Local plumber turned up to remove my old electric shower and supply and fit a replacement. The plumber replaced my 7KW shower with a 10.5KW shower. I was worried that the new shower was too powerful for the existing 6mm supply cable, the plumber assured me it was safe to use. I employed my own electrical contractor to inspect the work carried out by ERG, his report condemned the installation as unsafe. Raised a complaint with ERG and went through their complaints procedure. I asked for a full refund which they rejected saying the engineer they sent had stated the work was carried out to industry standards. I have employed an electrician to remove the shower ERG installed and replace it with the correct 7KW shower that complies with the 18th edition of the wiring regs. These people are cowboys steer clear at all cost. I am now pursuing a full refund through my credit card company.