Can i connect a 10mm cable to a 6mm cable.

[John-paul harkin]

Hello 

It is the cable running from the shower to the shower pull switch. I was smelt a burning smell today and when i opened up the cable was all burnt. It is a 9.5 kw shower. The cable that goes to the switch to the fuse box is 6mm too but that looks fine. Should i buy a 10mm cable or 6mm cable. Can i use a 10mm cable to the switch to the shower when the cable to the switch to the fuse box is only 6mm. Help please

 

[Andy™]

yes. but if the cable was all burnt throughout then there is a serious problem that needs looked at. if its just at the connections (more likely) then not such as issue once the damage is cut out / replaced

 

[ProDave]

Assuming the issue was at the switch, then as a matter of course replace the switch with a new one.  Loose connections or a faulty switch was probably the issue.

 

[John-paul harkin]

The switch was only replaced 2 months ago and it looks fine. The cable running from the switch to the shower was burnt especially the red wire. I bought another 6mm cable there now and i will try that to see if that works. I could have bought the 10mm cable but didn't want to use two different sizes of cable in the same circuit 

 

[Evans Electric]

As Dave  said ,    replace the switch  .   Was the burnt / discoloured  red  at the switch  terminal ?    It will probably have damage inside it . 

Those terminals need to be screwed down  tight  .

As Andy said ,   if the damage is all at the switch and you can cut it out  , back to good cable  then just do that .  There could be enough spare cable at the switch  to do that .   

Is the  6.00mm cable  covered in insulation  , presuming its in the loft ,   or is it lying free  , uncovered ?         Your shower takes just under 40A    which means it  needs to be lying  uncovered  by any insulation . 

 

[OnOff]

If the cable is covered by insulation than you basically HALVE its current carrying capacity. Even if it's covered up for just half a meter. It'll get very hot and floppy under such load...or worse.



How long btw is the cable run roughly?

 

[Doc Hudson]

The switch was only replaced 2 months ago and it looks fine. The cable running from the switch to the shower was burnt especially the red wire. I bought another 6mm cable there now and i will try that to see if that works. I could have bought the 10mm cable but didn't want to use two different sizes of cable in the same circuit 

'Looks fine' & 'Try that to see if it works' = Untested, unproven, could be dangerous, could burn your house down in my opinion.  Any situation like this where something has overheated to point of damaging part of the wiring then it is clear that either (a) it was designed incorrectly or (b) it was installed incorrectly.  A correctly designed and installed circuit with its associated switches will NOT give the symptoms you described.  Replacing a badly installed component with another badly installed component will give the same symptoms, possibly within a short period such as months that you mention. It is just as probably that the recently replaced switch is the cause of the over heating if installed incorrectly, or if a cheap square body switch was used. I would suggest getting the whole circuit retested fully in accordance with the specifications required in BS7671 wiring regulations, to prove every aspect is electrically safe. Get it wrong and it could burn your house down.  Please be aware that electricity always generates heat as it flows around a circuit, higher power devices (such as showers) generate more heat, as do bad joints. I am not aware of any methods of confirming compliance with BS7671 wiring regulations that can be done by purely using visual inspection alone. Correct test meters and measurements are needed. 

Doc H.

 

[binky]

cheap modern shower switches are rubbish! Single small screw terminals just about big enough to take 6mm just aren't good enough imho.

 

[Evans Electric]

Its certainly true for 10mm  Binky  .      Still the best on sale today is the big   Crabtree  50A  jobby ...the one that straddles a ceiling  joist .   Like a Dalek .