Routing feeder equipment grounding conductor OUTSIDE of conduit? 1

[NSee]

Where it is desired in existing facilities to add an equipment grounding conductor to an existing feeder, is it allowed to route the equipment grounding conductor OUTSIDE and strapped to the existing conduit. If not, WHERE is this specifically prohibited by the NEC?

Article 250.118 discusses the equipment grounding conductor routed "with" or "enclosing" (metallic conduit path is conductor). I see nothing in the code that either allows or prohibits augmenting an existing feeder w/ an equipment ground conductor.

Thanks

 

[rbulsara]

If you modify any existing equipment or feeder, the revised version must meet the current code. Ask your local building and electrical inspector. Also it is stated somewhere in the building codes.

Rafiq Bulsara

http://www.srengineersct.com

 

[dpc]

Article 250.4 requires that a low impedance return path be provided. Placing the ground wire outside of a steel conduit will result in quite a high inductive reactance for the ground return. If the conduit is non-ferrous, it might have some benefit, but if the conduit is steel, the exterior ground wire has very little actual benefit due to the high impedance. If you are trying to satisfy an NEC requirement for a grounding conductor, it will be up to the local AHJ, but I wouldn't accept it. If you are trying to supplement an steel conduit being used for a grounding conductor, I don't think you will really be accomplishing much with the ground wire outside of the conduit.



"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)

 

[NSee]

^ Thanks for the input. I have been looking into this pretty much all morning and have come to the same conclusion. This is an old building where the Owner wants the conductor. My direction is for them to price pulling out the 4 wire system and putting in a 5 wire system. The existing conduit is adequately sized at 2.5" to get in 5 250kcmil (THHN or XHHW). Which is what I need.

We have someone in the field now tracing the conduit to ensure it is all 2.5" and either EMT or rigid steel.

Thank you both for the input.

 

[itsmoked]

I have been forced to do that too. It works, but is certainly sub par.

You may help the owner "swallow the pill" by pointing out that copper theft is rampant and that he could easily have an exterior hung wire stolen. Inside a conduit protects it from not just accidental damage but from much more likely - theft.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[resqcapt19]

300.3(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).

 

[trosepe]

Why 5 #250 kcmil? First; that will be a tough pull even in EMT. Second; if #250 kcmil is the phase conductor size, then your overcurrent protection is probably 300 amps or less. Third; the equipment ground conductor needed for a circuit with a 300 amp overcurrent device is #4 (NEC Table 250.122). You won't gain much by pulling in the 5th #250 kcmil except make a difficult pull.