I have just moved into a house thats fitted with a Greenstar 25Si central heating boiler thats about 5 years old. I'd like to fit a frost stat because I'm away for weeks at a time and like to bring the heating on automatically when the temperatures tumble. The diagram for the boiler shows a very simple 2 connection circuit, ha ha thats easy I thought so went out and bought a Tower RFS Frost Stat from my local supplier. But when I opened it up, it has a small circuit and seems to need both live and neutral. T1 is live, T3 and T4 are nuetral connections. T3 shows an M inside a circle. T3 and T4 has a neon lamp across them. Have I bought the wrong stat, or can I still use it ? Advice on how to wire it will be greatly appreciated.