Rerouting Not Rewiring Cables - Need To Be Signed Off?

[SPECIAL LOCATION]

I think that started to change  by the  late 1960's   early '70,s  .

I think the least circuits I've come across was   4 way Wylex  rewirable   ,  1 X Lights ..1 X  ring main.... 2 X spare .           ( Im Htr connected to Ring )  

Just fitted a new CU on Tuesday in glorious Halesowen...

was an old 4-way Wylex box..

It is now a 7 circuit full RCBO board...  ( with some spare ways if needed in the future )

There were actually Two independent lighting circuits connected to the single 5A light fuse.

And 5x 2.5mm stuffed into one 30A fuse is now 3x Socket circuits ( 1x 32A ring, 1x 20A, 1x 16A {boiler+ a Socket})

[ Fitted new board + new oven circuit, so that we could add a new circuit on for the oven & Induction hob they had bought to replace the old Gas hob and Oven plugged into the socket circuit!]

I couldn't figure out why nobody had upgraded the board earlier as some of the wiring was Blue/Brown, so must be 2005/6 onward!?

Guinness  

 

[Evans Electric]

It never ceases to amaze me  how many times I see  , as Specs says ,   circuits added ...stuffed into fuseways  ...signs of sparks attending but never upgrade the board. 

The other one of course is also numerous  visits by sparks  over many years say ,  but not one of them has picked up on the loose earth clamp on the main cable  or , often in the Sutton Coldfield area by me ,    the total lack of a DNO earth on the TN-S  systems  .  Usually dependant on a water or gas pipe  .  

But the place has been rewired , say ,  or showers installed , new kitchens,   floodlights  etc etc  

 

[Risteard]

The majority of the time the quickest overall method timewise is to check each circuit individually from the start, so if you encounter low readings you know where to start looking. Guinness

Many RCBOs don't have functional earths attached, but of course it can be an issue. Also surge protection needs to be disconnected.

However, my point remains that if you test individual circuits then you must calculate the resistances in parallel to verify BS7671 compliance as the minimum values of insulation resistance are for the installation and not for the circuit.

 

[Ed51]

We bought a new Wickes consumer unit a few years ago. Would an electrician be able to use this in whole or in part to replace the mess on the main board?

Thanks.

 

[binky]

However, my point remains that if you test individual circuits then you must calculate the resistances in parallel to verify BS7671 compliance as the minimum values of insulation resistance are for the installation and not for the circuit.

so why do we have individual cct IR boxes to fill in on a standard test cert and no 'global value' box?  When was the last time anyone sat down and calculated a global IR value? It's a question that is never raised on the forum becuase nobody does it, and if you are correct, how come this isssue has never been raised on any of my annual assessments?  I think the wording of the big book is a little misleading, or has been worded to allow for global testing whether it is a good idea or not. Perhaps @Sidewinder could shed some light on this?

If you consider how much cabling is in something like a shopping mall and used global IR testing, I suspect it would have an 'ice-cream in hell' chance of passing  :^O

I once fully rewired a house that had been rebuilt in 1947 after being bombed. It was wired in ViR, it passed all IR testing and I was surprised how supple the rubber still was, except where it gets a little warming in the back of sockets - try moving the cable and the insulation disintegrated. This is where experience and the opinion of the tester comes into play. There was no way I would pass it a safe for continued use even if the test results said it was OK

 

[SPECIAL LOCATION]

Many RCBOs don't have functional earths attached, but of course it can be an issue. Also surge protection needs to be disconnected.

However, my point remains that if you test individual circuits then you must calculate the resistances in parallel to verify BS7671 compliance as the minimum values of insulation resistance are for the installation and not for the circuit.

In the real world it is never "IF" you test individual circuits...

As there are very few instances where you can omit testing individual circuits....

This is where the balance of common sense and practicality comes in, when evaluating the time spent doing an EICR -vs- the information needed to verify satisfactory or unsatisfactory outcome...

e.g.

A typical domestic installation, even those with older wiring, has the majority of circuits with IR's which are in high end double figures, more typically up in the hundreds of Megs.

and maybe one or two circuits with a low reading requiring further investigation.

(tested one earlier this week one circuit approx. 70meg, another 4.5meg, the rest all 200meg+   The 4.5meg one turned out to be the "surge protection multiblock still plugged in in the bedroom"  once removed 200meg+)

So if I wasted time doing a global, I'd still have split it down and re-tested individual circuits anyway.... :shakehead

And...

lets imagine a hypothetical 12 circuit installation where every circuit just happens to be bang on 150Meg...

that will give us a global IR of 12.5Meg  (1/((1/150)x12))...

Are you going to write 12.5Meg in all of the circuit IR boxes on the test results page, or put the 150Meg figure ?

Consider the model forms in GN3 which show sample results of +299meg written in every box on an example 7 circuit single phase installation

(see page 126 of current GN3)

Now in reality this could be a global IR of 45 or 50Meg...

