equipment grounding conductor size

[bennie]

Re: equipment grounding conductor size

Don: I call, forcing a high current to open a protective device, the "sledge hammer principal.

Like hitting a mosquito on someones head, with a sledge hammer, to save them from getting bit.

There has to be smarter overcurrent devices, with a reasonable price, to protect the failing electrical infrastructure.

 

[goodcode]

Re: equipment grounding conductor size

As Charlie pointed out there may be problems in determining the incident energy when dealing with utility conductors. When that is necessary they have some of the best engineers (charlie) in the business to assist the installer (when necessary) in determining the energy. As a rule of thumb we can consider utility conductors prohibitive to work in an energized state as they are not protected in accordance with the NEC. However we must not lose sight of the fact that the NEC does not govern the utility companys. The NEC covers only from the "service point downstream." The present proposals to modify 110.16 to include the incident energy marked in cal per cm squared are safety driven. The net result in our industry will be a new mindset working all new and existing systems with the foresight to limit the amount of potential energized work exposing employees.
Charlie also pointed out that we can have a problem when the amount of available short circuit current is small and we do not get to the instantaneous range of the OCPD on the time current curve. This is a problem which we will deal with, not a reason to throw the baby out with the bath-water.
Change can be difficult. For most of us the implementation of safe work practices and Panel markings in 110.16 may seem as handcuffs. We must shed the cowboy, working it hot is acceptable mindset or we will continue to suffer severe burn injuries and fatalities within our ranks. This change is good for the contractor (lower mod rates), the wireman (safer workplace)the owner and the public.
Im getting long winded like my friend Charlie, we usually do this over a few beers.

 

[bennie]

Re: equipment grounding conductor size

Calculations don't lie, but liars calculate.

Does this change mean the hazard potential shall be rated like the terrorist threat. Colors marking the degree of threat.

Is there any action to limit fault current? Detect a fault at lower current levels?

 

[don_resqcapt19]

Re: equipment grounding conductor size

I can't imagine that any contractor's liability insurance company will want the contractor to be involved in posting this information on a panel. What happens when I rely on this information to choose my PPE and the information is not correct. Maybe it was correct at the time it was posted, but some changes were made and now it is wrong. These calculations should be made by the contractor/person doing the work at the time the work is to be done.
Don

 

[bennie]

Re: equipment grounding conductor size

I still feel that making rules and conditions for killing people is wrong. The hazard level warnings are giving the go ahead for not shutting the equipment down and safetying it off.

There is no electrical equipment that can not be dumped and made safe.
We only need legal grounds to enforce it.

Insurance companies will drop a contractor who blows up his people, regardless of hazard level.

 

[Ed MacLaren]

Re: equipment grounding conductor size

Is there any action to limit fault current? Detect a fault at lower current levels?

"Ground" faults far outnumber phase-to-phase faults. High resistance grounding will limit ground fault currents to a few amps, but available systems are limited to installations where line-to-neutral loads are not served.

Perhaps a resistance grounding system that will work with the common residential/commercial three-wire service could be developed.

Ed

 

[Nick]

Re: equipment grounding conductor size

I have got to agree with Bennie and Don here. OSHA regulations prohibit ?hot? work except under very specific circumstances. Giving calculations to tell a person what PPE to use while working in this particular piece of gear seems like a contradiction of OSHA regulations to me. If a job meets one of the OSHA exceptions, let it be the requirement of the contractor doing the work to go to NFPA70E and figure out the appropriate PPE. I don?t want to be dragged into court 20 years after I did a job because some other contractor didn?t do his job in protecting his employees.

 

[bennie]

Re: equipment grounding conductor size

Everybody that has ridden a motorcycle for 5 years has some scars from injuries.

Every electrician that has been in the trade for 5 years has some scars from injuries.

There is some rare exceptions, but not enough to count.

We don't need permission to be injured.

 

[tom baker]

Re: equipment grounding conductor size

Back to orginal topic, the Steel Tube Institute has a free software program called GEMI, that caluclates the size of an equipment ground required for a given circuit length, with steel conduit or no conduit. The size of the OCPD does not enter into the calculation, but the arcing fault does. Most applications I looked at will require a equipment ground or larger ground over when the circuit length is over 300 ft. The program was developed by the Georgia Institute of Technology. www.steeltubeinstitute.com

 

[goodcode]

Re: equipment grounding conductor size

An excellent observation Don!
An electrical safe work program (built upon NFPA-70E for example)as part of a contractors overall safety policy will address the fact that a hazard analysis must be performed in all cases. Contractors could not enter a building or structure they knew nothing about and trust a marking that may be 20 years old.
However the posting of incident energy levels will be tremendously helpful in our industry. An example would be a manufacturing plant being constructed in the year 2005. Let's assume the language becomes code and incident energy levels are posted in the plant at each panelboard, MCC, disconnecting means etc.
The maintenance staff in that plant (they would be aware of any changes in the system) will have energy levels posted. If energized work was required due to infeasibility or greater hazard, they could quickly gain access to the required PPE and work safe.
Changes to an electrical system will reqire a reevaluation of incident energy and changes to the panel markings.
The markings in energy level may or may not make it into the NEC. The fact that a general marking is required by 110.16 and we are having this type of dialouge is healthy for our industry. Proposed changes of this type are improved by discussions both pro and con. Language to require remarking after a significant change to the system would be in order.

 

[charlie]

Re: equipment grounding conductor size

The problem I have with Goodcode's viewpoint is his statement, "Changes to an electrical system will require a reevaluation of incident energy and changes to the panel markings." The electric utilities will make changes often and can not notify everyone about the need to recalculate the incident energy levels in the plant. If you need to trouble shoot a motor controller, can you depend on the posted markings? In my opinion, they will be out of date before they are calculated and posted.

 

[bennie]

Re: equipment grounding conductor size

If displaying the hazard levels is for making workers aware, I have a better idea.

I had a friend named Sid. He got into 75 KV DC. The current was arcing into his head. His cap was set on fire, while I was shutting down the equipment, and installing safety grounds, so the fireman could remove his body.

Suggestion...Display autopsy photos of Sid.

I have a friend named Ray. He lost all the skin, and most of the flesh, on both arms when making contact with 12.4 KV.

Suggestion...Show pictures of his arms.

 

[charlie]

Re: equipment grounding conductor size

Bennie, I am sorry you have those two stories to tell.

 

[bennie]

Re: equipment grounding conductor size

Charlie: The sad part is the events were preventable. I don't refer to them as accidents, I feel they were intentional.

Both men wanted to shut down the equipment and safety ground the active conductors. The management would not permit the down time. The men knew the job would be done by others if they refused.

Laws to make mandatory jail time for supervisors, when an electrician gets smoked, will stop a lot of this.

[ May 07, 2003, 02:58 PM: Message edited by: bennie ]

 

[Nick]

Re: equipment grounding conductor size

Bennie,
That law already exists in California. If you, as a supervisor, direct an employee to do something you know is unsafe. You willfully disregard safety regulations and procedures, and the person gets hurt. You can be personally prosecuted and held personally liable. Jail time can be involved.

 

[charlie]

Re: equipment grounding conductor size

Nick, I generally think of California as a liberal state with overbearing laws but in this case, hurray! I think your state is right on.

 

[bennie]

Re: equipment grounding conductor size

Nick: As we have discussed before, California is the State where I started after the Marine Corps.

I am retired from Local 11, Los Angeles. My home local is 659, Medford OR.

I understand that California was the first State to pass the automatic arrest of excavation supervisors when there is a cave in fatality.

The arrest is an automatic conviction due the incident happening.

Cave in deaths dropped dramatically.