Adding Neutral to light switches

Discussion in 'Electricians' Talk' started by Stuart Daley, Dec 11, 2019.

  1. Stuart Daley

    Stuart Daley New Member

    I have separate lighting circuits for upstairs and downstairs, but I'm also trying to add smart switches, which is a problem as it's the standard 2c+e cabling.

    With the upstairs it would be easy to replace the cabling with 3c+e, as the walls all have trunking to the switches and I have easy access to the roses, runs, etc.

    However, the downstairs is more problematic. I've a flexible cable puller, so in theory I should be able to pull a new cable through if I can route it to the rose from the switch trunking.

    I'm assuming that I need to keep the neutral separate on each circuit. I.E. there's safety reasons for not sharing the neutral across the two circuits because of the RCDs.

    So, any advice? Should I instead look for the (much more expensive) smart dimmers that don't turn the circuit off completely, but have trickle power on "off" to maintain the smart wifi switching?

    On some of the switches, such as the living room, I've used a Fibaro Dimmer 2, which allows for two switched circuits by direct wiring one and having the other on wifi control (there are smart bulbs in the floor uplighters that the second switch controls). My main bugbear is the hallway/landing/porch light switch in the hall, that is also on a 2-way with another switch on the landing. That's the one that is giving the most concerns over the way to do it, as I need a 3-gang switch downstairs with a remote upstairs, but don't have the room for two Fibaros behind the switch without putting in another back box and blanking plate to hide them, or changing it to a double-back box to give the room.

    If anyone has experience or suggestions for this 3-gang replacement, please let me know.
  2. Bob Rathbone

    Bob Rathbone Screwfix Select

    If the switch drops have been put under capping or are though stud walls, then it may just be possible to draw a 3 core & e in using the original twin &e as a draw wire. I would suggest that great care will be needed when attaching the two cables as if they separate during the process, you will be stumped and will need to take up some flooring.
  3. Bazza

    Bazza Screwfix Select

    @Stuart Daley before you buy too many(any) smart switches. I suggest you do a trial run on just one switch to determine just how easy or difficult running new/additional cables will be.
    It’s very rare that you will get an easy route, down a wall to pull in a cable. Many cables are just plastered in to the wall and not run in capping/conduit.

    It will be hard to estimate the benefit of having super smart switches that you can control from your poolside in Majorca. Especially if you have spent many weekends and evenings sweating over cabling and had to chase out the walls and redecorate the house as a result.

    and PS. you are right about making sure you don’t share neutrals with other circuits.
    Your hallway/landing/porch light switch in the hall, Will probably need an upstairs and a downstairs neutral. Many smart switches don’t have provision for this, let alone two-way switching, so you’ll need to have TWO separate switches at that point.

    sorry to be negative, I’m a realist, not a Luddite.
    KIAB likes this.
  4. Tony Goddard

    Tony Goddard Screwfix Select

    Totally second Bazza's comments on trialling the idea first.

    To add to bobs suggestion, when I'm attaching two cables together for pulling I generally cut off the L & N ends flush with the end leaving the earth of both new and old cable sticking out, I then tie those with a linesmans splice and often solder them (I have a little gas soldering iron for that task). Finally putting a thin layer of tape over the join.

    It is good to have two people, a pusher and a puller to avoid the risk of shredding the insulation/sheath as you go.
    KIAB likes this.

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