QE Quality Run Capacitor 40 MFD 370 / 440 VAC
Motor Run Capacitor 40 MFD 370 / 440 VAC
How To Choose a Motor Capacitor:
The following factors should be used in determining a replacement motor capacitor, in order of importance:
Type: Start or Run.
Motors may have a start, a run, or both types of capacitors in it. Run capacitors typically have a smaller capacitance rating, usually less than 100 MFD, and a fixed value, such as 60 MFD (uF). They also are *usually* in a silver metal can. Start capacitors have a larger capacitance value, and usually are specified by a range, such as 270 - 324 MFD. They also are *usually* in a black plastic cylindrical package. Start capacitors are designed to only be in the circuit for a few seconds as the motor is starting up, then a switch inside the motor turns it off. Run capacitors stay in the circuit all the time.
Capacitance is specified in micro-farads, often abbreviated as MFD or uF. It is important to get a replacement value that is fairly close, but it doesn't have to be exact. Usually +/- 20% if sufficient.
This is the maximum safe operating voltage of the capacitor. The replacement capacitor should always be greater than or equal to the original capacitor voltage. It is ok if the rated voltage is higher than the original. Higher voltages usually result in a larger package, so size may become an issue on larger voltage ratings.
The size of the capacitor only matters in that the replacement capacitor needs to fit in the original housing, which is usually a metal can mounted on the top or side of the motor.
Motor Start Capacitors are used to boost the starting torque of single-phase electric motors by increasing the current through the start windings during startup. They typically only stay in the circuit for a few seconds before being switched off by a centrifugal or electronic switch inside the motor. If your single-phase motor will not start, very often, the start capacitor (if it has one), could be bad. It is a common failure mode in single phase motors.