Electrical separation (for the apprentice electrician)

[Lesterwyatt]

 I was board so I thought I would upload a video off the cuff with a industry story. This story led to why two items of class 1 equipment is bad on an electrically separated system.


https://youtu.be/KcavImqF6RE

[Brumby]

With two equipotential points where one is connected to Earth immediately causes the second to be referenced to Earth.  The voltage difference is then zero and presents no shock risk.

Two faults with live to case will not cause a shock hazard you describe - unless the plugs are unpolarised.  In this case, you would need one shaver plugged in with the case fault connected to the live and the other one plugged in with the case fault connected to the neutral.

Then you would have a problem.

[Lesterwyatt]

You are correct in your observation, shaver plugs are unpolarised tho and two line fault on both could be a neutral fault on one, depending how it was plugged in. i will make a note on the video! the video was done off the cuff with no preparation.

[IanMacdonald]

Ideally all hand tools including shavers should be Class 2. ROSPA stats indicate that the rate of accidents with Class 2 appliances is far lower than with Class1. The problem with earths in flexes is that they can come detached and contact the live terminal, which creates a worst-case level of hazard.

We had a case like this at the airfield I used to fly from, where someone got a nasty belt whilst working outdoors with an extension lead. Turned out that the supply cable had been pinched at the metal wall socket, and the live shorted to the (severed) earth connection, making both the socket case and any metal hand tool case live.  We'd known about the wiring problems for a long time (and nagged the bosses over it a few times) but management was reluctant to spend money on a remedy. I put in a full report on my findings, and thankfully that death trap was rewired as a result.

I think we got lucky on that one, they guy was working outdoors in wet conditions and it could easily have been a fatal. 

I also have a dislike of metal wall sockets. Another unnecessary piece of metal to earth. The less, the better.

[BrandonClarkson]

Thank you for your advice I had a similar problem. Since I am a beginner, I still could not solve this problem myself, although I did everything the same as you. And in the end, I had to turn to professionals. Good thing I found this company https://bates-electric.com/locations/miami-fl/ which provides similar services and made me everything quickly. In addition, I watched as the employee who came to me did all this and I remembered everything

[domika]

whether this tool has been tested