Electronics > Beginners
How is Neutral Wire Neutral in Mains Electricity?
paulca:
So this is mine. It needs modernised ... the dark green earthing cable is a give away to it's age. Consumer unit looks like it was replaced maybe 10 years ago, but at some point the place needs at least a partial rewire.
Oddly, the earth comes out of the tail block and into the side the main cable. Wah?
Gyro:
--- Quote from: Monkeh on January 16, 2020, 08:28:33 pm ---
--- Quote from: paulca on January 16, 2020, 08:27:17 pm ---
--- Quote from: Monkeh on January 16, 2020, 08:17:42 pm ---A 3-core cable is not the type of cable used to service a single dwelling..
--- End quote ---
You might have a point, I did think it was straight that these were poking up at the kerbs, not at the house where the foundations where already in. So maybe it's a 3 phase distribution cable and they connect single phases to houses later.
--- End quote ---
Likely - they'll tap off the armour (the CNE) and one phase to each properly, and drive an earth rod at some or possibly all of these joints. The cable to the building will almost certainly have been a straight concentric.
--- End quote ---
Yes they do. We lose a phase (usually ours) at least once a year where I live (badly installed paper insulated cable, I thing they bent it too much while burying). Three phase cores plus outer sheath neutral. Houses take taps between one phase and the Neutral sheath. I've watched them splicing in holes several times.
At least in the UK, most homes are TN-C-S. No earth spike, just Protective Earth bonded to Neutral at the entry and equipotential bonding to and between all pipework.
Monkeh:
--- Quote from: paulca on January 16, 2020, 08:40:42 pm ---So this is mine. It needs modernised ... the dark green earthing cable is a give away to it's age. Consumer unit looks like it was replaced maybe 10 years ago, but at some point the place needs at least a partial rewire.
Oddly, the earth comes out of the tail block and into the side the main cable. Wah?
--- End quote ---
That's a lead-sheathed cable (notice the wrapping, and the pitch marks on the board behind it) where the sheath has been connected to the neutral conductor. This likely means you've had major works on the distribution outside and been converted to a PME system. The lead will be acting as a nice earth rod for you - bonus.
The little white functional earth cable is odd. I don't think that RCD would use it, maybe there was a VOELCB there in the past.
All looks overdue an update, random loose breakers laying around is never a happy sign. Seals look to be missing (probably chopped when that RCD was fitted to replace whatever was there before).
If the cutout ever gets warm or starts leaking pitch (because it's warm..) call your DNO immediately. Those old cables are not the most reliable at terminations. Do not be tempted to wiggle anything or tighten the clamp.
paulca:
I checked it recently with a thermal camera and the only thing that looked even slightly warm was the mechanical meter itself. However I didn't put much load on the system when I checked it.
The RCD looks like it was installed when the electric shower was fitted. Not in the photo, but the tails are split, one set to the consumer unit and another to a single beaker+RCD for the 40A electric shower circuit. Anyway I seen it on a few spark videos on YouTube, it seems it's common polite practice now, that if you need to break the seals (or get the correct authorised company to do it!) you install an RCD or isolator so the next spark along can isolate the consumer unit easily to work on it.
Now (or when I can afford/justify it) would be a good time to update/rewire as the shower circuit can come out as I converted the place to natural gas combi this year. So I don't need that 40A circuit anymore and would prefer they split the upstairs downstairs plug rings instead maybe.
I think the little white earth wire is the earth sense for the RCD. It was it that popped when I cut the cable.
Not related to electric, but my main issue with this meter cupboard under the stairs is the holes and gaps in the boards go straight into the dead space under the house and as it was once a coal fired house it has half a dozen air brick vents. Literally, it's like 7*C in there right now and if I open a window in the house when it's windy the door gets blown open by the air rushing in through the floor! Costing a fortune to heat and on my list to seal it with thermal underlay panels.
Monkeh:
All seems very wrong. The RCD should not require an earth at all, and it's not appropriate for protecting a shower anyway..
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version