We work with a number of companies and everyone has their own policy and reasons (or in some cases lack of reasons for it). How you do it takes knowledge of standards but is mostly about using common sence (the least common of the sences) and good judgement.

Things to consider:

I believe that NFPA requires life-safety generators to be exercised every two weeks for 20 minutes, under load. This has been a long standing requirementy and I assume has some research behind it. However, its not applicable to a data center and a failure during testing only causes an inconvenience.

My belief is that a generator should be normally tested weekly without load, with at least one week per month under building load. Finally once a year with a full load bank test.

The monthly test under building load should be by opening the main, NOT by exercising the generator from a remote start/transfer control button.

My reasoning is that the ATS needs to be exercised regularly and including your voltage sensing relays and controls.



Could my PM/Testing cause a failure? Probably not, but it could cause a pending failure to show itself at the time of the test rather then when power fails and the generator is required. Some people believe that it's better to wait until the failure occurs rather then instigate a failure. This line of reasoning is naive and fear based. Consider that during testing you have the ability to switch back to untility power. Providing that your UPS should carry your critical load and you can retart the HVAC in a timely manner.

When should we test? If you test during normal business hours you run the risk of causing an outage during prime time. This is true but on the other hand, you likley have staff and other resources available to get you back up and running.

Precautions:
1.