Am trying to replace a damaged thermostat control unit with a new Honeywell T6360 thermostat I am having a problem with the wiring in the sense that I have 4wires that where used on the old thermostat as follows Red=Live Blue=nautral yel/green= Earth and this other wire that is yellow i have no idea where to connect on the honeywell thermostat on the old thermostat it was connected to earth..... Ant help very much appreciated