Its ok, the Honeywell can cope with anything from 24v to 240v, besides the unit is battery powered all you are providing is the switch from the boiler output (Ls) to the boiler return (Lr). It doesn't use the boiler output to power and run the clock and all its functions, this is done by the batteries.
Just connect Ls to A and Lr to B
Hope this helps
Just connect Ls to A and Lr to B
Hope this helps