Loose connection?

[reb78]

Pic below is the iaolator for the shower supply. Its an 8.5 kW shower so nothing too silly. I noticed some browning on the outside of the casing so switched the MCB off to it until I got a new isolator. Went to fit it today and uncovered the burnt mess on the neutral wire. It could fairly easily be pulled out of the connector and the screw was pretty loose. Is that what caused it? And how do presumably tight screws (i didnt fit it) loosen on something where there is no movement?!

Will have to trim this back obviously but this really wasnt far from melting the live sheath it was tight up against.

 

[sparkysy]

Thats a pretty standard problem with shower isolators!
The ones with two terminal screws are much better.

There was too much cable in that box, as it was pushed back up originally it could have wiggled the strands around and loosened them in the terminals.
When doing them keep them as neat as possible so that when you push the switch back up to the box you don't have to force it to go back in.
Nip the terminals up tight and check that the cable has deformed slightly to the terminal shape.
Once you are ready to fit it onto the box give it one last nip to make sure it's stayed tight!

Also thermal cycling will help loosen any screw type electrical connections as the cable expands and contracts, especially on high kw using equipment. That and 50 cycles per second!

 

[reb78]

Thanks for that.

Can you point me to a decent two screw switxh so I change for a better isolator (the one I have is also only single screw? (Preferably one in screwfix!)

What would have happened when (i dont think its just if) that neutral melted through to the live??

 

[Robotstar5]

The "frying fish" smell sometimes gives it away

 

[Onoff]

Crabtree were always the go to shower switch.

 

[brightspark]

remake the cable off and when stripped back twist the cores so they dont splay out when screwed up .line the wires up going in to the box with the terminal screws without twisting them round to get them in the switch should just push back if there all in line. i use click mode switches because they have large screws and fitted properly never had one burn out even on the 10kw showers . there 50 amp

 

[Robotstar5]

I'm using a Crabtree 50A pullcord, can't remember how many screws it has, but seems to be working OK.

 

[reb78]

remake the cable off and when stripped back twist the cores so they dont splay out when screwed up .line the wires up going in to the box with the terminal screws without twisting them round to get them in the switch should just push back if there all in line

Thanks. I will. Will have to wait till tomorrow now as i need to go in the loft to feed a little more cable down. I cant figure why whoever fitted it didnt do what you ay in the first place. Looks like thick cable that isnt easy to bend!

 

[sparkysy]

Crabtree 50A Pull Switch

www.toolstation.com

I'm sure these are twin terminal!

If it did melt through the insulation then the protective device in the fuseboard/consumer unit should operate and isolate the circuit.
How modern is your consumer unit?
A 'hard fault' like that would clear pretty quickly!

 

[brightspark]

sometimes i get customers buying there own poxy crap switches i just say bin em and il fit the ones i supply and il guarantee the job and switch for a few years but wont fit theres at any cost

 

[sparkysy]

I tend to like customers getting their own carp switches and sockets!
At least that way I get paid again to go back and swap it when it breaks and as many times as it breaks!!

 

[brightspark]

I tend to like customers getting their own carp switches and sockets!
At least that way I get paid again to go back and swap it when it breaks and as many times as it breaks!!

shower switches are a pain in the a.rse even if done properly dont want to ever go back

 

[sparkysy]

shower switches are a pain in the a.rse even if done properly dont want to ever go back

That is very true!
I'm lucky as I don't do that much domestic work any more, and every time I do, it reminds me why I don't do it!!

 

[brightspark]

That is very true!
I'm lucky as I don't do that much domestic work any more, and every time I do, it reminds me why I don't do it!!

i do a fair few that others have cocked up

 

[sparkysy]

i do a fair few that others have cocked up

I used to do loads for local authorities, bathroom upgrades and call outs ect. Used to drive me crazy!
Some of those were fitted by other sparks.
Most cases I have been called to seem to be the neutral that has suffered.

 

[Welderpaul]

Fit a rotary isolator on the ceiling

 

[Erie Fred]

Maybe these should come with a smoke bomb taped to it, so when the connection overheats.....

 

[Blobber]

Mad idea isnt it, pulling 30-40 amp through a pull cord switch and trying to stuff 2 10mm t+e cables in a back box and then mount them in a damp room, its never going to end well

 

[reb78]

Mad idea isnt it, pulling 30-40 amp through a pull cord switch and trying to stuff 2 10mm t+e cables in a back box and then mount them in a damp room, its never going to end well

Long term plan is to ditch the leccy shower in here. Now the rayburn is fitted we have plentiful hot water at mains pressure all winter. The thermal store has connections for water solar and immersions so plan is to fit solar of some sort for plentiful summer hot water. So... upshot is we want a nice shower that uses that, not an electric one that pees tepid water in the winter and uses lots of electric!

 

[dobbslc]

shower switches are a pain in the a.rse even if done properly dont want to ever go back

Same here! You have too get the cables just right before pushing them back up, I then gently pull it down again a d nip up the screws one last time.
I have two 3 bar shower pumps here running off the oil boiler, no messing with crappy electric jobs, it would cost me a fortune with my family!