Electrical

Collaborative Electrical Rewire – Part 3 : Installation Day 2 – Running more cables…

Thursday 15th December 2016

Lots more figuring best routing, running of cables. The house has become quite an exciting obstacle course with missing floorboards & loose (not yet live!) cables everywhere.

Some care needed to be taken when lifting boards – it is very easy to cause irreversible damage.

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The area just inside the door in the front bedroom had a lot of cables running through, which required drilling a larger hole through the joists. The Armeg Wood Beaver drill set was recommended by Sam & these were an essential purchase that made the job so much easier. They are an incredible design – they actively ‘pull’ through the wood & slice a clean hole quickly with ease.

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We bundled some of the cables together to make it easier to pull them through & to keep things tidy.

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An IP20 wall light was mounted on dochans in the bathroom – currently there is no bathroom ceiling which makes it awkward to install a ceiling light, plus I like the indirect ‘wash’ of light across the wall that this design creates.

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By the evening we hadn’t quite got to the stage of connecting the consumer unit up, which meant another night running lamps off trailing sockets… very atmospheric!

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Most of the cables have now been run to the correct locations, although most of the light fittings, switches or sockets have yet to be wired in.

As almost a complete novice to electrics, the extent of my knowledge only previously extended to how to wire a plug, rewire an blown fuse in an old consumer unit & switch back on a tripped circuit on a modern consumer unit.

I was surprised to learn that many more cables run to light fittings than to sockets! The lights were effectively on a radial circuit – ‘daisy-chained’ together. A single cable ran from the consumer unit to the first light fitting, then another cable ran to the next light fitting and so on. In addition, each light fitting had a single wire that ran to the corresponding light-switch.

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This became a bit more complicated for two way switching in the hallway, with the landing light being controlled by three switches which required 3 core & earth cable & an intermediate switch at the top of the stairs. I wanted to be able to control both the hallway and the landing light from both downstairs and upstairs, which required that we use a modular ‘grid’ type switch to create what we needed since 2-gang intermediate switches are not as readily available (although I might replace it with something like this in future)

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Cutting a board outside this bedroom door for access to figure out how to route the cables through the stepped area was unfortunate, particularly since a mistake was made with the poor angle (inaccurate use of a multi-tool) and location of the cut not being above the joist.

Looking back this frustrates me since this is a long, original board that we irreversibly cut (badly) and these boards are well-fitting, good quality, slow grown aged pine… it is almost impossible to get matching reclaimed boards nowadays. In fact, knowing what I do now after running a new water supply pipe, I realise we could maybe have run the cables under the floor in the bedroom through to the bathroom/kitchen to avoid this awkward stepped area. A little knowledge and over-enthusiasm can indeed be a dangerous thing. An important learning experience nonetheless.

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In the bathroom, the joists run in the other direction to the main section of the house, which meant we had to drill through a couple of joists to run the earth/bonding cable to the back of the house & the lighting/socket cables to the kitchen. I realise that these were also drilled in the centre of the joist span when ideally they would have adhered to these guidelines :

  1. Holes should only be drilled on the centre line of the joist. This is where the compressive and tensile load distribution is neutralised
  2. Holes should have a diameter of no greater than 0.25 times the depth of the joist
  3. Holes should be no closer together than 3 times the largest diameter permitted
  4. Holes should be no closer to the support than 0.25 times the span and no further away than 0.40 times the span

Hopefully since the span of these joists is much less than the rest of the house, there won’t be too many problems with springy floors in the future (as there is in the middle bedroom)

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Ian using a voltage detector pen to confirm that we can remove the cable rats-nest under the hallway safely :

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It became quite fun jumping across the gaps in the floorboards… it was a bit like a real-life platform game!

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More to come in Part 4

 

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