Proper grounding

[markessox65]

We have an MCC room with rigid conduit running out to varios 480v motors 10 to 75hp. They are using the proper size wires, but there is no ground wire. There was none pulled in. Should there be a ground wire back to the supply or is the rigid conduit addiquate?

 

[don_resqcapt19]

The conduit is suitable for use as the EGC. See 250.118. If there is a flexible connection at the motor, a bonding jumper will be required. Note that very often the job specs will require an EGC of the wire type to be used in the raceway.

 

[Strahan]

The conduit is suitable for use as the EGC. See 250.118. If there is a flexible connection at the motor, a bonding jumper will be required. Note that very often the job specs will require an EGC of the wire type to be used in the raceway.

Hello Don, I'm having a little trouble with this one. We are currently going through an electrical audit and the inspector is telling us that we need to use special compound on the threads since we are in a wet location and therefore existing conduit runs do not meet code. I'm having a hard time believing this. I never heard of special compound? Furthermore this conduit was run years ago and if the joints are all secure then the conduit should be an adequate ground. Any thoughts?

 

[don_resqcapt19]

Take a look at 300.6(A). This wording was added in the 2002 code and requires the application of a electrically conductive, corrosion-resistant compound for all field cut threads when the conduit is installed where corrosion protection is necessary. Installation in a wet location would trigger this requirement.
One product would be T&Bs KOPR-Shield and another would be CH "STL" thread lubricant. Both are pricy and the T&B product is messy to use.

The NEC is not retoactive so any conduit installed before the adoption of the 2002 code did not require the use of this compound.

 

[renosteinke]

FWIW, Noalox is also listed (and labled) for this use.

I don't think the compound you use MUST be listed. I do know that the usual anti-seize compounds, such as C5-A, have been used for this purpose for decades before the NEC mentioned the need.

Side note: Why isn't C5-A 'listed?' That I can answer. Last year I spearheaded an investigation into getting the product listed. The product is essentially identical to Kopr-Shield. Ultimately, after the investigation was complete, the parent company decided to forgoe the expense of listing. License and follow-up inspection fees can be substantial. They -with some justification- believe that they virtually invented this product, have been making it for decades, and see no value in having anyone 'supervising' them.

 

[don_resqcapt19]

The code does stop short of calling for a listed product, but does call for the use of an "approved" product. Many AHJs read that as "listed".

 

[Strahan]

The code does stop short of calling for a listed product, but does call for the use of an "approved" product. Many AHJs read that as "listed".

Thanks Don! This inspector is talking retroactive. Stating we need ground wires run in our RMC that has been existing. And he is also stating we need bonding wires from our receps to the boxes. I disagree with this as well as long as the receps are listed to be bonded when mounted to the box through the mounting screws.