suspended cable to Detached garage

[JohnW2]

I can only agree with all of this. The emboldened is actually an 'old chestnut' of mine too (and why none of mine at home have been changed to metal) ....

Glad you agree. Indeed, even if one didn't (agree), the present regulation, as written, seems totally daft, since it contains no requirement for fire 'containment' - provided only that what material is left is 'non-combustible', the front, sides and bottom of the enclosure can be covered in ~12mm diameter holes and remain 'compliant'!

but regardless I have to keep up with the times/fashion ...

That's up to you - but, as for me, if I stick with plastic CUs because my personal view is that metal CUs would not appreciably protect me from fire, but may expose me to increased risk of electric shock, it doesn't seem particularly 'right' that I should have less concern for the safety of tenants (if there were any) than myself.

and who knows what's going to happen in 10 yeaars when there have been too many metal box electrocutions?

Good question. As I've been saying from the start, I'm sure that it is "only a matter of time" (if it hasn't happened already before some such tragedies occur, and the LFB will seemingly have that on their conscience!

As for "what's going to happen", goodness only knows - quite probably 'nothing', I suppose. The present reg does not, of course, explicitly require metal, so it would not be impossible to change the requirement to "non-combustible (if they must! ) AND non-conductive".

Kind Regards, John

 

[JohnW2]

metal consumer units but with two layers of insulating material bonded to the metal

Even then there would probably have to be fairly complicated requirements in relation to conductive fasteners, glands etc. which passed though all the layers.

I know what I personally believe would be the best thing to do with/about this particular regulation

Kind Regards, John

 

[SimonH2]

I know what I personally believe would be the best thing to do with/about this particular regulation

And I suspect that pretty well all of us agree with that Might mean some committee members having to visit a proctologist

The present reg does not, of course, explicitly require metal, so it would not be impossible to change the requirement to "non-combustible (if they must! ) AND non-conductive".

We've been here before of course. As written, the reg does require ferrous metal as no other material would comply (even concrete is combustible in the right environment). Adding a "and non-conductive" clause would make the reg impossible to comply with.
The simple fix would be to define what they mean by non-combustible - as in "non-combustible means complies with clause foo of standard bar". Then it could be any material as long as the manufacturer can get it through the tests needed for clause foo of standard bar.

 

[JohnW2]

And I suspect that pretty well all of us agree with that Might mean some committee members having to visit a proctologist

Quite so. I never cease to be amazed/surprised (as well as disappointed and 'disillusioned') by the fact that a committee as large as JPEL/64, having the members which it has, should have succumbed to LFB's demands - even if (as is widely suggested) those 'demands came with 'threats' (of legislation).

Mind you, the same committee is moving progressively closer to 'requiring' SPDs, which is not even a 'safety issue' in the normal sense - so my disillusionment persists!

We've been here before of course. As written, the reg does require ferrous metal as no other material would comply (even concrete is combustible in the right environment). Adding a "and non-conductive" clause would make the reg impossible to comply with.
The simple fix would be to define what they mean by non-combustible - as in "non-combustible means complies with clause foo of standard bar". Then it could be any material as long as the manufacturer can get it through the tests needed for clause foo of standard bar.

As you say, the problem would largely go away (even though the reg might well still be 'unneceesary') if they defined the required material in some fashion such as you suggest - since that would very probably then encompass a good few non-conductive materials.

However, I'm not totally sure that you're right in saying that the present reg, as written, does require ferrous metal. They have specified an 'impossible' requirement, but then go on to 'deem' one material to satisfy that (impossible) requirement - so I'm not sure that necessary precludes others also doing some 'deeming'

It's actually very hard (at least for me) to understand why they wrote it as they did. If their intent was to say that it had to be ferrous metal, then they could simply have written that. The fact that they didn't seems (at least to me) to suggest that they deliberately wanted to leave some 'flexibility'.

Kind Regards, John

 

[SUNRAY]

Mind you, the same committee is moving progressively closer to 'requiring' SPDs, which is not even a 'safety issue' in the normal sense - so my disillusionment persists!

Kind Regards, John

The saddest thing about SPD's, and especially the way they are installed, is they are about as usefull as a chocolate tea pot.

 

[JohnW2]

The saddest thing about SPD's, and especially the way they are installed, is they are about as usefull as a chocolate tea pot.

Situations and experiences will obviously vary but, speaking for myself, they certainly appear (no matter how they are installed) solutions to a problem which I really don't think I have!

It's interesting to see how some people's thinking does U-turns. At least some of those who were, not too long ago, ridiculing (or worse), and describing as 'snake oil', anything to do with 'surge suppression' now seem to be advocating SPDs. ... and I don't think their rationalisation of the change of heart hold much water - speaking personally, I really don't think I now have any more ((allegedly) 'surge-susceptible' items of equipment in my home than when 'surge supression' was widely regarded as snake oil!

Kind Regards, John

 

[bernardgreen]

SPD = Spike Prevention Device is possible as most spikes are transients without much energy.

SPD = Surge Prevention Device is possible but how much surge energy can be absorbed by a few cubic inches of electronics snake oil

 

[JohnW2]

SPD = Spike Prevention Device is possible as most spikes are transients without much energy.
SPD = Surge Prevention Device is possible but how much surge energy can be absorbed by a few cubic inches of electronics snake oil

My personal view is the same regardless of the "S"

Furthermore, as I understand it the "SPDs" we're talking about are merely attempts at 'voltage limitation'. At least in theory, transients with very fast rise times can damage electronic equipment even if their peak magnitude is not very high - and the devices we're talking about can do nothing about them - only some sort of filter could even attempt to address that.

