Filler plates in a "dead-front" - derate kaic?

[grasfulls]

Using a SQD HOM612L100FCP as an example of a panel manufactured with no door. I have not looked at the specs, but I assume it is rated at 10kaic. I assume this rating means that, with breakers installed or not, and though there is no door, it can contain a surge up to 10kaic, not allowing it to blast outward and potentially cause damage to a person or property. If I break out one more space than I need, does a filler plate now degrade the inrush rating? Should all empty spaces in a panel be filled with unused breakers to maintain the panel's rating? The only thing a filler plate seems to do is protect from exposed live parts.

 

[LarryFine]

I would think only the manufacturer can answer that.

 

[infinity]

Good question but I don't think that it matters. Knock out seals don't have an AIC rating either.

 

[zbang]

If you use a Sq-D filler, I'd expect it to not affect the rating.

 

[jim dungar]

AIC is only applicable to the breakers.
The panel has a SCCR rating that is equal to the lowest rated breaker's AIC.

The SCCR of a panel board is based on its bussing support and insulation, so the presence or absence of covers, including deadfront, trim, and breaker slot covers never impacts its rating.

However the UL Type rating of the panel is impacted by the presence of openings in the enclosure, so the lack of breaker slot covers and knockout fillers would be violations.

 

[grasfulls]

However the UL Type rating of the panel is impacted by the presence of openings in the enclosure, so the lack of breaker slot covers and knockout fillers would be violations.

If a panel is subjected to an inrush within its SCCR rating (thank you for that), and a panel is approved to have a main breaker of, say, 22kaic and downstream (series) breakers of 10kaic (within a distribution section of the panel), does this then derate the listed SCCR? Then, if there is a short, though the gear can clear it without damage (is that correct?) might a filler plate blow out, exposing someone to an arc blast? Please forgive any incorrect terminology, I am just getting into all this NFPA 70E stuff because arc flash gear is so expensive and I am trying to determine when it is needed. My contention is that a filler plate may not necessarily remain in place under some feasible conditions.

I just looked this up, it is the "dissipation" that I wonder about, where will it built to dissipate to?

QUOTE "SCCR is important for preventing electrical hazards and ensuring that devices and systems can safely absorb and dissipate electrical energy" END QUOTE

 

[grasfulls]

If you use a Sq-D filler, I'd expect it to not affect the rating.

Thanks, I would somewhat expect for them to have that in writing, but I would hope if we use a manufacturer's plate that this would be the case.

 

[grasfulls]

I would think only the manufacturer can answer that.

Good point, I will ask them the full question. thanks!

 

[jim dungar]

might a filler plate blow out, exposing someone to an arc blast?

A blank space filler cover is required to prevent contact with energized parts thus reducing the possibility of an arc flash event from occuring, it is not designed to contain the flash.

NFPA 70E does not consider any equipment, even steel doors, as containing an arcing event unless the equipment is specifically designed for that purpose.

Arc blasts exist but they are not specifically addressed by NFPA 70E because there is no industry accepted method for calculating the potential 'size' of a arc blast.

 

[grasfulls]

Arc blasts exist but they are not specifically addressed by NFPA 70E because there is no industry accepted method for calculating the potential 'size' of a arc blast.

This is very interesting! Thank you.

NFPA 70E does not consider any equipment, even steel doors, as containing an arcing event unless the equipment is specifically designed for that purpose.dology fir calculating

Does an "event" include ARC and BLAST?

 

[jim dungar]

This is very interesting! Thank you.

Does an "event" include ARC and BLAST?

Yes. Can one occur without the other?
Assuming you mean arc flash incident energy and arc blast.

 

[grasfulls]

Sorry, yes, I meant arc flash and arc blast. And no, I do not think one can occur without the other but I was unsure if the word event was meant to encompass all. Makes sense that it does.

 

[grasfulls]

A blank space filler cover is required to prevent contact with energized parts thus reducing the possibility of an arc flash event from occurring, it is not designed to contain the flash.

