Reconit Products

Grundfos run capacitor

My neighbor installed the wrong type of capacitor on my Grundfos water pump motor. He installed a start capacitor with 30 mfd when he should have installed a run capacitor. Start capacitors which are intended to increase starting torque are designed for CSCR or CSIR motors. These systems will utilize a centrifugal switch, current relay, or potential relay to remove the capacitor from the circuit once the motor reaches ~75% of rated RPM. This usually will take less than 1 second. Start capacitors will overheat and fail if left in the circuit for extended periods. Your motor, which is a PSC, does not have a current or potential relay to remove the capacitor; and as a result the new capacitor has failed. This is why the motor will not start. I'll wager that if you put the correct 40uf run capacitor back in the circuit, the motor will start.

This article is to educate guests, not to replace defective capacitors with what ever you get.

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