⚠ Safety note: This guide involves working with plumbing. If you're not completely sure about every step, stop and call a licensed professional. Before you start, always switch off the power at the breaker or close the main water/gas valve.
1 Prepare a safe work area
Turn off the system at the controls and wait for the pipes and housing to cool down. Note the temperature, pressure, and error code before changing settings.
⚠ Warning: Do not repair gas lines, electrical connections, the refrigeration circuit, or safety devices yourself. Only an authorized person should work on those parts.
2 Determine the exact symptom
Open the thermostatic valves, bleed the radiators, and check the cold-system pressure according to the boiler manual.
3 Check the most common cause
Heat up the system and note the order in which the radiators warm up. The ones closest to the boiler usually need less flow on the return valve.
4 Eliminate the cause without improvising
Mark the starting position and adjust the return valves in small steps, leaving enough time between measurements. Do not close them completely.
? Tip: Take a photo of the starting state and change only one thing at a time. That makes it easier to see what actually fixed the problem.
5 Reassemble and test safely
Put the settings back, switch the system on, and watch one full cycle. For gas smell, smoke, leaks, overheating, or a repeated error, switch the system off immediately and call an authorized service tech.