Electrical Safety Council Question

[hightower]

So I'm reading through the questions at ESC and I got to #47:



Surely if the branching was all done in metal, you could prove it wasn't extraneous one day, then another spark comes in to work on apartment 2 and slaps bonding on 'to be safe' and all of a sudden every other apartment has an extraneous part that isn't bonded? So wouldn't best practice to be to bond it in this circumstance for fear it might get bonded somewhere else?

 

[Wilko]

Good thought HT ... Each flat is a separate electrical installation and in the situation presented the water pipe entering the flat is in metal, so I would bond. Like you say, I could never prove what happened to the metal pipe elsewhere. Maybe I'm bond-happy? Cheers, David.

 

[Midwest]

'Extraneous-Conductive-Part; a conductive part liable to introduce a potential.........'. So a metal pipe entering an apartment has the 'risk' of introducing a potential, therefore wouldn't need to be tested to see if it's extraneous. As they state, reg 544.1.2 says bond it.

 

[hightower]

Okay, another question while I'm on:



#81 states it is acceptable to add to a circuit having no CPC. Yet #83 states it isn't acceptable to install a new circuit

'Extraneous-Conductive-Part; a conductive part liable to introduce a potential.........'. So a metal pipe entering an apartment has the 'risk' of introducing a potential, therefore wouldn't need to be tested to see if it's extraneous. As they state, reg 544.1.2 says bond it.

I agree but this article seems to suggest testing it to see if it's extraneous. To me it might not be extraneous one minute and then extraneous the next so surely the article should just outright say to bond it.

 

[Wilko]

My 20p worth :
181 OK, as the class2 kit 'is safe' with no cpc and so it doesn't make the safety any worse.
182 if the bonding is proven to be inadequate (heat damaged say) then I would do no changes on the installation until it was investigated and fixed. If it's 6mm and in good condition perhaps another answer. (Am I too conservative?).
183 OK, as there is an immediate safety concern and the new addition will just make it worse. Fix, then extend.

 

[bigspark17]

So I'm reading through the questions at ESC and I got to #47:

View attachment 33169

Surely if the branching was all done in metal, you could prove it wasn't extraneous one day, then another spark comes in to work on apartment 2 and slaps bonding on 'to be safe' and all of a sudden every other apartment has an extraneous part that isn't bonded? So wouldn't best practice to be to bond it in this circumstance for fear it might get bonded somewhere else?

The pipework in question would need main bonding as a fault could be induced through another house, and each apartment has its own DNO not much diferent scenario to a row of houses with metal water pipe feeding them. If there was one DNO supply into building with submains rising from there i would suggest only main bonding would need doing once at MET.

 

[Midwest]

Okay, another question while I'm on:

View attachment 33171

#81 states it is acceptable to add to a circuit having no CPC. Yet #83 states it isn't acceptable to install a new circuit

I agree but this article seems to suggest testing it to see if it's extraneous. To me it might not be extraneous one minute and then extraneous the next so surely the article should just outright say to bond it.

I don't think you have to, because by definition it's extraneous. If a metal pipe in one of the apartments, enters its bathroom, you would have to test that to see if it was extraneous (i.e. into the bathroom).