Currently, the facility has a bus rated at 800 amp 240 v 3 phase. There are three feeders from this bus totaling 1450A. Most of load is RTU HVAC. There are two spare on bus each @200-225. How much additional HVAC load can be added to the bus and what section in the code applies?
If you have 1450A of bus plugs, and want to add more, calculating the load per NEC 220 will probably show that you are overloaded. You can follow NEC 220-35 exception 1.
