The problem is the the individual breakers on a 480/277 -Y systems are only designed to handle 300 volts per leg and this type of service a 480/277-Y can only deliver 277 volts per leg to ground this is why these breakers and panels are only designed to handle 300 volts per leg.
|Standard bolt down breaker for 480/277 Y|
|Frame breaker for 480 Delta|
But a 480 volt Delta service can deliver 480 volts per leg to ground. Breakers for a 480 delta system are rated to handle 600 volts per leg and are frame breakers and physically twice the size of a standard bolt down type 480/277-Y breaker. There also 3-4 times the cost which is why people are tempted to try and use the wrong breakers and panels. instead of spending the large amount of money required to install Delta breakers.( Bottom Picture)
Now yes the 277 /480 breakers can work and deliver power on a delta system but they will eventually break down and wear out in a couple of years much faster than there designed for Manufacturers will not sell them and recommend against this practice . However the biggest danger would be if there is a major overload like a motor having its rotor locked the amount of power developed in a short circuit on a 480 delta system would instantly overwhelm and destroy a 480/277 -Y breaker creating a huge Arc Blast sending a blast wave with molten metal everywhere which can kill instantly and cause major body trauma. in the case of this plant many individuals lives where put at risk should they have continued to hook up and use this equipment. There have been many people killed and or seriously 3rd degree burned in electrical arc blasts even several feet away due to the extreme conditions created by arc blasts.
This same problem is also true with 230 volt 3 wire delta and 208 volt 4 wire Y systems as well.
This is why you must properly design and purchase equipment or risk a catastrophic incident
Now there will be finger pointing back and forth and money lost on restock charges etc. and even more money spent. But more importantly everyone will go home to night and not in a coffin.
When you are an experienced professional like my self you have a duty to all those you work for to make sure there safe. regardless what any one thinks. Failure by myself to intervene and have these actions stopped could result in criminal and civil charges against me for not doing it had people gotten hurt. Lots of people bitch and complain because I interceded and stop foolish actions like this from happening but in the end I can put my head on the pillow and say yes I did the right thing and saved lives. I was not a foolish ass hole and yellow bellied individual and went with the flow and said nothing and let some one get hurt . We have too many people in the trades who go with the flow and say nothing and they are cowards.