Automatic Transfer Switch (ATS) transfer time requirements - Testing

What is the requirement for testing essential electrical system transfer switches (automatic and manual)?

Transfer switches that are part of the essential electrical system are considered high-risk utility systems equipment that have code-related (NFPA 99-2012  and NFPA 110-2010) testing requirements. There must be documentation of the result of testing for each unique piece of equipment or device in order to demonstrate that the testing has been completed as required. All automatic transfer switches are to be tested monthly. Testing activities are to be conducted in accordance with the assessed maintenance strategies that best suit the unique system design. Per NFPA 99-2012, the monthly generator load test must include a complete simulated cold start along with automatic and manual transfer of all essential electrical system loads. It is a best practice, but not a requirement, to initiate the load test with a different ATS each month.

According to NFPA 99-2012,, the essential electrical system must be maintained to supply emergency power within 10 seconds of loss of normal power. If the 10-second criteria is not met during regular testing, the organization must have a process to confirm on an annual basis that the 10-second criteria can be met.
Last updated on February 21, 2018
Manual: Home Care
Chapter: Environment of Care EC

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