Re: British (european?) kitchen counter electric outlets

On 18/06/2024 21:18, Don Y wrote:

On 6/18/2024 2:28 AM, Martin Brown wrote:

So, wire/cable just "hangs" (gravity) in that space?  Resting on <something>
as it enters the void and then supported by the connection at the distant end?

>
Remember that the void has steel wall ties about every 18" in each direction so the cables are resting on them but not tied down. They are fairly rigid so don't move once they are installed.

 But, gravity only exploits those for lateral support.  What about a wire
traveling down to an outlet or switch "from above"?  I don't imagine those are
manually secured to those ties?

No but the thickness of the cable and three solid core strands of copper make it almost rigid enough to be self supporting for 3' upwards and 3' down from above. Add in a bit of friction and it really doesn't move.

Convention is that most horizontal wiring is out of sight under the floor above or on the surface of timbers in the loft. In theory I think the code requires them to be anchored every couple of feet. In practice I have seen plenty of loose wires straggling across spaces (and even more horrific plumbing mistakes). In older homes where electricity was a later addition the cables are often buried in the plasterwork. Modern build they tend to be inside stud walls or the cavity. I've never looked to see how they do it but I'm pretty sure the brickies build the walls and the sparks only move in when the house is watertight with a roof on.

 In a framed wall, it would be common for a wire to travel laterally through
holes bored in the intervening studs.  E.g., the cable feeding an outlet (about
a foot off the floor) would likely come from (or travel off to) another outlet
AT (slightly above) that ~12 inch height.  This saves wire as the wire doesn't
have to climb to above the ceiling or dive to below the floor to make it's next
connection.
 There are rules governing WHERE the wire can penetrate the framing as it is
likely that occupants (with no awareness of where wires actually are run) can
opt to drive nails/fasteners into the wall at any point and potentially
encounter a cable (imagine a partial short creating a fire hazard inside the
wall)

Shorts caused by drilling or nailing into a mains cable can and do happen here too. At worst it should blow a fuse and at best take down a circuit breaker for unbalanced live neutral. Likewise for water pipes buried in plasterwork (which are much messier if you hit them with a nail).

If you opted to *add* some device (outlet, etc.), how would you tie into the
existing wiring?  Or, would you have to start back at the load center?

>
You could do either depending on which was easier. Breaking into a ring main isn't that hard and that is the normal configuration in the UK.

 Nut how, physically, do you do this, given that the existing wire is in this
"cavity" AND any new wire would also have to be "threaded" through it?  Here,
worst case, you cut a hole in the drywall, fish the wire through and then
patch/paint the hole.

You start from an existing fixture and track the cable back. Easy now that there are decent mains wiring detectors not so easy back in the 70's. The hard part is knocking out the brickwork to make a recess.
--
Martin Brown