Electric shower--has the plumber pulled one over on me?

[Kingfisher3]

I guess it will cause the cable to over heat. I always play safe because I don't like electric. If it's a short run then change the cable for 10mm.
Better safe than sorry. But that said it won't be you switch it on and it burst into flames.

 

[Agile]

Cable ratings depends on how easily the heat is disapated.

Whatever you do dont cover the cable with insulation like clothes or anything else that will reduce the heat loss.

Tony

 

[ColJack]

what size breaker feeds the shower already?
and what size cable?