Ground resistance value for Fire Pup Controllers

[federicop]

Is there a minimum ground resistance value for fire pump controllers using soft starters? I recently asked the supplier of a controller we are installing and he answered they don't have a value. I'm using the NFPA 70 value of 25 ohm minimum. Peer specialists have advised 5 ohm or less for equipment using electronic sensitive equipment. Thanks

 

[tom baker]

No. The NEC does not have a minimum ground resistance, 25 ohms is for a single rod electrode, if you add a second you are done. 5 ohms is a sometimes quoted but means nothing.

 

[jim dungar]

Resistance to ground (dirt) is only important for lightning protection and step potential ground grids.
This is why you cannot easily find a specific value to use in your specifications.