Here we go again, 6mm cable x 10kw shower x whack a 40A mcb in.

[old man sparky]

Just been to another one of those !!
Plumber replaces shower for upgraded version. 40A mcb replaces 32A. No problem mate !! that will work fine.
So 12 months later the owners girlfriend moves in with him.
So that poor old 6mm that was just starting to break a sweat for 12 months, suddenly ain't getting that quick 10 minutes and off cycle.
Nope its 10 minutes followed by 30 minutes to include washing those golden locks.
Over heated cable over heated shower switch. What's that funny burning smell ?
And that my friends is why 40A mcb's on 6mm cable cus now I have a much more powerful shower.
Is just pushing your luck a little to far, and one day the luck runs out.
Will they never learn ??

 

[Dustydazzler]

I guess it depends on how long the 6mm cable is and how it is run e.g clipped direct or fished under loft insulation.

JW did a vid showing how 2.5mm clipped can take about 60-65amps before it started sweating and a solid 70amps before it started smoking. This was only about a metre of cable clipped to a bit of mdf but it shows cable can take a lot more amps that the tabulated values depending on how its installed

 

[Soi disant]

I guess it depends on how long the 6mm cable is and how it is run e.g clipped direct or fished under loft insulation.

Yup - 47A for Method C.

So not necessarily wrong to use it for a 10kW shower. Unlike using a 40A OPD.

 

[Soi disant]

Over heated cable over heated shower switch. What's that funny burning smell ?

Maybe the smell was from the switch, occasioned by a poor connection?

Did you find damage to the cable anywhere except at the switch terminals?

 

[old man sparky]

Thermal damage showing at the mcb and isolator not down to loose connections. Shower actually rated at 10.5 kw. 6mm running 18 meters ref 101 for a good part of that. I'm not making excuses for a set up showing this kind of evidence. And after talking to the home owner about how and for how long the shower is usually used. This is clearly a case of pushing the limits and what happens when you do. Shower is all good its the cable size, the length of run, and the installation method that's causing the problems. Its a simple fix. Just needs to be done correctly. Its a classic all going fine until usage habits change. Then the weakness within the design will show, just like this has.
10mm install and you wont find yourself second guessing with depends on this depends on that ?

 

[telectrix]

with 10mm you'd need the click or the crabby 50A isolators. no way to get 10mm into the cheap shyte even with a decent hammer and exposing basic insulation above ceiling.

 

[old man sparky]

with 10mm you'd need the click or the crabby 50A isolators. no way to get 10mm into the cheap shyte even with a decent hammer and exposing basic insulation above ceiling.

About time the ruddy things were banned. Another case of manufacturers churning out the same crap from bygone days long after its use has become obsolete.

 

[DPG]

Was the 6mm cable definitely overheating? Or was it at the terminations in the switch etc?

 

[buzzlightyear]

Was the 6mm cable definitely overheating

more like old man sparky .lol.

 

[Pretty Mouth]

Was the 6mm cable definitely overheating? Or was it at the terminations in the switch etc?

I would bet good money it's loose connections. Otherwise the overheating would be apparent over the entire length of cable.