What’s the difference between a pressurised and drain-back system?
The system must be able to withstand extremes of temperature. In the winter, freezing fluid could cause damage to the collector and pipework. In the summer, temperatures of 200°C are possible which would cause the fluid to boil and cause excessive pressures. The two systems cope with these issues in different ways. Pressurised systems hold the fluid at a pressure which increases the boiling point of the fluid. They incorporate a pressure vessel which allows the fluid to expand as it heats up without increasing the system pressure.
