What Pressure Should My Boiler Be? (Cold vs. Hot) When cold and idle, a sealed central heating system requires a pressure reading between 1.0 and 1.5 bar (12–15 PSI). During active operation, dynamic system pressure naturally rises to between 1.8 and 2.2 bar (20–25 PSI). Readings consistently falling below 1.0 bar trigger low-pressure fault codes, … Continue reading What Pressure Should My Boiler Be?