Earth funnies and phantom voltages on lighting circuit

[securespark]

Red and black, changed to brown and blue in 2001

April 2004, but still 21+ years ago.

Having said that, PVC is much, much longer lasting than rubber, assuming it is not installed in contact with hot pipes etc...

 

[Ragnar_AT]

Induction requires large currents to give a noticeable effect, while capacitive effects only require voltage to be present, at least that’s what I‘ve been taught regarding this glowing/flashing LED business.

Earthing the circuit only fixes the other issue of potential tingles.

 

[JohnW2]

All cables, irrespective of type, especially old perished cables, can induce voltage near adjacent conductors without a functional earth.

True, except that I don't understand the "especially old perished cables" bit - since I can't see how that would make 'induced voltages' any more likely (or greater)?

 

[Harry Bloomfield]

True, except that I don't understand the "especially old perished cables" bit - since I can't see how that would make 'induced voltages' any more likely (or greater)?

JS obviously intended to suggest 'leakage', from one cable to another.

 

[JohnW2]

JS obviously intended to suggest 'leakage', from one cable to another.

Quite, and that's nothing to do with either inductive or capacitive 'coupling'. Rather, it's due to a (potentially dangerous) 'fault', whereas the 'coupling' can happen in the context of a faultless installation.

 

[thesled]

Induction requires large currents to give a noticeable effect, while capacitive effects only require voltage to be present, at least that’s what I‘ve been taught regarding this glowing/flashing LED business.

Earthing the circuit only fixes the other issue of potential tingles.

Right. Makes sense. However I wonder if what's happening is by actually earthing the earth wire in the lighting circuit you are effectively introducing an earthed plate in the 'capacitor'. The current then just runs to earth instead of powering the lamp. this could account for the 1ma drain current. I expect this happened all the time in old non-earthed lighting circuits but there was never enough power to make an old fashioned bulb do anything so no-one really noticed it.

 

[thesled]

13th edition was 1955, and I have no knowledge what was required before then, but the house did not comply with 13th edition as the wall lights had no earth, it was permitted until 1966 (14th edition) to have lights without an earth, but there were some conditions, like being filament lamps, and mounted at such a height that they cannot readily be touched, so the wall lights would not have complied.

I've been told this 'no earth on the lighting circuit' malarkey was permitted because of trying to save on copper in post-war austerity times.

 

[ericmark]

I've been told this 'no earth on the lighting circuit' malarkey was permitted because of trying to save on copper in post-war austerity times.

This was one of the reason for the ring final. But not sure about lighting and earths. But if you read the 13th edition 403 I think, thanks to @flameport the exemption from requiring an earth was "(ix) Lighting fittings using filament lamps installed in a room having a non-conducting floor, mounted at such a height that they cannot readily be touched and are out of reach of earthed metal." this is not just saying lighting does not require earthing. Fluorescent fittings did require an earth, yet I remember my dad buying a fluorescent fitting with a BA22d connector, so it simply plugged in. This in 1966 change to "D.6 At every lighting point an earthing terminal shall be provided and connected to the earth-continuity conductor of the final sub-circuit." and I knew lighting needed to be earthed from that point, but in 2008 looking through the regulations I was having a problem finding it. I did find it "A circuit protective conductor shall be run to and terminated at each point in wiring and at each accessory except a lampholder having no exposed-conductive-parts and suspended from such a point." Note the terminated, this has been a problem with some wall thermostats and the like, where there is no terminal to park the earth into. Most good quality products, even if class II have somewhere to park the earth wire, so it can be firmly connected to any continuation.

 

[Harry Bloomfield]

I've been told this 'no earth on the lighting circuit' malarkey was permitted because of trying to save on copper in post-war austerity times.

Nope, there was never a requirement for lights in a domestic environment, for ordinary lamp sockets. It was a requirement, to have metal light fittings and fixtures earthed though.

 

[JohnW2]

I've been told this 'no earth on the lighting circuit' malarkey was permitted because of trying to save on copper in post-war austerity times.

Who knows for sure? However, I don't think that earths on lighting circuits were any more common (probably quite rare) PRE-war, so I suspect that what you suggest wasn't particularly true.
I've always assumed that the main reason was probably that there was, 'back then', no real perceived 'need' for earths on lighting circuits.

 

[Harry Bloomfield]

I've always assumed that the main reason was probably that there was, 'back then', no real perceived 'need' for earths on lighting circuits.

With just a BC lamp, hanging from an insulated lamp holder, there was just nothing to earth, no reason for an earth. When florescent lights started to become popular in kitchens, then they would need an earth, and was one of the main drivers to change the Regulations, for the inclusion of an earth, at every light and switch.

