Task table work

[jimbo123]

This question is concerning working in 480 volt panels and mcc. Most places allow their workers to use the task tables in 70e and not to work at a task above a 2*. There has not been AF analysis or hazard study on any equipment.

If I am working on a task in a energized panel with the ppe listed for the work on am I safe ?, are there any other concerns I should be a where of with the electrical equipment before going to work in the panels ?

 

[ron]

Does the application fit within the short circuit available and clearing times in the requirements in the table notes?

 

[raider1]

Does the application fit within the short circuit available and clearing times in the requirements in the table notes?

I agree with Ron, you must make sure that the panel you are working in meets the available fault current limits and clearing times for the overcurrent protective devices before you can use the Tables in 70E.

Also what is the task that you are going to preform in the energized panel and is the work justified to be done with the panel not put in an electrical safe work condition?

Chris

 

[WorkSafe]

Huh, sounds like a situation I had last week, but the workers were just wearing safety glasses and ear plugs.

 

[jim dungar]

If I am working on a task in a energized panel with the ppe listed for the work on am I safe ?, are there any other concerns I should be a where of with the electrical equipment before going to work in the panels ?

No body knows if you will be adequately protected by PPE chosen based on the task tables. Only a complete study can tell you if your PPE is correct for the available incident energy.

The task tables were created basically by anecdotal experience, but they are better than nothing.

 

[jimbo123]

When using the tables we're told to use following method.
Where a detailed arc flash analysis is not performed for electrical systems the arc flash boundary is 4' using 2 cycles and the available fault current of 50KA or any combination not to exceed 100KA calculation.
Where are they getting the 50KA and 2 cycles from ?
This has nothing to do with the shock protection ?
Anytime we open up a 480 volt panel board to put a k o to install conduit we have to have an analysis on the panel board if we can't shut down the panel ?
Is this correct ?

 

[jim dungar]

Anytime we open up a 480 volt panel board to put a k o to install conduit we have to have an analysis on the panel board if we can't shut down the panel ?
Is this correct ?

Installing a knock-out into a panel is not one of the tasks listed in table 130.7(C)(9).

 

[zog]

When using the tables we're told to use following method.
Where a detailed arc flash analysis is not performed for electrical systems the arc flash boundary is 4' using 2 cycles and the available fault current of 50KA or any combination not to exceed 100KA calculation.

True, but 2 cycles is usually not realistic, even with an INST trip most breakers are 3 or 5 cycle breakers.

Where are they getting the 50KA and 2 cycles from ?

It is quantifing the total energy of the arc, not sure where the numbers came from, likely the same "magical" place the HRC's in the task tables came from, but 50kA is faily common for LV systems and 2 cycles maybe from a fuse clearing time.

This has nothing to do with the shock protection ?

Nope, whole different issue, llok at the LAB, RAB, and PAB for guidance.

Anytime we open up a 480 volt panel board to put a k o to install conduit we have to have an analysis on the panel board if we can't shut down the panel ?
Is this correct ?

Yes, or use the task tables, but why would you attempt to do this energized? Be careful of what you think "feasable" means.

 

[jimbo123]

Jim, removing the covers from these panels are listed in the tables.

 

[jim dungar]

Jim, removing the covers from these panels are listed in the tables.

Yes, that is true for most equipment.

But the HRC's for drilling a hole and using a punch are not listed.

I also notice that for "Panelboards or Switchboards Rated >240V and up to 600V (with molded case or insulated case circuits)", there is no task listed for removing covers.

 

[jimbo123]

Jim, not to prolong this ,if removal of bolted covers [ to expose bare , energized electrical conductors and circuit parts ] is not part of my scope of work listed in the tables than i,m wrong. They were general questions on energized work and how to use the tables. Still learning this. Have a good one.

 

[jim dungar]

I am partly playing devils advocate.
There are major issues with 'blindly' applying the task tables.

 

[zog]

Jim, not to prolong this ,if removal of bolted covers [ to expose bare , energized electrical conductors and circuit parts ] is not part of my scope of work listed in the tables than i,m wrong. They were general questions on energized work and how to use the tables. Still learning this. Have a good one.

What you need to understand is that the tables are not based on the actual "hazard" you are being exposed to, that information would come from an arc flash analysis. The task tables are based on "risk". Removing a cover has a lower "risk" than drilling a hole. They can't possibly list all tasks in the tables.

Now the real question is why would you do something like this with the panel energized? Shut it down. LOTO, verify de-energized before you do the work.

 

[jimbo123]

Zog, to answer your question. I asked questions to learn a new method of working . When you work for people who are not in the electrical field you have to convience them of the right way to do a job. To be perfectly honest I have not seen a electrician [contractors] yet who has deenergized a panel before taking the cover off.
Now if i asked the question I must be thinking about working safe. So I'll insist on de energizing before entering a live panel, box , mcc .

Thanks again to everyone for the great help .

 

[zog]

I wouldn't expect them to de-energize only to remove the cover, but to "work" in a panel is a different story. Sounds like you have the right idea though.