Doors closed

[zog]

For those guys that think there is no arc flash hazard when the doors are closed, here you go.



http://www.youtube.com/watch?v=O2uyyoGT1Wo



This is why the NFPA 70E requires PPE for interacting with equipment, regardless of energized conductors being exposed or not.

 

[hockeyoligist2]

I agree 100%! The door will not stop it! I practice the thing at the end, stand to the side with head pointed away. I haven't had a bad one, thank goodness, but I did have one blow the door open!

 

[chris kennedy]

I don't see where anything states what voltage that is although it states 'phase to phase' and that looks like a 600V SS. So I would guess 480???

 

[iwire]

Maybe it is just me but it seems that the manufactures should be required to make their equipment contain any flash as long as the equipment is used within its ratings.

Would we accept say a lawn mower that might fly apart at any moment under normal use?

 

[zog]

Maybe it is just me but it seems that the manufactures should be required to make their equipment contain any flash as long as the equipment is used within its ratings.

Would we accept say a lawn mower that might fly apart at any moment under normal use?

How could the OEM ever design for that? The available fault current is determined by the system it is connected to, and the clearing time of the OCPD is determined by the upstream OCPD to that equipment, those are the 2 main factors and the OEM has no control over those things.

Of course they could build them robust for a worse case situation, but that would cost more and peple no longer purchase quality, they go by price. You think a design build guy would use equipment like that? Nope, he will use the cheapest Chinesse made crap he can to win the job.

 

[iwire]

How could the OEM ever design for that? The available fault current is determined by the system it is connected to, and the clearing time of the OCPD is determined by the upstream OCPD to that equipment, those are the 2 main factors and the OEM has no control over those things.

Of course they could build them robust for a worse case situation, but that would cost more and peple no longer purchase quality, they go by price. You think a design build guy would use equipment like that? Nope, he will use the cheapest Chinesse made crap he can to win the job.

We could say the same thing about any product, cars are a great example, foreign cars have to meet the rules here to be sold here.

The other thing I find odd is you are saying they could not make an enclosure to contain a fault but we expect some PPE will protect us.

 

[G._S._Ohm]

The blast force can be equated to some amount of TNT.
I'd have plugs on the sides of the enclosure that give you enclosure integrity in case of fire but fail at less than the 2000 PSF that arc-flash can exert. Kinda' like freeze plugs in an engine block.

 

[charlie b]

The other thing I find odd is you are saying they could not make an enclosure to contain a fault but we expect some PPE will protect us.

1. The enclosure door is about 8-12 inches from the source of the arc. Your body would be another 12-18 or even more inches away. That amount of distance makes a huge difference.
2. The PPE will not stop the arc from causing some amount of bodily harm. It certainly will not prevent the arc from pushing you away, and possibly causing you to bump into something on the other side of the work space. But it will, if used correctly, prevent a fatal injury. That difference is also huge.

 

[zog]

We could say the same thing about any product, cars are a great example, foreign cars have to meet the rules here to be sold here.

They follow the standards that exist, recently there became an ANSI standard for arc rated switchgear, and for that equipment to be sold as "Arc rated" it needs to meet those specs, but that calss of gear is optional and not "required" to be used by anyone, and again it costs more and the end users accountants that make those decisions, thier numbers say it is cheaper to put PPE on thier guys than use arc rated switchgear.

The other thing I find odd is you are saying they could not make an enclosure to contain a fault but we expect some PPE will protect us.

Distance from the arc is a HUGE factor, and it is always assumed that you are at least 18" from the arc. So often PPE can protect you, but nothing can protect you from an arc flash >40cal/cm2. Sure they sell suits up to 140cal/cm2 now, nut that is only a heat rating, not pressure. >40cal/cm2 the blast can fatally damage your internal organs, so a 100cal/cm2 suit only means you can have a closed casket instead of an open one.

 

[sameguy]

Thanks Zog, brings things into view when the questions of who should work in the trade; day labor or a tradesmen.
Building items to contain the blast would be like the difference in price of NEMA rated equipment over IEC rated; NEMA 7,9 or NEMA 1. Could be higher than that too.

 

[zog]

Thanks Zog, brings things into view when the questions of who should work in the trade; day labor or a tradesmen.
Building items to contain the blast would be like the difference in price of NEMA rated equipment over IEC rated; NEMA 7,9 or NEMA 1. Could be higher than that too.

I believe 1.5x is a common adder for arc rated equipment.

 

[jim dungar]

I don't see where anything states what voltage that is although it states 'phase to phase' and that looks like a 600V SS. So I would guess 480???

They used 1000V. It appears their intent was to evaluate 'where to stand', so they created an arc flash that would be sure to blow the doors off. They admit it does not represent a typical real world event.

http://www.arcflashforum.com/showthread.php?t=780&page=3

This testing was done by causing a phase-to-phase fault with a wire (difficult in real life but they do happen) and with >480V to help arc sustain. <480V arcs are difficult to sustain in real life BUT they will sustain when they go three phase so to elminate chance in the testing we used overvoltage of about 1000V to assure the arc would last for the whole test.

 

[dbuckley]

I'vew mentioned this before; somewhere I have an old Siemens catalogue which has a photo of a 6300A switchboard containing an arc fault. There's huge amounts of smoke coming out the top, but the structural integrity of the cab is intact. It can be done.

 

[jim dungar]

I'vew mentioned this before; somewhere I have an old Siemens catalogue which has a photo of a 6300A switchboard containing an arc fault. There's huge amounts of smoke coming out the top, but the structural integrity of the cab is intact. It can be done.

Yes, it is called Arc-Resistant Switchgear. Most manufacturers offer it. UL and ANSI have standards for it.
It does not really "contain" the arc as much as it redirects it through specifically designed and located 'blowout' panels.

 

[cornbread]

Appreciate the video. I hear too often there is no arc flash problem if the door is closed. The video removes all doubt! Again thanks!