But the individual circuit readings need to be tested and noted to show the full composition and condition of every circuit...

So when testing an existing in service domestic installation you will need to verify individual circuits anyway..

There is no option about "If you test individual"..

It is actually the Global test that can be omitted as it is easily verified by calculation from your individual circuits results..

AND you don't have to document the global figure anywhere anyway.

:coffee     

 

[SPECIAL LOCATION]

We bought a new Wickes consumer unit a few years ago. Would an electrician be able to use this in whole or in part to replace the mess on the main board?

Thanks.

View attachment 9795

View attachment 9797

If you find an electrician that says they will...

I would make sure you don't employ them!

As that would appear to be a plastic enclosure, which hasn't complied with wiring regulations since Jan 16...

Ref wiring reg  421.1.201  requiring Non-combustible enclosure in domestic dwelling...

So you'd be unlikely to get a valid electrical certificate OR a building reg's compliance certificate for the work..

Which you will be needing if you want to sell the property without someone knocking a few grand off the price for electrical work...

Plus you will need to get RCD protection, that your Wickes board doesn't have. 

Guinness

 

[phil d]

Not rewiring could really affect the selling price, people may view, a lot may not if it says in the sales stuff that the house needs a rewire, then it's how much they'll knock you down by. A rewire may only be 2 or 3k, but add to that re-plastering, re-decorating etc and it all adds up. those that it doesn't put off completely may offer you anything up to £10k less, then it's whatever else a survey throws up. A lot of people are not practical today, they don't do diy, so they look at the cost of getting plasterers in, painters and decorators etc and it all  adds up.

As others have said, it would be better to get the work done before you sell, that way you can avoid a lot of problems.

 

[Risteard]

so why do we have individual cct IR boxes to fill in on a standard test cert and no 'global value' box?  When was the last time anyone sat down and calculated a global IR value? It's a question that is never raised on the forum becuase nobody does it, and if you are correct, how come this isssue has never been raised on any of my annual assessments?  I think the wording of the big book is a little misleading, or has been worded to allow for global testing whether it is a good idea or not. Perhaps @Sidewinder could shed some light on this?

If you consider how much cabling is in something like a shopping mall and used global IR testing, I suspect it would have an 'ice-cream in hell' chance of passing  :^O

I once fully rewired a house that had been rebuilt in 1947 after being bombed. It was wired in ViR, it passed all IR testing and I was surprised how supple the rubber still was, except where it gets a little warming in the back of sockets - try moving the cable and the insulation disintegrated. This is where experience and the opinion of the tester comes into play. There was no way I would pass it a safe for continued use even if the test results said it was OK

RE: Your shopping centre scenario, as I already pointed out, in larger installations it is permissible to insulation test each distribution board with all final circuits connected. So it isn't everything in the shopping centre together.

The requirement is very clear in BS7671 if you care to read it.

As for the boxes next to every circuit I am led to believe that the forms were designed the way they were because it looked neater.

 

[binky]

so why isn't there a global IR box on the forms? 

 

[Risteard]

so why isn't there a global IR box on the forms? 

I already answered that - the forms were designed to look nice.

And there is anyway. You could list it next to the distribution circuit or meter tails or whatever. Or just note it next to every circuit which is the norm.

Anyone disagreeing with me really ought to read 643.3.2 - and I can assure you that the same or similar text has appeared in previous Editions of the Regulations too.

 

[Sidewinder]

Strictly speaking the IR for each circuit should be done, and recorded, then, the global IR calculated.

It is doubtful that on most new installations you would get anywhere near as low as 1M Ohm.

On an EICR, you should do a global IR, then and only then if it is low should you break it down, but sometimes that is not practical either.

However, the global should always be calculated, even if it is not recorded, because it can always be calculated from the individuals.

643.3.2 is pretty much the one that Risteard is on about I believe.

 

[binky]

I'm not disagreeing with you, I just think you are mistaken  :^O .

It would be very simple to have added a box for global IR on any cert - got shed loads of boxes for everything else. 

 

[Risteard]

I'm not disagreeing with you, I just think you are mistaken  :^O .

It would be very simple to have added a box for global IR on any cert - got shed loads of boxes for everything else. 

Have you read 643.3.2 then?

 

[binky]

years ago.

Simple fact is if you look at any test cert there isn't any mention of global IR test results.  Now given that the various governing bodies that like to justify their existnece by making our lives more difficult have added pages and pages of codswallop to test certs but have failed to add a simple little box for what you are argueing..... This tells me you are in a minority of 1. 

However getting back to the original discussion of cable life, cable is, in most domestic situations, is definetly good for more than 25 years if installed properly.

 

[SPECIAL LOCATION]

I'm not disagreeing with you, I just think you are mistaken .

It would be very simple to have added a box for global IR on any cert - got shed loads of boxes for everything else. 

Have you read 643.3.2 then?

