12-2 NM cable as switch.

[don_resqcapt19]

Larry,

I am not very knowledgable in this area, but if what you are saying about IE is true; why wouldn't we need higher levels of protective gear at lower levels of available fault current instead of vice versa?

That is very often the case and the reason why you must have a true available fault current value to do the arc flash calculations. If the available fault current is less, it may move into the short time trip range of the OCPD and not the instantaneous range. If there is a longer trip time with a lower fault current, the incident energy may very well be greater than a higher fault current that causes the OCPD to operate in it's instantaneous range.
Don

 

[dlhoule]

And I still stand by my statement, don't use half truths.

And I still agree with that statement.

Amps kill, not voltage.

Please note, however, that that statement IS a half-truth.

All voltages are dangerous [and can kill].

That is the other half; that is what is needed to complete the truth.

Just for clarification: Amps kill, not voltage. Where did the amps come from? With the proper voltage I believe it can stop ones heart with very little current involved. In such a case without some other action taking place to restart the heart, you will be dead.

My stance is that it takes both to kill a person.

And yes all voltages can be dangerous!

 

[Gmack]

Just for information only

Just for information only

While working in 230 on a separate matter unrelated to this topic, I read the following in the commentary of:

230.82 Equipment Connected to the Supply Side of Service Disconnect

Self-contained meters or internal meter bypass switches should not be used to break the load current of a service having a voltage of over 150 volts to ground, because a hazardous arc could be generated. Arcs generated at voltages greater than 150 volts are considered self-sustaining and can transfer from the energized portions of the equipment to the grounded portions of the equipment.

An arc created while breaking load current on a 480Y/277-volt system (277 volts to ground) could transfer to the grounded equipment enclosure, creating a high-energy arcing ground fault and arc flash that could develop into a 3-phase short circuit. This hazardous arcing could burn down the meter socket and injure the person performing the work.

Just for information only.

 

[peter d]

Gmack, so what does that mean? Are you telling us you believe that arc flash is a danger? As myself and others have said, arc flash hazards are present in other systems besides 277/480.

Please tell us where you stand on the issue.

 

[peter d]

Gmack, would you please answer these questions too:

How does a GFCI work?

Why do we GFCI protect 120 volt receptacles?

And this one asked by Jim Dungar:

Gmack,
I would like to hear your direct answer to my question. Would you prefer:
23V between grounding conductor and grounded conductor in a residential swimming pool system
or
300V between a phase conductor and ground in an unbalanced ungrounded capacitively coupled system.