I have a Bosch 30 HRC boiler. Yesterday, I added water to the system, increasing the pressure from 1 bar to just below 2 bar. I vented each radiator in the house to bleed the boiler.
When I open the hot water tap, the boiler switches on for a few seconds. The temperature on the display increases rapidly (from ~70°C to 99°C) and the pressure shoots up (from below 2 bar to 3+ bar). One time, I saw the E9 error on the display meaning the temperature limiter was activated. The boiler subsequently shuts off. I have no hot water.
I am assuming this is a circulation problem, potentially caused by rust or dirt in the pipes. Does that assumption make sense? What can I do, other than calling an expensive technician?
For example, would it make sense to completely renew the water in the pipes, by draining the radiators and then refilling them?