I am trying to fit a Sunvic Programmable thermostat (wireless verison TLX RFP) to an Ariston Eurocombi.

The stat has Live, Neutral and Output.
The combi has a 3x2 block with red and black on one and three boilerside. On the other side of the block one and two are looped together, as are two and three.

I can't figure it out. Any idea how to sort this? The only way I have found which works is to remove the two loops in the bolier block, power the stat from the mains and connect its "output" cable to the red. This can't be right?

Thanks for any help.