DB earth fed direct from HRC fused cutout or from external MET first?

[eveares]

View attachment 132797
CU in my parents house. Few years old now clearly but see attached label by the MET

Why are there two cable ties on each meter tail out of the meter feeding the isolator?

 

[Risteard]

In Ireland we use an ISCO external to the DB. The DNO (NIE) require that it be external to the DB. I always apply the requisite warning. So do many others.

 

[Iggifer]

Why are there two cable ties on each meter tail out of the meter feeding the isolator?

That’s a British Gas thing. They say L and N on them, despite being blue and brown already, he had to double mark them! There’s also one tie on the tails feeding the meter to indicate it’s the feed

 

[John D v2.0]

They say L and N on them, despite being blue and brown already, he had to double mark them!

Before removing any customer tails from a meter, ukpn and probably all others have to confirm polarity and mark up the tails with stickers with the confirmed polarity. This is visual reminder that polarity has been confirmed whether or not the tails are coloured correctly. In case of distraction etc.

If the tails were incorrectly coloured and confirmation was forgotten, ukpn would be negligent to reconnect the installation the "correct" way round. Actually they'd refuse to work on the installation in all likelihood.
Like with flying a plane, there's no"use your common sense" in jointing manuals as it's not safe to decide any more than necessary when you're execution a safety critical task. If it takes 10 seconds longer but increases safety it's in the book.

 

[Iggifer]

I appreciate it’s a confirmation but the next person that comes along is also going to confirm polarity regardless - they would be negligent in not doing so - who’s to say since those tails were tagged something has gone awry and the polarity is now incorrect?

 

[John D v2.0]

I appreciate it’s a confirmation but the next person that comes along is also going to confirm polarity regardless

sorry I mean confirmation during the job - as you may know, the most common time for things to go wrong in a safety critical task is when there's an unexpected distraction causes someone to think they already did something when they didn't. A checklist is one way to help, but who ticks them one at a time? To have a relevant visible action associated (even if theoretically pointless in itself) is better than having a separate checklist. Then you can never be confused about whether you did the check or not regardless of distractions.

 

[JohnW2]

sorry I mean confirmation during the job - as you may know, the most common time for things to go wrong in a safety critical task is when there's an unexpected distraction causes someone to think they already did something when they didn't. A checklist is one way to help, but who ticks them one at a time? To have a relevant visible action associated (even if theoretically pointless in itself) is better than having a separate checklist. Then you can never be confused about whether you did the check or not regardless of distractions.

All true, and I suppose it must help, but even that is not going to be foolproof - any 'confirmatory action' (whether ticking a checklist, apply an 'pointless' cable marker or whatever) can go wrong if one is distracted, gets into 'autopilot mode' or whatever.

Just as most people don't tick items on a checklist 'one at a time', nor do I imagine that many would attach those cable markers, very close to the meter, whilst live meter terminals were still exposed for testing - so other actions (which might 'distract') would be necessary between testing and labelling.

Kind REgards, John

 

[ban-all-sheds]

In Ireland we use an ISCO external to the DB. The DNO (NIE) require that it be external to the DB. I always apply the requisite warning. So do many others.

You mean in "In Northern Ireland we use..."

 

[John D v2.0]

Just as most people don't tick items on a checklist 'one at a time', nor do I imagine that many would attach those cable markers, very close to the meter, whilst live meter terminals were still exposed for testing

So you are saying it's equally safe to not bother? I think it narrows but doesn't completely remove the window of opportunity for error. But if they are distracted in that time, they're much more likely to retest and mark than if there was no marking at all as there's a visual reminder right in their view that they didn't complete the test and mark task.

 

[JohnW2]

So you are saying it's equally safe to not bother?

Nope. As I wrote "I suppose it must help ... ", although I went on to say ".... but even that is not going to be foolproof".

In essence, human nature is such that any 'repetitive routine task' (whether ticking a checklist, applying a cable marker or whatever) is at risk of becoming so routine/'automated' as to lose some of its value.

I suppose that what is behind my thinking is the fact that polarity of meter tails is but one of countless things that can be 'got wrong' in an electrical installation and, particularly since DNO personnel are probably amongst the least likely to make this sort of error, one wonders how much, in relation to the big picture, is gained by applying this additional safety measure (if that is the reason for it) to just one of those countless 'potential points of error'.

Kind Regards, John

 

[John D v2.0]

I think your suggestion is overly cynical, but maybe I'm just optimistic! Unless there's a better way, it's all just cost Vs benefit.

particularly since DNO personnel are probably amongst the least likely to make this sort of error,

But could that be because of their calm adherence to procedure?
You could say the same about air line pilots, but they don't make many errors because the first thing they do in an emergency is start following checklists until they're on the ground. In fact everything from when they approach the plane to getting out, apart from the moment before landing, is from procedure.

 

[John D v2.0]

In essence, human nature is such that any 'repetitive routine task' (whether ticking a checklist, applying a cable marker or whatever) is at risk of becoming so routine/'automated' as to lose some of its value.

Agreed completely, in fact a previous colleague who did sky diving said the most common amount of jumps to result in death was something like 100 to 500. Before that you're being careful, and following procedure, then you start pushing the boundary when it gets routine, and then you get experienced.

 

[JohnW2]

I think your suggestion is overly cynical, but maybe I'm just optimistic! Unless there's a better way, it's all just cost Vs benefit.

I'm not disagreeing, merely suggesting that, yes, perhaps you are being a bit over-optimistic. However, my main thought is the one that I recently mentioned - that we're talking about just one place out of hundreds where 'things can be got wrong' (indeed, one of many where polarity can be got wrong), so I can't help wondering how an additional level of safety-checking in just that one very specific situation will impact on 'the big picture'.

But could that be because of their calm adherence to procedure? You could say the same about air line pilots, but they don't make many errors because the first thing they do in an emergency is start following checklists until they're on the ground. In fact everything from when they approach the plane to getting out, apart from the moment before landing, is from procedure.

Indeed, but even that is certainly not 'foolproof'. In a couple of the "Air Crash Investigation" programmes I've seen recently, complacency/'automatism' (or "familiarity breeding contempt") in relation to checklists led to disasters. In one case, a pilot so used to saying "Yes" (or "On" or whatever) 'automatically' did so when he should have said "No" (or "off"). In another case, the co-pilot correctly said "Off" (in relation to de-icing, which should have been on), but both he and the Captain were so used to hearing a correct/appropriate response that neither of them twigged that they had both 'accepted' a (correct/true) response which was to go on to result in countless deaths, including their own.

Total reliance on 'procedures' also puts tremendous responsibility on those who create those procedures, a difficult task since they often cannot be properly 'tested' until they are 'used in anger'. I've seen others of those programmes in which strict adherence to a 'flawed' checklist has been the actual cause of a disaster; whilst that invariably resulted in the checklist being subsequently revised, the price for 'correcting' it is, again, countless lost lives.

Kind Regards, John

 

[333rocky333]

That's what, apparently unlike EFLI, I was also not sure about, either, and maybe not even a metre - perhaps 500 or even 300 mm.

As I asked EFLI is it your practice to attach such labels to a MET which is very close to (but not inside) a CU/DB, and is it your experience that most others do this?

Kind Regards, John

 

[JohnW2]

<a photo of someone's work>

So what's the answer ....

As I asked EFLI is it your practice to attach such labels to a MET which is very close to (but not inside) a CU/DB, and is it your experience that most others do this?

Are you implying that the photo is of your work, and that's what you usually do, or what?

Kind Regards, John