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A nuisance trip is a situation in which a safety device has activated when no real danger existed. Circuit breakers tripping, fuses blowing, GFCIs opening, and motor overload contacts shutting off the power are all examples of such safety devices that can produce nuisance trips.

The most common cause for a nuisance trip is an over-sensitive safety device. The circuit breaker may be too small to handle the expected load, the motor overload contact may be sized for a smaller motor than what is installed, the GFCI may be detecting perfectly safe ground leakage caused by filtering capacitors, etc. A badly placed emergency stop button can even cause nuisance trips if it gets bumped. Regardless, the nuisance is that the power has been shut off needlessly. In extreme cases, this can happen too frequently and wear out the safety device.

    There are three common solutions for nuisance trips:
    Obligatory warning: The modification or replacement of safety devices is only to be attempted by qualified persons.

  • Correctly size the protected part for the safety device. This is the safest solution, but it is not always a viable option. In some circumstances the part which is tripping the safety device doesn't have to be quite as big or powerful as it is. Making due with a smaller working part ensures that the rest of the system is still rated to handle the load. Alternatively, if multiple parts are protected by one safety device and their combined load is causing the trip, it may be possible to protect each with a separate safety device that would only need to deal with a small individual load.

  • Correctly size the safety device for the given application. This requires expert handling, since oversizing the safety device is even worse than undersizing it. Rather than the power shutting off when there is no danger, you run the risk of leaving the power on when there is danger. Sometimes it is necessary to replace other parts of the system, such as the wiring, that were protected by the old safety device because the new safety device is not sensitive enough to protect them effectively.

  • Remove the safety device. This is only to be considered as a last resort, when no other options are practical. It is quite often a very bad idea, but not always. Consider first, is the safety device necessary in this application? Will anyone get hurt if it is removed? Most importantly, who needs to know that the safety device has been removed? Often when a safety device is installed, the people who use what it is protecting have come to rely on its existence. There are very few situations in which a safety device has been installed but is not actually needed. The decision to remove one is a very serious decision indeed and should not be taken lightly.

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