Fitting a 10.8kw shower on 6mm cable

[thompsonbrown]

here is a good example of why showers over 8.5kw
should be fitted with 10mm cable.

If you look at the live feed it has melted onto the live load.
Customer informed me when installed it used to trip out.
So plumber changed breaker for 60amp.
Its all too easy when fitting a new shower to think its a straight swap.
For your own benefit if your not sure, get someone who is.

 

[Best]

Bad connections (usually loose wire) will also do that, - even if the cable is correct size for shower kw.
Tip for fitting a switch, pull cord or wall type, is to make sure the cables are cut exact length allowing them to be in the correct shape & after tightening them nice & tight, push the switch into place. Remove it back out a little & retighten the screws as they often will slacken slightly. Proof of this is, - why do the cables melt usually only at the switch & not inside the shower (unless a botched wired connection)? Has to be poor wiring at the switch normally, or sometimes a faulty switch. Many switches I see are badly wired, including those done by sparks.
A bit controversial, but 6mm cable can do slightly more than 8.5kw if fitted correctly & not too long. That's what a lot of electrical guys tell me. Also some shower manufacturers say same.

 

[thompsonbrown]

Bad connections (usually loose wire) will also do that, - even if the cable is correct size for shower kw.
Tip for fitting a switch, pull cord or wall type, is to make sure the cables are cut exact length allowing them to be in the correct shape & after tightening them nice & tight, push the switch into place. Remove it back out a little & retighten the screws as they often will slacken slightly. Proof of this is, - why do the cables melt usually only at the switch & not inside the shower (unless a botched wired connection)? Has to be poor wiring at the switch normally, or sometimes a faulty switch. Many switches I see are badly wired, including those done by sparks.
A bit controversial, but 6mm cable can do slightly more than 8.5kw if fitted correctly & not too long. That's what a lot of electrical guys tell me. Also some shower manufacturers say same.

Tecnically your right, a 6mm cable will take 38amp which would supply a 9kw shower.
A lot of electricans calculate there own values using BS7671
but shower manufactures are not allowed to give cable sizing. Due to part p feb 2005
But unless you know how the cable was installed.
eg, Installed in conduit or clipped and plastered in walls.
peak load of appliance, cable length, thermal heat loss etc.
Its not worth running a cable at its max current.
This thread was aimed more at plumbers than electricians.
and is not used to question your electrical ability.

 

[AWheating]

the plumber who changed the protective device was an idiot. I agree with best, you tend to find high resistance joint causing the main issue in the switch.

All tradesmen need to understand there limitations including in there own trade.