objectionable current

[gregorsc]

Can anyone tell me what art.250.6.A is talking about. What would be considered "objectionable current"?

 

[barbeer]

Good question! Sounds maybe like they are talking about grounding loops or eddy currents and the like!? One of those gray areas

 

[dereckbc]

There is no definition. It comes down to preference. If you don't like the current you see on ground conductors, then it is objectionable.

Only place where I have seen any data is when I wrote the specs and engineering standards for a large telephone company that outlined objectional current on ground conductors. However these are standards, therefore not enforcable by any agency.

 

[radiopet]

A) Preventing Objectionable Current. To prevent a fire, electric shock, or improper operation of circuit-protection devices or sensitive equipment, electrical systems and equipment must be installed in a manner that prevents objectionable current from flowing on conductive materials, electrical equipment, or grounding and bonding paths.


Author’s Comment: Objectionable current occurs because of improper neutral-to-case bonds and wiring errors.
Improper Neutral-to-Case Bond [250.142]

Panelboards. Objectionable current will flow on metal parts when the grounded neutral conductor is bonded to the metal case of a panelboard that is not part of service equipment. Figure 250–28

Disconnects. Objectionable current will flow on metal parts when the grounded neutral conductor is bonded to the metal case of a disconnecting means that is not part of service equipment. Figure 250–29

Separately Derived Systems. Objectionable current will flow on metal parts when the grounded neutral conductor is bonded at the transformer as well as to the metal case on the load side of the transformer. Figures 250–30 and 250–31

Here's some of mikes information on it for you...

Here is another image from MIKE...man I love his images..

 

[bphgravity]

To me, objectionable current is any current on the grounding system or non-current carrying metal parts of the electrical system that are a result of poor design of the grounding system verses currents on the grounding system that are inherent to common or typical grounding practices.

I will give two examples of installation practices that could result in objectionable current.

1. A GEC is run from both the service disconnect enclosure and the meter socket enclosure to separate electrodes. The two electrodes are bonded together. The result is normally operating current flowing over the grounding system due to the parallel path to the source.

2. Complying with 250.58 of the NEC or, installing the smallest sized grounded conductor as permitted by the NEC to the service while at the same time creating a grounding electrode system with significantly low earth resistance. Both of these examples may increase or place objectionable current onto the grounding system.

 

[gregorsc]

Thanks

Thanks

Thank you for all of the excellent help.

 

[donselectric]

anywhere it aint supposed to be...:grin:

 

[brian john]

Pretty much sums it up., I would think.

To me, objectionable current is any current on the grounding system or non-current carrying metal parts of the electrical system that are a result of poor design of the grounding system verses currents on the grounding system that are inherent to common or typical grounding practices.
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[donselectric]

anywhere it aint supposed to be.....:grin: