Question 1: To meet the requirements of NFPA 110, 8.4.7 do I even need to complete a test proving that each transfer switch will start the EPS (generator) and transfer the load to each Life Safety (LS) and Critical Branch (CB) automatic transfer switch (ATS) within 10 seconds, or is the monthly test sufficient?
Answer 1: NFPA 110, 8.4.7, only references breakers in the emergency distribution between the EPS (generator) and the ATSs (transfer switches); not the normal (utility) distribution breakers. Therefore, these breakers are not used for the monthly test…only opening normal feed breakers are used as an option to utilize the test switch on a selected LS or CB ATS.
Note 1: All ATSs must be transferred during the monthly test.
Note 2: However, NFPA 99 nor 110 require each LS and CB ATS to be tested monthly to prove the transfer time of 10 seconds or less
Reference: NFPA 110, 8.4.7: EPSS circuit breakers for Level 1 system usage, including main and feed breakers between the EPS [generator] and the transfer switch load terminals, shall be exercised annually with the EPS in the “off” position. [emphasis added]
Question 2: If I do need to complete separate tests, can I electronically transfer load with the test switch on each transfer switch, or do I need to open the breaker to simulate a power outage?
Answer 2: Not applicable when referencing 8.4.7. However, you are allowed to use a test switch for transferring power at each ATS, including the ATS being used to start the test.
Question 3: Is 8.4.7 referencing the breaker at the EPS and the transfer switches?
Answer 3: Yes, and yes, but only the emergency power feed breaker to an ATS, not the normal power feed breaker.
Summary: NFPA 110, 8.4.7 does not apply to monthly testing/transfer of ATSs. It is a test to confirm the emergency breaker(s) itself will function. Typically, the EPS breaker is located on the EPS. The feed breakers from the generator to each ATS are usually located in a separate room dedicated to the EPSS distribution center.
If you have a parallel set up, then the breakers in the parallel cabinet exercise themselves automatically every month.
