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.
We're about to take you to the IET registration website. Don't worry though, you'll be sent straight back to the community after completing the registration.
Continue to the IET registration site
