How to Identify a Run Capacitor

Capacitors are kind of like a battery to start the pumps motor, but what it really does is energize the second phase winding (auxiliary coil) to create a rotating magnetic field while the motor is running. 

If your pump is not starting, but instead is making a "humming" or "Nnngh" type of sound, you may have a capacitor fault. Usually it is not uncommon for a capacitor to fail after many years of use and this is because over a long period of time the Microfarads can become reduced and therefore as a result the motor may fail to start / run on full power. 

Capacitors are normally located within the electrical box on top of the motor itself. You may be able to check if the capacitor visually appears to be bulged, cracked or otherwise damaged, if it is then you can assume that the capacitor has failed. You can also check for loose connections, crimps or broken wires with in the electrical box. Sometimes however even if the capacitor looks okay, it can still be bad and need replacing. 

If you are experiencing these faults, then it is best to replace the capacitor completely - Replace with a new capacitor of the same rating.

Why is it important to replace a capacitor with the same rating?
If a wrong capacitance value is installed, it will cause an uneven magnetic field around the rotor. This causes the rotor to hesitate at the uneven spots, resulting in irregular rotation, especially under load. This hesitation can cause the motor to become noisy, increase energy consumption, cause performance to drop and the motor to overheat.

How to identify your pumps Capacitor
Capacitors are fairly universal to each pump, however it is important to purchase a capacitor that has the correct Microfarad rating and connections. 

1. Unplug the pump from the mains supply.
2. Remove the cover plate on the electric box on the top of the motor to locate the capacitor inside. 
3. Use an insulated flat head screwdriver to discharge the capacitor from its holdings. 
4. Look on the side of the existing capacitor to read the microfarad size which is a number followed by UF
5. If you wish to remove the capacitor simply remove the 2 wire connected to the capacitor using a flathead screw driver or pliers. 

Be aware: Capacitors are capable of holding small amounts of charge, therefore always disconnect the pump from the electric supply and handle with care. 

Multiple Capacitors?

Whirlpool Bath Pumps
Normally pump for baths are only 1 speed and therefore only have 1 capacitor within the electrical box. 

Hot Tub Pumps
Can be 1 speed, however commonly you will find that these pumps are 2 speed and therefore have 2 capacitors. The reason for 2 capacitors is because 1 is for the Low Speed and has a smaller Microfarad rating and the other is for the High Speed and has a much higher number of Microfarad rating. 

Swimming Pool Pumps
Pool pumps may have two capacitors, one in the back (the start capacitor) and one on top (the run capacitor). The smaller, black capacitors, located in the rear of a motor, are usually labelled with a range of numbers, i.e., 161-193 MFD, while the larger, silver capacitors, typically located on the hump of the motor, on top - are sized by a UF number.

This Help article is intended for guidance only and Isell Ltd will not be held liable for the information within.