Spider Web Ground

[jamesoftn]

A facility has some serious electrical problems due to a very corrisive atmosphere, poor installations, and unqualifed maintance persons. The metallic enclosures ard badly deteoriated. In equipment ground has been used as the neutral also. Presently doing a upgrade. The EC wants to run a ground throughout the building in a PVC conduit branching off to different pieces of equipment while using the EGC for the neutral. Will start off with a large wire size, splice and drop off at various locations. I told him I did not believe this is to code. I have not found in the code where this is permitted. What do you guys think. If it is permitted please give code reference.

 

[iwire]

I am not following you entirely but at the least 300.3(B) requires the EGC and neutral to be run with the circuit conductors.

 

[jamesoftn]

the existing conduits and conductors are to be reused. He wants to add a EGC in a seperate conduit that goes through the facility and drops off where needed. Simliar to a spider web. Using the orignal EGC and reidentify as a neutral.

 

[augie47]

The only exceptions I can find to the EGC being run with the circuit conductors are in 250.134(B) and 250.136, but there may be something I don't see.
(if I missed it Dennis or Bob will find it)

 

[Dennis Alwon]

I don't believe you can do this and be compliant. First off, as Bob stated 300.3 limits you already and the exceptions to that don't appear to apply.

IMO, you need to run the egc in the raceway with the other conductors. I am not sure why your method would not be satisfactory but it is not compliant.

 

[don_resqcapt19]

... I am not sure why your method would not be satisfactory but it is not compliant.

There is a large increase in the impedance of an AC circuit where the supply and return paths are physically separated from each other. This impedance increase will cause an increase in the time that it takes for the OCPD to clear the fault. In extreme cases, it may limit the current so much that the OCPD does not clear the fault.

 

[kwired]

A facility has some serious electrical problems due to a very corrisive atmosphere, poor installations, and unqualifed maintance persons. The metallic enclosures ard badly deteoriated. In equipment ground has been used as the neutral also. Presently doing a upgrade. The EC wants to run a ground throughout the building in a PVC conduit branching off to different pieces of equipment while using the EGC for the neutral. Will start off with a large wire size, splice and drop off at various locations. I told him I did not believe this is to code. I have not found in the code where this is permitted. What do you guys think. If it is permitted please give code reference.

sounds to me like anything that gets upgraded needs to be done properly anything not upgraded needs to be evaluated as to just how safe it is to leave in its condition.

If corrosive envirionment is involved then you probably need non metallic raceways or pvc coated raceways, and non metallic or stainless enclosures. Don't know if they actually make stainless raceways but I have used short runs of stainless sch 40 pipe as a raceway a few times in a dairy plant. USDA and food inspectors do not like rust streaks running down the side of a piece of equipment in food processing areas. Everyone can now beat me down for using a non listed or approved raceway.

 

[Dennis Alwon]

There is a large increase in the impedance of an AC circuit where the supply and return paths are physically separated from each other. This impedance increase will cause an increase in the time that it takes for the OCPD to clear the fault. In extreme cases, it may limit the current so much that the OCPD does not clear the fault.

You are talking about the grounded cnductor and the ungrounded conductors in separate raceways. I was talking about the EGC being run separate from the grounded and ungrounded conductors.

The op has the grounded and ungrounded in one raceway and the egc in another. Would your example still apply?

 

[Volta]

...Everyone can now beat me down for using a non listed or approved raceway.

Come on now, no one here would do that! :roll:
But it is made.

You are talking about the grounded cnductor and the ungrounded conductors in separate raceways. I was talking about the EGC being run separate from the grounded and ungrounded conductors.

The op has the grounded and ungrounded in one raceway and the egc in another. Would your example still apply?

I think so, he was using the term 'return path' in this context as the EGC during a ground fault, I believe.

 

[kwired]

You are talking about the grounded cnductor and the ungrounded conductors in separate raceways. I was talking about the EGC being run separate from the grounded and ungrounded conductors.

The op has the grounded and ungrounded in one raceway and the egc in another. Would your example still apply?

Yes - during a fault the EGC is the return path

There is a large increase in the impedance of an AC circuit where the supply and return paths are physically separated from each other.

If the supply and return path are not in close proximity to each other the impedance of one or both can have a large increase and with high current levels that are involved with a fault this impedance is higher than with normal circuit current levels. That is why the equipment grounding conductor is required to be in same raceway or cable as circuit conductors.

 

[jamesoftn]

all the existing circuit conductors will be left as is, only the EGC will be in a different raceway. The only question was if code permitted this installation. It appears from all the answers it is not. THANKS

 

[don_resqcapt19]

Dennis,
As the other posters have said, I was talking about the separation between the ungrounded conductors and the EGC. The increase in the inductive reactance limits the amount of fault current that can flow on the circuit and increases the time to trip for the OCPD.

 

[Pierre C Belarge]

James
I am not sure which printing of the NEC you may have, but....if you take a real close look in your book (you may need a magnifying glass) you will see the small print that states:

"the equipment ground conductor may be installed as per Exception #1.

Exception 1.
All equipment ground conductors may be installed separate from the circuit conductors if:
a. the property owner has sufficient insurance to cover all damage to the building.
b. the property owner has sufficient insurance to cover up to 3 injured personnel or 1 personnel's death."


So as we can see it is not all about safety, $$ does count.

or

From Don's post
"
Dennis,
As the other posters have said, I was talking about the separation between the ungrounded conductors and the EGC. The increase in the inductive reactance limits the amount of fault current that can flow on the circuit and increases the time to trip for the OCPD."
__________________

 

[Volta]

James
I am not sure which printing of the NEC you may have, but....

Exception 1.
All equipment ground conductors may be installed separate from the circuit conductors if:
a. the property owner has sufficient insurance to cover all damage to the building.
b. the property owner has sufficient insurance to cover up to 3 injured personnel or 1 personnel's death."....

Yeah, I've been saving for that version forever, and just it keeps getting pricier!