Article 240(B)(2)

[yha3]

I was sizing tap conductors from Article 240.21(B)(2), and I was stumped!! How do I size my ground? To the feeder overcurrent protection device, the tap conductor or the tap conductor overprotection device?

 

[don_resqcapt19]

Re: Article 240(B)(2)

The OCPD that is protecting the circuit at that point is the feeder OCPD, so in my opinion, the EGC size should be based on the size of the feeder OCPD.
Don

 

[websparky]

Re: Article 240(B)(2)

yha3,

IMO;

Will the tap conductors land in an enclosure with an OCD? If so, I would imagine that you could size the EGC to that OCD and satisfy the requirement. Are you installing them in a metal raceway?

Hope this helps,
Dave

 

[iwire]

Re: Article 240(B)(2)

yha3

I would size the grounding conductor that is with the tapped conductors to the size of the OCPD that feeds the taps.

Once I got to the new OCPD that I added I would (or could) drop down the size of the ground conductor to a size indicated by Table 250.122. for the new OCPD

I base that on two things.

1)The wording in table 250.122.

Rating or Setting of Automatic Overcurrent Device in Circuit Ahead of Equipment, Conduit, etc., Not Exceeding (Amperes)

2)And what the ground has to be capable of, if some unfortunate person cut into the tapped conductors or if a tapped conductor burnt off the line side of your added OCPD and went to ground it would be the original OCPD that the grounding conductor has to be able to trip in a timely matter.

Example

Tap a 400 amp feeder with 2 AWG copper to a new 100 amp OCPD.

3 AWG grounding conductor from the tap to the new OCPD enclosure

8 AWG grounding conductors from the new OCPD enclosure downstream to the load.

But in know case would the grounding conductors have to be larger than the ungrounded conductors 250.122(A).

Bob

 

[brian john]

Re: Article 240(B)(2)

Sitting in front of the TV using my laptop (long explanation for no NEC available) But I believe at no time does the GEC need to be larger than the phase conductors>