Good evening to all. I am trying to replace my old Drayton electro mechanical dial stat with a new digital programmable Philex stat but making little headway. The old stat had 5 connections as in the diag. The new stat only requires two connections. I have tried connecting yellow and each red wire in turn but the boiler is dead. The stat itself seems to be operating ok in that it monitors the room temp and tries to call for heat using it's own batteries. I'm wondering if I need to join the two reds together before connecting and then connect yellow ?? There seems to be two seperate cables feeding the old unit. One cable has blue yellow red wires plus earth the other cable has red and black wires plus earth. All help most gratefully received.