There’s debate about exposed basic insulation in meter cupboards being satisfactory or not? Industry guidance (WRAG) say it’s satisfactory if the door’s in good shape, what’s people views on this ?
There’s debate about exposed basic insulation in meter cupboards being satisfactory or not? Industry guidance (WRAG) say it’s satisfactory if the door’s in good shape, what’s people views on this ?
Are you suggesting that SWA is being used for consumer's tails?
To extend tails from a switch-fuse, REC isolator, or Henley Block in the cabinet to a consumer unit, yes (cue discussion on what some DNOs/IDNOs permit and what others don't when "extending tails" ... and as I pointed out above, whether it's the correct solution in the first place)
We are, however, back to the point of "perceived risk"
Interesting subject ... but relevant here, I think ...
Exactly, and it is for the person installing the single insulated arrangement to assess that risk and to ensure that it is ALARP, irrespective of the semantics of 7671.
If I was assessing the risk, the use of single insulated cables in situations where ordinary folk have access, would fail to meet my ALARP threshold. I think I would be even more careful where the situation being considered was outside and contact with earth more likely.
Cast your vote and hopeful come the 4th edition this will no longer be permitted
I can advise this debate doesn't fit the timeline for Amendment 4. DPC comments closed in November 2024, and new work proposals were completed in advance of the DPC.
It would have to be part of a subsequent amendment ... but if the discussion in the industry never happens, we won't ever see any proposals.
I did try to advise earlier in the discussion, that the concept of preventing access to ordinary persons by limiting access only 'by the use of a key or [a] tool' is a concept that has a long history in electrotechnical standards for both products and installations ... a bit of background that's important to consider if we want to change these words in some standards.
(I put the [a] in brackets because, in BS 7671, the term appears with and without the second 'a', and both appear across electrical safety standards in English in general.)
How far back does this terminology go in the Wiring Regulations?
It first appears in the 15th Edition (1981) alongside the introduction of 'skilled person. and associated terms. 14th Edition used terms like "accessible only to authroised persons' and 'not accessible to unauthaurised persons' (before the terms 'ordinary', 'skilled' and 'instructed' were in use.
The terminology was also used in other electrical safety standards from earlier in time.
BS 3456-1:1969 Safety of household electrical appliances - Part 1: General requirements recognizes only a 'tool' rather than a 'key or tool' for gaining access to hazardous parts... but then again the same concept is present in it's current equivalent, BS EN IEC 60335-1:2023+A11:2023.
(The difference between an installation vs domestic appliances, is that installations aren't just domestic, and may have large items of switchgear and controlgear, for example, access to which is limited by key or tool ... hence the early use of the term 'key or tool' in BS 5486-1 Low-voltage switchgear and controlgear assemblies. Part 1: Specification for type-tested assemblies (general requirements) (the current modern equivalent being BS EN IEC 61439-1).
I have had the challenge of running swa in to meter cabinets a few times now. I have terminated in a switched fuse in a metallic enclosure, which creates it's own challenge. The metallic switched fuse enclosure is 3 or 4 times bigger than the plastic variety, I have had DNO engineers complain that it was in the meter cabinet, even though I had used a larger 3 phase cabinet to allow more space.
Bend radius is a major pain with SWA in any part of a domestic installation, only way in to the bottom of a meter cabinet is with the bend on the outside wall and then spacing the enclosure off the backboard or doing something else to get things in line.
I would code basic insulation exposed in a meter cabinet as a C3 if the door was in good condition and C2 if not. I don't know the solution but personally I think the industry needs to find a better way to extend supplies in domestic installations, especially retrofit.
I accept an extension from a "REC" isolator or Henley block as tails, but not a switch fuse.
In the case of a switch-fuse, is not the device DB1, and at the other end DB2 (probably the house's CU)?
That was what was installed here circa 1982. The SWA runs under what was originally the kitchen (suspended wooden floors) to the DB. All done properly!
If there were no switch-fuse, the cable would rely upon the DNO's fuse for fault protection. That does not seem quite correct, but if both fuses have the same rating, it is case of heads or tails which blows first. Happily, our fuses have remained intact for at least 29 years.
What other cables would be more suitable? Surly we could use H07RNF
SWA is usually used because it ends up running concealed somewhere (in a wall or under a floor) in such a way that if it wasn't armoured (or other means of having a concentric c.p.c.) it would need 30mA RCD protection - which obviously isn't desirable up front of an entire installation.Otherwise people could just use plain PVC/PVC sheathed single core 'meter tails'.
Personally I'd favour a version of SWA that had copper rather than steel for the c.p.c. (like DNO cables do) and then for termination into things that expect single cores, the ends are dressed with a (cold) shrink 3-way "trouser" boot -providing a sheath for the otherwise exposed cores and allowing much smaller bending radiuses (as individual cores are bent, rather than a complete multicore cable).
- Andy.
It would have to be part of a subsequent amendment ... but if the discussion in the industry never happens, we won't ever see any proposals.
I did try to advise earlier in the discussion, that the concept of preventing access to ordinary persons by limiting access only 'by the use of a key or [a] tool' is a concept that has a long history in electrotechnical standards for both products and installations ... a bit of background that's important to consider if we want to change these words in some standards.
My twopennethworth.... I don't think the intention is to prevent access by ordinary persons - after all access to keys is often driven considerations other than electrical safety (e.g. protecting property from theft or information from unauthorised access) and every Tom, Dick and Harry has a screwdriver. Rather, I suspect, the intention is to prevent accidental or unthinking access - along similar lines to access only being available after a 'deliberate action' we see elsewhere in the regs. If someone takes a screwdriver to an obviously electrical box, on their own head be it, it's more the innocent passers-by with not a clue of the dangers and weren't attempting to carry out any electrical work that deserve the protection.
So I think the problem arises when people expect to be able to open an enclosure and not expect an electrical hazard to result.
So I'd suggest that the 'by the use of a key or tool' bit is fine, but the general concept of an enclosure should be limited to a dedicated electrical enclosure - i.e. something that would only need to be opened to carry out electrical work on what it contains and for no other reason. So a socket or switch or joint box or CU would be fine. But something that people could genuinely expect to open for other purposes - a plumber opening a screwed down bath panel, or an ordinary person opening a meter box to take a meter reading, or a locked cupboard the caretaker also kept his brooms and cleaning materials in, or an entire building that happened to have a lock on every external door, would all be out.
There perhaps could be an alternative option of labelling, to draw attention to the electrical hazard, to cover any corner cases where an electrical enclosure also needs to be opened for other purposes and there's no interlocking or similar protection.
- Andy.
So I'd suggest that the 'by the use of a key or tool' bit is fine, but the general concept of an enclosure should be limited to a dedicated electrical enclosure - i.e. something that would only need to be opened to carry out electrical work on what it contains and for no other reason
This concept might be OK for private dwellings, but it is an issue for premises in which the Electricity at Work Regulations applies ... including, perhaps electrical laboratories and workshops.
Personally, I wouldn't object to such a rule for domestic installations, but it would make some provision of BS 7671 more complex.
I would further add, that there's nothing to stop any other enclosure using "meter box" or "lamp post key" in any type of installation ... and such keys are readily available.
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