Can any one tell me why my myson opollo fanfare s gas boiler has got 2 wires going into it?

Question

ive had a engineer in to change mid position valve but he could not wire it in he said the old valve (cant se what make it is) had 6 wires the new one (drayton mid position valve) has only got 5 he said that is ok but he cant understand why boiler has 2 wires to it he said i need an electrician to re wire whole system can any one tell me if this is realy needed.... i got the impression he didnt understand the electrics and just wanted to get away

Answer 1

this could be one wire from the power. and the other to a extention thermostat somewhere around the house