Earth checking for grounding

[EFLImpudence]

I figure this is the reason for the distinct terms (in this context) - "earthing" meaning to provide a low impedance path for fault currents so as to ensure circuit protection triggers without creating excessively high voltages on anything exposed, while "bonding" means ensuring that everything conductive in an area is as the same potential even if that isn't exactly the same as local earth.

 

[Adam_151]

I was once called to another friends house after she'd just moved in and she suspected a fault with a light switch. It was the only one with a metal front on it. She said it felt like it was vibrating. The switch was fine but when she said that her new iron felt 'furry' I began to form a picture that it was maybe the waveshape of the mains she might be sensing. It wasn't a new thing apparently, it's just that these were particularly prominent to her.

Sounds like a failed earth to me, I have noticed an apparent 'rough' feeling to metal light switches which have not been earthed and receiving a capacitivly coupled voltage, Just seems to be how a relativly low level current acts upon the nerves in the skin?

 

[Adam_151]

Horses apparently are much more sensitive to leakage than humans are.

That is indeed true, their footwear is not of insulating construction, and they have their legs quite far apart so vunerable to voltage gradients across the ground (also known as step potential), more so than humans who have feet quite close together, also the heart is in the path electricity would take from front to hind legs.

voltages below 50v are considered relativly harmless in most installations, but on farms on the like it falls to 25v.

 

[SimonH2]

Just seems to be how a relativly low level current acts upon the nerves in the skin?

I can get that from my laptop

Like many modern electrical items, it's only got a 2 pin supply, but probably has input filtering caps. At work it's fine as I have it connected to an external monitor and it's 'earthed' through the monitor, but elsewhere I can get a tingling feeling where my wrists rest on the case.
Just checked, using an earthed 3 core cable it's OK, using a "duckhead" adapter (no earth connection for the power supply) there's 40 to 45V on the case

voltages below 50v are considered relativly harmless in most installations, but on farms on the like it falls to 25v.

And I think back to how cavalier we used to be with 'lectrics when I were a lad and worked on a farm

Among other things, there was this long extension lead we used whenever we needed power away from the very few sockets. An old rubber job it was, with dozens of bits of tape over the cracks, and the 13A socket on the end had this lead coming out with a crocodile clip on it. No-one knew what it was for (I do now having read a few posts here), and it would often be clipped onto the bit of equipment we were using. The extension lead was 2 core - I now wonder if it wasn't some bodge up 'cause that's what was to hand, but rather an attempt at not exporting an earth from one building to another and the instructions for using the earth connection were never passed on.

And on another occasion I had to do some welding on a door. I recall that with the welding earth attached, I could feel "quite a tingle" off it.

Probably a good thing we mostly wore wellies