Build A NZ -UK Power Lead

[JohnW2]

In Germany Wago-style terminals became common on light switches in the 1970s and replaced screw terminals on sockets pretty much immediately as soon as the VDE allowed them in 1995. Wago 273/2273 connectors have been commonly used for at least as long. I‘d consider that decent long-term experience.

Fair enough. I was not aware of that, and it is, indeed, fairly reassuring. Whether there really is/was significant problem with (properly effected) screw terminals is perhaps a somewhat different matter!

 

[JohnW2]

It's a jolly good question. Perhaps the thinking is if something is not accessible for inspection, it will never be inspected, and that is true, but the reality is that most electrical installations practically never see a "thorough" inspection. With say a 10% sample inspection every 10 years, even if the sampling was random (which in reality I doubt it ever is) a substantial part of the installation would remain uninspected after a century.

Quite so. We're really only talking (at least, in the UK) about JBs and I personally very much doubt that anything like 10% of 'accessible' JBs get inspected in a high proportion of cases. Indeed, having observed quite a lot of inspections (PIRs/EICRs) being undertaken in my time, although a token number of accessory faceplates are not uncommonly removed, it seems far less common that an appreciable number (if any!) of JBs are inspected. Let's face it, electricians will often argue that joints that can theoretically be 'got at' through small holes in a ceiling are 'accessible' (hence don't need to be 'MF') I'm not sure that I've ever seen an 'inspector' to remove downlights to inspect the joints!

I have to feel that the reg about 'accessible joints' etc. must have been created by a group of people who had no real idea about the realities of electrical practices!

Or maybe the rules requiring joints to be accessible have just been copied from edition to edition without anyone ever really thinking about them.

Yes, very possible - as with many questionable things in BS7671 (and many other sorts of regulations)! As you imply, the requirement for joints (at least, screwed ones) to be accessible has been there for a long time, but the option to use ('spring-operated') 'MF' joints in inaccessible locations is a pretty recent development.

 

[plugwash]

The "MF" junction boxes thing is pretty new, but how long have the crimped, soldered, resin encapsulated etc options been there? I'm sure they have been there at least since the 16th but I don't know about before that.

 

[JohnW2]

The "MF" junction boxes thing is pretty new, but how long have the crimped, soldered, resin encapsulated etc options been there? I'm sure they have been there at least since the 16th but I don't know about before that.

Yes, that's what I meant. When I wrote "(at least, screwed ones)", I meant that it was really only screwed joints that had been required to be accessible for a very long time, since (at least as far back as my knowledge) it has 'always' been the case that virtually all other types of joint (crimped, welded, soldered, brazed etc. etc.) were allowed to be non-accessible.

Since they were not covered by anything else in that list of types of joint which were allowed to be non-accessible, I don't think that 'spring-based' joints (as in "MF" junction boxes) were allowed to be inaccessible until they (things to BS 5733) were explicitly added to the list, which I think (but am not sure) was probably in one of the Amendments to 'the 17th'.