There can be two faults with the tp5000si output. Remember it is just a switch, so even if faulty it will be either 'on' or 'off'. However, because the thermostat would be receiving its electrical supply from the programmer, even if the tp5000si were faulty it wouldn't result in....
Because there wouldn't be any power going to the tp5000si for it to switch in the first place.
Is it possible something else was causing the boiler to fire? do you have a frost thermostat somewhere for example?
I even went to the separate CH & HW programmer and switched the CH off from there but the boiler kept on running and wouldn't switch off!...
Because there wouldn't be any power going to the tp5000si for it to switch in the first place.
Is it possible something else was causing the boiler to fire? do you have a frost thermostat somewhere for example?