Service bonding required?

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greenspark1

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New England
We have a MDP with a 800A service via two 4" conduits. They enter the MDP via two punched holes and a standard locknut on each. I believe these need to be bonded per 250.92 but some say since it is a punched hole none is needed. Is a punched hole an 'impaired connection' and needs bonding? Thoughts?
 
greenspark1 said:
We have a MDP with a 800A service via two 4" conduits. They enter the MDP via two punched holes and a standard locknut on each. I believe these need to be bonded per 250.92 but some say since it is a punched hole none is needed. Is a punched hole an 'impaired connection' and needs bonding? Thoughts?
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You are correct. A standard locknut is not suitable for service bonding. Note a bonding locknut meets the requirement which is easier than a bonding bushing.

Not needing additional bonding on prepunched holes is generally for voltages above 250 to ground.
 
As noted, you are correct.. From 250.92 Standard locknuts or bushings shall not be the only means for the bonding required by this section.
Once the conductors are terminated it might be easier to use a "split" bonding bushing or some bonding wedges to accomplish the required bonding.
 
Thank you for the quick and simple response!
This is already installed so a bonding locknut won't be easy :) A two piece bushing should do it.

Last Q. Similar situation with metal conduit used for connection to building steel (GEC). Does a standard locknut and a punched hole pass muster? I think no per 250.92(E)(2).
 
Reading this again, to the original Q- doesn't 250.92(B)(2) permit threaded couplings to be used for bonding purposes? So rigid with a locknut would comply.
 
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