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Old 10-21-2023, 12:10 PM   #6
Bill
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Originally Posted by rickst29 View Post
But the WildKat 120-VAC input "hot" wire SHOULD BE on a circuit breaker limited to 20A (or, even better, just 15A): Your "27A" input current measurement should have tripped the breaker, if it continued for even a single second of duration. Because the breaker did not trip, AND because power from the rI suspect 2/3 of the measured input amperage is being lost in a ground fault, before reaching the WildKat.
Be real careful of that underlined statement, as it can draw you to some wrong conclusions. Circuit breakers don't trip instantly upon overload. They have what is called a time-current curve. It shows amount of overload on the horizontal axis (shown as a multiple of the breaker's rated current), and time-to-trip on the vertical axis. They show that trip time gets shorter as the overload gets larger. Makes sense, right? At rated current (shown as 1x on the horizontal axis), it will never trip. At 2x overload, most household-type breakers take many seconds to trip. This is what enables the breaker to withstand a momentary overload, such as a motor-start surge. At 10X overload, trip time will be on the order of 1 second. And at 100x, a small fraction of a second. In this thread, we are talking about less than 2x overload, so trip time will be long, and other protective circuits, in the genny for example, may kick in first.

The attached picture shows a generic time-current curve. It shows that at 6x overload, this particular breaker will trip in 0.6 seconds. At 2x overload, the trip time is above the chart, but looks like maybe 10 seconds. Again, this is generic. As you can imagine, different kinds of breakers have different trip characteristics, which are set when the breaker is designed.

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