Grounded subpanel

D

Dengineer

Member
Location
new york
Occupation
Electrical Engineer
Hello All,

Quick question about grounding. Pleaser refer to the image below for for more information.

I am an electrical engineer and would like some help understanding the grounding in the image below.

This is an parament in a 24 floor residential building. The space has a subpanel that's fed from a main breaker on another floor coming off a sub-meter in the building. There is no conduit running from the junction box entering the tenant space to the sub-panel. The main feeders are open to air and there is not grounding conductor or grounding bar, just a neutral. Other then not being code compliant is this a danger to the tenant? could it cause electric shock?



20230921_094241.jpg
 
hbiss

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Dengineer said:
is this a danger to the tenant? could it cause electric shock?
Click to expand...

If the tenant were to contact an appliance or anything else electrical that gets its ground from that panel and something like a water faucet, yes, there is the real possibility of a shock.

There is a reason that the CODE requires an EGC feeding a sub panel and that's it. It seems you know that.
Dengineer said:
there is not grounding conductor or grounding bar, just a neutral
Click to expand...


-Hal
 
Another C10

Another C10

Electrical Contractor 1987 - present
Location
Southern Cal
Occupation
Electrician NEC 2020
maybe the subfeed conduit is the grounded path if so, put the grounding wires on a separate ground bar threaded onto the panel enclosure.
 
D

Dengineer

Member
Location
new york
Occupation
Electrical Engineer
Another C10 said:
maybe the subfeed conduit is the grounded path if so, put the grounding wires on a separate ground bar threaded onto the panel enclosure.
Click to expand...
Yes that would be the normal case, but here there is no hard metal conduit that would create that ground coming from the main breaker enclosure downstairs. They have a junctions box on the floor where the feeder come up and from there to the panel there is no conduit. It's just conductors open to air feeding the panel.
 
D

Dengineer

Member
Location
new york
Occupation
Electrical Engineer
hbiss said:
If the tenant were to contact an appliance or anything else electrical that gets its ground from that panel and something like a water faucet, yes, there is the real possibility of a shock.

There is a reason that the CODE requires an EGC feeding a sub panel and that's it. It seems you know that.



-Hal
Click to expand...
Thats what I assumed, but was told otherwise.

My solution here would be to provide the metal conduit that should run from the junction box to the panel and then provide a new ground bar to separate the neutral and ground.

Now...what happens if we simply connect the neutral and ground here similar to the main service panel?
 
T

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
infinity said:
What kind of contractor does work like this in a 24 unit building?
Click to expand...
It is actually worse...24 floors, not units, according to the OP.
If the OP is correct in his description there are some pretty serious code and safety issues here. But I'm with you, how does something this flawed get done in a building of this size? This is not something you normally would see in a large high rise building environment.
 
Buck Parrish

Buck Parrish

Senior Member
Location
NC & IN
Dengineer said:
Now...what happens if we simply connect the neutral and ground here similar to the main service panel?
Click to expand...
You may not ever notice it, especially with all the plastic plumbing pipe today. But if you do it can be a problem, esspecially to a todler or some one not strong enough to pull away from an electic shock. . The equipment ground can be energized when your equipment ground is attached to the neutral bar.
One way I explain it to the old timers in rural Indiana. I say remember when you stood on the metal drain whilst taking a shower then you touched the spigot and you got a shock that made you forget about rinsing off.

It's the same thing only in many different variations. If this building was built using red iorn then the metal is connected to the neutrals main panel.

Any time you become a better path for the neutral to make it's way back to the source.
 
D

Dengineer

Member
Location
new york
Occupation
Electrical Engineer
texie said:
It is actually worse...24 floors, not units, according to the OP.
If the OP is correct in his description there are some pretty serious code and safety issues here. But I'm with you, how does something this flawed get done in a building of this size? This is not something you normally would see in a large high rise building environment.
Click to expand...
Sorry this is just one apartment! was just giving details.
 
D

Dengineer

Member
Location
new york
Occupation
Electrical Engineer
rambojoe said:
More importantly, what kind of electrical engineer asks such elementry questions...
Click to expand...
Still fresh to the field. I am new to the field work and sometimes get surprised by what I see. Huge difference between being behind a computer as a designer and then getting to see what's actually installed on the field, especially when its a messy install. I enjoy throwing question out and hearing other peoples opinions/solutions.
 
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