So are you saying the vessel was charged with 1.5 bar showing on the digital gauge with boiler empty?
That's right and that's why I queried it with them (father an son team of local, Vaillant registered plumbers).
They waited about 15 minutes with the gauges showing these settings, to see if the CH water cooling down would have an effect. They also allowed more water out. Neither had any affect on reducing the digital gauge which continued to show 1.5 bar.
No they didn't do any of this. I did list the 4 things that I've seen mentioned as reasons for the F.75 error:was the pressure sensor removed and checked/cleaned/replaced?
- Pump
- Expansion Vessel
- Pressure Sensor
- Filter
They were always of the opinion that it was an expansion vessel issue.
i would say analogue gauge would be correct due to gauge showing a pressure drop/rise on emptying/refilling (tube not blocked).
That contradicts what Vaillant technical support told me, but then they didn't really answer my question anyway, which seems to be a regular occurrence when I contact them (usually by email). The stock response is usually for me to get a plumber round - so what is the Homeowners Techincal Helpline for then?