with what was there before would be that the (much higher rating) new MCB was occupying the same position in the CU that the immersion circuit's one had occupied!!

Kind Regards, John

 

[JohnD]

I speak English quite well, and understand the difference between the meaning of the words "new" and "altered".

I have a five year old car. If I fit it with wide wheels, new tyres, a towbar, and replacement seats, is it a new car?

 

[JohnW2]

I speak English quite well, and understand the difference between the meaning of the words "new" and "altered".

I would say the same of myself, but that doesn't necessarily help either of us to understand the intended meaning of 'new circuit' as mentioned in the Building Regs.

I have a five year old car. If I fit it with wide wheels, new tyres, a towbar, and replacement seats, is it a new car?

But what if you replaced the entire body, engine, exhaust system, transmission, wheels, braking system, electrical system etc. etc. with new parts?

Back to electricity and the example I gave, if one started with a circuit consisting, in its entirety, of:

20A MCB - 2.5mm² cable - 20A switch - immersion heater
and then replaced components such that one ended up with:
45A MCB - 10mm² cable (different route) - 45A Shower isolator switch - shower

... would you really believe that what you had created was not a 'new circuit', simply because the new MCB occupied the same space in the CU which had once been occupied by the MCB for the immersion circuit? We may not know exactly what was in the mind of those who made 'new circuits' notifiable, but I think there is scope for the application of common sense in situations such as I have described.

Kind Regards, John

 

[stillp]

What about the fairly common situation of splitting a ring final into two radials? Aren't they new circuits?

 

[JohnW2]

What about the fairly common situation of splitting a ring final into two radials? Aren't they new circuits?

I was waiting for someone to bring that one up, since it is one case in which I find it hard to make up my mind, at least in terms of 'common sense'! It's tempting to think that there is at least one new circuit, since there is one more 'origin'/OPD than there was previously, but in other senses it's easy to feel that there are no 'new circuits'!

Equally, if not more, difficult (at least for my mind) would be the converse (admittedly much less common) - of combining two radials to create a ring.

Kind Regards, John

 

[PBC_1966]

I think you may have misunderstood me. {.....} In fact, the only sense in which the circuit had any relationship with what was there before would be that the (much higher rating) new MCB was occupying the same position in the CU that the immersion circuit's one had occupied!!

Ah, following you now. So we could, perhaps, take "new circuit" to mean that every single part of the wiring forming the branch circuit as it ends up is new, and if any part of the original wiring of that branch circuit (including fuse or MCB) was there to begin with, it's merely an altered circuit, not a new one. Of course, that means that so long as the fuse/MCB is satisfactory for your purposes, you could rip out everything else which was fed from it and wire in something completely new and different, but it still wouldn't be a "new circuit" because you're using the same fuse/MCB. Or if you do change the fuse but re-use a junction box from the old circuit somewhere, would that still count as altered rather than new?

What about the fairly common situation of splitting a ring final into two radials? Aren't they new circuits?

Or do you have one new circuit and one altered circuit? (Which would be notifiable anyway.)

 

[stillp]

What about the fairly common situation of splitting a ring final into two radials? Aren't they new circuits?

Or do you have one new circuit and one altered circuit? (Which would be notifiable anyway.)

Well, if you were to list the circuits on the CU before and after splitting the rfc, then 'after', you'd have two radial circuits that didn't previously exist, and one less rfc, which is irrelevant.

 

[PBC_1966]

Well, if you were to list the circuits on the CU before and after splitting the rfc, then 'after', you'd have two radial circuits that didn't previously exist, and one less rfc, which is irrelevant.

But couldn't it also be argued that the original ring-final circuit has merely been changed into a replacement radial circuit?

If I took a redundant 15A feed to an old immersion heater, fitted a switched flex outlet and a small heater in the cupboard to make use of that old circuit, then crossed out "Immersion heater" and wrote "Airing cupboard heater" next to the relevant MCB, have I created a new circuit just because the designation against that MCB has changed? Or perhaps more in keeping with your example where the rating would be altered, if I kept all that original 2.5 sq. mm cabling but replaced the MCB with a 6A one, would that change anything?

 

[stillp]

I suppose it could be argued that the rfc had been replaced by 2 radials.
No, changing the designation of a circuit doesn't make it a new one. As you said, you've "made use of that old circuit". Changing the configuration of a circuit might though.