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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.

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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?

  • Keep it simple first step back. You may not have a valve open or Hit a switch. Then maybe check the water ..We did it from the boiler but most were installed by us and boss always set it up for easy to work on. – user101687 May 25 at 22:30
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    Water real rusty ya maybe. clog couple of taps on pumps and pipe may help free up . feel if circulation pump gets hot makes noise – user101687 May 25 at 22:37
  • @RobertMoody Thanks, it worked before and I never closed any valve or disabled a switch. Tapping on pump is a good, simple idea. I'll try. – LBogaardt May 26 at 8:25
  • I tapped most pipes I could reach. I also drained all water and completely renewed the water. Some brown junk came out, but not much. The problem persists. – LBogaardt May 26 at 13:55
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    I do not know the layout you have..you may have pump not working.Check each one for heat and touch it... screw driver to ear worked for my dad and he kept hands on both sides of pump to feel any temp change in pipe. you may still have air in pipes. Shut zone valves down purge boiler. then work on one zone at a time sounds like air or pump. – user101687 May 26 at 19:26

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