Generators

[DMG_1]

I have sized a generator for an industrial application. I am now in the process of sizing the fuel tank which should be based on the Generator Class (run time). From my research I have been able to gather the following about generators:

Class - The total amount of time the the generator will need to run. This will determine the size of the fuel tank.
Level - Life Safety Classification
Type - The allowable Transfer Time (based on the Level)

I cannot seem to find any information on how to select or determine the "Class". Does anyone have some information for me?

Thanks.

 

[MEP_PM]

Good Question. I've had the same problem and no one has given me a good answer. Hopefully someone can give us a good explanation.

With that being said, generally our installation have been at least class 2 based on NEC 700.12(B)(2) requirement for 2-hr of back up. Or class-X (96hr) based on the Seismic requirements in NFPA 110 5.1.2.

 

[david luchini]

According to NFPA 110 - Standard for Emergency and Standby Power Systems, it is the role of "other" NFPA Standards to specify the applicable level, type and class of Emergency Power Supply Systems (EPSSs).

I know of two standard that specify EPSSs. NFPA 101 requires a Class 2 EPSS for mechanical ventilation equipment in smokeproof enclosures. NFPA 99 requires Class X EPSSs for Type 1, 2 & 3 essential electrical system power sources. Class X means whatever time is required by the application, user or other code.

Basically the runtime is up to you based on your application or user needs.

 

[hillbilly1]

Keep in mind also that tanks over a certain size require routine federal inspections.