The early wiring systems, used a sort of timber trunking, with just two slots cut in it, one for the live, one for the neutral - no slot for an earth wire. This was installed by joiners/woodworkers, who became the first electricians.

 

[ericmark]

It was a requirement, to have metal light fittings and fixtures earthed though.

If electric, of course

these don't need an earth. When I was a lad, still some homes with wall gas or oil lamps, easier to reach on the wall to either light them or lift them off their spigot, but the oil and gas lamps were not used, by my time there was electric in most homes, even if 110 volt DC.

Abergeirw is a hamlet located in Gwynedd, North Wales.
The village of nine properties is located between Dolgellau and Trawsfynydd.

On 19 December 2008 National Grid plc connected it to the UK national electricity power grid, making it the last village in Wales to be supplied with mains electricity.

It does seem odd when Trawsfynydd had one of the early nuclear power stations. But when a lad, Llwyngwril had its own generator by the side of the river, and the local farm had a line from it, mainly to work the water pump to bring spring water to the farm. At 110 volt DC, so everything had to be special for that supply. I would guess they got national grid when I was around 7 so around 1958-62.

The caravan site, used a wind generator to light the toilets, but there was a petrol station on the main road, and I can't recall how they got power. I went there on holiday every year.

Much latter, worked on the Falklands, most settlements had generators, but not running 24/7, so oil lamps and candles still used a lot, earths seemed to be unknown to them. And my attempts to fit earths were to no avail as somewhere in the inaccessible loft space there must have been a junction box.

And this seems to be even in the UK a big problem, as one simply can't access many junctions. In theory, we don't really need an earth to stop shocks, birds can land on the power lines without a problem, so what we need is bonding, it does not matter if the whole house is 230 volts in relation to true earth, as long as it is all the same voltage, and entrances are so you can't touch house bonding and true earth at the same time.

OK, it would mean that a RCD may not work, and a line to bond fault may not blow a fuse, so not something we want to do, but in real terms only premises made of metal are really a problem. So caravans, narrow boats, and mobile homes have a problem, and are not permitted to have a TN-C-S (PME) supply, but in a brick, stone, or wood home, as long as all is bonded there is no problem with shocks.

The problem is a sink with a waste disposal unit, a washing machine, and dishwasher may be where you can touch all three at the same time. And if the sink has not been bonded, it may become a different voltage to the washing machine, and dishwasher, and the sink due to pipe work, likely will mean more items are it its voltage to the washing machine, and dishwasher, so we get a shock when touching the washing machine, and dishwasher, but the fault is down to the sink. Clearly, the waste disposal unit should have been bonded, but also a central heating pump, or motorised valve, cylinder thermostat, or immersion heater, could all cause the sink not to be at the same voltage as the washing machine, and dishwasher.

So we bond, not necessary to earth, but all should be same voltage, even with a loss of PEN.

 

[Harry Bloomfield]

My father, then working on the railway, had a remote from where we lived garage to store his car. Space for the garage, rented from the railway, near a shunting yard. Located near the garage, was a large, rambling house, obviously built by the railway. Railways were quite slow to move from gas lighting, to electric lighting, and this house was entirely gas lit, and remained gas lit, until it was eventually demolished in the 1980's.

 

[JohnW2]

With just a BC lamp, hanging from an insulated lamp holder, there was just nothing to earth, no reason for an earth. When florescent lights started to become popular in kitchens, then they would need an earth, and was one of the main drivers to change the Regulations, for the inclusion of an earth, at every light and switch.

Possibly but, back then, goodness knows what (particularly irons) were plugged into those BC lamp holders (via some sort of 'adapter'). Furthermore, a good few of the lamp holders were brass (not 'insulated') and therefore would, per present-day thinking, need to be earthed.

The early wiring systems, used a sort of timber trunking, with just two slots cut in it, one for the live, one for the neutral - no slot for an earth wire. This was installed by joiners/woodworkers, who became the first electricians.

Indeed, but the slots in that 'timber trunking' were often multiple and quite wide. There are a few remnants still present in dusty and neglected corners of my present house and, as can be seen from photo, the slots are able to accommodate T+E ...

 

[JohnW2]

.... Railways were quite slow to move from gas lighting, to electric lighting, and this house was entirely gas lit, and remained gas lit, until it was eventually demolished in the 1980's.

Where I lived during my youth, in the outer suburbs of London, the street lighting in our road was gas until the late 60s or 70s.