grounding from service panel

Status
Not open for further replies.

pschleicher

New member
Location
Shawnee KS 66226
I have a question about grounding the sub panels from the service panel, is it permissible to ground the sub panels from the service panel and not bound the neutral at the sub panel? Or should the sub panel have its own ground from a ground rod and not a ground from the service panel? Thanks
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
A sub-panel located in the same structure as the service panel would be grounded by an equipment grounding conductor meeting the specifics of 250.118 installed from the service panel.
A sub panel in a separate structure, beginning with the '05 or '08 Code, also requires an equipment ground from the service panel PLUS a grounding electrode.
The neutral (grounded) conductor as a sub-panel ground was allowed in detached structure under certain conditions prior to the Code change
 

kwired

Electron manager
Location
NE Nebraska
I have a question about grounding the sub panels from the service panel, is it permissible to ground the sub panels from the service panel and not bound the neutral at the sub panel? Or should the sub panel have its own ground from a ground rod and not a ground from the service panel? Thanks

Equipment grounding conductors must run with all feeders and branch circuits after leaving the service equipment or first disconnecting means of a separately derived system. Some instances this EGC can be in the form of metal raceway.

Never use the earth as a EGC pathway, you will almost never achieve low enough resistance to use as an effective EGC. A resistance of 5 ohms is very good for a ground rod - but still only allows 24 amps of current to flow if the voltage is 120 volts. This will leave even a faulted 20 amp circuit energized for some significant time before tripping a 20 amp overcurrent device, where a solid metallic path will be low enough resistance that current will go up quite a bit and trip the OCPD in it's instantaneous time ranges.
 
Status
Not open for further replies.
Top