Installing FCUs for bedside lamps

[ledderss2020]

I'm currently refitting a bedroom which has 3 double sockets and a 13 amp FCU (for a wall mounted TV). On inspection the wiring is as shown in the attached pic 'Existing'. Two sockets and the 13amp FCU are on the ring main but one is spurred from a traditional round junction box under the floor boards fitted before I moved into the house. Since moving in, the electrics have been tested and certified by a qualified electrician following the replacement of a consumer unit a few years ago.

What I want to do is shown on the attached pic 'Proposed'. Rather than have plug-in bedside lamps I want replace the double bedside sockets with a single socket with USB. From this single socket I want to run 2.5mm t+e spur to a 3amp FCU, and from the FCU chase 1.5mm t+e up the wall to bedside lamps fitted to wall. I also want to fit a new double socket elsewhere.

I believe this is all fine but I am unsure whether the presence of the junction boxes creates an issue. My informed but not professional opinion tells me the junction box does not create an issue because the spurred double sockets are from the junction box and not the proposed single socket. Is this the case?

Given the floor will be covered in a new wood floor, the junction boxes will no longer be accessible, so I propose to the replace the junction box with a Wago 221 connectors housed in the corresponding Wagobox, which I believe, although not absolutely sure, conforms to the regulations.

Any advice or suggestions two these two questions would be awesome. Thanks for reading!

 

[pc1966]

It looks unnecessary complicated.

Do you need the FCUs at all, or could they be just 13A sockets to make any future changes easier?

Also if doing wiring and stuff under the floor you should aim to have less/no junction boxes if at all possible, but if they are used they should be maintenance-free ones.

Can you route the ring to both double sockets shown, and in place of the socket & FCU beside the bed just put in new double sockets?

The existing JB would still need something there to extend the ring, but that could be a through-junction that is maintenance free style if it is impractical to replace that section of cable to avoid hidden joints..

 

[pc1966]

Personally if you do want FCU for wired-in light, then have the ring gi via them and the single sockets so each terminal only has two wires, not three, to be reliably clamped.

And instead of another junction box, just run the double length of cable to make the new right-side socket part of the ring as well, if necessary making it the ling between the right bed socket & FCU.

 

[pc1966]

This idea:

 

[ledderss2020]

This idea:
View attachment 84339

This looks much simpler and possible, albeit with a bit more routing out of the walls than I planned, but I suppose a job worth doing is worth doing well. Cheers for taking time to sketch this out.

 

[pc1966]

This looks much simpler and possible, albeit with a bit more routing out of the walls than I planned, but I suppose a job worth doing is worth doing well. Cheers for taking time to sketch this out.

How much extra routing? I imagines most of the wiring is already in place, but for the extra double socket. And for that new socket you would need to do some sort of cut or use the wall cavity / floor space.

I assumed you showed single socket and FCU as planning on using something like this to replace a double back-box:

1 + 1 Gang 35mm Dual Dry Lining Box

Internal dry lining/plasterboard plastic back box

www.cef.co.uk

 

[ledderss2020]

How much extra routing? I imagines most of the wiring is already in place, but for the extra double socket. And for that new socket you would need to do some sort of cut or use the wall cavity / floor space.

I assumed you showed single socket and FCU as planning on using something like this to replace a double back-box:

1 + 1 Gang 35mm Dual Dry Lining Box

Internal dry lining/plasterboard plastic back box

www.cef.co.uk

Won't need much additional chasing I suppose, other than the right side bedside so I can connect the new cable for the additional socket. I'm in an old house with solid plaster walls so the existing cable is well and truly plaster in and can't be fed through the cavity. In terms of the back box - yes - will be using a metal dual back box and connecting the FCU and single socket inside the box

Appleby 1 + 1-Gang Galvanised Steel Knockout Box 35mm - Screwfix

Order online at Screwfix.com. Steel knockout box. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

I assume there is no minimum length of t+e required between sockets, other than of course ensuring there is enough cable to make maintenance straightforward without causing the cable inside the back box to get damaged??

 

[pc1966]

Won't need much additional chasing I suppose, other than the right side bedside so I can connect the new cable for the additional socket. I'm in an old house with solid plaster walls so the existing cable is well and truly plaster in and can't be fed through the cavity. In terms of the back box - yes - will be using a metal dual back box and connecting the FCU and single socket inside the box

You might want to consider putting in some PVC conduit for the run of T&E cable so it can (theoretically!) be pulled through later if ever needed. If nothing else it protects the cable from plasterer's trowels, etc when it is put in.

If doing so then wipe the cable with a little lubricant to make it easier to pull through:

Ideal Yellow 77 Wire & Cable Pulling Lubricant 950ml - Screwfix

Order online at Screwfix.com. General purpose cable lubricant reduces friction in electrical and communication cable pulling operations. Speeds-up installation and reduces risk of cable damage. Wax-based formula provides lubrication and clings to cable throughout long pulls. Dries to a thin...

www.screwfix.com

Some folks prefer the "oval" conduit as (I think) you can get two T&E runs in parallel along it but it is shallower to bury in plaster or a chased channel in brickwork. However, the 20mm round stuff can be conveniently fixed to the back-boxes.

Steel conduit is hard to work and to thread the ends, etc, so not really a DIY option.

I assume there is no minimum length of t+e required between sockets, other than of course ensuring there is enough cable to make maintenance straightforward without causing the cable inside the back box to get damaged??

