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Circulator pump efficiency hit by magnetite build-up

Xylem circulator pumps fitted with permanent magnet motors are at increased risk of magnetite build-up which is badly affecting both pump and central heating system efficiency.

The warning, from Xylem, comes in the wake of increased concerns that modern circulators are at risk of magnetite build-up which can affect system efficiency by between 10% and 50% in extreme cases. This increased power consumption does not meet the requirements set out under the ErP 2009/125/EC directive, which is the driving force behind the increase in the use of high efficiency circulators.

Magnetite, also known as ‘black sludge’, is dissolved metal caused by the natural erosion of radiators and other heating system components, which is held in the water running through a heating or hot water system.

According to Xylem, the problems stem from the fact that the majority of modern high-efficiency circulator pumps are equipped with a permanent magnet motor which attracts the magnetite where a magnetic field is present and reduces motor efficiency unless, as part of the pump design, the flow of water is separated from permanent magnetic parts.

Chiara Musola, Global Product Manager Circulators at Xylem AWS commented: “To combat this problem, we would recommend the flushing of the system together with an inhibiter and a magnetic dirt separator. In addition, circulator pumps fitted with ‘anti-block technology’ have the capability to separate the main flow of the transferred liquid from the permanent magnetic parts, meaning the pump will never be susceptible to blockages from magnetite or sludge.”

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