Grounding,Double ended MCC

[Cableman]

I have a double ended MCC (tie breaker in the middle, normally open). Each side is fed the following: from the utility to a meter/ct. from meter/ct to a main breaker which feeds one side of the MCC bus.
The engineer is proposing the following system grounding:
There should be a total of three ground wells with ground rods. two for the meter cabinets and one for the MCC. The ground rods shall not be connected at a single point. At the meter cabinets, neutral and ground must not be bonded together. The neutral to ground bond must take place at the MCC.

Is the engineers recommendation correct?

Thanks for the time and help

 

[RUWired]

The GEC can be located at any acessible point along the way up to the main breaker for each service to the equipment provided (250.24(A1), or it can be made at the tie section. 250.24(A)3. If you choose a seperate GEC for each service, they are required to be bonded together per 250.58.

All enclosures and raceways for service conductors are required to be bonded together including the ct cabinet. If the engineer chooses to float the neutral in the ct cabinet, the enclosure will still need to be bonded.(250.92(A)1 and 2)

Rick

 

[brian john]

I have a double ended MCC (tie breaker in the middle, normally open). Each side is fed the following: from the utility to a meter/ct. from meter/ct to a main breaker which feeds one side of the MCC bus.
The engineer is proposing the following system grounding:
There should be a total of three ground wells with ground rods. two for the meter cabinets and one for the MCC. The ground rods shall not be connected at a single point. At the meter cabinets, neutral and ground must not be bonded together. The neutral to ground bond must take place at the MCC.

Your engineer seems to be over thinking this IMO. What does he think he will gain by this?


The real issue comes when you get into the service in this case the MCC, and how you ground the neutral and how the GFP CT’s are situated. In testing these systems the number we see installed improperly in the field and quite often from the manufacture is fairly high.