Do i need to rewire or upgrade consumer unit for EICR??

[SimonH2]

If you have the skills to do it safely, as mentioned before you can do :
IR tests. If there's anything on the low side you can investigate that and deal with it.
Continuity tests. r1+r2 on everything, and of course, check all the rings are actually rings.
Plus one not mentioned - check for borrowed neutrals on landing lights (i.e. a light fed from one circuit, but using the neutral from another - typically upstairs and downstairs). This is something that (if split across different RCDs or RCBOs) will make RCDs trip consistently all the time if not fixed.
As mentioned, if you can find and fix any of these issues, then it'll be cheaper than paying someone else to do it. A spark won't use your results, but if should give you confidence that there won't be major problems once work is under way to replace the CU.

 

[jcaan]

If you have the skills to do it safely, as mentioned before you can do :
IR tests. If there's anything on the low side you can investigate that and deal with it.
Continuity tests. r1+r2 on everything, and of course, check all the rings are actually rings.
Plus one not mentioned - check for borrowed neutrals on landing lights (i.e. a light fed from one circuit, but using the neutral from another - typically upstairs and downstairs). This is something that (if split across different RCDs or RCBOs) will make RCDs trip consistently all the time if not fixed.
As mentioned, if you can find and fix any of these issues, then it'll be cheaper than paying someone else to do it. A spark won't use your results, but if should give you confidence that there won't be major problems once work is under way to replace the CU.

Thanks this is exactly what I wanted to know! Yeah I'm going to make a start of it on Monday!

How would i check if the neutral is borrowed? I guess it will be down to the way the lights are wired. Has anyone got a diagram to show me of this kind of scenario?

Thanks for any help.

 

[JohnW2]

..... There's a youtube channel I watch similar name to yours. I've watched and understood the continuity and insulation resistance testing for lighting and sockets. Which was a great help.

I've only just noticed that bit above ... No, I am not that "John W" (many of whose YouTube videos are excellent). However, he is heree, and has been participating ion this thread, under the name of "flameport".

Kind Regards, John

 

[JohnW2]

How would i check if the neutral is borrowed? I guess it will be down to the way the lights are wired.

Good question. As you say, it's entirely down to how the lights aree wired.

However,the first question is whether you currently have two (or more) lighting circuits in your CU. 'Borrowed neutrals' (or sometimes 'borrowed lines') are almost invariably related to lighting circuits, and nearly always relate to hall/landing lights (which can bee switched from either floor) - but the issue can only arise if there is more than one lighting circuit.

If you do have two or more lighting circuits, I'll give you my attempt at some of the rest of the answer to your question

Kind Regfards, John

 

[SimonH2]

Those with more experience please correct me if I get this wrong.

Lets assume you have two lighting circuits, and if you drop the tails out of the fuses/MCBs and neutral bar you have two T&E cables. If there are no borrowed lines or neutrals, you should have a good IR reading between the two cables (with lights turned on). If, when you turn on the landing light (this is the most common as it has switches upstairs and downstairs) you find that the IR drops to a very low value, then you have a borrowed wire.
As an example of one way it could be wired, the live may be tapped off the downstairs circuit by linking from the live that is present for the hall light on a two gang switch. A 2 core (+E) cable is then run to the upstairs switch to provide the switched live for the light. But the neutral is taken from the upstairs lighting circuit. It might have been done this way to save the extra cost of a 3 core+E cable between the switches compared with 2 core+E, or perhaps the person doing it didn't have any 3 core+E in the van, or simply because in the past it was a common way of doing it (and it didn't really matter all that much, except for someone working on circuits that could become unexpectedly live*, prior to RCDs).

* If the offending light is off, then you could switch off a circuit, check it for dead, and be working on it. You might have the connections out (lets say you are replacing a ceiling rose in a bedroom for example). Someone switches on the landing light and a) it doesn't work, but b) one of your neutral wire ends sticking out of the ceiling is now live via the landing light. If the landing light were on, then as soon as you pull the neutrals out, one of them will go live.

 

[JohnW2]

Those with more experience please correct me if I get this wrong. .... Lets assume you have two lighting circuits, and if you drop the tails out of the fuses/MCBs and neutral bar you have two T&E cables. If there are no borrowed lines or neutrals, you should have a good IR reading between the two cables (with lights turned on).....

