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'.

 

[Ragnar_AT]

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!

I‘ve done quite a bit of electrical work in central Europe and have seen plenty of melted choc blocks and screw terminals but very few damaged spring connectors or terminals. One socket had two conductors in a terminal designed for one and on top of that it was a particularly poorly built socket. Another socket was badly melted but I really can’t tell whether that was a fault in the moulded plug (dishwasher), the socket contacts or the push-in terminals. That socket was fairly new, about two years, and had tested fine when I installed it.

Choc blocks do last if tightened properly but it is a lot easier to install them incorrectly than with spring connectors, which is why you find quite a few melted ones. By far the worst connection method I‘ve come across in building wiring was looping multiple solid wires around an M3 screw with nut and washers though, these splices are pretty much all loose. This method was very popular in Austria until the mid-1960s.

 

[ebee]

Looks like a few of us at least, are thinking pretty much along the same lines really.
I myself do not have a problem with Wagos etc on lighting circuits but my trepidation starts to creep in on power circuits really.
Yet logically I know that they have certainly been aware that they have been in use for quite a while now I did not actually realise how long but still those "what ifs" do not quite subside to almost nothing.
I might not be as logical as I think I am though and yes perhaps I should be a little more logical with comparisons.
I still favour tunnel terminals to cage clamps too.

 

[JohnW2]

I‘ve done quite a bit of electrical work in central Europe and have seen plenty of melted choc blocks and screw terminals but very few damaged spring connectors or terminals.

Are you suggesting that melted choc blocks and screw terminals are more common in central Europe in the UK? If so, why do you think that is?

One socket had two conductors in a terminal designed for one ..... Choc blocks do last if tightened properly but it is a lot easier to install them incorrectly than with spring connectors .....

I'#m not sure that is necessarily true. Even with my limited experience, I've seen a few cases of two conductors put into one terminal of a Wago (so similar to the incorrect use of choc blocks you mention) and I've no under how well spring connectors perform if that is done.

 

[JohnW2]

Looks like a few of us at least, are thinking pretty much along the same lines really.
I myself do not have a problem with Wagos etc on lighting circuits but my trepidation starts to creep in on power circuits really.
Yet logically I know that they have certainly been aware that they have been in use for quite a while now I did not actually realise how long but still those "what ifs" do not quite subside to almost nothing.

Like you, my 'intuition''/guts are inclined to favour screwed terminals, probably because that's what I was 'brought up on', but I accept that the 'facts' probably support the idea that spring terminals are at least as good, perhaps better.

 

[ebee]

Like you, my 'intuition''/guts are inclined to favour screwed terminals, probably because that's what I was 'brought up on', but I accept that the 'facts' probably support the idea that spring terminals are at least as good, perhaps better.

Yes you could well be right about that John.
Things we were brought up on tends to (in our minds) give them more credance.
We are capable of being biased no matter how hard we try not to be.

The ring final versus radial final might be one example.
A pressure spring connection versus a screwed terminal.
My own dislike of caged terminals versus screw terminals (enhanced by the "Wylex" lack of two screws - first on the N block and later on the L fuseways - and the dome tip anchor).
The E pull out defence in a Plugtop.
Some bias must be involved !!!

 

[SUNRAY]

Yes you could well be right about that John.
Things we were brought up on tends to (in our minds) give them more credance.
We are capable of being biased no matter how hard we try not to be.

The ring final versus radial final might be one example.
A pressure spring connection versus a screwed terminal.
My own dislike of caged terminals versus screw terminals (enhanced by the "Wylex" lack of two screws - first on the N block and later on the L fuseways - and the dome tip anchor).
The E pull out defence in a Plugtop.
Some bias must be involved !!!

Heh, wassa plugtop?

I'm going to say I recall 2 overheated wires in screw terminationed accessories (I'm convinced one was the switch contact itself rather than the terminal) in the last dozen or more years, Vs a handful or so overheated or otherwise failed spring type. However I'm convinced at least a couple of those were due to incorrect use (2 wires in a terminal, 10mm² wire). Although I have that statistic I haven't yet come up with a 'real hate' of them.
Equally I have mixed feelings about cage clamp Vs screw, especiallt where a terminal is expected to accomodate anything upto to 35mm².