17th Edition

[stevesey]

Chapter 54. Other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against its removal....

So, tell me how you can guarantee that? Nothing's permanent. So you can't do it. So why include it??

Technically there is nothing ambiguous about that statement - it says a precaution must be taken - not that the precaution should guarantee it can't be removed. As you have quoted it any precaution will unambiguosly satisfy the regulation. What it doesn't do is define what is an acceptable precaution - which would be helpful.

Similary - but off topic - I noticed that part P says cable replacement (of damaged cable) is not notifiable if the cable is of the same current carrying capacity. Now if I replace 1mm2 with 1.5mm2 is that notifyable? The cable is more than capable of carrying the same current, so is it of the "same current carrying capacity", or are they after equality rather than equal to or greater than. Has anyone had any clarification on this one?

 

[securespark]

Anything other than like for like is notifiable AFAICT.

What is madder is this:

You replace a damaged shower feed cable with the same size cable, following the same route.

Unfortunately, the cable is 4mm² and now feeding a 10.5kW unit via a route touching hot pipes & through much insulation.

A customer I met recently had almost this scenario.

 

[stevesey]

Anything other than like for like is notifiable AFAICT.

AFAICT - so hardly conclusive then

Your scenario is one where I think part-p goes to far - by making a simple one for one replacement of an upgraded cable (with better routing) a notifiable job. Personally I think it would make sense to have treated the replacement of an underspec'd cable in a similar way to a damaged cable (i.e. not notifiable).

 

[securespark]

No. But reading the Document would be. So go and do it, instead of being lazy & asking others to do it for you.

 

[stevesey]

No. But reading the Document would be. So go and do it, instead of being lazy & asking others to do it for you.

I think you will find that "the same current carrying capacity" is a direct quote from the document

 

[plugwash]

Chapter 54. Other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against its removal....

So, tell me how you can guarantee that? Nothing's permanent. So you can't do it. So why include it??

It only says precautions not gaurantee.

In a domestic house i would probablly agree this was a bad idea (much like a non-earthed lighting cuircuit protected by class 2 insulatio) but in a place with a strong health and safety policy and good plans i wouldn't see a problem.

I strongly belive that you can't gaurantee an electrical installation you have installed is safe without understanding of those who will use and maintain it after you are gone.

an example someone brought up was a school who had rcd protected CEEFORMS outside but people still took extention leads from the unprotected sockets inside through windows because they had no way to connect to the CEEFORMS.

 

[empip]

Chapter 54. Other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against its removal....

So, tell me how you can guarantee that? Nothing's permanent. So you can't do it. So why include it??

Technically there is nothing ambiguous about that statement - it says a precaution must be taken - not that the precaution should guarantee it can't be removed. As you have quoted it any precaution will unambiguosly satisfy the regulation. What it doesn't do is define what is an acceptable precaution - which would be helpful.

Similary - but off topic - I noticed that part P says cable replacement (of damaged cable) is not notifiable if the cable is of the same current carrying capacity. Now if I replace 1mm2 with 1.5mm2 is that notifyable? The cable is more than capable of carrying the same current, so is it of the "same current carrying capacity", or are they after equality rather than equal to or greater than. Has anyone had any clarification on this one?

How could anyone know?? You do not have to retain the damaged cable as evidence - and if there has been no electrical certification EIC / PIR etc on the property no one could know things are different apart from the 'new cable' ... How many damaged cables over time are you allowed??
The law doesn't actually say 'like for like' either... Unless I read the wrong one ..

b) replacing a damaged cable for a single circuit only;

(c) re-fixing or replacing enclosures of existing
installation components, where the circuit
protective measures are unaffected;

(d) providing mechanical protection to an existing
fixed installation, where the circuit protective
measures and current carrying capacity of
conductors are unaffected by the increased thermal insulation.

It's a funny old game ...