A magnetic filter is a protective device that captures and removes magnetic metallic particles (including magnetizable magnetite, also known as black sludge) and other sediments present in the water of closed-loop heating and cooling systems. Within the magnetic filter, powerful magnets retain ferritic particles, while a high-precision stainless steel filter element removes fine, non-magnetic particles. The collected impurities are easily removed through the cleaning flange and drain port. This dual separation effectively protects pumps, valves, heat exchangers, and boilers/heat pumps from wear and fouling.

The use of magnetic filters is a recommended practice for radiator and underfloor heating systems, fan coil units and air handling units (AHUs), boiler and chiller return lines, and heat pumps. Metallic wear particles in the system lead to premature pump bearing failure, three-way valve seizing, reduced efficiency of plate heat exchangers, and a decrease in temperature difference (ΔT). By continuously reducing this dust load, magnetic filters improve energy efficiency, extend maintenance intervals, and significantly decrease the number of breakdowns. This results in increased system performance, which translates into greater comfort and an optimized total cost of ownership.

The most effective location is on the return line of the boiler/heat pump/chiller, before it enters the heat generator and pump. This location protects the equipment from the return flow, where impurities are most concentrated. It can be installed vertically or horizontally, with the flow direction aligned with the arrow on the housing. Sufficient clearance must be provided around the top cover and cleanout flange to facilitate maintenance, and shut-off valves should be installed at the inlets and outlets to easily isolate the circuit during maintenance operations. The connection type (threaded, flanged, or welded) can be preferred, depending on the application standard.

During maintenance, the inlet and outlet valves are first closed to safely reduce the pressure. The magnetic rod is then removed, any internal sediment in the housing is drained, and the stainless steel filter is cleaned. All seals are then checked, and the filter is put into operation. For newly installed systems or those that have not undergone chemical cleaning, weekly checks are recommended for the first month; once the system is established, monthly or seasonal checks are sufficient, depending on the level of contamination. Regular maintenance helps limit pressure increases and pump energy consumption, thus extending component life.

The main selection criteria are the pipe diameter, nominal flow rate, permissible pressure drop, operating temperature and pressure range, and connection type. In systems where large volumes of impurities are expected, a larger sedimentation chamber and higher magnetic retention capacity are preferable; for glycol applications, the chemical compatibility of the surfaces and seals used must be verified. By incorporating this information into the design, the magnetic filter can be configured with the appropriate housing and accessories to provide high retention efficiency without reducing flow rate.