Dilemma

[TxEngr]

Petersonra ? I based my ?guestimate? on the information provided. For a 200 Amp, 480V panel, I would expect the rating to require at least a HRC2 and possibly HRC 3 or 4 depending on the age of the equipment feeding it. Removing the cover, I personally would wear HC4. One small slip up and the panel rotates into live bus. About the only exception I will make is if the door is properly hinged to control it and I know the arrangement of the contents of the cabinet to be clear of the area. Even then, we wear the correct PPE when opening the door. At my facility, we generally don?t remove covers from panels on energized equipment anymore, even for infrared work. We have started a program of adding infrared viewing windows to the gear for that purpose. Much safer since some of our equipment is old and is HC4. And we find the windows just as effective if placed properly.

 

[Jraef]

I find this discussion fascinating, and also indicative of what I see in the field. A lot of "old timers" think it's all a bunch of hooey fostered by "the nanny state", but anyone who has been in an arc flash, like me, thinks it is a necessary inconvenience. I was working on a 480V 400HP motor starter when someone energized the switchgear feed just as I was closing the enclosure doors. The doors hadn't latched yet and the arc flash blew them open against my hands, but because I already had them to the point of the lips overlapping, the bulk of the flash was directed up and down instead of right at me, so I escaped relatively unharmed (slight heart attack...). Everything inside the box was toast though and the electrician who pushed that button on the breaker lost his job.

All that said, there is such a thing as overkill as well. I was at a GM / Toyota plant (NUMI, now closed) a couple of years ago and they said they had identified over 15,000 electrical boxes that needed arc flash evaluation because they were counting every junction box, including those that had just control and signal wiring. Not that they didn't know that was ridiculous, but just that someone had to officially evaluate every one of them to put a sticker on it saying that it was "safe" WRT arc flash hazard. That's a lot of money to be spent.

 

[petersonra]

Argue with which statement? That a long chat is in order? That 208 volt panels don't have arc flash potential? That a study is needed? :-? I agree with the first and third, and I have already posted a disagreement with the second.

My understanding is that the majority of 208/120 PBs are fed by transformers small enough that they have been deemed to have no arc flash potential.

You will note I did not say all 208/120 PBs have no arc flash potential, just that most don't.

Am i wrong about the relative quantities of 208/120 Pbs that have versus don't have arc flash issues?

In any case, HC0 PPE appears to be the same as if there is no arc flash hazard at all. at least to my eyes.

 

[charlie b]

I think that the phrase "no arc flash potential" is attempting to say too much. A better phrase might be to say that they have an available arc flash energy that puts them in the lowest category (level zero). Keep in mind that the five categories (0,1,2,3,4) have ranges of energy levels, and that the lowest level is defined as "less than 4 calories per square centimeter." So if you are under 4, then no matter what the actual energy level might be, it will just be included in the level 0 group.

I have read that if a panel rated 240 volts or lower is powered by a single transformer rated 125 KVA or lower, it is not necessary to perform an arc flash analysis. Such a panel could automatically be treated as a level zero hazard.

 

[Lady Engineer]

Thanks!

Thanks!

I'm really grateful for the responses. He wanted me to open the 200A/480V plug-in switch on a 4000A/480V bus duct as well to check the feeder size, as well as take the cover all of the 480V panel fed from the 200A switch. I told him, those are the types of switches only open when the the switch is in the off position. I will not take the covers off of 480V panels.

Is he nuts? I don't know about anyone else, but I don't like fooling around with 208V, let alone 480V.

It turned into a big thing today where he blew a gasket, so I said well you go out there and get arc flashed burns. The only reason he didn't go over my head, because he said I can't say anything to a "PE", cuz he's unlicensed. However, he doesn't mind endangering my life! Shouldn't matter if I'm a PE or not...it's not safe!

No thanks...

Thank you all...

Patty

 

[jumper]

I'm really grateful for the responses. He wanted me to open the 200A/480V plug-in switch on a 4000A/480V bus duct as well to check the feeder size, as well as take the cover all of the 480V panel fed from the 200A switch. I told him, those are the types of switches only open when the the switch is in the off position. I will not take the covers off of 480V panels.

Is he nuts? I don't know about anyone else, but I don't like fooling around with 208V, let alone 480V.

It turned into a big thing today where he blew a gasket, so I said well you go out there and get arc flashed burns. The only reason he didn't go over my head, because he said I can't say anything to a "PE", cuz he's unlicensed. However, he doesn't mind endangering my life! Shouldn't matter if I'm a PE or not...it's not safe!

No thanks...

Thank you all...

Patty

Smart move ma'am.

