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Neta specs for CB current multiple

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    TrapFlyVenus is offline Junior Member Pro Subscriber
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    Neta specs for CB current multiple

    Is there a neta spec for what current multiple to use to test circuit breaker functions? I was told to only use 300% the plug rating for a long time trip but 600% makes much more sense considering most delays are based off that.

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    Kalbi_Rob is offline Experienced Member Pro Subscriber
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    Quote Originally Posted by TrapFlyVenus View Post
    Is there a neta spec for what current multiple to use to test circuit breaker functions? I was told to only use 300% the plug rating for a long time trip but 600% makes much more sense considering most delays are based off that.
    NETA ATS 7.6.1.1.B.5 Determine long-time pickup and delay by primary current injection.

    NETA ATS 7.6.1.1.D.5 Long-time pickup values shall be as specified, and the trip characteristic shall not exceed manufacturer’s published time-current characteristic tolerance band, including adjustment
    factors. If manufacturer’s curves are not available, trip times shall not exceed the value
    shown in Table 100.7.

    NEMA AB4 6.5.4.2 With the test circuit breaker closed, energize the test circuit and quickly adjust the transformer to the required 300% test current.

    So, NETA does not require you test at 300%, and I have found myself testing at lower values multiple times before due to test equipment limitations. Any current multiple is allowed, as long as it falls within the manufacturer specifications. That being said, I would never test at 6x, simply cause it causes more problems in the long run, especially with larger sized breakers and bus/cable limitations. NEMA AB4 also provides tables for suggested bussing and cable sizes.
    If you have a breaker fail, and send it back to the customer, they may find the OEM arguing that you did not test per NEMA AB4 (NEMA = National Electrical Manufacturer's Association). Thus, it is recommended to test per NEMA AB4 since it is the standard used for testing per the Manufacturer, and they call for testing LT at 300%.

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