Current in earth wire to light switch?!

[mattylad]

Much of my lighting circuit appears to have no earth.
Thats how it was in ye olde days it seemeth. (1855 terrace)

 

[JohnW2]

The RCD is the airbags. ... the RCD is there to try and limit your injuries when things have gone very badly wrong (the airbags)

Is that what you meant to type and, if so, could you possibly explain?

In any event, my point remains. If one drove a car 'with no brakes' then someone or something would almost certainly get damaged (maybe killed) on the first day one did that driving 'with no brakes'. On the other hand, if one drove a car without airbags, it is very unlikley that anyone would die or be injured as a result of the absence of those airbags even during decades of driving without them. I still would suggest that, in terms of probabilities, living with an ineffective earth is much closer to the latter than the former!

I hope everyone is keeping well and safe.

Kind Regards, John

 

[RF Lighting]

If you got in a car you knew had no brakes you could drive it slowly and use the gears to control your speed and probably be ok.

We managed without RCDs for decades and installations were still relatively safe, but RCDs make them safer and are now pretty standard on most new installations.

Having an installation without an effective earth and voltage showing on exposed conductive parts is not a safe situation to start with, and could with no warning kill someone.

 

[Harry Bloomfield]

That’s an open circuit earth wire. You need to trace the wiring back and find out where it has become disconnected.

I agree, that is probably what it is. It could just be that your lighting circuit was wired without any earth, it was quite normal back in the pre-1970's - then someone has come along and added an extra later cable which included an earth, but didn't actually earth it.

Capacitive coupling between the earth wire appearing at your switch and a live wire, being enough to light a neon screwdriver.

Having an installation without an effective earth and voltage showing on exposed conductive parts is not a safe situation to start with, and could with no warning kill someone.

The voltage is probably just capacitive/ inductive pickup. Any metalwork close to a live conductor, which lacks an earth, will show some evidence of this 'pickup'.

 

[JohnW2]

If you got in a car you knew had no brakes you could drive it slowly and use the gears to control your speed and probably be ok.

You could. Similarly, if you were living with an electrical installation which you knew had some deficiencies of braking, you could be careful not to touch any exposed-c-ps, and would "probably be OK". However, if you did not know that the car had no brakes (in the same way that most people wouldn't know of the earthing deficiency), then you would quite probably come to grief pretty quickly, whereas the vast majority of people living with an (unknown to them) deficiency of earthing would "probably be OK" for decades, or a lifetime.

We managed without RCDs for decades and installations were still relatively safe, but RCDs make them safer and are now pretty standard on most new installations.

Yep, just in the same way that we lived without airbags for decades, but airbags "made them safer and are now pretty standard".

Having an installation without an effective earth and voltage showing on exposed conductive parts is not a safe situation to start with, and could with no warning kill someone.

That would certainly be true IF there really were "('true') voltage showing on exposed-c-ps" (not just a neon screwdriver lighting up!) - because that would be like driving a car whose brakes had already failed.

I prefaced all my comments by saying that, because of the potential danger, it is certainly a situation that needs to be investigated (ideally as a matter of some urgency) and, if necessary, rectified.

Kind Regards, John