sub panel grounding

[sminor]

I need a reminder about sub panels in seperate buildings, what conditions require re-bonding the neutral to the ground?

 

[roger]

Read 250.32(B)

Roger

 

[slick 50]

I need a reminder about sub panels in seperate buildings, what conditions require re-bonding the neutral to the ground?

this would be considered an out building. I beleive the panel will need a main and need its own ground rods

 

[Jesse7623]

yes but don't re-bond the grounded conductor.

 

[slick 50]

yes but don't re-bond the grounded conductor.

correct, it is still a sub panel but requires a main and ground electrodes. Neutral remains isolated.

 

[roger]

yes but don't re-bond the grounded conductor.

Neutral remains isolated.

Depends, if you are under a previous code cycle you could reground the neutral, for example, see 250.32(B)(2) in the 2005 NEC.

Roger

 

[RUWired]

this would be considered an out building. I beleive the panel will need a main and need its own ground rods

What kind of main does it need. A main disconnect or a main OCPD. Don't you just hate the technical correctiveness of the code.
Rick

 

[LarryFine]

What kind of main does it need. A main disconnect or a main OCPD.

The former. The OCPD is at the source end (unless the panel's rating is lower than the feeder and its OCPD.)

 

[slick 50]

What kind of main does it need. A main disconnect or a main OCPD. Don't you just hate the technical correctiveness of the code.
Rick

Just a disconnect unless the sub panel is further than 200' away because the short circuit current rating drops to 300 amps available instead of 500.

 

[Twoskinsoneman]

Just a disconnect unless the sub panel is further than 200' away because the short circuit current rating drops to 300 amps available instead of 500.

Can you please explain this sentence?

I understand what short circuit current is and the fact that you have a long circuit with a higher impedance would mean less available short circuit current available right?

What is the reference to 300amps and 500amps?

lil help please

 

[Twoskinsoneman]

Can you please explain this sentence?

I understand what short circuit current is and the fact that you have a long circuit with a higher impedance would mean less available short circuit current available right?

What is the reference to 300amps and 500amps?

lil help please

Bump. Hoping to get reply.

 

[Jim W in Tampa]

Bump. Hoping to get reply.

add a bump ,i wanta know too.

 

[glene77is]

I need a reminder about sub panels in seperate buildings, what conditions require re-bonding the neutral to the ground?

Per 2005 Code, for sub-panels.

Never "Re-Bond" the insulated Neutral. It is 'created' in the primary panel.
... this violation would send neutral current from the sub-panel
back down the EGC to the primary panel.

Always Bond the EGC, the un-insulated ground wire from the primary panel.
... this is the return path for equipment faults to ground.

Always use a Ground Rod.
... for lightning/HV shunt to earth reference ground.

Can use a Back-Fed CB for the Main.

And never hammer your staples onto the Romex,
it can setup a condition called 'pyroformic-carbonization'.
I think this term can be found in the NEC Handbook, '05.

I can give you a money back guarantee
this advice is from NEC. :smile:

 

[roger]

Per 2005 Code, for sub-panels.

Never "Re-Bond" the insulated Neutral. It is 'created' in the primary panel.
... this violation would send neutral current from the sub-panel
back down the EGC to the primary panel.

Glen, you are correct that it could not be re-bonded to an EGC however, a neutral to an out building can be regrounded per the 2005 and earlier NEC if the installation is installed per 250.32.

Roger