when is 4 pole ATS required

[skyline1977]

Hi,
Per NEMA or IEC when are 4 poles ATS required?

 

[waross]

The choice is mostly dependent on the neutral grounding method.
A four pole ATS is used when the neutral must be switched to accommodate grounding requirements.
Many methods of measuring ground fault currents require the use of a four pole ATS.
The code requirement is indirect in that if the ground fault protection requires a switched neutral, then you must use an four pole ATS.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[cuky2000]

In contract with a solid neutral system where a 3-pole ATS is normally used, a 4 poles ATS for is used on a separately derived power system that ultimate is associated with the earthing (grounding) for the emergency system and the ground-fault protection scheme.

Below is a schematic & a switch rendering indicating the neutral pole switched by the ATS.

^{>>>>>> _{REFERENCES: NEC Sections 230.95,250.24(A)(5), 700.6 (D), K MacKenzie & J. Stark}<<<<<<}

>>>>>