CGEC for Separately Derived Systems in Multiple Buildings

Status
Not open for further replies.
T

T-EC

Member
Location
Seattle
Occupation
GC
Hey team,
I am working on a project and this question came up.

If I have five buildings that are all feed by the service in building one, and each building has a Separately Derived System. Do we need to run a Common Grounding Electrode Conductor to all the Separately Derived Systems?

This has been the case in a single building with separately Derived Systems on every floor, but dose it apply to separate buildings feed with feeders from the main building?

Please lend us your input. Thanks.
 
Each building needs its own grounding electrode system and the SDSs at those buildings can connect to the building grounding electrode system.
 
infinity said:
Are these 5 separate structures connect by underground raceways?
Click to expand...
Hey Infinity,
there are 5 separate underground raceways. One to each building.

The service in the main building is a 3000 amp 480 volt services. That is feeding 3 different transformers. one in building 2. one in building 3. one in building 4.
 
don_resqcapt19 said:
Each building needs its own grounding electrode system and the SDSs at those buildings can connect to the building grounding electrode system.
Click to expand...
hey Don,
each building will have a ufer ground installed and attached to a ground bar and tied to building steel, water, and gas.
 
I would say yes, every feeder needs an EGC run with it from the main service and tied to a GEC system in each building.

And no, the individual SDSs need not tie back to the main service, but most likely inadvertently will anyway.
 
T-EC said:
View attachment 2558757
Here is a drawing.
Click to expand...
That looks like the EGC from the main building it going to XO at the transformers in the other buildings. While there will be a path via the system bonding jumper, the feeder EGC does not directly connect to XO. It connects to the transformer enclosure as the fault clearing path for a ground fault on the primary side.
 
don_resqcapt19 said:
That looks like the EGC from the main building it going to XO at the transformers in the other buildings. While there will be a path via the system bonding jumper, the feeder EGC does not directly connect to XO. It connects to the transformer enclosure as the fault clearing path for a ground fault on the primary side.
Click to expand...
I guess the question is, do I need a CGEC?
 
LarryFine said:
I would say yes, every feeder needs an EGC run with it from the main service and tied to a GEC system in each building.

And no, the individual SDSs need not tie back to the main service, but most likely inadvertently will anyway.
Click to expand...
✅ Awesome. ECG is on the list, but do we need a CGEC?
 
Don't all SDS's in a given building that are grounded have to have those grounds interconnected, i.e. a common ground electrode conductor? Typically building steel can provide that path, but it would depend on building construction and whether building steel is accessible in which case a common wire or bar type system could be used.

You do not need a common GEC between buildings, just an EGC.
 
suemarkp said:
Don't all SDS's in a given building that are grounded have to have those grounds interconnected, i.e. a common ground electrode conductor? Typically building steel can provide that path, but it would depend on building construction and whether building steel is accessible in which case a common wire or bar type system could be used.

You do not need a common GEC between buildings, just an EGC.
Click to expand...
hey Mark,
The Project we are doing is in Kent WA.

I agree with you. I want to make sure that a CGEC is not required for building to building. Make sense for SDS in the same building.
 
T-EC said:
in the drawing above, the CGEC is going from the main service to each SDS. Is this correct based on code 250.58 and 250.64?
Click to expand...
There is nothing in the code that would require that. It appears to me that the wire in question is really the feeder EGC, but shown being connected at the wrong location at the transformer.
Also there needs to be a building disconnect for each of the buildings. If the transformers are outside of the building the OCPD on the secondary to protect the secondary conductors and, if the primary protection is over 125%, to protect the secondary winding could serve as the building disconnect.
 
don_resqcapt19 said:
There is nothing in the code that would require that. It appears to me that the wire in question is really the feeder EGC, but shown being connected at the wrong location at the transformer.
Also there needs to be a building disconnect for each of the buildings. If the transformers are outside of the building the OCPD on the secondary to protect the secondary conductors and, if the primary protection is over 125%, to protect the secondary winding could serve as the building disconnect.
Click to expand...
hey Don,
the EGC will tie into the XO on the Transformers. The SDS will have a 480 volt panel with the breaker acting as the disconnect next to the transformer.

I hope that Helps.
 
T-EC said:
hey Don,
the EGC will tie into the XO on the Transformers. The SDS will have a 480 volt panel with the breaker acting as the disconnect next to the transformer.

I hope that Helps.
Click to expand...
The EGC from the feeder does not directly to XO. It ties into the grounding bar in the transformer that is required by 450.10(A). Yes there will be a physical connection between the two via the system bonding jumper.
 
Status
Not open for further replies.
Top