Kind Regards, John

 

[SimonH2]

However, I'm not totally sure that you're right in saying that the present reg, as written, does require ferrous metal.

Really ?

They have specified an 'impossible' requirement

Exactly, it's impossible to comply - even steel doesn't comply (lookup oxygen lance) except for ...

, but then go on to 'deem' one material to satisfy that (impossible) requirement

And that is the only way steel complies - because they added a note saying it does.

- so I'm not sure that necessary precludes others also doing some 'deeming'

But how ? Put some nominally non-combustible material through as many certification tests as you like. Stick it in the right conditions (oxygen rich is usually good) and I'm sure someone can show it combusts and so is not "non-combustible".

It's actually very hard (at least for me) to understand why they wrote it as they did.

I agree - it's a phenomenally bad bit of text and you have to wonder how it got past a committee of supposedly prefession people.

 

[JohnW2]

But how ? Put some nominally non-combustible material through as many certification tests as you like. Stick it in the right conditions (oxygen rich is usually good) and I'm sure someone can show it combusts and so is not "non-combustible".

If a regulation imposes an impossible requirement then there are only two options. Firstly, one can simply ignore it, on the grounds that it is impossible to comply (I seem to recall that being BAS';s suggestion). Secondly, everyone (both writers and readers) have to make some judgement as to what would be reasonable in terms of the presumed spirit/intent of the (impossible) requirement.

The authors of BS7671 have done that, by saying that they 'deem' ferrous metal to comply, but they don't say that nothing else could. I would therefore suggest that other readers could equally do the same.

I agree - it's a phenomenally bad bit of text and you have to wonder how it got past a committee of supposedly prefession people.

Indeed. However, as I said, it's not only 'phenomenally bad text' and clearly ridiculous, it's also more complicated (for them) than it could have been had they wanted to insist on ferrous metal. It would have been simpler for them to just insist on ferrous metal but, as I said, the fact that they didn't seems to me to imply that they were intending some flexibility. The fact that they didn't include any requirement for 'fire containment' merely strengthens my view that they just didn't think this through!

I would imagine that there must be some non-metal materials which would be sufficiently resistant to fire for the purpose, maybe even to the satisfaction of LFB, so they could perhaps modify their Note to say something like:

"Examples of acceptable materials include ferrous metals and XYZ"

Kind Regards, John

 

[plugwash]

I can't help but feel that both the metal consumer units reg and the recent practice of adopting torque screwdrivers, are papering over a generally poor design. Devices that have a standard size and shape, but not a standard busbar arragenement, leading to half-assed assemblies that mostly work when someone uses a different brand (or sometimes even a different generation of product from the same brand). Screw terminals onto busbars that leave no good way of verifying that the terminal is actually gripping the busbar tightly rather than missing the terminal or bound-up on a thread imprefaction. Large flat surfaces that require the use of materials with high impact resistance.

 

[SimonH2]

I can't help but feel that both the metal consumer units reg and the recent practice of adopting torque screwdrivers, are papering over a generally poor design.

Surely you're not suggesting design & manufacturing quality have gone down over the years

 

[billm]

I've now disconnected the aerial cable that was crossing from the house to the garage, it was 2 x 1mm t&e wired off the lighting circuit so it was inappropriate for the job. Presumably done by the house builder to provide lighting only in the garage. And now it's disconnected the property is compliant per the Certificate.

I asked an electrical wholesale shop what cable is best to use so I can have a socket & lights in the garage and he suggested either a) a 2.5mm t&e Rubber cable (photo attached) which looks like a larger version of a flex cable as it won't deteriorate in the sun or b) what looked like an armoured cable but with a silver / translucent outer sheath, again in 2.5mm.

I'm still going to use the tensioned wire to support the span to avoid digging up the patio and I assume the armoured cable he showed me will be the better choice ?

If I terminate it at either end in a Jcn box inside each building there's no need for glands etc. Then run normal 2.5mm t&e from the attic jcn box to a fused outlet or a socket fed from the ring main and at the garage end run normal 2.5mm t&e from its jcn box to a double socket and a fused spur to the 2 garage lights.

Nice & simple, no need for a garage CU and can be unplugged / isolated in the attic if ever I need to.

Does that sound ok ?
thanks

 

[JohnW2]

I can't help but feel that both the metal consumer units reg and the recent practice of adopting torque screwdrivers, are papering over a generally poor design.

Quite. It's not the enclosures that cause fires, but what is going on inside them, and it's rather odd to have a regulation which may (perhaps!) sometimes reduce the impact of such a fire (but not be required to 'contain' it!!) but which does nothing to address the reason why the fire started in the first place.

How would people feel if mobile phones had a habit of 'bursting into flames' and the official response was (only) to 'requite' them to always be kept within fire-resistant enclosures?

Kind Regards, John

 

[mattylad]

That cable "what looked like an armoured cable but with a silver / translucent outer sheath" sounds like SY cable and should NOT be used outside as it is generally not suitable for the UV (although some brands are) - I would not use it.

For the length you want why not go full SWA?