TWH
I see you are correct in applying the rule and you win the argument but I still think you are arguing this so you can avoid changing to a 90 amp breaker. I know I am splitting hairs but for 1/8th of an amp you are going to up 9 7/8 amps because you can? A fuse or circuit breaker needs around 6 times it's current rating to operate in its instantaneous range so we now need between 500 and 600 amps to trip in the instantaneous range instead of about 60 amps less with a 90 amp o/c device. never mind a high impedance fault. The first subrule in 26-256 says maximim of 125% so it is obvious that the intent is to limit the overcurrent device to some level below 125%. Subrule 3 gives you the ability to match OC devices to the products available at the wholesaler and to be able to ensure tha transformer O/C won't open on excitation. For that 1/8th of an amp the inspector might have to allow the installation as you have done it but he is still correct in asking you to use a 90 amp O/C device.
Imagine for a moment you were installing a big transformer and the breaker was 1000.125 amps. Next size larger is 1200. Of course you wouldn't do that if it also meant spending another 2500 for the next frame size.
So I concede you have met the code but have made a less safe installation on principle. Who wins? Maybe you actually installed the 90 amp breaker and am just looking for a moral victory.
I think I would have told you to install the 90 amp O/C and let you appeal it. I don't intend for this to become a pi**ing match and it is a valuable argument for discussion purposes. It also made me think about the question from a different perspective. I can see from your other postings you do know how to read a code book.
