just moved into my new flat and would like to know; if the electrical feed from the control box should be connected to both emmersions or just one wired into the off peak?
cos the emmersions on my boiler are both wired up to the printed circuit board but the supply fed cable is only connected to the off peak. so the top emmersion is redundant.

tim stelling, December 2008

Bottom I/H = OFF PEAK. Top I/H is auxililary, this is operated by an independent control, fixed on wall. It will have three options: half hour, one hour, two hours.
You will never use it, unless you turn off boiler when you are going away. Never do this, it is false economy.

Ivor Molegrip, January 2009