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Partial rewire advice please
Russ 11001215397
Joined 22/05/2020 - 4 Posts
Question
I have wiring in singles in plastic trunking. I want to have accessories flush to the wall and wiring chased in.  After much thought I plan to work on one room, take out singles to the sockets, change singles to T&E using wago connectors and boxes. So the one room would be done but not back as far as the CU. Because I am doing it as a DIY er and I’m not an electrician. The work would be in permitted zones. I’m thinking the wago boxes could be buried behind coving outside the bedroom I’m working on. I understand that any break in the circuit could potentially weaken the overall integrity, however each accessory is a break so will my work be any different than adding in extra sockets for example? Having the wiring chased in would look a lot better and would be safer than it is now. In some places now, the singles are exposed as they enter the sockets. 

I would be very grateful for any advice. Does my plan sound good?
7 Replies
Russ 11001215397
Joined 22/05/2020 - 4 Posts
AJJewsbury:
The walls are mostly hollow with cardboard squares and not many wooden batons
That sounds rather like paramount partition board (a.k.a. eggbox walls) - take care with those as both the plasterboard and cardboard are needed to maintain the strength of the partition (as you noticed there's no timber or steel studwork as there would be in a conventional partition wall, just a batten to support each joint) - cutting either horizontal or vertical chases can weaken the whole structure quite significantly.
   - Andy.

Yes this is exactly the wall I have. And I did not know this until now- I was expecting batons at 600mm. If I weaken the wall I plan to add in more structure so that is fine. I'll put some wood in.
Originally- as the wall is open and I can now see what's going on- the electric cables were run in plastic conduit alongside the baton between sheets of plasterboard. This meant that light fittings and accessories were positioned according to the joints in the wall. So not really in positions that made much sense. Then when the flat was rewired using surface trunking, the electricians kept the same positions for accessories and even removed some sockets that made their work easier to do. The work I am planning will really be an improvement. The problem I have is that we live in the flat and I have to work around lots of people! 

Russ 11001215397
Joined 22/05/2020 - 4 Posts
I am going to take notes as I go and I will work with all power off. I haven't actually started with the electrical work because I need enough time to work on one part and then make safe before I need the power on in the house. I agree with you that it would be extremely disappointing to cut into a live wire because I have no one else in the house to make good the partition walls if I am not here and in command. 

It is reassuring to know that I am not doing anything notifiable. 

Another two questions- I was expecting to be told that I should be taking the rewire back to the CU. I am glad that my proposal sounds good though. Should I use multiple wago boxes rather than group together too many cables? Is that what you mean about the heat?

Also would you be able to tell me how to do the ohms testing? Sometimes it appears that testing is done on live installations but I am relieved that you are saying test connection on dead circuit. 

I think that I will avoid errors by working slowly and methodically. So identifying each group of 3 wires and then swapping them exactly for T&E. 
AJJewsbury 77361768
Joined 13/08/2003 - 1433 Posts
The walls are mostly hollow with cardboard squares and not many wooden batons
That sounds rather like paramount partition board (a.k.a. eggbox walls) - take care with those as both the plasterboard and cardboard are needed to maintain the strength of the partition (as you noticed there's no timber or steel studwork as there would be in a conventional partition wall, just a batten to support each joint) - cutting either horizontal or vertical chases can weaken the whole structure quite significantly.
   - Andy.
mapj1 80733779
Joined 22/07/2004 - 1901 Posts
If you are in England, then the work is only notifiable if a complete new circuuit is created, or there is new wiring within 60cm of a bath or shower.
Additions, subtractions and modifications are not notifiable. However, the work you propose is so significant, it would probably be sensible to have it checked over in any case.
Checking with a multimeter on the ohms range that there is no connection between things that should not be connected,  and that there is a connection to things that should be, may not be a full set of tests, but it detects all the really bad errors, that can sneak past the plug and pray approach, like missing earth connections  or L-N reversal, both of which make things very dangerous may  appear to work OK. Rings that are not actually a ring are harder to detect - keeping notes helps.
Please be aware that cable ratings are reduced when they are grouped, as heat cannot escape, sometimes 'neat' layouts need opening up a bit.
Also realise that we have no idea of your level of competence, so please do not be offended if this is 'obvious' but please only test on ohms on wiring you know for sure to be dead, and plan your work so that you can get it all insulated before you stop and have to re-energise to cook dinner or whatever. In general, assume the wire you are about to cut may be live until you have proved it is not - the other way round can lead to extreme disappointment,
Russ 11001215397
Joined 22/05/2020 - 4 Posts
Thank you very much for taking the time to advise me. 

The situation is that I am in a flat in a tower block. Therefore no access to ceiling or underfloor. My CU is in a cupboard by the front door. From that CU there is  trunking coming out of the cupboard and then along the top of the ceiling coving and thereafter to every accessory. When the flat was built (mid 70s) the wiring was within the cavity walls in plastic conduit. It was then rewired and the original wiring just disconnected and left in place and the new set up in trunking. 

My aim is to rewire one room in the first instance. This will look much better aesthetically and also be safer as at the moment there are some singles going into sockets and the basic wiring is visible as it jumps from conduit and up to sockets. I also intend to move both wall light fittings along to centre them, and I also want to add two sockets to the circuit in that first bedroom. The room is next to the cupboard with the CU. 

I am not confident to take the new wiring directly to and from the CU. This probably sounds like I shouldn't attempt at all but I am confident in my plan as follows.

Strip out a section at a time and mark up each individual set of 3 wires LNE and take it back to the cupboard and swap the section for T&E using a wago box and connectors. Now having read both you advice here (again I am really grateful for your time), I will not make the boxes inaccessible. I can maybe put them inside the cupboard near the CU. 

I have cut into the plasterboard and will be using either plastic capping or oval conduit (I have bought both). Then the plasterboard will be made good. The walls are mostly hollow with cardboard squares and not many wooden batons (not as many as I expected to see) so it is messy but actually pretty easy to get the wiring hidden. Of course my absolute priority is safety of the installations. 

All wiring will be in permitted zones and follow a very logical and safe path. 

Further questions I have-

I am pretty sure that this work will need to be checked and signed off by a qualified electrician afterwards. Is that correct?

Is it straightforward for me to add an extra two sockets to the room circuit? By just extending the circuit as I go? This is not the same as taking a spur off a socket is it?

Can I check as I go using a multimeter? 

I intend to do each accessory one at a time so that I am not disturbing the original set up much. So that I identify each set of three wires and swap for t&e exactly as it is now. Does this sound like a good plan?

Would/ should I use separate wago boxes for each part of the circuit so that I am not overloading or risking heating a wago box?

At the moment I am planning and cutting the walls and have not started on the electrical work. 

 
AJJewsbury 77361768
Joined 13/08/2003 - 1433 Posts
It is a bit unusual to have singles in mini trunking in a house,
Agreed - where I have seen things like that (or indeed in conduit) it's been in flats with concrete floors & ceilings (and indeed walls, once with steel doorframes!). The originals had conduit cast into the concrete when the place was built, but all subsequent alterations were surface as chasing into the concrete wasn't practical - and indeed could have caused structural damage if attempted.

If a joint box is going to be inaccessible - e.g. covered with plaster coving - it should really be of the the maintenance free (MF) type - not all combinations of wago boxes or wago terminals will be - and even where they are there are some restrictions on both the individual terminal rating and "aggregate current" that are significantly lower than normal ratings. If you're working one room at a time and can plan ahead, it can make life easier to run some oval conduit in the chases in a few places rather than burying the T&E direct - thus allowing cables running from one room to the next to be re-arranged or replaced without disturbing the decor you've already made good.

   -  Andy.
davezawadi (David Stone) 28267643
Joined 26/06/2002 - 423 Posts
Where do your singles go? Presumably the mini trunking either goes into the ceiling or floor depending on room. Is yours a house or a flat, as a house with roof access, is the normal place to have some of the wiring, and under the floors as convenient. Whilst putting boxes behind coving most would prefer them in an accessible position, like the roof space or under the floors. Replacing the whole length of each circuit might be easier too, particularly as you are chasing the walls. A chasing machine (hired?) makes this job much easier and cleaner than a hammer and chisel.

It is a bit unusual to have singles in mini trunking in a house, as singles cost more than T&E, however not a problem. Wago or Ideal type push-in connectors seem OK and should not reduce the reliability of your installation if you decide to extend the singles. My own choice for houses is under the floors where possible and the upstairs lighting circuit in the roof but the option is yours, but heavily insulated roofs make the installation difficult so the lot buried in the walls and ceilings may be the answer. Keep cables in safe zones and all circuits require RCD (30mA) protection.

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