I generally work with the EE if they want a field study of small panels, and I use an EC for the big stuff.

EE's are not allowed to inspect on their own, qualified or not.

 

[jim dungar]

I think that the phrase "no arc flash potential" is attempting to say too much.

Along this line, because this a very common misunderstanding

Category 0 does not mean 0 arc flash.

 

[zog]

OK, Jim said it all, we can close this now

Lady Eng, you are 100% right, stick to your guns and don;t let anyone force you to be stupid.

 

[brian john]

We are hired by Engineering Firms to do this sort of work, cheaper and we are properly prepared.

 

[Lady Engineer]

We are hired by Engineering Firms to do this sort of work, cheaper and we are properly prepared.

I agreed, and I'm licensed to do design only. I'm not an Electrician, and I am not trained nor skilled to do this sort of work. I'll leave that to the professionals.

However, thanks again guys. You made me feel tons better!

 

[Dennis Alwon]

I agreed, and I'm licensed to do design only. I'm not an Electrician, and I am not trained nor skilled to do this sort of work. I'll leave that to the professionals.

However, thanks again guys. You made me feel tons better!

Hope we don't get you fired. :grin:

 

[Lady Engineer]

Hope we don't get you fired. :grin:

Wait a minute....

I hope not either!

 

[zog]

Wait a minute....

I hope not either!

If you do you have a nice lawsuit to file.

 

[Johnny26]

Yes talk to your boss about it and ask some protective gear.

 

[wiredoc]

Call me old school,but a boss should never expect you to do something he's not willing to do himself!

 

[jim dungar]

Call me old school,but a boss should never expect you to do something he's not willing to do himself!

So, because the boss is willing to risk his safety by ignoring procedures and PPE, you should risk yours?

I don't think this came across the way you meant it.

I am more than willing to remove panel covers during data collection exercises. At least one of my engineers, also, has no problem with removing covers. Two of my engineers don't want to know how to use a screw driver. I never expect my employees to do a task, on energized equipment, they are uncomfortable performing. Their job is to make sure the data is collected, using the proper tools, even if one of them is a 'qualified panel cover removerer'.

 

[Girl Engineer]

What kind of testing are you doing? Hooking up a power logger? If so, the panel does not need to be energized while you are connecting it.

I would say, Okay, I will just have to de-energize the panel and lock it out. You will still need the PPE to test it dead. I would not take the cover off without that panel being dead.

Other options?
Can you clamp on to the feed that is coming into the panel, or is it run in cable? How about at an LB or junction box?
Could you clamp on at the MCC? This is easier to isolate if the line side of the breaker is guarded.

 

[CPorter]

Keep in mind that the five categories (0,1,2,3,4) have ranges of energy levels, and that the lowest level is defined as "less than 4 calories per square centimeter." So if you are under 4, then no matter what the actual energy level might be, it will just be included in the level 0 group.

I have read that if a panel rated 240 volts or lower is powered by a single transformer rated 125 KVA or lower, it is not necessary to perform an arc flash analysis. Such a panel could automatically be treated as a level zero hazard.

I believe this is wrong HRC 1 is defined as being between 1.2cal/cm^2 and 4.0cal/cm^2 and HRC 0 is below 1.2cal/cm^2. There is a possibility of arc flash energy in an HRC 0 rated panel and enough to give you a 2nd degree burn. This is also predicated on the belief that the panel is in good working condition with all it's screws. There is also a sixth level over HRC 4 that the company doing our Arc Flash study just labeled as "dangerous".

 

[charlie b]

I believe this is wrong HRC 1 is defined as being between 1.2cal/cm^2 and 4.0cal/cm^2 and HRC 0 is below 1.2cal/cm^2.

You are right. Mea culpa.

There is a possibility of arc flash energy in an HRC 0 rated panel and enough to give you a 2nd degree burn.

Which is good to mention. Some people see a ?category 0? sign and think that that means there is zero risk of being hurt by an arc flash.

There is also a sixth level over HRC 4 that the company doing our Arc Flash study just labeled as "dangerous".

I think that is for anything over 40 cal/cm^2. It means that no amount of protective clothing would protect a worker from serious injury or death, and that the system cannot be safely worked on live. There are some types of control schemes that can reduce the arc flash category from ?dangerous? to a lower level. One example is to put a ?maintenance mode? on the main breaker on the main switchboard. That mode has a faster reaction time, and would reduce the amount of arc flash energy that could be released during a fault. When in that mode, the system loses its selective coordination. That means that a short circuit on a small load might be able to trip the main breaker. So you won?t want to leave the system in maintenance mode all the time. But it may allow work to proceed for a short period, while reducing the risk of injury from arc flash.