Please help! Is this electric shower setup ok?

[tbe]

From the CU - RCBO (40A/30mA) - 11m of 6mm2 T&E cable going up inside the wall (i'm sure it's an uninsulated wall), into the loft and along to the isolator switch casing (the cable is not under the loft insulation). This cable was put in when the house was built. I bought a section of 10mm2 cable before checking the size that was already there. So is it ok to have 6mm2 going into the isolator switch and 10mm2 coming out of the isolator switch, going down between the wall and then into the rear of an 8.5kw electric shower.

Hope you can help, thanks.

 

[electronicsuk]

Assuming everything running up to the switch is up to scratch then there is no reason not to use a larger CSA cable between the DP isolator and shower.

 

[JohnD]

6mm cable has a capacity of 35Amps*, so you are overloading the existing cable. It all needs rerunning in 10mm, which will carry 47A*

*subject to installation method, in a wall, not in conduit inside the wall, no insulation, no bunching, no hot environments.

Your current shower takes about 37A (check manufacturer's documentation and voltage in your house) but no doubt you will buy a bigger one next time, and you say the RCBO is 40A

 

[ricicle]

6mm cable has a capacity of 35Amps*, so you are overloading the existing cable. It all needs rerunning in 10mm, which will carry 47A*

*subject to installation method, in a wall, not in conduit inside the wall, no insulation, no bunching, no hot environments.

6mm² has a CCC of 46A when clipped direct
10mm² 63A

 

[tbe]

Many thanks for the replies. If the 6mm cable is clipped to a wall in the loft and running free with no restrictions though wouldn't this mean that it would have a capacity of 47A?

Thanks.

 

[tbe]

Thanks ricicle. We cross posted.

 

[JohnD]

... 11m of 6mm2 T&E cable going up inside the wall ...

not clipped direct, then.

 

[tbe]

About 3m of it is behind the wall. The wall has like a cavity behind the CU (i can tell when i knock the wall) and the cable runs directly up to the loft in the space in the wall.

 

[ricicle]

... 11m of 6mm2 T&E cable going up inside the wall ...

not clipped direct, then.

Still Method 1 though, embedded in building materials?