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Discussion in 'Ian's Corner' started by Ian Gills, Aug 5, 2009.

  1. Ian Gills

    Ian Gills Senior Robin Hood Guy

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    The IEC develops international standards for switchgear. South Africa though has developed its own standard for circuit breakers which is 95% similar to IEC standards but with an important difference. IEC mandates that circuit breakers should be able to operate at 230 volts +/-5% but the South African requirement is 230 volts +/- 10%. Most circuit breakers on the world market cannot meet the South African standard, and are more expensive for those countries that do make them (e.g. Siemens). This affords some protection to the South African industry.
  2. hj

    hj Moderator & Master Plumber Staff Member

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    circuit breakers

    I thought circuit breakers measured amperage, not voltage, which is why they can operate at either 120v or 240v, or any other voltage that does not create an over load. If voltage caused a problem they would be tripping all over the place when the utilities face a brown out.
  3. codeone

    codeone Code Enforcement

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    Where did you find these facts? Something doesnt seem right. Would like to see the reference. Thanks in advance. Mel
  4. Ian Gills

    Ian Gills Senior Robin Hood Guy

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  5. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

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    How is 230v +/- 10% (2.3v)

    more restrictive then

    230v +/- 5% (1.65v)

    :confused:

    Isn't it easier to meet the +/- 10% standard?
  6. Bill Arden

    Bill Arden Computer Programmer

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    I don't know about the standards in question... or even if they exist.

    However a +/- 10% operation is harder to meet since that means you have a higher worse case voltage.

    Then again those few extra volts won't make any difference in the unit's operation, it's just a certification issue.
  7. Ian Gills

    Ian Gills Senior Robin Hood Guy

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    I think it refers to the recovery voltage.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    As the voltage drops, the current increases, so the latching and tripping characteristics need to handle a wider range; this would require a different design with different ranges or you'd get false tripping (well, really it would be still valid, but a nuisance for a transient).

    When I lived in Jordan, the voltage would vary +/- probably 50vac, and it made it really tough on any appliances...refrigerator compressors just didn't like it! I had a motor driven variac on my computer, and at certain times, you could hear that ajusting all over the place. This was before UPS devices were readily available and reasonably priced. The PS in the TV could handle it, but some other stuff had problems as well.

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