Generator Questions

[mkgrady]

I'm confused about when a generator output must be run through a service rated transfer switch. And I'm also confused as to when a generator output must have a disconnect before it feeds a load in a building.

My situation is I am supplying a 12 KW Briggs&Stratton gen to feed certain circuits in a home that has a 200 amp service, I am going to use a 200 amp ats (it was cheaper than a 100 amp due to package pricing). All of the circuits I plan to feed with the generator will be fed from a 100 amp subpanel which will be fed from the service or the generator through the ats.

Do I need a generator disconnect outside or inside the house to isolate the generator feed? The generator has a disconnect but it is inside the enclosure.

Does the ATS need to be service rated? And if not, when does an ATS need to be service rated?

 

[JES2727]

If you were backing up the entire service you would locate the ATS downstream from the meter but on the line side of the 200A main breaker. You would need a service rated ATS in this situation. Your application does not require a service rated ATS.
The generator output breaker inside the enclosure satisfies the disconnecting means required by 445.18.

 

[jwelectric]

see 702.11 in the 2008 NEC

 

[LarryFine]

. . . when does an ATS need to be service rated?

When it's the first thing (after the meter) the service conductors hit.

 

[mkgrady]

Thanks for the rerplies

 

[Hendrix]

If you were backing up the entire service you would locate the ATS downstream from the meter but on the line side of the 200A main breaker. You would need a service rated ATS in this situation. Your application does not require a service rated ATS.
The generator output breaker inside the enclosure satisfies the disconnecting means required by 445.18.

The enclosure has to be service rated. If it isn't you would need the disconnect or a service rated ATS.