sokkerdude
Member
- Location
- Arkansas
Can some please explain these articles. And how I go about getting the calculations. Thank you
110.9 and 110.10
- Thread starter sokkerdude
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Available fault current is a property of any electrical system just as voltage, frequency, etc. The determination of the AIC is an engineering calculation, but, for utility supplied systems POCO can usually give you a "starting number" so you have some idea what you are dealing with.
That number can be altered by the components in the system such as motors and by the size and length of the conductor runs and thats where the engineering is needed.
For safety it is imperative that this issue be addressed.
As a general rule most overcurrent gear is a minimum of 10,000 AIC and services 200 amps or less will normally not come close to that so a lot of AHJ's don't ask for calculations on services up to 200 amps (some only require a 400, etc)
That number can be altered by the components in the system such as motors and by the size and length of the conductor runs and thats where the engineering is needed.
For safety it is imperative that this issue be addressed.
As a general rule most overcurrent gear is a minimum of 10,000 AIC and services 200 amps or less will normally not come close to that so a lot of AHJ's don't ask for calculations on services up to 200 amps (some only require a 400, etc)
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
110.9 deals with Amps Interrupting Capacity (AIC). The requirement is that all devices that are intended to break fault current (fuses and breakers) are rated for the amount of fault current available at their line side terminals.
110.10 deals with Short Circuit Current Rating (SCCR) and Withstand Current Rating (WCR). The requirement is that equipment (i.e. wire and bus bars) be able to carry fault currents until the protective device operates.
Fault current is usually called Short Current Amps (SCA). SCA amps are calculated by knowing information about the source (generators, POCO, and large motors) and the impedances of the conductors and transformers.
110.10 deals with Short Circuit Current Rating (SCCR) and Withstand Current Rating (WCR). The requirement is that equipment (i.e. wire and bus bars) be able to carry fault currents until the protective device operates.
Fault current is usually called Short Current Amps (SCA). SCA amps are calculated by knowing information about the source (generators, POCO, and large motors) and the impedances of the conductors and transformers.
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