The following is just my opinion. It may be based on one or more of the following: scientific fact, science fiction, pure fiction, rumors, supposition, tribal lore, unfounded guesses and random thoughts.
Long ago, the card edge connectors used in early computers were not manufactured to very tight tolerances. One common maintenance procedure on the Apple II was to shut the computer off, open the case, remove each card and reinsert it. This cleaned off the accumulation on the card edge connectors and would sometimes restore normal operation of the computer. Modern devices are made with tighter tolerances and this type of maintenance is much less commonly required. Modern automobiles are full of various connectors and they commonly work for 20 years without somebody having to disconnect and reconnect every connector for maintenance. However, that was all about low power connectors. I would expect that things would be different for high power connectors. If there is any significant current flowing, any coating or oxidation on a contact surface would raise the resistance leading to heating. The heat will either burn off the contamination leading to a restored connection, or it will increase the resistance of the connection leading to a rapid failure of the connection. It would seem unlikely you could have some type of contamination causing imparted performance for extended periods of time in a high power connector. I would recommend against cycling circuit breakers. The detents will wear down with repeated actuations. This can reduce the holding force leading to the breaker tripping at a lower limit than originally specified. Opening a breaker under load will result in arcing in the breaker which can degrade the contacts. High quality breakers should have good arc suppression mechanisms. Generally, manual operation of a breaker is fairly benign and shouldn't be a significant issue. That being said, GFCI, AFCI and RCD circuits with monthly test buttons should be tested monthly. The device is designed to handle a monthly test for decades without significant degradation. My biggest concern in power circuits would be that repeated disconnection and reconnection could degrade the contact over time. Spring forces and detents could be weakened leading to a poor connection. If the connection is degraded until there is a small air gap, arcing could lead to heating and failure. Commercial and industrial circuit breakers do require regular maintenance. Please note that the article linked below is from an electrical construction trade magazine. "Low voltage" means less than 1000 V. The test procedure recommended in the article calls for a high current source rated for at least 1000 A, so it is safe to assume that this is for much larger breakers than most of us will see. http://ecmweb.com/content/maintaining-low-voltage-power-circuit-breakers It seems to me that regularly disconnecting and reconnecting high power circuits isn't generally necessary. If you would like to try it, I recommend that once a month, you unscrew and reinsert every light bulb in your house followed by unplugging and reconnecting each lamp and appliance. Ted Eckert Compliance Engineer Microsoft Corporation [email protected]<mailto:[email protected]> The opinions expressed are my own and do not necessarily reflect those of my employer. From: Crane, Lauren [mailto:[email protected]] Sent: Friday, May 23, 2014 12:50 PM To: [email protected] Subject: [PSES] "exercising" connections for health? I am puzzling over a notion that it is prudent to exercise connectors in power circuits "every once in while" (e.g., disconnect and reconnect them). I suppose the underlying idea is to scrape the touching surfaces and potentially disrupt forming oxides or accumulated pollution. I saw the other day an article suggesting circuit breakers should be cycled every so often (~ once a year) for possibly similar reasons. Does anyone know of a code of electrical maintenance, or similar, that might support or refute this notion? Regards, Lauren Crane KLA-Tencor - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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