70E Question

[samo5150]

Hello All,

Our facility is finally starting to look at 70E and what is needing to be done to vaguely comply with this document. We attended training several months ago and the trainer mentioned that anytime we would disturb the normal condition of a panel, gear etc we would be exposing ourselves to a arc flash danger. He even mentioned toggling a tripped breaker back to reset as a condition justifying PPE.

Any help on the subject would be greatly appreciated. I have so many questions its unreal, I am also looking for any resources to get additional help.

Thanks,


Brian-

 

[Jraef]

Boiled down version:

There are two ways to determine what is needed; a full blown arc flash incident energy and risk assessment for your facility, or the use of pre-defined tables in which the PPE levels are established for certain tasks. In either case, the PPE Level or Risk Assessment determines the level of risk involved in "interacting" with equipment, which then determines the appropriate level of PPE required for the task. So for example pushing a broom to sweep the floor in front of a piece of enclosed switchgear is not "interacting" with the equipment, but turning a breaker on or off, or resetting it, IS interacting with the equipment, but still it only MIGHT need special PPE.

When you actually look at the numbers in the tables (which is pretty much what you get to if you do the study), it's not as onerous as most people think. For example anything 240V or less is almost never more than PPE 1. But even before you get to that, the first table of tasks, Table 130.7(C)(15)(A)(a), defines WHEN you even need to HAVE ANY special PPE. In that table, a lot of every day tasks such as opening, closing or resetting a circuit breaker WITH THE DOORS CLOSED OR COVERS ON, does NOT require any special PPE (as long as the equipment is properly installed and in good working order, et. etc. etc.)

Basic PPE of a long sleeve Arc Resistant shirt, Arc Resistant pants and Safety Goggles should be every day wear for anyone doing electrical work now. No more "wife beater" undershirts and cutoff jeans. But you only need the face shield (full wrap), leather gloves and hearing protection once you get to needing PPE 1.

Here's a little hint by the way. The rules have changed a lot in the last few years and a lot of the stuff on the internet is already old, yet remains in place for the search engines to find. One quick way to weed out the old info is to look at what they call the clothing. Fire Resistant, FR, Flame Retardant, etc. etc. etc, means the info is old and not to be trusted any more. The clothing terms changed to "Arc Resistant" (AR) in 2012, so by looking at that you can assess quickly what is worth reading and what is not now.

 

[don_resqcapt19]

And an off topic comment about resetting the tripped breaker...the OSHA rules do not permit you to reset a tripped breaker unless you have determined and corrected the condition that caused the trip. (yes, I am aware that almost no one does this)

 

[petersonra]

And an off topic comment about resetting the tripped breaker...the OSHA rules do not permit you to reset a tripped breaker unless you have determined and corrected the condition that caused the trip. (yes, I am aware that almost no one does this)

Just how you make this determination is never stated by OSHA though.

The most common way this determination is made is via circumstantial evidence such as noting an unusual number of devices that were on simultaneously connected to the same circuit. Put a hair dryer and an electric heater on the same circuit and it is not all that surprising that it tripped the CB.

 

[wbdvt]

When you actually look at the numbers in the tables (which is pretty much what you get to if you do the study), it's not as onerous as most people think. For example anything 240V or less is almost never more than PPE 1.

Not sure what is meant by the sentence in parentheses but the important point to remember is that to use the tables you need to be within the parameters of the tables. For example, for the 240V mentioned above, in order to use the table for 240V equipment, the fault current limits are a maximum of 25kA and a clearing time of 2 cycles (0.03 seconds). So you walk up to a 240V Panelboard in your facility and need to remove the cover to perform an infrared survey. Do you know the available fault current at that panelboard? Do you know that the protective device feeding that panelboard will trip in less than 2 cycles for the available fault current? I doubt it. Therefore, you cannot use the tables to determine the PPE.

 

[petersonra]

Not sure what is meant by the sentence in parentheses but the important point to remember is that to use the tables you need to be within the parameters of the tables. For example, for the 240V mentioned above, in order to use the table for 240V equipment, the fault current limits are a maximum of 25kA and a clearing time of 2 cycles (0.03 seconds). So you walk up to a 240V Panelboard in your facility and need to remove the cover to perform an infrared survey. Do you know the available fault current at that panelboard? Do you know that the protective device feeding that panelboard will trip in less than 2 cycles for the available fault current? I doubt it. Therefore, you cannot use the tables to determine the PPE.

what UL489 CB does not clear a short circuit within 2 cycles?

 

[jim dungar]

what UL489 CB does not clear a short circuit within 2 cycles?

How about if the short circuit is only 2000A?

 

[wbdvt]

what UL489 CB does not clear a short circuit within 2 cycles?

What if the actual fault current is less than the instantaneous setting of the breaker? For example: A 400A breaker with instantaneous trip set at 4000A but fault current is 2000A.

 

[petersonra]

How about if the short circuit is only 2000A?

The question was about a CB opening a circuit at its maximum available SCC. Unless there is something really wrong with the electrical system it is going to be well into the trip curve where it is going to trip very fast.

 

[jim dungar]

The question was about a CB opening a circuit at its maximum available SCC. Unless there is something really wrong with the electrical system it is going to be well into the trip curve where it is going to trip very fast.

