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. Our Tech Tips are also very helpful for our wholesalers as we present product information that can help as contractors have questions.
This is why we have dedicated a section of our site for contractors and wholesalers. 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.
I heard that the power factor of an ECM is different than that of a PSC motor. What is the power factor?
Power factor is defined as “the ratio of the real power that is used to do work and the apparent power that is supplied to the circuit.” This typically has not been a characteristic that has been considered important when evaluating the performance of permanent split capacitor motors (PSC) in that their power factor is about .9, or close to one.
Watts are the measurement commonly used for determining power consumption. We pay for our electricity based upon the Kilowatts that we use. One thousand Watts equal one Kilowatt. Normally we see Watts law shown as Watts = Volts x Amp, which is fine when the power factor is near one. However, the equation needs to include power factor when the power factor is not near one. It then is Watts = Volts x Amps x Power Factor. So, Power Factor = Watts/(Amps x Volts). When the power factor is near one, the impact is negligible on Watts.
Let’s make a comparison between a PSC and an ECM, and see the impact of power factor. We’ll look at a particular operating point or static pressure in a 115 Volt system and assume that a PSC and an ECM blower are both operating at that point. We’ll also assume that at that point both blower motors measure 6 amps and delivering the same amount of CFM. The power factor of electronically commutated motors is about .6, and as mentioned above, about .9 for a PSC. These assumptions are presented only to show a comparison between the two blower motors. When we evaluate the two blowers we find the following:
PSC 115 Volts x 6 Amps x .9 Power Factor = 621 Watts
ECM 115 Volts x 6 Amps x .6 Power Factor = 414 Watts
There is a substantial difference in Watts between the two, resulting in considerable energy savings with the ECM. These characteristics are used in determining the Fan Energy Rating (FER) established by the Department of Energy (DOE) for centrifugal fans (blowers). It is a relationship between the Watts required to produce a specific amount of air or CFM. Manufacturers must now meet specific FERs for their blowers used in certain residential ducted equipment. This is to ensure a minimum amount of air per Watts.
Power factor has not been a big part of residential air conditioning discussion. However, with the establishment of the DOE’s requirement of FER standards for the manufacturing of blowers and the broader use of ECMs, it has become an important tool for better analyzing performance and energy consumption, resulting in energy savings.
What are the Power Factors of a PSC and an EC motor?
- PSC .75, ECM .75
- PSC .6, ECM .8
- PSC .9, ECM .6
- PSC 60%, ECM 80%
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