Checking proper operation of circuit breakers

[baz]

How do you ensure your boat's 110v circuit breakers are function correctly ?

I use a Kill-A-Watt meter. I plug this device into one of the 110v outlets and place an electrical load such as a tea/coffee maker into it. Knowing the wattage of the tea/coffee maker the Kill-A-Watt meter will register that wattage (or close to it). Now remove the Kill-A-Watt device and plug in the tea/coffee maker directly as you now know its wattage draw and in the other 110v outlet on the same circuit (such as the galley outlet) re-insert the Kill-A-Watt device and place another device that you can vary the wattage draw with such as a small ceramic heater into it -- one that can draw as much as say 800 watts when running at max temperature setting. Start the heater at low and observe the wattage draw and then slowly increate the temp setting and watch the wattage draw increase. Typically with a tea/coffee maker AND and electric heater on the same circuit it will be possible to exceed the circuits max current draw and cause the circuit breaker to trip. When it trips note the wattage draw of the heater and add that to what you observed for the tea/coffee maker. The total aggregate wattage should be at or close to the circuits designed max value. If the breaker does not trip then you have some research to do to figure out why the breaker did not trip when it was supposed to.

This same procedure can be applied to the other 110v outlets to ensure their circuit breakers are operating as they should.

To me, this simply test will ensure that electrical fires or melted wires will be avoided and that the breakers are functioning as they should do.

 

[Rebel]

A circuit breaker is designed to trip in a very short time if there is some type of a fault in a circuit, such as when you touch two wires together or you ground the hot wire. A circuit breaker is a thermal device at its rated current and will therefore take some time to trip if the load only matches the circuit rating of the breaker. The National Electrical Code (NEC) limits the design load for a circuit breaker to 80% of its nameplate value. Therefore on a 20 amp, 120 volt circuit breaker the continuous load should be no more than 20 x 120 x .8 or 1920 watts (assuming that the load is purely resistive such as a heater element). For a 15 amp circuit the load should be limited to 1440 watts for a purely resistive load. At these values the breaker should never trip. The load is limited by the NEC to assure that the wire leading away from the circuit breaker will not heat up if the load is left on continuously if the wires a properly sized for the breaker installed. A 15 amp circuit should have at least a #14 copper wire and a 20 amp circuit should have at least a #12 copper wire.
You may all know this stuff but I thought I would just add my two-cents worth.
John