In article , Mike Tomlinson
writes
In article , fred writes

Mine is on an MCB only and I am perfectly happy with that, it's even one
of the early Dolphin ones with a direct and uninsulated heating element
in the water flow.

eeeek! That can't be right, can it? It sounds as if you're saying the
live element is immersed in the water?

:-D, I wondered if anyone would do a double take.

On the basis that a picture is worth a 100 . . .

http://i36.tinypic.com/34t95bc.jpg

V clever little design, transparent plastic case in two parts with a
central divider, keeping the two elements apart and forming a narrow
channel for the water to pass over the coiled resistance wire elements.
Unsurprisingly, the cold water enters on the blue flexible plastic pipe,
flows left along the bottom and returns to the right along the top
channel, exiting on the red.

The plastic inlet & outlet pipes are a good 50cm long so there's a good
long 'insulating' path through the water from live to the heavily earth
bonded metal in let & outlet fittings.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs