ATS control from external source such as PLC


Do any auto transfer switch experts her know if it's possible to control an ATS from an external signal?

E.g., can I block/prevent a transfer if an external signal (say from a PLC) is present/wired to the ATS controller?

I'm asking because they are requesting some more complex than usual control schemes using multiple ATS's/ interlocking etc.


Senior Member
Most commercial/industrial rated switches will have this natively or be available as an option. As others have indicated, if this ATS is for Article 700 load(s) this would not be allowed.
Agree. I have done a previous install which the client asked to redo when the ATS transferred to emergency power in 42 seconds!


Senior Member
San Francisco
Self Employed
As others have stated, this is a common accessory/ option provided by all manufacturers on the newer microprocessor controllers. The cut-sheet View attachment GE 50R-2016 R15D_Q3 acc.pdf is attached that shows the R15 load shed and Q3 transfer inhibit options for the GE-Zenith ATS.
If this feature is required on the older ATS units with relay logic then a simple circuit can be added using an interposing relay to prevent transfer to emergency.