Can I leave 2 plug sockets permanently disconnected? Ask questions and find answers to many subjects relating to electrics and electrical work

[jeatsy]

A few days ago our CU started tripping a lot. I called out an electrician and he narrowed down the problem to a cable between 2 adjacent plug sockets (one in the landing, the other in a bedroom) and has disabled those sockets. This is probably either because we had some rodents under the floorboards a year ago, who might have chewed the cable, or because we have a small but persistent leak from the bathroom, which is near one of the sockets.

To fix it he says we need new cable between the 2 sockets, but that’ll be quite intrusive as they’re a long way apart and it’ll involve either lifting carpets and drilling into the chipboard beneath them, or running trunking around the room and through a solid wall (not a stud wall).

I asked if we could just leave those 2 sockets permanently disconnected, but he said this’ll mean we won’t have a true ring main and hence the capacity of the house will be significantly reduced. That’s a particular issue in our case because the downstairs and upstairs sockets are on the same circuit.

I was wondering how much of an issue this really is, given that (a) only 2 people live here, (b) we rarely use high-power appliances and certainly not lots at once, (c) we can run the fridge, freezer, kettle, microwave and toaster off the (separate) cooker circuit. Opinions would be really useful – thanks.

[Mr White]

The "problem" is that when the ring is "broken" you could have 25A going one way and 7A the other way. (Depending on what you plug in and where it is plugged in on the now broken ring.) The cable is only rated around 17A, which means it could cause a fire.

So no, it must be a ring as that is what was designed. You could have the MCB changed to a 16A one and have two radials. (But I wouldn't.)

[jeatsy]

You could have the MCB changed to a 16A one and have two radials.

My electrician has confirmed this too, so I've swapped the existing 30A cartridge fuse (it's not an MCB) for a 15A one.

Is there a way of now finding out which sockets are on which radial, so I can split the load evenly when I need to plug lots in at once? ("Lots" is now relative, of course !!)

[Mr White]

Is there a way of now finding out which sockets are on which radial

Yes, but your electrician would have to do it.

[ericmark]

Consumer units can have cartridge fuses, but very unusual, can't remember when the type tested distribution unit came out, I think in the 90's before the type testing they were simply fuse boxes.

The problem is although BS7671 is not retrospective, once you do any alterations then it needs to comply with current regulations, and the electrician has to sign to say "I being the person responsible for the Design, Construction, Inspection & Testing of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the Design, Construction, Inspection & Testing, hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2018, amended to .............(date) except for the departures, if any, detailed as follows."

See page 4 here https://electrical.theiet.org/media/220 ... ficate.pdf

The electrician has his hands tied, he must issue the certificate you should already have one for the temp repairs, although I would suspect he is considering it as work in progress.

So the ring final must to comply with regulations use cable which can carry 20 amp, in the main that means 2.5 mm² but before we went metric it was 7/0.029 cable which was more like 3 mm² but even 2.5 mm² has a range of current carrying capacity, one down to insulation, mineral, thermal setting plastic, or thermal plastic plastic, and also where it runs, if in any insulation etc. This chart http://www.batt.co.uk/upload/files/tabl ... 390425.pdf shows same cable can be rated 17 to 27 amp.

We hope everything installed correctly to start with, and nothing has changed, the latter is unlikely, I know as managed to blow a fuse with a line - earth error as a lad my parents house did have a good earth, but some 40 years latter that earth was missing, how and why is guess work, seems likely it used the water main, and the main was replaced with plastic.

So we are told every 10 years, 5 years with English rented, or change of occupant, we should do an EICR (electrical installation condition report) to high light problems, OK hands up not done it on my own house, I suspect few do.

However my house has all RCBO's which is a MCB and RCD combined. The RCD was first used for TT installations (uses an earth rod) but since 2001 the regulations have required it to cover more and more, and have reduced it from 100 mA typical for TT to 30 mA.

This has caused no end of problems, specially with old homes, and we are still moving on with better and better protection, so the S type 100 mA RCD rarely tripped, but the 30 mA type AC has caused so much food to be dumped due to freezer failure one has to really ask has it been worth it.

Major problem was in early years we would group circuits together, so typical home had either just half RCD protected or only 2 RCD for whole of home.

We have moved on, we will use double pole switches for outside lights, and we have learnt the problem of all eggs in one basket, and although some still do only use 2 RCD's most use at least some RCBO's plus with the new breed of electronic equipment where we have semi-conductors on the 230 volt part, the use of SPD (surge protection device) has increased.

No longer do we run cables through the cavity wall, however cavity wall insulation installers seem to fill the wall even if the cables do go through the cavity.

EV chargers and solar panels have added to the problem, and even some central heating boilers now stipulate type A RCD's.

So if you are still using tungsten bulbs, and living in the dark ages, then maybe the distribution unit you have is good enough, but that is unlikely, so your looking at at least £1000 bill to correct the fault and upgrade the consumer unit.

From moving in to this house to getting SPD and all RCBO's took me around 6 months, landlords with rental property were given 28 days to upgrade, but we have to be sensible, better wait 6 months or a year and get it done properly than rushing into it and loosing a freezer full of food.

So now is the time to plan when, you have had the wake up call, now time to plan what you will do in the future.