No, and if it is in a double box like that you can have it completely stripped (i.e. overall sheath removed). Just remember to put the green/yellow sleeving on the CPC (earth) wires.

While the obvious attraction of having as many accessories as possible on the ring is the current-sharing between each of the "legs" back to the CU, a less obvious reason for doing so it testing. If you measure the end-end resistance of each ring (L-L, N-N, E-E) you get a very comprehensive check that all are connected.

True, it is not a guarantee, as some might have been twisted together (not seen as good practice today, but not uncommon and often promoted 30+ years ago) and come out of the fixing screw on the accessory, but it gives you high confidence all is connected.

A poor or missing live connection (L or N, both carry current normally) is usually obvious by something not working, or worst case a buzzing sound and smell of overheating plastic, but a missing E is not obvious. Until a fault when it was supposed to save a life by ensuring rapid disconnection of the supply.

I don't know if you have any test equipment at all, but at the very least if you plan on changing sockets, etc, then get one of the better socket testers that reports the earth loop impedance, not just saying "OK" to wet string. For example:

TIS Socket Tester With Loop & RCD Check

A pocket sized checker for indicating loop impedance, socket polarity and RCD 30mA are all ok. Indication is by LED's and buzzer. An ideal unit for initial "checking out" of a 13A socket and will advise if the circuit is ok, needs attention, or needs urgent attention. An ideal product for...

www.toolstation.com

Kewtech Loopcheck 107 Plug In Socket Tester 128 x 80 x 68mm | Toolstation

Easy to use, advanced socket tester. Checks socket connections, RCDs, mains polarity and earth fault loop impedance. Indicates safety via high definition LEDs. Checks quality of or earth loop return path.

www.toolstation.com

 

[pc1966]

Basically a cable's outer sheath is for mechanical protection, so it should extend in to any enclosure and, as appropriate, be clamped by any cable restraint.

The conductor sheath ("primary insulation") is there for electrical insulation, so it should not be exposed outside of any accessory or junction box, etc. Inside a box just make sure it is not crushed by the accessory itself, or by one of the fixing screws when fully inserted.

Of course, also have grommets on box entry holes or conduit bushes so the cable is not at risk of cutting/damage.

 

[ledderss2020]

You might want to consider putting in some PVC conduit for the run of T&E cable so it can (theoretically!) be pulled through later if ever needed. If nothing else it protects the cable from plasterer's trowels, etc when it is put in.

If doing so then wipe the cable with a little lubricant to make it easier to pull through:

Ideal Yellow 77 Wire & Cable Pulling Lubricant 950ml - Screwfix

Order online at Screwfix.com. General purpose cable lubricant reduces friction in electrical and communication cable pulling operations. Speeds-up installation and reduces risk of cable damage. Wax-based formula provides lubrication and clings to cable throughout long pulls. Dries to a thin...

www.screwfix.com

Some folks prefer the "oval" conduit as (I think) you can get two T&E runs in parallel along it but it is shallower to bury in plaster or a chased channel in brickwork. However, the 20mm round stuff can be conveniently fixed to the back-boxes.

Steel conduit is hard to work and to thread the ends, etc, so not really a DIY option.


No, and if it is in a double box like that you can have it completely stripped (i.e. overall sheath removed). Just remember to put the green/yellow sleeving on the CPC (earth) wires.

While the obvious attraction of having as many accessories as possible on the ring is the current-sharing between each of the "legs" back to the CU, a less obvious reason for doing so it testing. If you measure the end-end resistance of each ring (L-L, N-N, E-E) you get a very comprehensive check that all are connected.

True, it is not a guarantee, as some might have been twisted together (not seen as good practice today, but not uncommon and often promoted 30+ years ago) and come out of the fixing screw on the accessory, but it gives you high confidence all is connected.

A poor or missing live connection (L or N, both carry current normally) is usually obvious by something not working, or worst case a buzzing sound and smell of overheating plastic, but a missing E is not obvious. Until a fault when it was supposed to save a life by ensuring rapid disconnection of the supply.

I don't know if you have any test equipment at all, but at the very least if you plan on changing sockets, etc, then get one of the better socket testers that reports the earth loop impedance, not just saying "OK" to wet string. For example:

TIS Socket Tester With Loop & RCD Check

A pocket sized checker for indicating loop impedance, socket polarity and RCD 30mA are all ok. Indication is by LED's and buzzer. An ideal unit for initial "checking out" of a 13A socket and will advise if the circuit is ok, needs attention, or needs urgent attention. An ideal product for...

www.toolstation.com

Kewtech Loopcheck 107 Plug In Socket Tester 128 x 80 x 68mm | Toolstation

Easy to use, advanced socket tester. Checks socket connections, RCDs, mains polarity and earth fault loop impedance. Indicates safety via high definition LEDs. Checks quality of or earth loop return path.

www.toolstation.com

Great advice, you've left no question unanswered, much appreciated. Nice to engage intelligently with a forum user. I've been abused elsewhere when asking questions - the stock response being if I'm asking questions I don't know what I'm doing, which as we know is just a ridiculous position to take. I'd never do anything the law wouldn't allow or that I felt was unsafe. So, thanks again!

 

[DPG]

Great advice, you've left no question unanswered, much appreciated. Nice to engage intelligently with a forum user. I've been abused elsewhere when asking questions - the stock response being if I'm asking questions I don't know what I'm doing, which as we know is just a ridiculous position to take. I'd never do anything the law wouldn't allow or that I felt was unsafe. So, thanks again!

We can do abuse as well. All services offered ?³