Generators: Ground rods required all the time?

[Finite10]

Talked to a sales rep supplying generators and UPS gear.
He said they always require ground rods at all generators.

1) If the grounded conductor is not switched at the ATS, and there's a EGC run with the phase conductors - doesn't a ground rod give a second path to ground?

This seems like a second system bonding jumper with respect to the OCPD trying to clear a fault.

250.35 (B) Permanent and nonseperately derived generators.

 

[chris kennedy]

All the large genny install instructions I have seen require a gnd rod. For a non-sds, remove the genny's SBJ, run an EGC with the feeder, hook up the GEC to the frame and your good.

 

[Dennis Alwon]

Talked to a sales rep supplying generators and UPS gear.
He said they always require ground rods at all generators.

1) If the grounded conductor is not switched at the ATS, and there's a EGC run with the phase conductors - doesn't a ground rod give a second path to ground?

This seems like a second system bonding jumper with respect to the OCPD trying to clear a fault.

250.35 (B) Permanent and nonseperately derived generators.

Does a neutral bonded at a service with a ground rod to earth create a path to ground? Not usually, there is so much impedence between the rod and the pole thru the earth that there would be virtually no current travelling back.

 

[ceb58]

All the large genny install instructions I have seen require a gnd rod. For a non-sds, remove the genny's SBJ, run an EGC with the feeder, hook up the GEC to the frame and your good.

Agree with Chris. Even the smaller units instructions call for a rod. And by code it can fail for not being installed 110.3B

 

[augie47]

I spent a great deal of time on the phone one day with a GENERAC technician question as to the need for a ground rod. He went through an elaborate detail about protection but never convinced me .... dosen't matter for as ceb58 says 110.3(b)
It simply becomes a 250.53 auxilary electrode

 

[Finite10]

I spent a great deal of time on the phone one day with a GENERAC technician question as to the need for a ground rod. He went through an elaborate detail about protection but never convinced me .... dosen't matter for as ceb58 says 110.3(b)
It simply becomes a 250.53 auxilary electrode

Seems to me that the EGC would be the low impedence path to ground and that it sould be capable of handling a lightning strike - maybe not- that is not a big issue around here.

250.4 talks about the earth not being an effective sole path for fault current, as Dennis mentioned. But seems to me that the wire from the generator frame/bus to the rod would be. If I were a ground fault I might head that way, and not all the way back to the OCPD via the EGC run with the phase conductors.

I can see a rod for portable generators that have rubber tires and are SDS. Still not convinced that a cut sheet from a supplier would convince the ground fault to reference physical earth for the OCPD, and not just head for the nearest ground rod.

 

[tesi1]

generator bonding

generator bonding

:lol:depending on the fuel type most require bonding the frame or tank due
to the fuel & or gas code

 

[tom baker]

Mike Holt and I argued with managment at Generac on this same issue. They wanted him to produce a mike holt type book on generators and he would not unless they removed the blanket requirement for ground rods.
Our AHJs will often require if the instructions required ground rods - 110.3(B)

 

[mstaylor]

I use generators on a regular basis, 100KVA or larger. I am the gen tech, so the ground rod debate directly affects me. I have always grounded them because I am using them to power sound, lights and stage power for festivals. Because of the sound aspect, does that change your opinion?