Building Electrical Connection: Available Fault Current 18,000 Amps ?

[Watts_Up]

I noticed this recently remodeled apartment building of 8 units with the following sign:

Available Fault Current 18,000 Amps
​

- To who publishing the "Available Fault Current" might be useful ?

- Since there are three phases of 120 V, would the "Available Fault Current" be 6,000 Amps or 18,000 Amps on each phase?


I noticed in this forums someone mentioning for example that their main panel was updated to 200 A,
but I never heard someone mentioning anything about "Available Fault Current".

- So is there any correlation between a Panel capacity and the "Available Fault Current"?

- Can someone guess how much Amp each unit might get?
(I will try one day to check the value of the circuit breakers, but those are cover and are not visible)

 

[iluvmacs]

Available fault current (also known as short-circuit current rating) is a measure helpful for engineers designing the electrical system as a whole, utilities, and regulatory bodies. It is not a helpful number for circuits and appliances you actually connect (i.e. you do not get to pull 18,000 amps under any normal circumstance). This is basically a measure of how much current can this panel can withstand under a short-circuit condition before it melts/vaporizes/starts on fire.

Prospective short-circuit current - Wikipedia

 

[power.saver]

Can someone guess how much Amp each unit might get?

100A max to each of the eight APTs.

 

[Watts_Up]

@iluvmacs Thank you for your explanations.

I was wondering if it was very common or if there is any requirement to display the "Available Fault Current"
which is not very useful to know for a typical customer, in particular if you want to add a plug for an EV?

Or may be this a just a gimmick from the landlord to provide some bragging numbers
for what seems to be a Frankenstein house, or may be a potential pot farm...

In fact the "Available Fault Current" don't seems related to the building but to the electrical company delivery
ability to sustain any major shortcut without experiencing a blackout from a burning transformer.

To give some perspective, what could be the "Available Fault Current" for the Firebaugh, CA, Supercharger
with 56 V3 stalls powered by 14 cabinets of 1 MW peak or any future CyberTruck or Tesla Semi Superchargers?

 

[iluvmacs]

I've never seen such a prominent display of it like that before, but that could be to local jurisdiction rules. I sincerely doubt it's a gimmick from the landlord, because why would they even be aware of it or know about it, and why would they expect any tenants to notice or care?

I would guess that most of the electrical cabinets at Superchargers have fault currents of around 50-100kA.

 

[Patrick66]

It is a newer code requirement, needed for electrician safety for arc flash protection. However, the “18,000A” is a dead giveaway that a calculation has not been done and they are just using a maximum utility value.