![]() The connected circuit, regardless of voltage is protected from exceeding that amperage. In summary, each leg of a single, double (2 phase) or triple (3 phase) breaker is capable of allowing the amount of current denoted on the breaker. If you removed the tie and only one breaker tripped, there would still be 120 volts connected to the outlet. This ensures that all power to the outlet is disconnected. Therefore, if the rated current, (100 amps), is exceeded on either breaker, that breaker will trip and the other breaker will trip via the mechanical tie. Each of these hot wires are connected to the two terminals of the two-pole breaker.ĭue to mechanical tolerances, one breaker will most likely trip before the other. The current flows out and back at the same 60 Hz but this time via the two hot wires (generally black and red). ![]() Because they are out of phase, the potential difference is twice the voltage of each line or 240 volts. In other words, as leg 1 is flowing "out", leg 2 is flowing "back". You are using two "legs" of 120 volts each that are 180 degrees out of phase with each other. In a 240 volt circuit, there is no neutral wire. Only the hot wire is connected to the breaker. The amperage in the hot and neutral wires are the same (in the perfect world). In a 120 volt circuit, it flows "out" toward the device via the hot (generally the black wire) and "back" via the neutral (generally the white wire). In AC current, electricity flows in both directions. So why are they tied together? That is done when the two-pole breaker is to be used to power a 240 volt circuit. If you then powered two, separate 120 volt devices from the two breakers, each breaker would allow 100 amperes to pass to each of the devices before tripping. In actuality, you always had two 100A breakers. To understand this, imagine that you remove the mechanical tie from the two-pole breaker. It does not matter if that breaker is physically tied to another 100A breaker. I believe the 1+N breaker described by in another answer refers to stand-alone circuit breakers.The breaker will trip at the amperage notated on the breaker. In my first paragraph, I was referring to circuit breakers of the type mentioned in the question that plug in to North American distribution panels. Even purchasing new-old-stock circuit breakers is less then the best idea. It is not a good idea to install any circuit breaker that is not purchased new. There should be sufficient information marked somewhere on each breaker to identify each one as a circuit breaker if separated. If a device is a two-pole circuit breaker with two handles tied together, the trip rating should be marked on each handle. That is true whether it has one handle or two handles tied together. ![]() Such an assembly must not be offered for sale as a two-pole circuit breaker.Ī two-pole circuit breaker is two circuit breakers that open simultaneously if either one trips. It would be more than unusual to find such an assembly offered for sale today. There may be or may have been at some time, a legitimate use for a circuit breaker connected to a switch with a handle-tie. If not both can trip, what would happen if the live line that shorts to the enclosure is connected to the breaker side that doesn't have short circuit protection? I need to know this because I'm powering up 240v load and there is ground wire to the enclosure. Presumably, breakers made to be used as single-pole provide both protections in a single breaker, as do double-pole breakers used as a unit." It’s unknown which side may provide over current protection. We found that only one side of our double pole breaker provide short circuit protection. We then tested the breakers on a test circuit. This must have been a huge overload, far beyond 20 amps. We found this out the hard way when we had a total short in one of our circuits and the 20 amp breaker did not trip, but instead melted a #12 AWG wire. The double-pole breakers are NOT just two single pole breakers physically joined. "The assumption that the two halves of DP breakers can serve as SP breakers proved to be very wrong. The person who tested the 2-pole breaker to have only 1 side tripping is an US citizen who has done many tests with it. Anyone familiar with it? Does only one side trip? Someone stated that only one side of the double pole breaker provided short circuit protection. How many of you have used double pole breakers?Īre double-pole breakers just two single pole breakers physically joined?
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