I am still thinking about this Jim, please do no take further questions as argumentative, they are borne of ignorance on my part. If it is only deigned to prevent contact, then it feels safe to say it has made the metal cover it has been installed into less that it was designed for, so some sort of derating

NFPA 70E does not consider any equipment, even steel doors, as containing an arcing event unless the equipment is specifically designed for that purpose.

Who provides the SCCR rating, is this UL? Is NEMA involved at all? Does the SCCR not mean it is built to withstand, in essence, the maximum inrush it might see, without damage? How can equipment be designed for it if :

Arc blasts exist but they are not specifically addressed by NFPA 70E because there is no industry accepted method for calculating the potential 'size' of a arc blast.

I almost wanted to research before I commented... I appreciate the "no industry standard" it tells me there are methods (I will start looking for them, just to know) that some make use of to figure how to assign ratings to equipment. It also seems to indicate further changes to standards, like NFPA 70E (I did buy the book finally). Is a fault the cause of flash and blast and equipment may not be able to protect from these after effects?

 

[grasfulls]

Here is what spawned all of these questions. We have a small electrical room wherein a switchboard (someone says that is the proper name, I used to say switchgear) resides. It has a 400 amp disconnect and a labeled rating of 22kaic. Downstream is a distribution section with filler plates and duct tape and some openings not sealed. Someone removed a cover to a small section and installed a 10kaic rated load center with two breakers. Then, they cut the cover and reinstalled it - pre my time there.

My contention has been that anyone who enters the room is now technically exposed to live parts and should have arc flash gear on. There has been a lot of resistance, even some anger over this assertion. Ultimately, I started thinking of the filler plates, as I learned of arc faults and what equipment is supposed to do, and felt the filler plates cannot do what the original metal cover was meant to do.

At this point I still believe that but want to know more. If I am in the wrong forum or have taken this thread too far off track, please let me know.

 

[jim dungar]

Arc Flash has little to do with the Short Circuit Current Rating of equipment which is based on available bolted fault conditions. Inrush current is not a factor
Arc Flash has to do with the amount and duration of calculated arcing fault current and protective device clearing time.

The typical panel board enclosure does not really come into play when determine the SCCR of a panel by testing agencies like UL. NEMA writes some product manufacturing standards but it leaves testing standards to UL. Manufacturer's listed breaker slot closing plates, even snap-plastic ones, would be included in the SCCR of the panel if it is in the standards.

The most common formulas for determining arc flash incident energy come from IEEE and do not consider the strength nor integrity of the enclosure around an arcing fault. The presence or absence of a metallic deadfront, much less a simple closing plate, is not addressed in the calculations.

 

[grasfulls]

wow, that is almost discouraging but great information Jim! I have to look these up, and I will - breaker slot closing plates, are they the same as what I called a filler plate?

if it is in the standards

what standards?

The most common formulas for determining arc flash incident energy come from IEEE and do not consider the strength nor integrity of the enclosure around an arcing fault. The presence or absence of a metallic deadfront, much less a simple closing plate, is not addressed in the calculations.

Do you see a day where equipment is built and rated around all of these considerations? If an arc flash incident can overwhelm a structures integrity because it is not taken into consideration.... well, where should its integrity be taken into consideration?

 

[jim dungar]

Do you see a day where equipment is built and rated around all of these considerations?

Not for general purpose commonly used products like disconnect switches and panelboards.
It is easier to prevent an arc flash event rather than contain one that has started.

Perform risk analysis don't just look at potential arc flash incident energy values.
Spend time worrying about the work and maintenance procedures that can lead to an arc flash occurring.
Have you ever seen any statistical information, from any source, showing a passer-by being injured by an arc flash event other than when equipment was being 'worked on'?

For more discussion related to NFPA 70E you may want to look at other forums, like the one found at brainfiller.com.

 

[grasfulls]

Have you ever seen any statistical information, from any source, showing a passer-by being injured by an arc flash event other than when equipment was being 'worked on'?

No, Anyway, this is another good point and makes inhibiting access to exposed live parts much more important.

For more discussion related to NFPA 70E you may want to look at other forums, like the one found at brainfiller.com.

I will check it out, thanks Jim.