Saturday, September 8, 2012

Misaplication of 3 Phase Power equiptment could have lead to a deadly Arc Blast

I was helping with a project at a local factory  where there installing new equipment when I caught the fact the lead electrical contractor had installed the wrong type of 3 phase breaker panels . The factory is feed with 480 volts 3 phase 3 wire delta  service and he was installing panels designed for a 3 phase  4 wire 480/277 - Y style  service which is used for offices and malls etc. not industrial power systems.

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.

(top picture)
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.

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