The Sufficiency of NEC rules

[jim dungar]

Refer to the accident statistics if you have any.

They try to make you think statistically, guys.

So what do you see as the statistical difference between 'likely' and 'possibly'?

You keep asking if the NEC requirements for bonding, in article 250, should be expanded. Yet when I point out that the NEC authors purposely limited the range of 250, and acknowledged more stringent requirements in article 527, your response was 'SO'. You should be able to explain why my statement is not germane to this thread.

Evidently you are not interested in positions that do not agree with yours.

 

[kwired]

Neither did I say that there was any need to make all metal objects bonded to electrical grounding system.

The scope of discussion is much more limited: whether the criterion is worthy of becoming a requirement.

Seems we are going in circles with the conversation. Bottom line and kind of what this thread started with is that we commonly do use grounded conductors for circuit conductors, particularly at the 120 volt and 277 volt level in the US. If stray voltages are a concern, my suggestion is not to use grounded conductors for anything except for equipment grounding, or minimize the use of grounded current carrying conductors as much as possible, then there will be little or no current that can go stray in "normal" conditions.

Then the conversation kind of shifted to bonding of metallic items - especially those that have little or no risk of becoming energized. If you want to see something in particular to be included in what the NEC requires to be bonded then you are welcome to submit a proposal and a reason as to why, remember it needs to be convincing enough reason to the CMP or they will reject it.

I don't see a metal railing that is fairly effectively isolated from earth and no electrical equipment attached to it having much of a chance of being accepted as something the CMP will think must be bonded, but nothing says it can not be bonded either.

 

[Sahib]

So what do you see as the statistical difference between 'likely' and 'possibly'?

In the present case, the electric shock from simultaneous touching of energized metal conduit of a receptacle in the balcony of a residence and nearby metal hand railing is possible. But how much is it likely? i.e what is the probability of its happening? To answer it, the statistics of that particular electrical accident is required. If we know the probability of that electrical accident, we may use 'likely'; otherwise ''possibly''.

You keep asking if the NEC requirements for bonding, in article 250, should be expanded. Yet when I point out that the NEC authors purposely limited the range of 250, and acknowledged more stringent requirements in article 527, your response was 'SO'.

By stating 'So', I wanted you to continue your reasoning as I was not able to see where it was leading to. Now I am able to understand. I do not agree with the CMP. Because the European wiring regulations in general and British wiring regulations in particular include it For example the article below covers it.
Supplementary equipotential bonding - IET Electrical
As such, it is beneficial to include the criterion stated in earlier posts in the code.

Evidently you are not interested in positions that do not agree with yours.

No I am also interested in positions that do not agree with mine.

 

[kwired]

In the present case, the electric shock from simultaneous touching of energized metal conduit of a receptacle in the balcony of a residence and nearby metal hand railing is possible. But how much is it likely? i.e what is the probability of its happening? To answer it, the statistics of that particular electrical accident is required. If we know the probability of that electrical accident, we may use 'likely'; otherwise ''possibly''.

The OP of the balcony railing thread doesn't have a metal conduit within reach of the railing. All the more reason to reduce the risk factors and not require bonding of the railing. If you introduce items that create more risk the rules may change. My point all along with the railing was that as the OP described it, doesn't have much justification for bonding it. You keep wanting to throw in conditions that do not exist as reasoning to bond it. Many of them are certainly valid reasons - if the condition you threw in existed.

 

[jim dungar]

Because the European wiring regulations in general and British wiring regulations in particular include it For example the article below covers it.
Supplementary equipotential bonding - IET Electrical

The author of your article clearly states that it is erroneous to 'blindly' connect all metallic objects simply because they are within a zone.

It is typically not practicable to take B.S. practices and directly incorporate them into US installations.
We do not use RCD protection and, other than in small buildings, our wiring methods typically use protective raceways (as mentioned in your reference) rather than exposed non-metallic cables.

 

[Sahib]

The author of your article clearly states that it is erroneous to 'blindly' connect all metallic objects simply because they are within a zone.

Yes. That is why the author further indicated to take into account the operating time of the upstream OCPD of the electrical device within the zone to make a decision.

It is typically not practicable to take B.S. practices and directly incorporate them into US installations.

Only what is relevant is discussed here.

We do not use RCD protection and, other than in small buildings, our wiring methods typically use protective raceways (as mentioned in your reference) rather than exposed non-metallic cables.

The discussion here involves OCPD and not any RCD.

 

[jim dungar]

Yes. That is why the author further indicated to take into account the operating time of the upstream OCPD of the electrical device within the zone to make a decision.

Only what is relevant is discussed here.

The discussion here involves OCPD and not any RCD.

The author specifically discussed RCD.

 

[Sahib]

The author specifically discussed RCD.

When the bonding conductor resistance is many hundreds of ohms; this is not the case here.

 

[Besoeker]

It is typically not practicable to take B.S. practices and directly incorporate them into US installations.
We do not use RCD protection and, other than in small buildings, our wiring methods typically use protective raceways (as mentioned in your reference) rather than exposed non-metallic cables.

Although not specifically excluded, in is not at all common for installations, regardless of type of building to have exposed non-metallic cables. In residential is is generally for aesthetic reasons.
Industrial installations are almost always steel wire armoured cables.

 

[jim dungar]

....
Industrial installations are almost always steel wire armoured cables.

Which is not the case in the vast majority of US electrical installations.

 

[Besoeker]

Which is not the case in the vast majority of US electrical installations.

I know that.