It is now some 2 weeks since I contacted the fitter and no response. I have contacted Worcester Bosch and they kindly provided the following information:
"A consistent discharge from the pressure relief pipe-work would indicate that the boiler is, or has been, regularly exceeding an internal pressure of 3 bar and thereby opening the valve to release excess water.
Incorrect pressures within the expansion vessel, the item re-pressurised with air using a foot pump, may cause issues with the system pressure when in operation. However we would not expect this from a new installation.
We would advise that ***** should investigate potential issues whereby water from the cold mains feed may be being introduced into the primary circulation within the boiler and causing a rise in pressure. This could include problems with the filling system, or a potential breach on the secondary plate heat exchanger."
What I would like to know is whether 3 months of high pressure is likely to cause any long-term damage to the boiler and what should I be asking the fitter to do. From previous postings the inhibitor needs to be topped up and pressure relief valve possibly replaced?