Horizontal safe zone with 'dry lining' back boxes

[Harry Bloomfield]

I've already agreed about the common sense of that, and it wouldn't personally worry me to have cable routed as I've suggested.

However, as for 'pedantic', and as previously said, I asked the question because I know there are some people who would regard it s anything but 'pedantic', thinking/writing things such as ebee recently did ...

Rules are made as simple as possible to follow, sometimes you just have to apply a little common sense to the rule too. I half remember reading an early copy of the Regulations, which suggested as much. It said something like - if an installer breached the regulations, it was acceptable, providing the installer could justify that breach.

 

[JohnW2]

Rules are made as simple as possible to follow, sometimes you just have to apply a little common sense to the rule too.

That is also my view. However, in addition to ebee, it is unfortunately not the view of Mr Jobsworth and his friends and family, a good few of whom seem to undertake EICRs

I half remember reading an early copy of the Regulations, which suggested as much. It said something like - if an installer breached the regulations, it was acceptable, providing the installer could justify that breach.

I think you'll find that even the present edition of BS 7671 says that alternative approaches are acceptable if it can be shown that they do not result in an installation being less safe than it would be if fully compliant with its regulations. However, in the present context, I'm not sure how one could really claim that deviating (even if only slightly) from BS 7671's specified zone was not 'less safe'' than complying with the reg.

The problem with this, as with many other things in the regs that one can 'debate' on the basis of common sense, is that it comes down to attitudes to tiny risks. As with most things in life, BS 7671 (and some relatives of Mr Jobsworth) has become progressively less tolerant of tiny risks, including ones so tiny that many people's idea of common sense would tell them that they were not issues worth worrying (or even thinking) about.

When doing things, electrical or otherwise, in my own home, I work primarily on the basis of common sense, resulting my sometimes doing things which would probably seriously raise some people's eyebrows (or worse!), here and elsewhere. However, I would not usually talk/write about such things 'in public', and certainly would not advise other people to 'do as I do'!

 

[Harry Bloomfield]

The problem with this, as with many other things in the regs that one can 'debate' on the basis of common sense, is that it comes down to attitudes to tiny risks. As with most things in life, BS 7671 (and some relatives of Mr Jobsworth) has become progressively less tolerant of tiny risks, including ones so tiny that many people's idea of common sense would tell them that they were not issues worth worrying (or even thinking) about.

Would Mr Jobsworth doing the inspection, even be sufficiently aware, your cable example ran a few mm out of the zone, I think not, without opening up the PB.

When doing things, electrical or otherwise, in my own home, I work primarily on the basis of common sense, resulting my sometimes doing things which would probably seriously raise some people's eyebrows (or worse!), here and elsewhere. However, I would not usually talk/write about such things 'in public', and certainly would not advise other people to 'do as I do'!

I'm the same, I was brought up in an era when risks were simply mitigated, rather than avoided completely. Often the process of avoiding, involved higher risks, than simply mitigating the risk and cracking on with it. I was taught to work live, I prefer to work live, with instant results. Some problems, can only be satisfactorily diagnosed by live testing.

 

[SUNRAY]

I'm the same, I was brought up in an era when risks were simply mitigated, rather than avoided completely. Often the process of avoiding, involved higher risks, than simply mitigating the risk and cracking on with it. I was taught to work live, I prefer to work live, with instant results. Some problems, can only be satisfactorily diagnosed by live testing.

My main electrical work has been in controls, particularly building/maintaining/modifying control panels, some of which are huge and the wire numbers run into 10,000's, (one elderly panel I reduced the size of by removing nearly 10m off one end when their boilers were changed) and on many sites I've had a strict no live working rule imposed on me. The customer is not impressed when I make a note on the job sheet to that effect and unable fault find then ask them to sign it as an aborted visit as I'm leaving. I'm all in favour when it comes to safety but a total ban on something is impossible sometimes.

 

[Harry Bloomfield]

My main electrical work has been in controls, particularly building/maintaining/modifying control panels, some of which are huge and the wire numbers run into 10,000's, (one elderly panel I reduced the size of by removing nearly 10m off one end when their boilers were changed) and on many sites I've had a strict no live working rule imposed on me.

Similar here, that's what I spent time in Italy doing, and a similar number of wires to sort out. It was an absolutely a nightmare of a job. The Italians had bought a second-hand brass extrusion press, from Germany. It took billets of red hot brass in one end, then extruded them, via dies, into what ever shape was needed. There were around 15 control panels, all left out in the weather, unprotected, simply ripped out, plus the massive machinery. It was all built with relay logic, mechanical limit switches, and timers. I'd wanted to scrap the lot, and redesign it with modern logic.

One guy had gone out, seen the mess, panicked, and gone back home. I'd agreed with two days notice, to go out and see what could be done in three months, and flew out. There were hundreds of drawings, all in German, it was the only one of it's type, and lots of undocumented modifications whilst it had been in use in Germany, plus it was worn out.

Apart from the engineers trying to put the mechanical bits back together, I was on my own. The idea had been, that the Italians had there own electrician, who would be assisting me. He never did assist once, instead, I had the teen-aged factory owner's son, keen to learn English, helping when he had time, and another 14-year-old relative, when he finished school, to help. Rather than the suggested three months, I was out there a solid 12 months, and nowhere near completed, when the Italians ran out of money to continue the job.

It stands as the only job I ever took on, but never finished

 

[JohnW2]

Would Mr Jobsworth doing the inspection, even be sufficiently aware, your cable example ran a few mm out of the zone, I think not, without opening up the PB.

As I said before, if he looked behind the accessory and saw that the cable going to a horizontally-aligned accessory was going through a hole in the top of the backbox, then he could at least suspect that a tiny bit of that cable could be outside of the zone! Trivial and 'pedantic', yes, but that's why he's called Jobsworth

I'm the same, I was brought up in an era when risks were simply mitigated, rather than avoided completely.

