Sergio Fernandez said:

Did you find what caused the issue in this picture?

I think it relates to "blue to red" sometimes equals "blew to bits" in the picture in the post from Sparkingchip  10 hours ago?

Sparkingchip said:

The reason for the issue in the previous photo. 

I posted these photos a few years ago,  they are classic examples of unexpected issues that are potentially lethal.

It didn’t take long to sort out!

Checking using socket tester costing less than twenty quid would have identified an issue at the time of installation.

John Peckham said:

So I was taught, and teach, when testing rubber soled shoes

But not surgeon's rubber soled shoes please. In olden days when inflammable anaesthetics such as ether were used, operating theatre footwear had a conducting plug in the sole to prevent the build up of static electricity.

Returning to locking off, does anybody have much faith in dolly locks? It can be a real fiddle to get them to stay on in the first place and a sharp tug could easily remove one.

I can imagine that if a ladder slipped an outgoing device or even main switch (including the REC2 type of main switch in a box device) could be closed accidentally.

I can imagine that if a ladder slipped an outgoing device or even main switch (including the REC2 type of main switch in a box device) could be closed accidentally.

Unlike the traditional British 'up for off, down for on' most modern devices follow the European convention of up for on - so much less likely to be closed accidentally by falling objects. Not impossible perhaps, but reasonably unlikely.

One of the major flaws for testing for dead is that it doesn't take account of things changing with time - e.g. downstream of something on a timeswitch, or thermostat or even a second lightswitch somewhere out of sight  (typical with 2-way switching) - pull the upstairs lighting fuse, "prove dead" then someone absent mindedly switches on the switch in the hall - which had a borrowed L from the downstairs circuit.

   - Andy.

Have a look at YouTube for John Ward.  Video title name

Diverted Neutral Current Demonstration - Normal, Open CNE, Current Circulation (Part 2)

Would you class an Electric car doing car to grid as a battery?

Afternoon Chris

I do a few 710 inspections of operating theatres (Group 2 locations). I was doing an inspection in a famous London hospital and found a broken back box around an equipotential bonding point. Drinking tea with the theater nurses who were going to clean up and prepare the theatre for use and mention that they needed to get the defect fixed before they used the room. They said don't worry we never use them anyway. I said but you do open heart surgery in there and she said no one uses them.

Speaking to a colleague of mine he said the same.

So is this true that we have BS 7671 regulations to provide them but  they are never used? Also if you did use them what would you connect to them? Me thinking if the installation was fully compliant with 710 ( I have yet to see one) everything would be bonded anyway.

JP

"What would you connect to them?" Here is the back of a medical camera unit such as are used everywhere nowadays. I assume that the pin on the back (zoom in if you wish) relates to 710.415.2.1. I cannot think of a better way of creating trip hazards than trailing coils of G&Y across the floor of an operating theatre, etc.

Graham will probably be on in a mo to say that symbol of a triangle with a circle in it is not the right sort of ground symbol for equipment like that To me it would read as 'ground zero' on a circuit.

Anyway it is neither a safety nor a functional earth sign that I recognize.

I'm also not surprised that no one wants any more trailing wires that the minimum.

Mike.