I get the feeling were having a bit of misinterpreting what others are posting going on here.....

Just been scanning back over the thread...

I don't think anyone has actually said that bottom line IR acceptable value doesn't refer to the global figure...

Or that you can do a global test reading at the DB...

(if you want to)...

But one hell of a lot of the time individual circuits need to be tested as well to get the bigger picture about the condition of an installation ...

And 643.3.2  quotes detail relating to both Global and Individual circuit testing..

As does GN3, Examples (i) Global and (ii) Final circuit IR testing.. (Pg 51 onward)..

e.g.

eight final circuits all at 6Meg individual = Global 0.75Meg

Is a big difference than seven circuits at 200meg and one at 0.77Meg = Global 0.75Meg

OR...

eight final circuits all at 8Meg individual = Global 1.0Meg

Is a big difference than seven circuits at 200meg and one at 1.1Meg = Global 1.0Meg

In Both of the above example the second illustration has an installation where over 87% of it is in top-notch good condition only 12% is dubious..

whereas the first illustrations 100% of the installation has deteriorated down into single figure IR values...

If you just did the global value you'd miss an incredible amount of perspective on the condition of the overall installation for continual use and/or your recommended next inspection interval..

Hence why the schedule of test results have boxes for individual circuits NOT just a global value... 

(which would have been easier and neater with just one box))

As a side note...

during the old annual assessment watch the monkey do his tricks performance...

I have never been asked to do a "Global IR"...

get asked for Ze's,  PFCs,  R1+R2's,  Zs's,  Ring Continuities,  RCD trip times  and IR's on Final Circuits...

But NEVER a global IR!

Bit like when my car comes back from MOT...

I do rather like to see individual Tyre tread depth readings..

Not just a global  "All tyres are ok" comment.

Guinness  

 

[Risteard]

As I said RECI always insist on a global insulation resistance test, and rightly so.

 

[Ed51]

Not rewiring could really affect the selling price, people may view, a lot may not if it says in the sales stuff that the house needs a rewire, then it's how much they'll knock you down by. A rewire may only be 2 or 3k, but add to that re-plastering, re-decorating etc and it all adds up. those that it doesn't put off completely may offer you anything up to £10k less, then it's whatever else a survey throws up. A lot of people are not practical today, they don't do diy, so they look at the cost of getting plasterers in, painters and decorators etc and it all  adds up.

As others have said, it would be better to get the work done before you sell, that way you can avoid a lot of problems.

Appreciate the sensible advice,

Thanks

 

[Ed51]

If you find an electrician that says they will...

I would make sure you don't employ them!

As that would appear to be a plastic enclosure, which hasn't complied with wiring regulations since Jan 16...

Ref wiring reg  421.1.201  requiring Non-combustible enclosure in domestic dwelling...

So you'd be unlikely to get a valid electrical certificate OR a building reg's compliance certificate for the work..

Which you will be needing if you want to sell the property without someone knocking a few grand off the price for electrical work...

Plus you will need to get RCD protection, that your Wickes board doesn't have. 

Guinness

OK thanks for that, appreciated

 

[binky]

I get the feeling were having a bit of misinterpreting what others are posting going on here.....

Just been scanning back over the thread...

I don't think anyone has actually said that bottom line IR acceptable value doesn't refer to the global figure...

Or that you can do a global test reading at the DB...

(if you want to)...

But one hell of a lot of the time individual circuits need to be tested as well to get the bigger picture about the condition of an installation ...

And 643.3.2  quotes detail relating to both Global and Individual circuit testing..

As does GN3, Examples (i) Global and (ii) Final circuit IR testing.. (Pg 51 onward)..

e.g.

eight final circuits all at 6Meg individual = Global 0.75Meg

Is a big difference than seven circuits at 200meg and one at 0.77Meg = Global 0.75Meg

OR...

eight final circuits all at 8Meg individual = Global 1.0Meg

Is a big difference than seven circuits at 200meg and one at 1.1Meg = Global 1.0Meg

In Both of the above example the second illustration has an installation where over 87% of it is in top-notch good condition only 12% is dubious..

whereas the first illustrations 100% of the installation has deteriorated down into single figure IR values...

If you just did the global value you'd miss an incredible amount of perspective on the condition of the overall installation for continual use and/or your recommended next inspection interval..

Hence why the schedule of test results have boxes for individual circuits NOT just a global value... 

(which would have been easier and neater with just one box))

As a side note...

during the old annual assessment watch the monkey do his tricks performance...

I have never been asked to do a "Global IR"...

get asked for Ze's,  PFCs,  R1+R2's,  Zs's,  Ring Continuities,  RCD trip times  and IR's on Final Circuits...

But NEVER a global IR!

Bit like when my car comes back from MOT...

I do rather like to see individual Tyre tread depth readings..

Not just a global  "All tyres are ok" comment.

Guinness  

totally concur, imho global testing is a short cut and nothing more!