Indeed. Some of the 'risks' which regs such as BS7671 seek to address are so incredibly small as to be essentially irrelevant in comparison with all of the other inevitable 'risks of life' (such as driving cars, crossing roads, climbing ladders or using tools etc.) . As I've often said, it rather amuses me when people who smoke, drink large amounts of alcohol, or engage in 'hazardous sports/pursuits' etc. worry or fuss about these incredibly small theoretical risks!

 

[securespark]

Some common sense also helps. Having seen the evidence of this having been done (evidence of chases) on stripped walls, I usually assume that, although it would be very much non-compliant ('out of zones'), one should be aware of the possibility of a 'diagonal' cable route - for example, between a light switch and a wall light it operates, between an FCU and socket or between a cooker control unit and a 'non-aligned' output plate etc. etc

Don't know if it still exists in the 18th, but a solution for diagonally laid cables is to run them in earthed steel conduit.

 

[JohnW2]

Don't know if it still exists in the 18th, but a solution for diagonally laid cables is to run them in earthed steel conduit.

Sure, buried cables in earthed steel conduit (or even just cables with an earthed outer covering, like SWA, but also including non-'armoured' ones) are allowed to go via any path, in any direction(s).

The cables I was talking about were 'diagonal' ones with no such protection!

 

[333rocky333]

Plasterbox knockouts are usually angled and recessed , i assumed that was so the cable would always exit slightly lower or higher forcing horixontal cabling to be behind the box and in zone, subject to room behind the box

 

[JohnW2]

Plasterbox knockouts are usually angled and recessed , i assumed that was so the cable would always exit slightly lower or higher forcing horixontal cabling to be behind the box and in zone ....

Interesting thought but, having looked, I don't think it true of any I have here. In fact, it looks as if, unless there was a lot of space behind the box, it would not be possible to get a cable through the knockout and into the horizontal zone without an extremely tight bend in the cable - and it looks as if even that would be difficult. Do you know what make of box you're thinking of?

..... subject to room behind the box

... which, of course, is not something I had - which is also the reason that I was being daft to ask the question in the first place (since I should have immediately thought of using a metal box!)

 

[Harry Bloomfield]

it would not be possible to get a cable through the knockout and into the horizontal zone without an extremely tight bend in the cable - and it looks as if even that would be difficult.

True, if you bring the cable out at right-angles, to the top of the box - what is wrong with taking the cable out of a 20mm knockout, at an acute angle, thus avoiding the sharp 90 degree bend?

 

[JohnW2]

True, if you bring the cable out at right-angles, to the top of the box ....

Indeed

- what is wrong with taking the cable out of a 20mm knockout, at an acute angle, thus avoiding the sharp 90 degree bend?

Are you talking about a knockout on the back? On the backs of those I have here, some have a 20mm knockout and some have a square or rectangular knockout but many do not have any rear knockout. To do what you suggest would be the obvious way but, as we discussed way back, it wasn't something that I could have done because it requires space behind the box which I didn't have.

Anyway, once I had 'seen the light' (i.e. stopped being silly!) I avoided the issue by simply using a metal box!

 

[ebee]

I reckon the “zone of protection “ idea is based on some common sense originally.
Where would the ordinary “thinking” person reasonably expect to find cables buried without much protection, so they can make an informed decision before proceeding.
You can not cater for the unthinking uncaring person, they will blast away regardless anyway.
So we make a set of rules and ask everybody to have a decent understanding of those rules.
I can not pretend to be completely happy with all of those rules to the same degree.
My preferences are
1/ Verticals - I think this is the best one and probably best if most used.
2/ Horizontals - OK if obvious they might have been used ( Kitchens, example and a few other places where distances are small).
3/ corners - more likely a cupboard etc might have a fixing screw there so beware.
4/ top 6 inches of a wall - ok but fir the case of pinning a cornice whilst it’s cemment sets.
5/ buried greater than 2” - how many heavy (cupboards) use screws not exceeding 2”? Hmmm becoming a problem but wat lengths would be deemed reasonable.

That is pretty much a list of my pretences in order of merit before you start to think about “armour protection “.
And in all cases a 30mA RCD must (usually ) be strongly favoured too.

So a set of sensible rules providing we make those rules as widely known as possible seems to be a good start.
Edge towards making things as obvious as we can that something might be hidden and so might be avoided.

Anyone tried nailing a pin or drilling a tiny hole thru SWA without touching the armour or nailing thru one if those “safe plates” 3mm steel sheet with or without a nail gun?
Can be a bit worrying and if you put a sheet of steel over it then do that then do you Earth it?

 

[Harry Bloomfield]

Are you talking about a knockout on the back? On the backs of those I have here, some have a 20mm knockout and some have a square or rectangular knockout but many do not have any rear knockout. To do what you suggest would be the obvious way but, as we discussed way back, it wasn't something that I could have done because it requires space behind the box which I didn't have.

Nope, I meant out at an acute angle at the top, or bottom, of the dry lining box you had.

 

[JohnW2]

I reckon the “zone of protection “ idea is based on some common sense originally.

Indeed - but, as I've said, I think the same remains true today, not just "originally".

Where would the ordinary “thinking” person reasonably expect to find cables buried without much protection, so they can make an informed decision before proceeding.

Indeed.

However, and I imagine you understand, the only reason I asked the (seemingly pretty 'pedantic') question is that it is far from unusual to see people being criticised, here and elsewhere, for having cables that are very slightly outside of the defined 'zones' - and I'm not sure that really corresponds with 'common sense' - particularly in a stud wall, where it's usually difficult to be certain of exactly where a cable 'is'.

Kind Regards, John