SCCR and its impact on AFIE and PPE requirements

[GlennGould]

Have mercy - this is my first post:
I am wondering what precisely to do under the following circumstances:
1) During the course of an AFHA, a multitude (70% or more) of the OCPDs and withstand ratings on panels are below the SCCA.
2) In addition, there are numerous code violations - particularly 450 and 240.21(C).
3) My "software" (and I use that term liberally) does not make provisions for underrated OCPD clearing (or exploding) times.
4) I have seen AFHA performed and delivered to customers noting underrated devices and providing PPE requirements based on AFIE calculations with no apparent nod to SCCA upstream versus an underrated device.

Usually mitigating these issues amounts to about 10 percent or so. Mostly it redounds to a service visit. No hot work at all . . . .

In this type of analysis - I am hesitant to place a Category 0 calculated sticker on a HDSS fed from an OCPD which may be at face level above it (or near by) which is blatantly underrated. Or that someone could be walking by with no PPE when the accident happens downstream.

The requested advice is do I follow my conscience and force AFIE on downstream busses to the level last proper OCPD/Panel SCCR and or IR can clear or hold? Or do I just inform them (the customer) that perhaps the utility closed their delta and a large portion of their system is dangerous? Give them two sets of stickers? Overlay TCCs showing the difference? Sell a bunch of current limiting fuses? Or use the calculated PPE or what?

Sorry for so many words. But this is kind of a bugger!:?

 

[petersonra]

Have mercy - this is my first post:
I am wondering what precisely to do under the following circumstances:
1) During the course of an AFHA, a multitude (70% or more) of the OCPDs and withstand ratings on panels are below the SCCA.
2) In addition, there are numerous code violations - particularly 450 and 240.21(C).
3) My "software" (and I use that term liberally) does not make provisions for underrated OCPD clearing (or exploding) times.
4) I have seen AFHA performed and delivered to customers noting underrated devices and providing PPE requirements based on AFIE calculations with no apparent nod to SCCA upstream versus an underrated device.

Usually mitigating these issues amounts to about 10 percent or so. Mostly it redounds to a service visit. No hot work at all . . . .

In this type of analysis - I am hesitant to place a Category 0 calculated sticker on a HDSS fed from an OCPD which may be at face level above it (or near by) which is blatantly underrated. Or that someone could be walking by with no PPE when the accident happens downstream.

The requested advice is do I follow my conscience and force AFIE on downstream busses to the level last proper OCPD/Panel SCCR and or IR can clear or hold? Or do I just inform them (the customer) that perhaps the utility closed their delta and a large portion of their system is dangerous? Give them two sets of stickers? Overlay TCCs showing the difference? Sell a bunch of current limiting fuses? Or use the calculated PPE or what?

Sorry for so many words. But this is kind of a bugger!:?

What is AFHA? HDSS? AFIO?

If you are doing some kind of audit of the power system (or perhaps an arc fault hazard analysis) and come across a bunch of problems, I would suggest it is up to you to list them for your customer and let them deal with them.

I don't see how you can put a PPE sign on something you know has a good chance of failing during a short circuit event.

Current limiting fuses may or may not do you any good. Unless they have been tested with the existing OCPD it will not be an acceptable fix.

OCPD for transformers and their respective conductors seems to be something not well understood by many in the field.

 

[charlie b]

AFHA = arc flash hazards analysis
AFIE (your AFIO must have been a typo) = arc flash incident energy.
HDSS eludes me. My guess is that that is also a typo, and that HVSS (high voltage service switchboard) was intended.

 

[petersonra]

AFHA = arc flash hazards analysis
AFIE (your AFIO must have been a typo) = arc flash incident energy.
HDSS eludes me. My guess is that that is also a typo, and that HVSS (high voltage service switchboard) was intended.

That would have been my guesses for the first two. The third one baffles me.

 

[Jraef]

HDSS = Heavy Duty Safety Switch perhaps?

One thing to keep in mind: blind data collection on IC ratings of OCPDs can get you in trouble. In the case of series combination devices like combination motor starters, there are incidents wherein the sum of the total is greater than any individual part standing alone. We tend to think of the rule that the maximum SCCR is never greater than the lowest rating in the box, but the caveat to that is if they are tested and listed together to be higher. UL does that for mfrs.

So for example it's entirely possible to have a combo starter in which the breaker is rated 35kAIC, the starter and OL relay by themselves say 5kA SCCR, but when used in a specific tested combination, are listed at 65kA SCCR. In the case of Saftey Switches, the raw label may say the switch is only good for 10kA, unless there is a fuse in it, in which case it is good for up to the rating of the fuse. What I have seen unfortunately is that some survey companies are hiring grunts to just collect raw data on nameplates, without interpretation.

 

[GlennGould]

Clarifications

Clarifications

Sorry
HDSS is a Heavy Duty Safety Switch
The others are as translated

To clarify:
Consider 35,000 SCC amperes on a bus, utility data driven, not an infinite assumption situation
With a FAL36xxx breaker rated at 18kAIC
Non-tested, non-engineered series ratings aside

Your "software" calculates a 0.1 cal/cm² AFIE at 18" at the load, arc in a box.

