I changed my fp715 with a fp720 and changed to back plates over. wired it up the same but i have no hot water. The red led lights up when the time it is set comes round but it doesnt show the tap symbol in the display. i changed to motorised valve with a new spare I have. wondering if its wired wrong or i havent got the settings correct? The system is an Trianco oil boiler with Megaflo water tank. 2 motorised valves and a mechanical thermostat