Maximum Available Fault Current

[jmoore284@gmail.com]

According to 110.24 service equipment is required to be marked with the maximum available fault equipment. Downstream devices such as MCC's shall have their maximum available fault current documented but marking is not required.

I am looking to perform a short circuit study for a client in which I will determine the maximum available fault current throughout their power system. The plan is to then apply labels to each distribution device (MCC's, PDP's, breaker panels, etc.) identifying the maximum available fault current and the date of the calculation. I will also provide a report listing each devices maximum available fault current as well as it's withstand or SCCR rating.

The idea of labeling each distribution device with its max AFC is to make it easier on contractors to properly size new equipment they are installing to ensure their properly rated for the fault current at that point.

Has anyone labeled or seen labels like this? I'm also curious of everyone's thoughts on the idea.

 

[Jraef]

According to 110.24 service equipment is required to be marked with the maximum available fault equipment. Downstream devices such as MCC's shall have their maximum available fault current documented but marking is not required.

I am looking to perform a short circuit study for a client in which I will determine the maximum available fault current throughout their power system. The plan is to then apply labels to each distribution device (MCC's, PDP's, breaker panels, etc.) identifying the maximum available fault current and the date of the calculation. I will also provide a report listing each devices maximum available fault current as well as it's withstand or SCCR rating.

The idea of labeling each distribution device with its max AFC is to make it easier on contractors to properly size new equipment they are installing to ensure their properly rated for the fault current at that point.

Has anyone labeled or seen labels like this? I'm also curious of everyone's thoughts on the idea.

Most, if not all, of the industrial labeling suppliers have those available, pre-printed with spaces for you to fill in the data with a Sharpie, or blank for you to use in a printer.

 

[romex jockey]

It's the calories thing for me

~RJ~

 

[wbdvt]

The maximum available fault current will be needed to be obtained from the utility. This will be for how the system is currently configured and may change in the future. If you are worried about equipment sizing, then your best option is to use the infinite bus fault current. Therefore this will only change if a transformer is changed. Then for labeling, just use the infinite bus fault current of the transformer feeding the equipment.

Do not use this fault current if you are also doing an arc flash analysis.