Bingo. Apples and oranges as far as breaker ratings go. You cannot apply ratings across rating agency specifications. Meaningless exercise.
Originally Posted by jim dungar
I think I understand what you are attempting to do here; you don't know what is there other than the breakers and you are attempting to extrapolate an Available Fault Current based on the theory that the breakers that are being used are an indirect indicator of a minimum amount of fault current. For example if there was only 35kA available, they would not have used 65kA breaker, so you know the AFC must be over the next lowest value but not higher than the lowest stated value of any one breaker you see installed.
Originally Posted by Voltaco
It's a noble attempt to do something without the proper information, but really, you cannot ASSume anything from what you have so far with regards to any reasonably accurate Arc Flash study. Whatever you extrapolate is useless when it comes to a real Arc Flash Hazard Risk Analysis. You must have REAL data on what is AVAILABLE as far as Fault Current, which has almost no meaningful bearing on what was used in the equipment design. For all you know, the equipment you have pictures of may actually have a "Series Rating" with something else up stream, so the values shown on the individual breakers themselves may be rendered meaningless in terms of what you are basing your assumptions on. For example you may actually have 85kA of AFC, but this panelboard may be rated 85kAIC when used behind some other Current Limiting breaker upstream, so that they can use 65kAIC rated components. But that will have no bearing on the AFC as far as your Hazard Risk Analysis. Sorry.
Many people are shocked when they discover I am not a good electrician...