A few other things have come to mind, if, which I think you have, a open vented system, you might check that there is no pump over through the vent above the F&E (feed and expansion) tank, on CP3 or higher, and also obviously that it contains water.
If you have a mid position diverter valve then the water can recirculate on pump overrun.
the default overrun time is 5 mins, you might reduce this to 2 /3 mins and the default anti cycling time is 20 mins, assume you have reduced this to something like 3 mins. The table below shows anti cycling times but afraid I can't interpret it, any ideas?.
A few other things have come to mind, if, which I think you have, a open vented system, you might check that there is no pump over through the vent above the F&E (feed and expansion) tank, on CP3 or higher, and also obviously that it contains water.
If you have a mid position diverter valve then the water can recirculate on pump overrun.
the default overrun time is 5 mins, you might reduce this to 2 /3 mins and the default anti cycling time is 20 mins, assume you have reduced this to something like 3 mins. The table below shows anti cycling times but afraid I can't interpret it, any ideas?.