The new Vaillant eco TEK boiler I am fitting during the xmas holiday has pump over-run control from the boiler. The system has three zone control valves and a few rad's with TRV's directly connected to the F & R.
There will be occasions when the pump will be activated by the boiler and there is no path for the water so the first job is fitting a Comap 22mm differential bypass directly between F & R.
The unit is adjustable between 0.1 and 0.5 bar. My problem is that it is not obvious what setting to use. There is no external indication when the thing operates.
Does anyone have advice on how to determine the correct setting? My guess is to keep increasing the pressure until it shuts under normal conditions. Hopefully it will be possible to detect a flow through the valve by temperature change.
Finally, it seems obvious to me that a better solution would be to have the boiler open one of the zone control valves when pump over-run is required. I can see how to do this with relays but is there a more elegant solution?
Merry xmas
Brian