Trying to upgrade but........

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C

cleveland

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Midwest
We are wrestling with replacing 3 single phase transfomers in a vault. This is an old installation with the classic three cans along the wall, side wall secondary spade lugs on the transformers and cables running from the lugs up to a bus duct at the ceiling. The bus then runs through a wall into main switchgear with a main OCP device. These transformers and the primary service are part of our own distribution system. The total length of cables and bus duct exceed any transformer "tap" rule. Do we have to put a new close coupled overcurrent device at the transformers to meet current code? This also leads to the question of: do we now need close coupled overcurrent devices at our pad mounted transformers to protect out-going cables? We are not a utility but have miles of cables and numerous 15 kV breakers and fused switches and fused cutouts protecting the system. Could we consider the cables and bus duct as service conductors? Would that help in not needing the close coupled OCP?

Thanks for your time.........
 
No, not an airport but if it helps to think we are fine. 2000 plus acres so you can have a few miles of cable without a problem......... I can't believe we are the only place around that runs into this issue. To the point though, we do not have room in the existing vault to add any secondary OCD. I find it hard to reconcile that it is really needed. The existing installation is decades old and has been providing power just fine. It would seem that if we could consider the cable and bus duct from the transformers as service conductors we'd be okay with the main OCD as is. If we were a utility this would be the case. But we are not...........
 
There are a lot industrial installations installed in this manner. The code does not do a good job in some of these type of installations and is often ignored under engineering supervison. Over the years the substantation for a number of code changes has been "industry has been doing it this way for years with no problems".
Don
 
I imagine that simple replacement of individual components an a system does not require changing the configuration of other parts of that system, if compliant when orginally installed.
 
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