Do you . . . .

a) Stick the load panel with the Category 0 sticker
b) Push the bus to the AFIE on the next bus upstream with a valid SCCR OCPD
c) Ask someone on the Mike Holt Forum or
d) Punt
:lol:
Sorry for the confusion
Hoping for another good response.

 

[wbdvt]

Sorry
HDSS is a Heavy Duty Safety Switch
The others are as translated

To clarify:
Consider 35,000 SCC amperes on a bus, utility data driven, not an infinite assumption situation
With a FAL36xxx breaker rated at 18kAIC
Non-tested, non-engineered series ratings aside

Your "software" calculates a 0.1 cal/cm² AFIE at 18" at the load, arc in a box.

Do you . . . .

a) Stick the load panel with the Category 0 sticker
b) Push the bus to the AFIE on the next bus upstream with a valid SCCR OCPD
c) Ask someone on the Mike Holt Forum or
d) Punt
:lol:
Sorry for the confusion
Hoping for another good response.

Ok, so a couple of items:

1. There is no Category 0 in NFPA 70E anymore with the 2015 revision. Additionally the 2015 revision states that categories cannot be used if and incident energy analysis has been performed, so the actual Incident Energy is to be listed.

2. So, an IE has been calculated for the load in a box which could be anywhere from 10ft to maybe 200 ft from the breaker. Therefore the device could either interrupt the arcing current because the arcing current is less than the withstand rating of the device or the device fails violently also interrupting the current. But one is away from the failure. Note that AR PPE is not designed to protect against flying projectiles.

3. If the immediate device is overrated, this device could be ignored in an analysis so the actual device doing the clearing would be the next upstream device. This should result in a higher incident energy.

4. As far as what to do, list the overdutied devices which are a code violation. Then perform the analysis with those devices not providing any protection, use the next upstream device.

 

[petersonra]

Sorry
HDSS is a Heavy Duty Safety Switch
The others are as translated

To clarify:
Consider 35,000 SCC amperes on a bus, utility data driven, not an infinite assumption situation
With a FAL36xxx breaker rated at 18kAIC
Non-tested, non-engineered series ratings aside

Your "software" calculates a 0.1 cal/cm² AFIE at 18" at the load, arc in a box.

Do you . . . .

a) Stick the load panel with the Category 0 sticker
b) Push the bus to the AFIE on the next bus upstream with a valid SCCR OCPD
c) Ask someone on the Mike Holt Forum or
d) Punt
:lol:
Sorry for the confusion
Hoping for another good response.

perhaps you can explain more about what you mean by "software".

I don't see how you can in good conscience not tell the person paying for whatever it is you are doing that you found this issue.

I don't understand what you are trying to get at with option (b).

 

[Jraef]

Leaving an 18kAIC breaker into a systems where there is 35k SCC makes the entire question of the AFIE and PPE kind of moot. It's like discussing the seat cushion qualities on the life boats of the Titanic... it's not going to make a hill of beans of a difference when it is needed. The PEE is not intended to protect you from the flying shrapnel of a breaker that exploded because the interrupting capacity was exceeded.

 

[jim dungar]

If there is 35kA available at the line side of the 18kA rated breaker, it needs to be replaced with a properly rated one. This breaker should not be closed onto any possible short circuit (e.g. it should not simply be reset if it trips).

At what point in the system did you determine your calculated AFIE of 1.2cal/cm^2? Probably not at the line side of a breaker which is part of the service entrance equipment. Surely not at the immediate load side of the breaker as any fault there would likely also involve the line side. It most likely is a calculation at some downstream location, which means the bolted fault current flowing through the breaker is likely going to be less than the 35kA on its line side.

But NFPA70E requires you to perform a risk analysis (e.g. the odds something will happen) as well as the hazard analysis.
What is the risk that the breaker will try to clear a 35kA fault when no live work is being performed on the circuit?

Finally let me state: the breaker must be replaced before it is required or attempts to clear a fault above its 18kA rating.

 

[GlennGould]

A good choice . . . .

A good choice . . . .

. . . . 4. As far as what to do, list the overdutied devices which are a code violation. Then perform the analysis with those devices not providing any protection, use the next upstream device.

Thanks wbdvt for the response.
That is what I did.
As for 70E 2015 . . . .

 

[petersonra]

4. As far as what to do, list the overdutied devices which are a code violation. Then perform the analysis with those devices not providing any protection, use the next upstream device.

Just out of curiousity.

How can you know that a short circuit downstream of a device that is failing will be properly interrupted by an upstream device? There is no way to test such a combination to know.

 

[jim dungar]

4. ... Then perform the analysis with those devices not providing any protection, use the next upstream device.

How do you know the overdutied device will not try to interrupt the fault before the upstream device does?
This could add additional resistance to the circuit thereby lowering the arcing fault current through the upstream device, maybe to the point where its clearing time is impacted.
Do you recommend 'setting' changes to the upstream device to insure it operates first?

 

[tish53]

I would not continue with the Arc flash analysis if I encountered the overdutied breaker. It needs to be replaced and then an new arc flash analysis can be run.