can I safely put 3 brkr fed subpanels ( 60a 100a
100a ) on a 225a 120/208v 3ph panel ,the 225amp main brkr is already feedin2 2 42 cir panels
supply is from a 75KVA 480 x 120/208v xmfr
where can i find a code refrence?
You can supply as many panels as you wish as long as you can serve those loads. You need to perform a load calculation to deterine the remaining capacity, if any, the service can handle.