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RES Technical Corner by Brett Eliasz
Technical Corner
Any legally required NEC 700 Emergency systems require maintenance and testing in order to assure proper function of life safety equipment when the time arises. What happens when you need to test or perform maintenance on this system and there happens to be a utility failure at the same time?
Using the 2017 NEC, section 700.3(F) is where you will find the requirements to aid in this scenario. Interestingly, the 2014 NEC did not even have this section and the 2020 NEC appears to match the 2017 code language.
The first illustration shows a loss of utility power as well as a loss of the permanent generator due to maintenance which would ultimately leave the facility in the dark. The solution could be to have a roll up generator at the sitedepicted here.
The second illustration shows a loss of utility power during load bank testing on the generator system. When power is lost the generator power is redirected back onto the system which will cover the facility.
Each of these scenarios will require the addition of a Triple Switch which is shown in the illustrations.
Illustrations courtesy of ESL Power Systems
There are a few other ways to accomplish what is required by this code section not shown here and of course there are some exceptions. One would likely utilize the exception which basically states to perform the testing and maintenance when the building is not occupied. I’d have to say that most buildings do have fully functional fire suppression systems (See Exception #2). These questions should be asked during the design to be sure we can meet the exception.
One last point is that these requirements during testing and maintenance are not listed under NEC 701 for the year 2017 and 2020.
Hopefully this article finds you well and can be used as a reference for your project needs. If anyone would like to contribute to the RES magazine and add an article or would like to request information on a specific topic (not limited to Electrical) just email me at beliasz@bergmannpc.com. As always, any comments are appreciated…! Thank you for reading.
