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Testing performed on various manufacturers’ capacitors reveals that nearly all new capacitors seem to perform the same off the shelf. The capacitors in Figure 1 were tested right out of the box using a TPI 135 digital multimeter. All three readings fall within the 45μF ± 6 percent tolerance. A capacitor is considered passing if it has a microfarad reading between 42.3μF and 47.7μF. As shown in Figure 1, all of the capacitors meet the criteria. Unfortunately, capacitance, when new, does not provide an indication of long-term reliability, but the industry standard, EIA-456-A, can.
The Electronic Industries Alliance (EIA) issues quality standards for capacitors. EIA-456-A is the standard for metalized film dielectric capacitors intended for use with, among other things, ac motors. The test consists of subjecting a set of capacitors to 125 percent of their rated voltage and 10°C above their rated temperature for 2,000 hours. The EIA-456-A test simulates 60,000 hours of field life.
A capacitor’s estimated operational time per year is 5,000 hours; therefore a 60,000 hour capacitor could last approximately 12 years in the field. EIA standards require capacitors that meet EIA-456-A.
Figure 1 illustrates that all three capacitors tested perform the same based on initial readings, and that they yield a reading that is consistent with the rating that is stated on their labels. Based upon these initial readings, it would seem that all three units are good capacitors. However, it’s in the rigorous EIA-456-A testing that capacitor quality can be determined more definitively.
Quality Products and Warranty Costs
For purposes of modeling, the following example assumes that the warranty period of a manufacturer provides coverage for both parts and labor in the first year. After the first year, only the parts are covered and the labor is absorbed by the contractor. The three capacitors shown in Figure 1 were tested to the EIA-456-A standard. Listed below are the test results for each capacitor for one, five, and 10 years of simulated field reliability. As previously mentioned, a capacitor’s estimated operational time per year is 5,000 hours.
Figure 2 demonstrates that over time, the capacitor failure rate begins to increase depending on the manufacturer. After an estimated five years in the field, one manufacturer had zero failures, one had significant failures, and the third only had one failure. With only one failure, Figure 3 demonstrates the very real effects that a 10 percent failure rate has on a company’s bottom line.
Figure 3 provides detailed information that has been broken out into three sections: Initial purchase price of 500 capacitors, warranty claims/cost, and total cost of ownership. Based on the testing conducted, the data provides the long term/warranty results for each manufacturer and demonstrates the true total cost of ownership for a business.
Through the established results in Figure 3, even though Manufacturer C has a minimal 10 percent failure rate after five years in the field, it will cost a business roughly $3,500 in warranty costs. In addition to price and warranty cost, there is the tangible lost potential when technicians are spending time on repeating service calls.
As Figure 4 illustrates, higher priced capacitors will cost more upfront, but what is being purchased is quality and reliability. Many cheaper capacitors degrade quickly and can cost a business thousands of dollars in labor on warranty claims, not to mention the damage to your reputation.
Over the past five years, there is increasing feedback from contractors stating capacitors “are not the same as they were back in the day” or “they do not last as long as they used to.”
When capacitors do not meet the performance ratings specified on their labels, the entire system can be affected. A failed capacitor will cause the motor to run hotter, the bearings and insulation to wear out, and the noise level to increase. Those factors will eventually cause the motor or compressor to fail.
Total cost of ownership hinges on the quality of the product. You may be able to save $2 by purchasing a less expensive capacitor, but the warranty costs will eventually surpass the higher upfront cost due to poor reliability from inferior products. Even though the manufacturer will replace damaged parts under warranty, it is ultimately the consumer relationship that is being damaged each time you replace a faulty capacitor. Isn’t your reputation worth more than a $2 savings?
Publication date: 6/18/2012