Grounding System for attached building

C

chocony

Member
Location
Atlanta
Occupation
Electrical Designer
Hi Everyone,
We had a project for a 3-story building a few years ago. Client now wants to expand the building with another smaller 3 story building connected by outdoor hallways in each level. Do I need to provide a grounding system in first floor electrical room, or can be bonded to the existing main electrical room grounding system?


Thank you.
 
chocony said:
Do I need to provide a grounding system in first floor electrical room, or can be bonded to the existing main electrical room grounding system?
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If it's a detached structure (according to the building department), it will need its own main disconnect as well as electrode system (unless it can be connected to the existing electrode system).
 
LarryFine said:
If it's a detached structure (according to the building department), it will need its own main disconnect as well as electrode system (unless it can be connected to the existing electrode system).
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Hi Larry, it will be connected by outdoor hallways for all 3 levels, so it is attached building by outdoor hallways. The panels are fed from the existing switchboard. If we are to be connected to the existing electrode system, what do I need to provide? There is trenching in between the old and new electrical room with a handhole in between.

Thanks!
 
To add, your new panels should be wired as sub-panels either way, so we're only discussing whether there should be electrode connections to the EGCs.

I say yes; earth, metallic water service and/or distribution, etc.
 
LarryFine said:
That sure sounds like detached to me.
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There are physical halls attached to them that might mean otherwise. I think only the building department can say for sure. But likely I think you are right just because it would simplify things a lot if for fire and building regulation purposes the buildings were not one structure.

In any case it won't hurt to bond the EGC to cee and metal water pipe if there is a metal water pipe.
 
chocony said:
Client now wants to expand the building with another smaller 3 story building connected by outdoor hallways in each level. Do I need to provide a grounding system in first floor electrical room
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Since the buildings are clearly attached a separate GES is not required. If there is no CEE in the existing building and a new one is present at the addition I've seen inspectors require then to be connected to the building GES. If you're not touching the service then it's debatable as to whether or not using the new CEE is required.
 
Let's ask another question- if the outdoor hallways* are removed, are the buildings separate structures and each needing a GES? And I know it's not "code", but simply connecting two otherwise standalone buildings with a 10' wide corridor does not make them one.

* what does that really mean- roofed but open to the weather? completely closed and climate controlled? something in between? That doesn't affect the NEC but it very well may affect the AHJ.

My take is to assume they are two completely separate structures excepting that instead of taking a service, the second takes a feeder from the first. If there's little added cost, I'd also design it so that they can be separated in the future if that's conceivable.
 
Thank you Everyone. Per architect the building is considered as one building. Not 2 buildings. The project is in Construction, and we do not want to add any cost is possible.
 
chocony said:
Thank you Everyone. Per architect the building is considered as one building. Not 2 buildings. The project is in Construction, and we do not want to add any cost is possible.
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Since it's a single building you do not need to do anything regarding connections to the existing GES. The EGC run with the feeder(s) is all that's required.
 
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