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	Subject - Amp clamp David Hyatt If you have a 3 phase 225 amp main breaker, what is the max you should read with a amp clamp per phase? 225/1.732? What about single phase 200 amp? Ryan_J I would say 80% of 225 cs409 a 3 pole 225 amp 3phase main breaker is protection for 225amps per phase...as a 2 pole 200amp single phase is 200amps per pole etc etc........either leg of that CB exceding its limit, will trip all phases/poles,,,,or suppose to! hope this helps..... JimmyDee Because most breakers have both a thermo unit and magnetic short circuit trip, you may see higher amps for short periods of time than the rated size. Jim David Hyatt If thats the case then, then you could actually pull four hundred amps balanced perfectly at all times, on a 200 amp main breaker. 200 amps on phase 1 and 200 amps on phase two???? Then you would be over the panel rating? But in theory this is true??????Right??// Don't seem right but does make sense. 3/0 copper is 200amps per phase. More comments please. JimmyDee Yes, you are correct but you would not have overloaded the panel because it is rated for 200 amp at each leg. Jim cs409 that is why you see a lot of over kill with the DIY installs,,,they dont understand its per pole/phase... renosteinke One detail: with three-phase systems, it is possible that there is "harmonic distortion" that will throw off your meter reading. By comparing the reading from a "true RMS" and a "standard" amp-clamp, you can see just how much harmonic distortion is present. As a rule of thumb, if there is 12%-15% (or more) difference between the readings, you will want to look into dealing with the problem.