Sometimes components in our reports might indicate a higher fault current than what is calculated at the bus in which the components are attached to. Below is a high level explanation as to why this might be:
See the example table below, specifically notice that the breaker named LEFT GEAR - OFFICE AC has a higher 1/2 Cycle (kA) Duty than the other three breakers connected on the exact same bus (see picture of table below)
ANSI has a standard that specifies how manufacturers test breakers
When a breaker is to be rated greater than 10kA but less than 20kA it must pass it's test with an X/R ratio of 3.18.
When a breaker is to be rated greater than 20kA it must pass it's test with an X/R ratio of 4.9.
If a breaker is then installed on equipment with a system X/R ratio less than the tested value, no math is needed.
However, if a breaker is installed on equipment with a system X/R ratio greater than the tested value, a multiplier is required.
In the example system above, LEFT GEAR has an X/R ratio of 4.34, this means that three of the breakers were tested at an X/R ratio greater than what they are now being exposed to (each of the three have 25kA, 25kA and 30kA ratings). One of them though, LEFT GEAR - OFFICE AC (rated to 18kA), was tested at an X/R ratio less than what it is now connected to. ANSI has an equation (which is built into engineering software such as EasyPower and SKM) that increases the duty cycle appropriately then that value is compared to the actual rating of the device. 28.215kA (LEFT GEAR - OFFICE AC duty cycle, the new value is 24.397) includes a multiplier vs. 26.426kA (the rest of LEFT GEAR duty cycle, new value is 22.744).