Pics showing the wiring at the boiler end. This works perfectly for your vaillant boiler Eco Tech Pro 28. The pic shows the wiring to the 24v side of the PCB. Note the blue block “boiler off” has a loop (red wire) Leave this in. If you are having issues with the thermostat check the thermostat...
Hi Anton, judging by the pic of the board you have. It’s the same board as explained by Stem. The wiring explained as above. Assuming the receiver you are fitting is single channel these are the wiring pics from your mains feed and wiring from the boiler to receiver. The cable with the red mark...