EICR coding of 521.8.1 violations (3P over 2 cables)

[pc1966]

Another thread asked about two circuits sharing a common multi-core cable and regulation 521.8.1 was mentioned. A friend of mine has inherited the "opposite" issue of a 3P circuit spilt over two T&E runs. Yes, I know that is bizarre and not something you really would expect to meet. However, that got me wondering how would you code this in an ECIR?

It seems less of a risk than the "borrowed neutral" C2 installation fault, after all you commonly see two or more cables run from the same MCB for, say, lights or a RFC split as the least-worst fix, etc, so having to verify the isolation of each and every cable you are working on is normal.

So while not a good indication of skill in installation, C3 would appear to be the obvious coding. Any thoughts?

 

[Rockingit]

I think I'd be giving that a C3, too. When you read the full 521.8 section it has no issue with multiple conductors in parallel, individual phases run as singles and so on, or multiple ciruits in the one cable - it just asks that you do one or the other, not mix and match! So therefore it would be an infringement that needs improvement rather than being a tangible risk to a person of BA1. This is also why we teach safe isolation of every conductor to every conductor, not just "yeah, the brown one's dead...."

 

[davesparks]

How old is the T&E and what is it's maximum working voltage rating?

Over the years there has been T&E which does not have a suitable working voltage rating for 3 phase, which would be a C2 in my opinion.

 

[Rockingit]

How old is the T&E and what is it's maximum working voltage rating?

Over the years there has been T&E which does not have a suitable working voltage rating for 3 phase, which would be a C2 in my opinion.

That's fair enough, but in terms of the OP, where do you stop the metaphorical ball of string - Method? Unsupported spans? Terminations..... etc.

 

[littlespark]

Nobody is going to expect 400v between cores in a t&e although Prysmium website states a nominal voltage of 300V or 500V for 6242Y cable

 

[westward10]

300/500v means 300v between a live conductor and the cpc and 500v between live conductors.

 

[pc1966]

Nobody is going to expect 400v between cores in a t&e although Prysmium website states a nominal voltage of 300V or 500V for 6242Y cable

Maybe the Spanish Inquisition would do?

It is odd that the vast majority of 3&E cable is used for two-way switching on SP circuits even though the cable is colour coded for use as a 3P+E cable.

 

[pc1966]

How old is the T&E and what is it's maximum working voltage rating?

Over the years there has been T&E which does not have a suitable working voltage rating for 3 phase, which would be a C2 in my opinion.

I would be surprised if T&E is not able to deal with the 3P voltages as each core is rated to at least the nominal Uo to earth, and as that is between conductors they see nothing different. Even between the two lives on one side of the CPC in 3&E cable there is now double the thickness of primary insulation, and so something getting towards double the breakdown voltage (not double as I doubt the electric fields are uniform, etc).

But you are certainly right this is a C2 circuit but for many reasons:

• Violation of regulation 521.8.1 on splitting a circuit over multiple multi-core cables = C3 (agreed?)
• The pair of T&E cables are run together, clipped direct, and not in any path of likely damage = no code, good!
• Cables painted multiple times with oil paint (AFIK) probably leading to degraded outer sheath = C3 ?
• Use of 1mm cable on a power circuit, was C3 but now permitted by regs so no code.
• Protection is by means of (as far as I could judge) 20A fuse wire in BS3036 holders shared with other circuits = C3 as it might meet adiabatic (not checked Zs), but fails to provide overload protection against a jammed motor or loss of one phase since no signs of any motor protection (e.g. proper starter, etc)

It is not any of my professional business as such, but it is not something I am happy seeing continue anywhere, let alone a friend's property now.

 

[Rockingit]

I would be surprised if T&E is not able to deal with the 3P voltages as each core is rated to at least the nominal Uo to earth, and as that is between conductors they see nothing different. Even between the two lives on one side of the CPC in 3&E cable there is now double the thickness of primary insulation, and so something getting towards double the breakdown voltage (not double as I doubt the electric fields are uniform, etc).

But you are certainly right this is a C2 circuit but for many reasons:

• Violation of regulation 521.8.1 on splitting a circuit over multiple multi-core cables = C3 (agreed?)
• The pair of T&E cables are run together, clipped direct, and not in any path of likely damage = no code, good!
• Cables painted multiple times with oil paint (AFIK) probably leading to degraded outer sheath = C3 ?
• Use of 1mm cable on a power circuit, was C3 but now permitted by regs so no code.
• Protection is by means of (as far as I could judge) 20A fuse wire in BS3036 holders shared with other circuits = C3 as it might meet adiabatic (not checked Zs), but fails to provide overload protection against a jammed motor or loss of one phase since no signs of any motor protection (e.g. proper starter, etc)

It is not any of my professional business as such, but it is not something I am happy seeing continue anywhere, let alone a friend's property now.

Genuinely interested to hear your thinking on how a multiple occurrence of C3’s adds up to a C2. I think from what you say here that there is actually a C2 (1mm line conductor on a 20A OCPD??) but unless I’m reading it wrong after a vino or two (or is a typo) you’ve suggested as a C3. As an aside, I remember having a discussion on a thread on here about painted cables with Lucien and the conclusion was that it made no tangible difference.

 

[pc1966]

Genuinely interested to hear your thinking on how a multiple occurrence of C3’s adds up to a C2. I think from what you say here that there is actually a C2 (1mm line conductor on a 20A OCPD??) but unless I’m reading it wrong after a vino or two (or is a typo) you’ve suggested as a C3. As an aside, I remember having a discussion on a thread on here about painted cables with Lucien and the conclusion was that it made no tangible difference.

Yes, last one ought to be C2 from BPG#4:

Circuits with ineffective overcurrent protection (due, for example, to oversized fuse wire in rewireable fuses)

However, it has been mentioned before that an "unsatisfactory" judgement could be based on a lot of poor C3 factors combined, rather than one blindingly obvious C1/C2 fault in the design/installation. Methinks that is another thread that could run and run!

 

[davesparks]

. As an aside, I remember having a discussion on a thread on here about painted cables with Lucien and the conclusion was that it made no tangible difference.

The only time I've seen it make a noticeable difference was in a farmhouse where lord knows what had been painted on the exposed beams and it had eaten into some of the old surface run T&E.

 

[Rockingit]

The only time I've seen it make a noticeable difference was in a farmhouse where lord knows what had been painted on the exposed beams and it had eaten into some of the old surface run T&E.

At a guess I'd say original Creosote. That stuff was nasty!!

 

[brianmoooore]

Creosote will degrade PVC, but used on beams inside a house? That stuff stinks.

 

[Rockingit]

Creosote will degrade PVC, but used on beams inside a house? That stuff stinks.

True. Although I'd hazard a guess that things like woodworm treatment are probably chemically quite similar? Don't know.