Terminology

They're mixing apples and oranges.

It should read "short-circuit current" and cite the figure in amps, or it should read "short-circuit resistance" and cite the value in ohms, or it should read "short-circuit conductance" and cite the figure in siemens.

Now possibly they're citing the short-circuit current under an assumed (and evidently unspecified) value of resistance (and of course, voltage) but, no, kA is not a resistance; it's a current.

So if you had to guess when they say

Short circuit resistance and then write 50KA what would you think that means

I thought it looked suspicious to me also which is kind of why i was asking

To me it looks like short circuit availability of the feeder

"... it looks like short circuit availability of the feeder"

Yep.

Sounds to me like they do not know what they are talking about. I would steer clear of such a company, they cannot tell oranges from apples, much less compare them.

Basically what we have here is a failure to communicate....because we are too stuck on acronyms. The draftsman probably had no idea what SCCR is and deduced it must have been SCR that he was told to add and that was, well, we see what ended up on the drawing.

"short-circuit current"

Or someone dropped a C, as the term SCCR is also frequently used. UL loves that term.

or they dropped the 'r' out of sccr?

In that SCCR term, the R may stand for "rating" rather than "resistance"; "resistance" is a bad choice, because it also means something else. "Short circuit withstand" is decent phraseology, too.

Yes - that is what it is. I never questioned that.

UL has the SCCR in all their literature on the subject. We were given special sessions on this subject when becoming UL 508A certified.

The draftsman making the drawing screwed up...

I did get some clarification

It sounds like what they are specing is the breaker size from the plant switch gear that is feeding this particular panel.

And it was meant to be "short circuit availability

As if a direct 3 phase fault occured from the feeder to ground

Atleast that is how im interpreting what they drew

Sounds like someone needs to bring that draftperson up-to-date as to what is meant by 'resistance' and the units used.

probably a moonlighter that is used to printing religion tracts?

The best thing to do is to ask <...they...>, by cutting out the sleeping beauties here and going directly.

<...Anyone want to take a guess...>

Except they no longer exists

Old drawing from a company that is out of business

or i would of done that

What they tried to indicate was what the minimum fault current handling ability of the equipment should have been.

The only one who can accuratly derive the fault current that the feeder can supply under a bolted fault condition is the entity responsible for the feeder itself.

Everything from the "stifness" of the utility feeding the transformers that energize the feeder down to how well coordinated the OC devices are in the circuits that energize the feeder come into play in coming to a value for the fault current the feeder can dump into a fault.

The only one who can accuratly derive the fault current that the feeder can supply under a bolted fault condition is the entity responsible for the feeder itself.

You'd be surprised how many times a big time consulting engineering firm asks us to calculate the fault current available at the input to one of our panels. So we have to take exception and tell them that we can tell you what our panel will be rated for, but the available fault current in the plant is NOT something we can calculate here - ask your customer. This is a foreign subject to many electrical engineers.

I hear ya! But... no, not a surprise. You would not beleive the junk we get from some engineers. As an AHJ, we pretty much do discounted plan reviews for them.

Electrical Power Engineering is basically a non-subject in most undergraduate curriculum. Most younger EEs are conversant in microprocessors, microcoding, and microamps, but have never calculated anything in megavolts, kilowatts, or kiloamps, nor do they know the difference between three phase and single phase power calculations. It's a lost art.

And that problem dates back to at least the late 1960's. I wanted to be a power engineer and I only able to select a total of two EE courses on the subject, even in those days, and they were not applied courses, but pure theory. The remaining courses were solid state and circuitry. The strange thing was, this was at PSU and the Pa based power companies hired many PSU electrical engineers. I guess they accepted training on the job.

My first taste of fault currents came one year after graduation, as I was chosen to learn this subject and do calculations for the consulting engineering firm that hired me. It was a bit of a new concept to the electrical engineers of the day.

Another thing that has been lost by most EEs (both senior and junior), assuming it had ever been "found", is exactly how important it is to understand the nature of the various loads our feeders and branch circuits supply energy to.

Getting some of these bone heads to grasp what a "continous load" vs a "non-continous load" is all about and how this needs to impact the various sizing calculations that must be performed is beyond beleif and comprehension.

When you get right down to it, we are lucky here in NA that the AHJ community has such good plan review sections.

I shudder to think what could happen if we just allowed some of these so called "EEs" to install what they think needs to be installed.

50KA is the Interrupting Rating, "...the maximum short-circuit current that an overcurrent protective device can safely interrupt under standard test conditions...".

From here.

I'm thinking that this is simply a translation error if the term "withstand". Short Circuit Withstand ratings were common before the terminology changed to SCCR here in North America, but it means the same thing; the ability of a piece of equipment to keep from becoming a bomb during a short circuit event of the given magnitude. So if a device says it has a 42kA withstand rating, that means if the SC current gets to 42kA, it survives, but at 50kA it may not. I just think that someone was trying to translate "withstand" and chose "resistance", meaning MECHANICAL resistance, which was an unfortunate choice given that resistance has a specific meaning in electrical systems.

I think it is about the "circuit withstanding short-circuit" since in usual technical language "resistance" and "withstanding" are synonyms.

See M.Webster dictionary withstanding=to resist successfully.

I did not advertise anything. I posted my thought and a link on the other resource (it's true) but no AD. Here is my original message:
I'm always get lost in the terminology. Even people who write college essays for sale sometimes make wrong statements based on terminology. It is not an end of the world but you need to be careful at official events or presentations.