While our customers are wholesalers, Packard knows that you, the contractor, have a choice. You are often presented with many buying options, and being well-informed about your purchase can help make your job easier and more successful.
This is why we have dedicated a section of our site for contractors. In this section, you will find helpful product tips, tools and some clips from our training classes. We’ve also provided a distributor locator so you can find the nearest wholesaler who can give you access to Packard products.
What is the correct capacitor for a PSC motor?
The correct capacitor for a PSC motor is the rating that the motor calls for. The motor manufacturer designs the motor so that best performance is achieved when using the capacitor identified on the nameplate and operating the motor at rated voltage with the load shown on the nameplate.
It’s OK to use a capacitor with a higher voltage rating, but never lower. The capacitor voltage reflects the back, or counter, electromotive force (EMF) that the motor develops. This voltage is a result of the speed (RPM) that the rotor is rotating within the motor winding. Using a capacitor with a higher voltage rating extends the acceptable operating range in respect to this back EMF.
When performing properly the speed of the rotor will not result in back EMF exceeding a voltage higher than the rated capacitor volts. If the motor has a load greater than for what it is designed, a reduction in RPM can occur resulting in lower capacitor volts. If there is less load than what the motor is designed, the RPM will increase and capacitor volts will increase. Both of these scenarios will result in higher motor winding temperatures, which will shorten motor operating life.
Using a capacitor with the microfarad rating that matches that on the motor nameplate will provide the peak motor performance when operated at rated voltage and load. Using a capacitor with a different microfarad rating will result in lower operating efficiency of the motor. This will increase the winding temperature of the motor, resulting in a shorter motor life.
This nameplate shows that the motor requires a 5 microfarad, 370 volt capacitor
As the winding temperature of the motor increases, the life of the motor is shortened. A good rule of thumb is that for every 10° C/18° F change in winding temperature, life is impacted by 50%!
The bottom line: Use the right capacitor! When you don’t, the life of the motor will be reduced.
Packard has developed a complete HVACR critical components training program, which has received approval by North American Training Excellence (NATE) - the leading certification program for HVACR technician, and the only test approved by the entire industry. Below are some video excerpts from our instructor led training courses which we hold at Wholesaler locations nationwide.
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