2 AWG CU EGC to equipment

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tom baker

tom baker

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Master Electrician
I am reviewing plans for a ultra violet water treatment facility. It the typical PLC and equipment cabinets. Voltage is 380/277 and 120/208, about a 500 ampere service. The plans call for a 2 AWG copper EGC to all cabinets and equipment such as motors.
I feel this is excessive, lets use the EGC in the supply circuit to clear a fault and not create a parallel path to lessen the fault current in the supply circuit.
Comments?

It almost seems like it was spec'd from a power plant design. The duct bank is sch 80 PVC with 4,000 psi concrete, #4 rebar around it.
I normally use sch 40 and call it good.
 
tom baker said:
I am reviewing plans for a ultra violet water treatment facility. It the typical PLC and equipment cabinets. Voltage is 380/277 and 120/208, about a 500 ampere service. The plans call for a 2 AWG copper EGC to all cabinets and equipment such as motors.
I feel this is excessive, lets use the EGC in the supply circuit to clear a fault and not create a parallel path to lessen the fault current in the supply circuit.
Comments?
Click to expand...
You lost me with the parallel path on an EGC... They are often parallel all over the place... Or do you mean GEC?
 
tom baker said:
...
I feel this is excessive, lets use the EGC in the supply circuit to clear a fault and not create a parallel path to lessen the fault current in the supply circuit.
Comments? ...
Click to expand...
The additional grounding paths do not lessen the fault current in the supply circuit. As you lower the impedance of the fault return path the amount of fault current flowing increases and causes the OCPD to operate quicker. While it may very well be overkill, it does no harm, other than increasing the project costs.
 
Chances are the EE that designed it is airing on the side of caution due to the application. From every drawing and speck I have worked with, that were designed by our engineers for the state, they will do things that do seem to be over kill. When I ask one of the engineers why they did it that way he explained they want to design and build something that will last and exceed any code. They justify it by it lasting longer with out upgrades at a later date, and even if it cost more now it will save money in the long run.
 
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