S.07 is the pump overrun time, default setting (D.01) 5 mins. S.08 is Temporary shutdown after heating procedure. Not sure if this is the anti cycle time (D.02), default setting 20 mins but the actual anti cycle time then depends on the heating target temperature, if the target temperature is 70C then the anti cycling time is 2.5 minutes with the 20 min default setting.Thanks. I'm not sure what the 24v link is I'm afraid. There is a wee junction box floating around underneath the boiler. Is that it?
I was not standing next to them while they were working but I did notice at some stage they had opened up the pump in order to remove air. That led to some water spillage.
Just now I switched on the hot water at the timer. This appeared to make the boiler more reluctant to fire which I did not expect. The boiler now seemed to be shedding heat through the pipe to the hot water tank but with the boiler off.
CH man said he would replace the automatic air valve on top of the boiler tomorrow, and generally do some diagnostic pondering. I can see his point in that, as they did not do anything other than replace radiatiors, and then struggle with air, some trapped air may be gumming up the works. Why that would make the boiler get stuck in this S7 - S8 - S7 loop, and keep the water hot in the bypass loop I even though heat is not asked for I find mysterious.
Reasons for above?: normal behaviour after heating or DHW period. If the boiler reaches its target temperature +5C for whatever reason, boiler minimum output > heating demand, or, perhaps in this case, mot.valves shut but boiler firing due to faulty end switch, or maybe this 24V link left in.
Apart from the above problem I hope the engineers havn't changed the pump settings causing this pump over into the (feed and expansion) tank as these systems can be very sensitive to the pump settings.
Hopefully, tomorrow will bring some answers.