ATS Testing

Q: Is it permissible to have Automatic Transfer Switches (ATSs) tested every other month when conducting monthly emergency generator testing? For example, when you have one (1) generator but two (2) to four (4) ATSs. Our contracting service company that does training and annual load-bank testing advises "yes." Thank you.

A: Here is another example why you should not trust contractors to know and understand the codes and standards. Apparently, the contractor in question is providing you with bad advice.

No, it is not permissible to test ATS every other month. Section 8.4.6 of NFPA 110-2010 says transfer switches shall be operated monthly. The monthly test of a transfer switch shall consist of electrically operating the transfer switch from the standard position to the alternate position and then a return to the standard position. Monthly means monthly, not every-other month.

Why is it that a trusted contractor, who is considered an expert in what they do, does not know this basic requirement for testing ATS? You should ask them that question.