Full rewire required?

[DefyG]

So would the EICR establish the wiring configuration or simply establish the non compliances of the existing system?

It would establish what was compliant or non-compliant about any given circuit. Non-compliances are coded. No code = compliant circuit.

not particularly difficult but time consuming (and perhaps unnecessary).

Yes which not necessary part of EICR as customers do not want to pay the extra time.

 

[TinnyB]

Schematic? No not normally. It will for example, provide the number of sockets on each circuit and what areas covered for compliance with BS7671 so shouldn't be too difficult to draw your own schematic from the EICR.
'Circuit Arrangements/Configuration' as far as BS7671 goes will include circuit type, cable type/size, protective device type/rating, floor area (in the case of radial circuits for 13a outlets) etc.

How simple would it really be to draw the schematic? In this case there are 8 sockets (sockets BB) and CC)) - connected in the ring main. There are 18 sockets connected as spurs with 11 of these being 'intermediate' spur sockets (sockets AA0 and DD)) and 7 being 'end' spur sockets. I find it difficult to see how the actual configuration could be determined without testing specifically for this purpose

 

[TinnyB]

Every socket which is part of a RFC can feed a spur*. It used to be quite common to find a RFC feeding upstairs sockets only, with spurs being taken from them to each feed a socket in the room below.
What cannot be done is to have an unfused spur in 2.5mm2 from a RFC, which then loops on to another socket.

* Wouldn't be considered good practice now, but still within regs.

Are you sure that you cannot have an unfused spur which loops on to another socket? What if the consumer unit MCB is selected to protect the radial type connections. As far as I can determine this would be compliant - hence the tentative proposal floated in my original post. In post #8 pc1966 at least seems to concur.

 

[brianmoooore]

A radial circuit can have sockets looped from one to the next, but a conventional RFC, fused at 32A and made up entirely with 2.5mm2 cable can only have one socket (single or double) on the end of an unfused spur.

 

[TinnyB]

A radial circuit can have sockets looped from one to the next, but a conventional RFC, fused at 32A and made up entirely with 2.5mm2 cable can only have one socket (single or double) on the end of an unfused spur.

Quite so. No disagreement with this. Hence the final para of my original post. And for example post #18. I apologise if somehow I have suggested that what you say in post #19 was not the case. I did not mean to do so. I agree with what you say in post #19

 

[DefyG]

How simple would it really be to draw the schematic?

Simple but time consuming! Time costs!

I find it difficult to see how the actual configuration could be determined without testing specifically for this purpose

Depends what you mean by ‘actual’?
Without ripping a place apart the actual cable routes cannot be determined during an EICR for establishing the circuit arrangement.

 

[brianmoooore]

The two requirements are that no cable and no MCB is likely to be overloaded. Non standard circuits can be used, as long as these conditions are likely to be met, as determined by a 'competent person'.
There are also things like voltage drop and loop impedance to be considered in the design.

 

[TinnyB]

In this case there are connections to

Simple but time consuming! Time costs!

Depends what you mean by ‘actual’?
Without ripping a place apart the actual cable routes cannot be determined during an EICR for establishing the circuit arrangement.

I was thinking of what each cable connects to at each end - as opposed to the physical layout of the cables. On reflection perhaps it doesn't matter - if the idea floated in my original posting is adopted. Voltage drop could be an issue but presumably that could be assessed based on system impedances which presumably would not be difficult to measure.

 

[brianmoooore]

You have to determine where the 'far end' of radial circuits are, whether they are lighting or power circuits, in order to measure the loop impedance.
Repeat EICRs are much easier than the first one you undertake at a particular installation, as long as your records are good enough to be able to establish if any changes have been made.

 

[TinnyB]

You have to determine where the 'far end' of radial circuits are, whether they are lighting or power circuits, in order to measure the loop impedance.
Repeat EICRs are much easier than the first one you undertake at a particular installation, as long as your records are good enough to be able to establish if any changes have been made.

Presumably you could measure the loop impedance at each socket which would tell you where the 'effective far end' of the radial circuit is?

 

[TinnyB]

Thanks for all the info and ideas. I have a follow up question.

I have now determined that connections GG) and HH) are both what I have termed ‘end of radial’ type connections making a total of 10 (connections EE), FF), GG) and HH) in my original post). There are 4 sockets connected as ‘origin of radial’ connections (BB) in original post). Hence there must be a total of 6 branches in the radials. Socket AA) is one branch and I have sighted one branch which is at an underfloor junction box and can easily be eliminated. That leaves four branches at one or more (four seems most likely) junction boxes.

Presumably non intrusive testing could provide at least an indication of the integrity of these junction boxes. My question is - how reliable would such testing be?

Alternatively I could identify and eliminate the branched cables, or upgrade the junction boxes (to Wago boxes perhaps). This could be a major task and of course it is possible that there are other junction boxes in the system which would not be identified by my testing – although this seems fairly unlikely.

Thanks again everyone for all the help so far.

 

[Deleted account]

Thanks for all the info and ideas. I have a follow up question.

I have now determined that connections GG) and HH) are both what I have termed ‘end of radial’ type connections making a total of 10 (connections EE), FF), GG) and HH) in my original post). There are 4 sockets connected as ‘origin of radial’ connections (BB) in original post). Hence there must be a total of 6 branches in the radials. Socket AA) is one branch and I have sighted one branch which is at an underfloor junction box and can easily be eliminated. That leaves four branches at one or more (four seems most likely) junction boxes.

Presumably non intrusive testing could provide at least an indication of the integrity of these junction boxes. My question is - how reliable would such testing be?

Alternatively I could identify and eliminate the branched cables, or upgrade the junction boxes (to Wago boxes perhaps). This could be a major task and of course it is possible that there are other junction boxes in the system which would not be identified by my testing – although this seems fairly unlikely.

Thanks again everyone for all the help so far.

I thought I understood, but I’m totally confused now. Sounds like you;understand your system, so with the help of a sparkies yo7 should crack it good luck.