I make no claims about 'experience', but if one is happy to play inside thee CU, then it's easy enough to determine whether there are any 'borrowed/shared' neutrals (or lives) at work, without the need for any measurements ...

If there is no such 'borrowing' between lighting circuits, then all lights on a circuit will continue to work, even if other lighting circuit(s) are disconnected (both L and N) at the CU. If there is any 'borrowing' going on, then some of the lights will stop working when another lighting circuit is disconnected (L&N).

I say 'both L & N' since, although it is most commonly a neutral which is 'borrowed', that is not always the case.

However, as I said in my recent post, if there is only one lighting circuit, ther isn't really anything to 'investigate'!

Kind Regards, John

 

[flameport]

Those with more experience please correct me if I get this wrong.

All correct.

Before changing a consumer unit, insulation resistance tests are desirable, link L&N together for each circuit, then test between each linked L&N for every combination of circuits with loads connected and switched on.
Doesn't take much longer, as you can also do L&N - E for each circuit at the same time, which will reveal most types of insulation faults on the individual circuits.

While connections between lighting up/down is fairly common in older properties, there can be others particularly where there is evidence of alterations. Single L to an existing light switch and connecting the neutral to a nearby socket upstairs for that outside 500W floodlight is a popular one. So is heating systems with the boiler connected downstairs and the rest of the controls connected upstairs through two separate FCUs.

Neutrals can become live when disconnected, which is why checking for live parts before and after disconnecting is essential 100% of the time on 100% of items.

 

[jcaan]

Thank you so much guys!

So as I've said my house is a terraced and 4 floors, which includes cellar and attics..

Looks like the 1st and 2nd (attic) floor lights share the same MCB as the cellar floor..no idea when the 1st and 2nd floor MCB was taken out!

so would this give any indication as to the circuits ?

 

[SimonH2]

Well there's a C1 straight away - there's an open hole you could stick your finger in and touch live parts.
Probably there was a fault, and someone just moved the live to another breaker rather than try and find a new breaker. As to what feeds what, take anything written on the CU with a pinch of salt and there has clearly been at least one change without updating the labels.

 

[Murdochcat]

So it’s your house then. On the basis of the photo, and assuming you plan to rent it out, I would recommend a new cu with RCBOs and SPD

Just because 2 cables leave a MCB doesn’t make it 2 circuits. 1 x OCPD = 1 circuit

 

[ebee]

Just because 2 cables leave a MCB doesn’t make it 2 circuits. 1 x OCPD = 1 circuit

correct

 

[jcaan]

So it’s your house then. On the basis of the photo, and assuming you plan to rent it out, I would recommend a new cu with RCBOs and SPD

Just because 2 cables leave a MCB doesn’t make it 2 circuits. 1 x OCPD = 1 circuit

No I just wrote my house because its just easier saying it , rather than keep repeating my families house etc

I was thinking of just getting an RCD in the existing one. But as you say it maybe wise to just upgrade the whole thing.

 

[Murdochcat]

I was thinking of just getting an RCD in the existing one. But as you say it maybe wise to just upgrade the whole thing.

Upfront RCDs we’re never a good idea nor are compliant with the regs so RCBOs is the only way forward

And those Proteus boards are absolute carp sold by absolute carp CEF

 

[plugwash]

but the issue can only arise if there is more than one lighting circuit.

While less common, my understanding is it's not unheard of to find wall lights with their live taken from a lighting circuit, but their neutral taken from a socket circuit.

 

[JohnW2]

While less common, my understanding is it's not unheard of to find wall lights with their live taken from a lighting circuit, but their neutral taken from a socket circuit.

Fair enough.

People often criticise me for the length of my writings, including forum posts, but I've learned through bitter experience that if I don't try hard to think of of and write about 'all conceivable possibilities' (even very improbable ones), someone will jump in with a "bit you haven't considered XYZ" comment

If one wanted to cover the possibility you've mentioned, I suppose that one would have top modify what I suggested to say that if a light still works when (L and N of) all other lighting circuits, and all other conceivably involved sockets (or whatever) circuits, were disconnected at CU.

Kind Regards, John