Ufer and modular buildings

T

TealHeals

Member
Location
Oregon
Occupation
Journeyman Electrician
I have an 800 amp main distribution panel that will feed four 200 amp panels in four separate modular buildings. The main distribution panel will be grounded via ufer on the common concrete pad. The question of whether each of the 200 amp sub-panels will need separate grounding or not has been brought up.
Can you help me get my thinking straight on this? My take is that a sufficiently grounded main distribution panel is fine. Each of the sub-panels receives the appropriately sized EGC. I'm about to dive back in to section 250 and refresh my knowledge; but for some reason, I'm just thinking in circles about this.
 
Welcome to the forum.

Yes, at each separate structure, anything more than a branch circuit requires an electrode system.
 
To go with Larry's post.

250.32 Buildings or Structures Supplied by a Feeder(s)
or Branch Circuit(s).
(A) Grounding Electrode. Building(s) or structure(s) supplied
by feeder(s) or branch circuit(s) shall have a grounding
electrode or grounding electrode system installed in
accordance with Part III of Article 250. The grounding
electrode conductor(s) shall be connected in accordance
with 250.32(B) or (C). Where there is no existing grounding
electrode, the grounding electrode(s) required in 250.50
shall be installed.
Exception: A grounding electrode shall not be required
where only a single branch circuit, including a multiwire
branch circuit, supplies the building or structure and the
branch circuit includes an equipment grounding conductor
for grounding the normally non–current-carrying metal
parts of equipment.
Click to expand...
 
LarryFine said:
Welcome to the forum.

Yes, at each separate structure, anything more than a branch circuit requires an electrode system.
Click to expand...
I'm having such a hard time reconciling the visual that goes with the code.
It's 1 building with 4 separate sub-panels. The main distribution panel might be mounted to the building with its own ufer. And I just can't see each sub-panel as having its own electrode system. Is my brain in rebellion mode? What am I missing?
 
LarryFine said:
We can't give a definitive answer with changing facts. Is it one or four buildings?
Click to expand...
Yes - maybe this is why my brain is wrestling with this situation. I mis-spoke the first time. It is NOT 4 separate buildings like I initially thought. The drawings and what people were telling me were not aligning. We've got it sorted out, and my relationship with article 250 is looking better.
 
If it's a single structure, and not fire-wall separated buildings, the feeder EGC is all you need.
 
And if it is 4 separate modules sitting on a common slab, you might have arguments about it being 4 buildings or 1 building. But if the 4 modules are joined together without firewalls, then IMHO it is pretty solidly 1 building
 
You must log in or register to reply here.
Top