Equipment grounding conductor

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lurch

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Is there a code reference that either allows or disallows the use of a separate(redundant) equipment grounding conductor on portable cord connected, 3 phase(delta), welders. These machines are sometimes used in a wet environment, and the idea is to protect the persons using these machines in the event that the equipment grounding conductor in the cord is compromised.
These redundant equipment grounds were added to portable cord connected welders after several near misses and one death at a company for which I formerly worked. The rule was that if the external equipment ground was compromised in any way the machine could not be used until the equipment ground in the power cord was proven good and the external ground was repaired. The assured grounding checks were made to the equipment grounding conductor in the cord on a regular basis, as required by OSHA. After these changes were implemented there were no more incidents.
I have found a reference to an external equipment grounding conductor on cord connected equipment that is to be used in wet areas in a DOE electrical safety document, but I don't see where it's specifically referenced in the NEC.
 
Re: Equipment grounding conductor

I am pretty sure there is no prohibition on bringing in multiple EGC to a piece of equipment, nor am I aware of any prohibition on permenantly bonding a portable piece of equipment.
 
Re: Equipment grounding conductor

The external equipment grounding conductor would be a violation of 300.3(B). All conductors must be in the same raceway or cable.
Don
 
Re: Equipment grounding conductor

Don, I understand what you are saying, but what would prevent you from installing a supplemental bonding conductor in addition to the required EGC in the raceway with circuit conductors.

This is common practice in my industry, for example a SRG (signal reference grid) connected to cabinets.
 
Re: Equipment grounding conductor

Dereck
250.134(B) exception 2 allows it to be ran seperate for DC circuits

But if this "ground wire" could be called a bonding conductor then it would be allowed but only for 6' as per 250.102(E)
 
Re: Equipment grounding conductor

Wayne I am aware of 250.134(B) exceptions. In data centers and the like, it is a pure AC enviroment. SRG and other such systems are performance based systems and out of the scope of the NEC safety requirements. They are detailed in FIPS-94, IEEE Emerald book, MIL-STD.197, ITU K.37, and numerous other design applications. I just do not see how this is really any different.

It's just got me scratching my head where the exception lies. :(
 
Re: Equipment grounding conductor

Originally posted by hurk27:
But if this "ground wire" could be called a bonding conductor then it would be allowed but only for 6' as per 250.102(E)
Click to expand...
But this does not prohibit an external bonding conductor, it just requires the cord to have one as well.
 
Re: Equipment grounding conductor

Thanks for the replies everyone--The construction of these redundant equipment grounding conductors that we're using on our 3 phase cord connected welding machines are aproximately 4-5 ft. long, with a lug on one end bolted to the machine frame, with a pointed type c-clamp on the other end. All the boxes for the welder outlets are on structural I-beam columns in the plant, which are bonded to an underground ground loop. The clamp is attached to the I-beam before the welding machine is used.
 
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