Q: Is there a standard that says we need to write the start and stop time on our monthly generator load test for 30 minutes?

A: In so many words there is. I agree that you won’t find a specific standard that says you must record the start and stop times of each test, but section 8.4.2 of NFPA 110-2010 says diesel generator sets in service shall be exercised at least once monthly, for a minimum of 30 minutes, using one of the following methods:

1. Loading that maintains the minimum exhaust gas temperatures as recommended by the manufacturer
2. Under operating temperature conditions and at not less than 30 percent of the EPS nameplate kW rating

If you do not record the start and stop times, then how do you prove to a surveyor that you tested the generator for 30-minutes?

It is reasonable and logical for a surveyor to expect you to record the start and stop times to ensure you tested the generator for 30-minutes.