UK Shower switches burning

[Bob Geldoff1234]

I have just been called out to another burning shower switch.Upon removal the wires had been burnt and chared.One thing I've noticed on all burnt shower switches is that the stranded wires haven't been twisted and just put in straight.I always twist the standed cables to make one solid conductor before inserting into the terminal.My thoughts are that the screw only clamps a few strands when they are straight,leaving the other stands either side of the screw.With the load on a shower I feel this is a weak point and hence why they burn out.Obviously it can also be caused by loose terminals but back in the day when shower switches had two screws per terminal,I don't recall having to replace that many switches.Prehaps they should bring back the two screw method?

 

[nicebutdim]

Has anyone worked out why it is more often the neutral rather than the line connection that fries?

That's a question I'd love to see answered with something better than speculation.

 

[Rockingit]

That's a question I'd love to see answered with something better than speculation.

The ‘theory’ that I’ve always heard touted around on this is that (think Fleming’s rules…) the direction of current in the neutral encourages the screws to loosen. My gut has always told me to claim BS on that whilst my head has always told me to find more facts either way…

 

[brianmoooore]

The ‘theory’ that I’ve always heard touted around on this is that (think Fleming’s rules…) the direction of current in the neutral encourages the screws to loosen. My gut has always told me to claim BS on that whilst my head has always told me to find more facts either way…

I think that the fact that the direction of current flow in the neutral is identical to that of the live, just 1/100th of a second later, rather disproves this theory.

 

[Taylortwocities]

I think that the fact that the direction of current flow in the neutral is identical to that of the live, just 1/100th of a second later, rather disproves this theory.

Indeed, Kirchhoff's Laws IIRC!

 

[mainline]

Has anyone worked out why it is more often the neutral rather than the line connection that fries?

Maybe because more attention is given to tightening the L conductor.

 

[nicebutdim]

Maybe because more attention is given to tightening the L conductor.

Do you think that really seems likely?

 

[Mikegh]

There doesn't seem to be any reason why it should happen

 

[mainline]

Do you think that really seems likely?

I think that some people take a bit more care with the L.

 

[nicebutdim]

I think that some people take a bit more care with the L.

I don't doubt that, but can't imagine it explaining such a high percentage of apparent issues on neutral side.

 

[mainline]

I don't doubt that, but can't imagine it explaining such a high percentage of apparent issues on neutral side.

Maybe reversing polarity on the shower circuit would stop it

 

[Mikegh]

That's a question I'd love to see answered with something better than speculation.

Doesn't seem any logical explanation. Contacts make simultaneously, give or take ? and current alternates

I'd expect one or two of the boffins round here to have stepped in if there was a viable theory

 

[7029 dave]

As @nicebutdim states when terminating cables into terminals they will relaxe after a minute so you need to revisit and nip them up a few times.

 

[oscar21]

As @nicebutdim states when terminating cables into terminals they will relaxe after a minute so you need to revisit and nip them up a few times.

Oh definitely, the amount of tails that I come across in consumer units barely nipped up is staggering, I always tighten them, wait a minute, give them a bit of a wiggle any you usually find you get another complete turn of the screw fairly easily.