Understand the true value of “magnetic filters”!

Currently, most condensing wall-hung boilers come standard with protective additives, gas filters, and magnetic filters. However, there is a lot of confusion in the market regarding the actual value and effectiveness of magnetic filters for heating equipment or systems. Today, we’ll explore this topic together. It’s easy to assume that installing a compact magnetic filter on the boiler’s return line is essential for cleaning and protecting the system—that it acts as the pipeline’s “cleaner.” However, the reality is neither that simple nor that straightforward!

Why?

There are five compelling reasons why system cleaning cannot rely solely on a magnetic filter (except for systems with only minor contamination):

1. It relies entirely on the standard heating system circulation pump to drive dirt and sludge toward the magnetic filter, and the system may be quite long. Circulation pumps are designed for relatively slow flow rates, causing larger dirt and sludge particles to detach during circulation and accumulate in low-flow areas, such as the bottom of radiators or underfloor heating units, or in elbows and other bends. Scientific research has proven that the amount of dirt and sludge removed from a water system is directly related to the speed of the flushing water flow. The higher the velocity, the better the results. Without high flow velocity, heavier and larger dirt/sludge particles lack the momentum to move and will simply continue to settle and accumulate. 

2. As for corrosion debris, the circulation pump itself acts as a “magnet” that continuously attracts and traps such debris. The magnetic field generated by the motor draws debris accumulated in the pump passages and impeller, significantly reducing the already slow flow rate. This is an issue that has increased with the introduction of new, high-efficiency circulation pumps to the market. Most circulation pumps on the market today use permanent magnet motors, which generate a magnetic field at all times—not just when the pump is running. Users and manufacturers have begun to pay attention to potential problems with circulation pumps installed in systems containing corrosion debris, and it is essential to ensure a higher level of system cleanliness for new wall-hung boilers/boiler systems (using permanent magnet motors). In systems containing a large amount of corrosion debris, a layer of magnetic debris will gradually accumulate on the pump impeller, significantly reducing the efficiency of both the system and the pump. Corrosion debris can also cause the impeller to seize. Therefore, the system must be thoroughly flushed after installing a new circulation pump, not to mention when installing a new wall-hung boiler or boiler.

3. In heating systems, pumps force water to flow in only one direction. This results in low-flow areas—typically at the bottom of underfloor heating pipes or radiators—where the accumulation of dirt and sludge obstructs water flow. Unless the flow direction can be rapidly reversed, this buildup will persist.  

4. Without the assistance of the high flow rates generated by a turbulent flow cleaner, magnetic filters can only capture debris and sludge within a few centimeters of the filter. Accumulated deposits will remain stationary while radiators and pipes are in operation, continuing to reduce system efficiency. Sludge and corrosion products complicate matters. Sludge is a mixture of magnetic and non-magnetic particles. Engineers must be aware that non-magnetic particles will not be captured by magnetic filters and will continue to circulate unless they can be flushed out of the system by high flow rates. 

5. In central heating systems, a temporary (or permanent) magnetic filter has no effect on cleaning or removing existing scale/sludge from the primary water side of plate heat exchangers; therefore, plate heat exchangers must be cleaned separately. Particles smaller than 15 gm are sufficient to obstruct flow and cause the boiler to “lock up”! Are magnetic filters worthless? Certainly not. While their value for cleaning the system is indeed limited, they can prevent debris from entering the boiler, eliminate large amounts of air bubbles that may be present in the system, and serve as a port for adding protective agents in the future.