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 Post subject: SWD rated breakers
PostPosted: Wed Jan 26, 2011 12:40 am 

Joined: Wed Jan 05, 2011 3:01 am
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This question came up on another forum, and it's worthy of asking here.

Does a molded case breaker marked with SWD (switch duty) pose less of an arc-flash hazard when interacting with it than a breaker not marked SWD? By interacting with it, I mean opening and closing the breaker with the covers on the enclosure.


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PostPosted: Wed Jan 26, 2011 5:43 am 
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Is it really a molded case breaker or a molded case switch that you are referring to?

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PostPosted: Wed Jan 26, 2011 8:13 am 
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CowSparky wrote:
This question came up on another forum, and it's worthy of asking here.

Does a molded case breaker marked with SWD (switch duty) pose less of an arc-flash hazard when interacting with it than a breaker not marked SWD? By interacting with it, I mean opening and closing the breaker with the covers on the enclosure.


Great question. I'm not aware of any supporting data but here is my thought.

SWD rated devices are designed for repeated switching operations. A non SWD breaker is not intended as a switch, I have seen cases where the contact could fail.

With that said, this seems more like an arc flash hazard from "Interaction" question and the issue of interaction is more of a judgement. We just had the interaction discussion at a conference this week and there is in fact judgement involved - it is not black and white.

I would think either could technically fall under the "hazard from interaction" but it would seem logical that the SWD rating would be less likely to pose the problem.

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PostPosted: Wed Jan 26, 2011 8:48 am 
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CowSparky wrote:
This question came up on another forum, and it's worthy of asking here.

Does a molded case breaker marked with SWD (switch duty) pose less of an arc-flash hazard when interacting with it than a breaker not marked SWD? By interacting with it, I mean opening and closing the breaker with the covers on the enclosure.


The SWD rating simply deals with the breaker's ability to switch fluorescent ballast loads. It is only available on 1P 15A and 20A breakers.

It may have some bearing on how you decide to interpret NFPA70E's FPN no. 1, to the definition of Arc Flash Hazard, "Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard".


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PostPosted: Sun Jan 30, 2011 3:56 pm 

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wbd wrote:
Is it really a molded case breaker or a molded case switch that you are referring to?
Ahem...
CowSparky wrote:
Does a molded case breaker marked with SWD...


Thank you for your answers.

Now it seems to me that a properly utilized SWD rated breaker (used on 15 and 20 amp single pole circuits for fluorescent lighting) wouldn't pose much or any arc flash hazard, even if it were to catastrophically fail anyhow. It's sort of a moot point, in that case.


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PostPosted: Thu Nov 07, 2013 5:59 am 
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Ok let me continue with this thread.....what are the PPE requirements for operating a SWD breaker in a panel? The panel in question has an IE of 0.6 cal/cm^2 @18" with an arc flash boundary of 12". This would be HRC 0 PPE if one was working within the AFB but if all one is doing is operating the breaker with head and torso outside the AFB of 12", does one need hearing protection? Safety glasses are required in the facility so that point is moot in this instance.

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PostPosted: Thu Nov 07, 2013 9:03 am 
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wbd wrote:
Ok let me continue with this thread.....what are the PPE requirements for operating a SWD breaker in a panel?


If you follow the task tables the PPE is outlined in NFPA70E.

If you perform calculations to determine the arc flash incident energy, then PPE selection is per your company's Electric Safe Work Practice program.


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PostPosted: Thu Nov 07, 2013 9:28 am 
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Thank you but I think you missed a point in my posting. Does one need hearing protection since an analysis was done (no tables) and the AFB is 12" If one is operating a SWD breaker in a bkr panel that is 0.6 cal/cm2 at 18", the only part of your body that is within the AFB is 12" of your arm to operate the bkr. Do you need hearing protection?

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PostPosted: Thu Nov 07, 2013 12:28 pm 
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wbd wrote:
Thank you but I think you missed a point in my posting. Does one need hearing protection since an analysis was done (no tables) and the AFB is 12" If one is operating a SWD breaker in a bkr panel that is 0.6 cal/cm2 at 18", the only part of your body that is within the AFB is 12" of your arm to operate the bkr. Do you need hearing protection?


What are the results of your risk analysis?
Does your ESWP included language about not needing PPE when you are outside of the AFB?

You have 'discovered' one the grey areas of NFPA70E - What PPE is required to protect a worker, when calculations have been performed.
Many, if not most, companies are reluctant to make this decision, therefore they use NFPA70E tables backwards by equating an HRC, and its PPE, with a calculated incident energy level.

This issue may get worse with the next edition of 70E.


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