Article 250.64(E) What does it mean to your installation?

[pjholguin]

Just browsing through article 250; Just looking for different opinions.

250.64(E) Electrically Continuous...What does this mean to you in reference to raceways and enclosures?

Feedback appreciated,
PJHolguin

 

[Dennis Alwon]

Just browsing through article 250; Just looking for different opinions.

250.64(E) Electrically Continuous...What does this mean to you in reference to raceways and enclosures?

Feedback appreciated,
PJHolguin

250.64(E) continuous is in reference to the grounding electrode conductor not raceways

 

[GoldDigger]

And while we are on the subject, remember that if you put a GEC inside a metallic (not just ferrous) raceway, you need to bond the GEC to the electrically continuous raceway at both ends.
If the raceway (or metal protective sleeve which looks suspiciously similar to raceway) is not itself continuous, you would need to bond the GEC to each end of each segment or bond the segments together.

Reason: A metallic raceway will allow a flow of current around the circumference of the raceway which causes it to act as a choke (inductive impedance) which can decrease the conductivity of the GEC for lightning spikes and other high current events and to potentially heat up drastically from the circulating current. The raceway is a one turn transformer secondary linked to the fractional turn of the GEC itself.
If the raceway is ferrous as well, there are other possible effects, also bad.
Allowing the fault current to flow through the sleeve instead of the GEC inside it avoids these effects.

 

[texie]

250.64(E) continuous is in reference to the grounding electrode conductor not raceways

Yes this is for the GEC enclosure or raceway.

I think the OP is asking about extra bonding to be per 250.92 which requires "special" bonding when the enclosure is of ferrous metal.

 

[Dennis Alwon]

Yes this is for the GEC enclosure or raceway.

I think the OP is asking about extra bonding to be per 250.92 which requires "special" bonding when the enclosure is of ferrous metal.

Yep-- I see that- Golddigger got it with the bonding

 

[texie]

Just browsing through article 250; Just looking for different opinions.

250.64(E) Electrically Continuous...What does this mean to you in reference to raceways and enclosures?

Feedback appreciated,
PJHolguin

It means it does not have to be mechanically continuous. If you use a ferrous metal raceway it could run from a service enclosure but not be connected the grounding electrode. However, it must be electrically continuous in a manner specified by 250.92. In other words the GEC would have to have a bonding jumper to the end of the raceway or use an approved fitting made for this purpose.
This is one reason you see mostly PVC used to enclose a GEC as it saves some installation requirements.

Maybe somebody has a graphic of this.

 

[pjholguin]

That is exactly what I am thinking...Thank you all for the input!

PJHolguin.

It means it does not have to be mechanically continuous. If you use a ferrous metal raceway it could run from a service enclosure but not be connected the grounding electrode. However, it must be electrically continuous in a manner specified by 250.92. In other words the GEC would have to have a bonding jumper to the end of the raceway or use an approved fitting made for this purpose.
This is one reason you see mostly PVC used to enclose a GEC as it saves some installation requirements.

Maybe somebody has a graphic of this.

 

[don_resqcapt19]

And while we are on the subject, remember that if you put a GEC inside a metallic (not just ferrous) raceway, you need to bond the GEC to the electrically continuous raceway at both ends.
If the raceway (or metal protective sleeve which looks suspiciously similar to raceway) is not itself continuous, you would need to bond the GEC to each end of each segment or bond the segments together.

Reason: A metallic raceway will allow a flow of current around the circumference of the raceway which causes it to act as a choke (inductive impedance) which can decrease the conductivity of the GEC for lightning spikes and other high current events and to potentially heat up drastically from the circulating current. The raceway is a one turn transformer secondary linked to the fractional turn of the GEC itself.
If the raceway is ferrous as well, there are other possible effects, also bad.
Allowing the fault current to flow through the sleeve instead of the GEC inside it avoids these effects.

If you are bonding the non-ferrous metallic raceway, you would be making it electrically continuous and 250.64(E)(1) says:

... Nonferrous metal raceways and enclosures shall not be required to be electrically continuous.

It is also my understanding the the choke effect is very minor if the raceway is nonferrous.