Potteron Promax 24HE boileer - running constantly

[geffers54]

Potteron Promax 24HE boileer - running constantly
The bolier and circulation pump running constantly with the controller demand for CH and HW both off.
There is a minimum heat flow circuit (2 radiators) being heated constantly. The only way to switch off is switch off supply to controller and boiler.
All diverter valves opertae from the timer control and room thermostats in correct order.
Whta is the reason for the demand to start and run constantly?

 

[45yearsagasman]

One of the end switches in the zone valves is remaining closed even when the system is off at the programmer. A simple test with a multimeter will find the culprit. If you have standard S plan wiring, then one of the orange wires from the zone valve will still be powered up.