Burnt electic shower switch

[Tom JE]

Chaps,

I had a new electric shower refitted last year. The old shower was a 7.5kw Triton and i replaced it with a newer 7.5kw triton. The old 6mm cable was used but a new 45amp shower pull cord was fitted. The fuse box was updated at the time also. All work was carried out by a electrician and certified. Not so long back though the shower pull switch wouldnt turn off and upon inspection found that the "load" live terminal had burnt so badly it was practically gone. Nothing on the fuse box tripped and the shower 'seemed' fine. The electician came out and couldnt find anything wrong so replaced the pull switch. It seems ok now but am worried it'll happen again. Does anybody have any idea what could've caused this?

Cheers in advance

Tom

 

[rjb]

Could had been a poor termination in the pull cord. If the connection is poor ie not screwed in correctly then it increases resistance and generates heat.

 

[nashbharat]

I had the same problem and was told to check connections, when I fitted a new switch I double checked all the connections and 2 months later I had the same problem.
Not too sure what I am doing wrong ?

 

[Steve]

I had the same problem

Really? 6mm cable, 7.5kw shower, new switch old cable?

 

[JohnD]

When a copper cable overheats, the copper is softened by the heat.

Soft copper doesn't make a good joint, over time it flows away from the pressure of the clamping screw.

A poor joint leads to poor electrical connection

the poor electrical connection then overheats. The heat expansion and contraction make it increasingly loose, and the loose joint burns away from electricity passing through the poor connection.

So it happens again.

The cure is to cut back the heat-damaged wire and make a joint with new wire. If there is not enough slack then a new piece has to be permanently joined on using a crimp.

 

[andy2k7]

Your going on about loose connections but was size breaker is in the distribution board? Showers should be backed by an 30MA RCD!

 

[JohnD]

(if specified in the manufacturer's instructions)

And is that relevant to the presenting problem: ""load" live terminal had burnt so badly it was practically gone"

 

[andy2k7]

use a crimp for a 6mm cable?????

 

[JohnD]

Is that a question? Please explain what you're asking.

 

[andy2k7]

You cant crimp a 6mm cable!

 

[JohnD]

Shall we have a small wager? £25 says you can.

p.s. if you're offering good odds, you may get some other takers.

edited: to be precise, I should have said "£25 says I can." I have no knowledge of your abilities.

 

[andy2k7]

Well i thought a high rated Junction box would be safer?

 

[JohnD]

screw terminals are not as secure

A crimped joint is and permanent.

Can I have my £25 now please

 

[ColJack]

and the winner is johnD...

you can crimp ANY size cable with the right tools..

as it hapens, all insulated crimp tools come with 1.5, 2.5, and 6mm crimping holes..

yellow crimps are 4-6mm

blues are 2.5 and red is 1.0-1.5mm ( though smaller can be used if doubled over.. )

 

[andy2k7]

can you get junction boxes higher than 30amp to do the job other than crimp it?