I had one of these Siemens 100 Amp Double Pole Breakers go bad I was curious what went wrong. The failure mode was one phase was good under a load of 20 or 30 amps but the second phase dropped to around 60 or 70 VAC under load. You can see in the video that the copper braided cable had a weld that failed. I make some wrong assumptions along the way, I had always thought that double pole breakers were simply 2 single pole breakers bolted together as one unit and didn’t have any interaction other than the linking bar. As you will see in the video they have a mechanism of tripping each other. The trip mechanism is quite simple, it was tested with a direct application of heat rather than enough current to actually trip it since I am thinking it would take a sustained 120 or 130 amps to make it trip and I don’t have anything that can supply that kind of current.
To see the pictures of the breaker in Hi Res click here.
