The risk of magnetite in circulator pumps with permanent magnets
Circulator pumps with permanent-magnet motors are at increased risk of magnetite build-up, which badly affects the efficiency of pumps and central-heating systems — according to Xylem. In extreme cases, system efficiency can be reduced by 10 to 50%, and the increased power consumption does not meet the requirements of ErP 2009/125/EC Directive, which is the driving force between the increase in the use of high-efficiency circulators.
According to Xylem, the problems stem from a permanent-magnet motor attracting magnetite unless, as part of the pump design, the flow of water is separated from parts that are permanently magnetic.
Chiara Musola, AWS global product manager circulators at Xylem 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.’