Junction box under floor

It's an interesting point. I wonder how Wagos would fare after 20 years? Would they suffer from vibration-induced metal fatigue, and their spring grip be lost? And as they aren't screwed down, would the terminal screws have become loose if subjected to the same treatment? In other words, if the screws had been in "flying" connector blocks, and so subject to little - if any - vibration, would those have become loose?

Out of interest, why do the wiring regs require junction boxes to be screwed down? They don't tend to move around with twin and earth cables in them, anyway. Why would you expect them to move under floorboards or in ceiling spaces?

Jeff I don't know about the wiring regs, but in my case the junction box was near the CH drain off points and although I can drain off most with a hose to get the last dregs out I have to let it flow out under the floor. The amount of water at that point is minimal and soon dries out but I did not want the junction box getting wet.

Richard

This does seem to happen for screwed connections whether in sockets or junction boxes. Maybe some sort of thermal ratchetting caused by temperature variations following current variations. Hence requirement for "accessibility".

Life of Wagos is certainly an interesting question but I assume the guys designing and certifying them think about this.

I had a sort of parallel interest in the lifetime of PVC and ABS pipework a few years ago. We had a failure of some 40 year old pipe in a nuclear power station. When it was introduced both for civil and industrial applications the life was estimated at around 40 years (there was an upper temperature limit). Quite a bit of the pipework had been replaced by stainless steel as a precautionary measure. Although this was a somewhat brittle failure (partly along the "spider lines" from the extrusion process) the pipework did not appear to be significantly more brittle than new, or younger, pipework. It certainly hadn't got anywhere near to the state where it snaps with bare hands, that you see in moulded thermoplastic storage boxes after a few years exposure to light.

Also in the "nuclear" field, trying to decide whether polymers (e.g. rubber O rings) will last for several hundred years (for waste storage) is quite tricky. What you can say, from archaeology, is that some organic materials containing polymers (like pitch and leather) retain their properties provided you can retain their moisture and natural oils while avoiding attack from insects and things microbial.

In my experience screwed terminals or connection blocks cause most of the faults in wiring which has been in for some years. I think the copper actually relaxes and hence the screw seems loose, assuming of course there is no nasty corrosive environment around them. Only a few months ago I had to tighten screws in a 13A socket that was getting warm. Brian