250.92(B), 250.97

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Dale001289

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Location
Georgia
Here's my scenario: Construction has installed hundreds Chase Nipples through sheet metal plates in the Substation flooring (no concentric/eccentric knockouts in plates), into 480V, 5kV and 15kV Motor Control Centers and Switchgear.

They have NO bonding jumpers, NO bonding-type locknuts, etc - just standard bushings on the straight-threaded Chase nipples where cables enter the enclosures.
Quality Control Inspectors are demanding they 'redo' everything, which will result in thousands of additional manhours for a project that's already $500M over budget and behind schedule.

Construction is asking for a 'work-around'. I've suggested they perform random continuity checks to ensure there are no loose connections, but this will do little to satisfy the NEC requirements or the inspectors.

Any suggestions?
 
A chase nipple with a standard locknut is fine on 480 volts when there are no concentric or eccentric KO's. Is the requirement at 5 kV and 15 kV different?
 
Dale001289 said:
...
Construction is asking for a 'work-around'. I've suggested they perform random continuity checks to ensure there are no loose connections, but this will do little to satisfy the NEC requirements or the inspectors.

Any suggestions?
Click to expand...
From what I gather, the gear is not service equipment... so I suggest that you suggest to your inspectors that they read [and comprehend, which is very important in this matter :D] ....

250.97 Bonding for Over 250 Volts. For circuits of over
250 volts to ground, the electrical continuity of metal raceways
and cables with metal sheaths that contain any conductor
other than service conductors shall be ensured by
one or more of the methods specified for services in
250.92(B), except for (B)(1).

Exception: Where oversized, concentric, or eccentric knockouts
are not encountered, or where a box or enclosure with
concentric or eccentric knockouts is listed to provide a
reliable bonding connection, the following methods shall
be permitted:

(1)Threadless couplings and connectors for cables with
metal sheaths

(2) Two locknuts, on rigid metal conduit or intermediate
metal conduit, one inside and one outside of boxes and
cabinets

(3) Fittings with shoulders that seat firmly against the box or
cabinet, such as electrical metallic tubing connectors,
flexible metal conduit connectors, and cable connectors,
with one locknut on the inside of boxes and cabinets

(4) Listed fittings
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What I think they can complain about, but I'm not certain because I do not know the details of construction, is that the sheet metal plates in the flooring may not be properly bonded...???
 
Smart $ said:
From what I gather, the gear is not service equipment... so I suggest that you suggest to your inspectors that they read [and comprehend, which is very important in this matter :D] ....



What I think they can complain about, but I'm not certain because I do not know the details of construction, is that the sheet metal plates in the flooring may not be properly bonded...???
Click to expand...


The bottom cable entry plate is firmly bolted to the Switchgear enclosure. The Switchgear enclosure is bonded internally to the horizontal grounding bus which is bonded to the equipotential grid (#4/0 bare copper electrode). Chase nipples and bushings are seated firmly against the plate (no grommets, etc in between) and made-up 'wrench-tight'; I believe its a foregone conclusion all is well-bonded.
I just have to educate the inspectors on Monday.

Thanks to all for input.
 
Dale001289 said:
Quality Control Inspectors are demanding they 'redo' everything, which will result in thousands of additional manhours for a project that's already $500M over budget and behind schedule.
Click to expand...

Are the so called QC inspectors claiming it is a NEC violation? If so they need to prove that contention.

OTOH, it is possible the spec does not allow what was done.
 
petersonra said:
Are the so called QC inspectors claiming it is a NEC violation? If so they need to prove that contention.

OTOH, it is possible the spec does not allow what was done.
Click to expand...
The first thing I did was review the Construction Specification - its not defined. Basically if its not defined in the spec, everything defaults to NEC

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