Pressurised Heating Systems

Pressurised heating systems lower the risk of pressure being too high or low, stopping knock-on effects on the day-to-day operation of premises and improving overall stability in pressurised heating systems. Linked to the pressurisation sets there is also pressure vessel, to take up the expansion in the system. These pressurisation units have a small CAT5 break tank with one or two small peripheral pumps throughout the system to maintain pressure. Sometimes pressurised heating systems are also known as fill and spill systems and vice versa, depending on how the pressurised heating systems are configured. Fill and spill systems are typically found on larger applications. In principle the systems work the same, however a pressurisation set doesn’t have a spill system, it uses a pressure vessel instead.

Fill and Spill System

The fill and spill system is designed to maintain consistent pressure within a heating or closed water system to support stable pressurised heating systems by actively responding to changes.
It operates by monitoring system pressure using either a pressure switch or a pressure transducer. When the pressure drops below the required level, pumps automatically activate, drawing water from the tanks and introducing it into the system to restore pressure. Once the correct pressure is achieved, the pumps switch off.

If the pressure rises too high, a spill valve—either a mechanical valve or an electric solenoid—opens to allow excess water to return to the tank, safely reducing system pressure.

This pressure fluctuation typically results from temperature changes. As the system heats up, the water expands, increasing pressure. When it cools, the water contracts, causing a drop in pressure. The fill and spill system manages this cycle efficiently, ensuring safe and reliable operation at all times.