Swimming Pool Blog

Swimming Pool Pump Motor Capacitors

Sean Griffin, February 5, 2010

Swimming Pool Pump Motor Capacitors


start capacitors (black) and run capacitors (silver)Capacitors play a vital role in various types of electrical appliances. Transmitters and receivers for television and radio, automobile ignitions, the flash for your camera, and swimming pool motors are all made possible by a wide range of capacitors. A capacitor is similar to a battery but is capable of discharging energy stored within at a faster, potentially lethal rate.

Capacitors are modern day electrical components but examples of similar energy storage and dispersal have been around since the beginning of time. Lightning is released from the sky above on the same principles that may be giving your pool motor the energy needed to begin to rotate. A thunder storm cloud is both positively and negatively charged making it an enormous capacitor, drifting in the wind waiting to discharge its electron build up in the form of a lightning bolt.
The Leyden Jar, developed by Pieter van Musschenbroke, would become one of the stepping stones in the advancement of the capacitor. Benjamin Franklin, not only a founding father of the United States but a pioneer in electrics, became interested in the Leyden Jar. Through his experiments with the Leyden Jar, Franklin was able to develop the flat capacitor, also known as the Franklin square.
how a capacitor worksA British chemist and physicist by the name of Michael Farraday would later follow in the footsteps of Benjamin Franklin. Michael Farraday is credited with the first practical applications for the capacitor discovered when trying to store unused electrons from his experiments.  Farraday also discovered electricity could be made by moving a magnet inside a wire coil. This led him to build the first electric motor. Because of his outstanding accomplishments in the field of electricity, the unit of measurement determining the capacitance, or storage potential of a capacitor is called a fared.
Farads and voltage help determine exactly which replacement motor capacitor you will need if your pool motor has some issues getting up to speed.
The winding design on certain single phase motors requires a start capacitor to get the rotor/shaft up to the proper RPM and then disengage. Motor start capacitors are typically non-polarized electrolytic types. You may have seen this on your pool pump. Typically pool motor capacitors are located either in an external casing (hump on top of the motor) or secured by a bracket within the end cap of the motor next to the centrifugal switch, mounted at 9 o'clock.  Some pool pumps are designed to be switchless and will have slower initial torque.
There is a procedure to test to see if a capacitor has been compromised and is “shorted” or dead. First, discharge the capacitor by slipping a heavy piece of paper between each terminal, making good contact. Then attach an Ohmmeter, or good multi-meter that measure Ohms; one lead to each terminal. The Ohmmeter needle should move rapidly to the right and slowly drift left.
When a capacitor goes bad, this can be indicated by a motor that will only hum even with proper electric supply and a shaft that isn’t seized (impeller turns). Sometimes damage will be visible and required replacement to get pool pump back to normal is obvious.
Sure signs that a capacitor will need to be replaced include: cracking, warping, melting, exploding and/or black oil like substance oozing from casing. In some cases the capacitor will appear to be in working condition. Fortunately switching a capacitor on your pool pump is relatively easy and relatively cheap. When you replace a capacitor, match the Fared rating printed on the capacitor. Most pool motor capacitors are expressed as Uf or MFD, both are abbreviations for the micro-fared (a millionth of a Fared).
Find your pool pump capacitor at our pool motors and pool motor parts page. If you are unsure as to what your capacitor reads you can use your motor model number to cross reference the replacement through the manufacturer.
Always replace your pool pump capacitor with an identical replacement.
Whether a capacitor is external or within the motor's back compartment, replacement usually consists of removing two wires and replacing these wires onto terminals of the new capacitor. How you access capacitor will depend on exact motor design.touchscreens use capacitors
Capacitors have evolved over the years since discovered by the electric pioneers of earlier times. Capacitors are designed for a wide variety of uses and come in a wide range of sizes and capabilities. Recent applications include touch screen pads found on newer cell phones. Voltage is used to create a grid of capacitors. Bringing a finger or conductive stylus close to the surface of the phone changes the local electrostatic field.
 Image Credit to Bryan Rosengrant

Super capacitors also help power electric and hybrid cars. Judging by the advancements of the capacitor and seeing how it has continued to evolve, a Flux capacitor mounted in the back seat of Marty Mcfly’s
DeLorean might be in the not too distant future.