Hello, i am replacing an old drayton room thermostat rts1 for a sunvic 7501s model. there are 4 wires going into the old one, a blue one going into N, a red one going into L, a yellow one with a bit of red tape around it going into 3, and a yellow and green one going to a symbol with a vertical line and two horizontal lines underneath, earth i presume. The sunvic only has three connections, which wire goes where? any help much appreciated.