RichardCS2:

So, at a friend's house there is a 6 mm^2 bond to an up-and-over garage door, fitted so far as I can tell when the house was built in 1990. I would expect all the houses on this estate to have them though I haven't checked. Now would anyone like to argue that the risk associated with this large metallic surface with a conductive handle, touched regularly whilst standing on the driveway and connected to a PME-labelled earth terminal is significantly different to the car plugged in on the driveway?


Yes it could be argued that this connection could be removed, though on a wet and windy day perhaps the door measures just a few kiloohms to true earth and it is simultaneously touchable with a bonded metallic gas pipe. It may even make contact with the pipe some of the time, at the moment there's a ~1 mm gap but that could easily disappear.


I am unconvinced that there is a new risk associated with TNC-S and electric cars, rather that the risk is comparable to the others that have existed since the start of the PME era and have either been ignored, not been recognised at all, or deemed acceptably low.

 

1. This particular garage door would have been bonded under 15th Ed - only a couple of years later, under 16th Ed, we'd moved away from doing that sort of thing as we saw it wasn't a good idea.
   
    

• The PME risk is perhaps becoming worse, as the fortuitous earthing provided by metal gas and water pipes in the street is reducing in effectiveness, as the metal pipes are being replaced by plastic (gas because of corrosion of the metal mains leading to explosion risk, water because corrosion was causing a public health risk, and also leak management).

RichardCS2:

So, at a friend's house there is a 6 mm^2 bond to an up-and-over garage door, fitted so far as I can tell when the house was built in 1990. I would expect all the houses on this estate to have them though I haven't checked. Now would anyone like to argue that the risk associated with this large metallic surface with a conductive handle, touched regularly whilst standing on the driveway and connected to a PME-labelled earth terminal is significantly different to the car plugged in on the driveway?


Yes it could be argued that this connection could be removed, though on a wet and windy day perhaps the door measures just a few kiloohms to true earth and it is simultaneously touchable with a bonded metallic gas pipe. It may even make contact with the pipe some of the time, at the moment there's a ~1 mm gap but that could easily disappear.


I am unconvinced that there is a new risk associated with TNC-S and electric cars, rather that the risk is comparable to the others that have existed since the start of the PME era and have either been ignored, not been recognised at all, or deemed acceptably low.

 

1. This particular garage door would have been bonded under 15th Ed - only a couple of years later, under 16th Ed, we'd moved away from doing that sort of thing as we saw it wasn't a good idea.
   
    

• The PME risk is perhaps becoming worse, as the fortuitous earthing provided by metal gas and water pipes in the street is reducing in effectiveness, as the metal pipes are being replaced by plastic (gas because of corrosion of the metal mains leading to explosion risk, water because corrosion was causing a public health risk, and also leak management).