In certain commercial facilities the 2104 National Electrical Code requires that a surge suppressor be installed on all panels fed by emergency generators. The NEC recognizes that there is a need to protect the equipment fed by the emergency panel from surges or dirty power coming from the generator. This is true whether there is a storm or other event causing loss of power and generator operation, or whether the generator comes on during its monthly testing (generators need regular maintenance and testing to be reliable). Today’s custom homes have electrical and electronic equipment similar to the lighting systems and controls, automation systems, HVAC systems, etc. found in commercial facilities, so home electrical panels have the same need of protection from dirty power originating from the use of generators. Installing protection upstream from the ATS will protect the circuit boards and power supplies within the ATS. If a surge were to knock out the ATS, the generator will not come on at all. Click here to see sample design diagrams of protecting transfer switches.