| 摘要 |
A pump for a central heating system having a tubular housing and a motor for driving an axial flow impeller which is mounted within the housing, the motor having casing mounted within the tubular housing, forming a liquid flow passage between the outer surface of the casing and the inner surface of the housing, the motor being adapted to be powered by electricity supply of a frequency greater than 70 Hertz, wherein the impeller is mounted upstream of the motor, and guide vanes are mounted in the annular passage to smooth the flow of liquid from the impeller.
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