Where in the task table requirements does it say the breaker opens at it maximum available SCC?

There are two independent requirements.
1) there must not be more than XXkA available fault current,
AND
2) the breaker must open within 2 cycles.

In my example the 2000A is definitely below the max requirement, know we just need to know how fast it opens.

 

[petersonra]

So you walk up to a 240V Panelboard in your facility and need to remove the cover to perform an infrared survey. Do you know the available fault current at that panelboard? Do you know that the protective device feeding that panelboard will trip in less than 2 cycles for the available fault current?

This what the poster said that I replied to.

Why would a properly designed and maintained system ever not trip in less than two cycles?

I think one that had problems, or one that was improperly done could potentially not trip in 2 cycles under the available short circuit current, but that would certainly not be the norm.

 

[jim dungar]

This what the poster said that I replied to.

Why would a properly designed and maintained system ever not trip in less than two cycles?

The breaker will not trip if the available current is below its Instantaneous pickup point. My point is, if you do not know the fault current and the breaker performance, you probably shouldn't be using the task tables.

 

[samo5150]

(as long as the equipment is properly installed and in good working order, et. etc. e

(as long as the equipment is properly installed and in good working order, et. etc. e

That's one of my points. We have 1000A + main breakers that have not tripped/moved in the 4 years I have been there, and in asking around not in any others memory who have been there for decades. They date from the 60's-70's, obviously old and do not get exercised on any type of basis. (BTW we are in a medical facility). We have many, many panels and I have never heard of any facility testing ALL breakers annually by a vendor certified as "working".

Am I off base? How does one establish-determine a "Normal/Working" condition on existing breaker and be documented as such.

Example: Electrician responds to breaker tripping, finds it and sees it's a old breaker. Cause is confirmed to be load over current and is corrected. The plastic could be brittle, internals bad. Hasn't been exercised in a long time by the looks of it. That exact description was given to the trainer, he stated PPE2 for this 277/480 volt condition. What do you think?

Thanks again for all responses on my inquiry.

Brian-

Boiled down version:

There are two ways to determine what is needed; a full blown arc flash incident energy and risk assessment for your facility, or the use of pre-defined tables in which the PPE levels are established for certain tasks. In either case, the PPE Level or Risk Assessment determines the level of risk involved in "interacting" with equipment, which then determines the appropriate level of PPE required for the task. So for example pushing a broom to sweep the floor in front of a piece of enclosed switchgear is not "interacting" with the equipment, but turning a breaker on or off, or resetting it, IS interacting with the equipment, but still it only MIGHT need special PPE.

When you actually look at the numbers in the tables (which is pretty much what you get to if you do the study), it's not as onerous as most people think. For example anything 240V or less is almost never more than PPE 1. But even before you get to that, the first table of tasks, Table 130.7(C)(15)(A)(a), defines WHEN you even need to HAVE ANY special PPE. In that table, a lot of every day tasks such as opening, closing or resetting a circuit breaker WITH THE DOORS CLOSED OR COVERS ON, does NOT require any special PPE (as long as the equipment is properly installed and in good working order, et. etc. etc.)

Basic PPE of a long sleeve Arc Resistant shirt, Arc Resistant pants and Safety Goggles should be every day wear for anyone doing electrical work now. No more "wife beater" undershirts and cutoff jeans. But you only need the face shield (full wrap), leather gloves and hearing protection once you get to needing PPE 1.

Here's a little hint by the way. The rules have changed a lot in the last few years and a lot of the stuff on the internet is already old, yet remains in place for the search engines to find. One quick way to weed out the old info is to look at what they call the clothing. Fire Resistant, FR, Flame Retardant, etc. etc. etc, means the info is old and not to be trusted any more. The clothing terms changed to "Arc Resistant" (AR) in 2012, so by looking at that you can assess quickly what is worth reading and what is not now.

 

[wbdvt]

That's one of my points. We have 1000A + main breakers that have not tripped/moved in the 4 years I have been there, and in asking around not in any others memory who have been there for decades. They date from the 60's-70's, obviously old and do not get exercised on any type of basis. (BTW we are in a medical facility). We have many, many panels and I have never heard of any facility testing ALL breakers annually by a vendor certified as "working".

Am I off base? How does one establish-determine a "Normal/Working" condition on existing breaker and be documented as such.

Example: Electrician responds to breaker tripping, finds it and sees it's a old breaker. Cause is confirmed to be load over current and is corrected. The plastic could be brittle, internals bad. Hasn't been exercised in a long time by the looks of it. That exact description was given to the trainer, he stated PPE2 for this 277/480 volt condition. What do you think?

Thanks again for all responses on my inquiry.

Brian-

I know it is difficult but a pm program needs to be established to excercise and or test at least the larger breakers. What is also interesting is that you say it is a medical facility. Depending on what that means, code would be a totally selective coordination system for which the breakers need to be maintained.

As far as PPE 2, I have seen 480V panelboards ranging from less than 1 cal/cm2 to greater than 40 cal/cm2 so I don't know the basis for that blanket statement. Again, if a study done, then the proper PPE should be known and if not, how to use the tables if the short circuit current AND trip times are not known?