replacing mains fuse box and socket loading

[xyz123]

hi

we moved into a house few months ago and had an electrician come out today to fix a problem with bathroom extractor fan. all fixed now.

however he looked at the mains box and said that it appears that all sockets in house are in one ring circuit of 30A. thats not a good practice as i understand it.

now i have been looking to replace the mains box as the box is old type which is non RCD type. i dont know how old is it. though i have not had any problem with it to be honest since we moved in.

what the guy mentioned is the concealed wiring might have been damaged so before he changes the box he normally does testing to see if the insulation resistance is within limit as otherwise it will cause RCD to cause nuisance tripping. he said he can check insulation resistance but cant really check if due to all sockets on one circuit, wires may be overloaded and hence insulation may have been damaged. and particularly if the earth loop impedance is high with all sockets on one circuit then there is a problem with him having to identify it on the electric works certificate and then i may have to get it fixed soon. apparently he will need to write it into the report and then my home insurance may become invalid due to me not fixing a known problem!

Of course its not possible to split the socket circuits into two without significant re-wiring which is very difficult in a "decorated" house.

advise i would like to ask is:
1) with regards to mains box, is it a case of if it aint broke, dont try to mend it considering the uncertainty with earth loop impedance
2) if i decide to have it and then if earth loop impedance is problem, i understand that other than re-wiring there is no solution. am i correct?
3) how do i go about finding out if current equipments are overloading the 30A circuit or not? do i simply add ampere rating of all equipment or do i apply a diversity and if so what value?

to be honest to him his quote for total work was around £300 + mains box cost for testing and replacement work. this sounded reasonable compared to another quote i had. he didnt try to scare me with anything so i am trying to consider the points he raised!

thanks a lot for reading my post.

 

[Octopus]

The price sounds a little on the low side and do you have bonding in place? Is the person registered with a scheme and have they confirmed they will provide a EIC and LABC notification?

You need to be aware that the testing my identify faults in your house, so the final bill may well be higher.

Hope that helps.

 

[trev]

If your house is wired to an older version of the regulations and everything is within the specified parameters then this will not invalidate any insurance as the regs are not retrospective. You could get the report and see what it says then take it from there.
As there is only one ring final circuit then the potential for overloading it does exist, your options then are pretty limited. A) leave it as it is or B) rewire.

 

[BrianDB9]

£300 to change a consumer unit to latest Hi Intgrity type and test is a bargain maybe too much of a bargain.

A simple 5 minute check on the age of the wiring eg is it green earth sleeving (indicates over 35 years old) and and observations on provision of sockets eg 1 single socket per bedroom will add to a plan to manage the electrical installation - whilst changing the board may be a nice to have it can cause problems - is it in an inaccessible position now - if so you would be better relocating at the same time as changing the board ? Not everyone will agree and its your money but buy cheap pay twice comes to mind.

 

[baggy61]

Surely 2.5 t&e on 30A fuse can't be overloaded if the ring is continuous & if EFLI is high RCD protection will help meet disconnection times. A modern c.u might cause occasional inconvenience but if it improves safety it's a good trade off, innit ?