# Portable generator grounding



## Kaffeene (Feb 11, 2014)

Here we go!!!


----------



## Kaffeene (Feb 11, 2014)

Driving a ground rod will not bring the stage to the same potential. However the stage should be bonded. 
Supplying more than cord and plug connected equipment. This seems like a separately derived system to me and a ground rod should be installed if a metal water pipe electrode or structural metal electrode is not available.


----------



## [email protected] (Jan 16, 2013)

Thanks for the reply. As I think this over it seems to me the EGC pictured is bonded to the stage. It would provide a low impedance path for any fault to open the OCP. Driving a ground may at best be a back up however, the ground is so dry and the impedance so high doubt it would have much effect. I'm I seeing this correctly ?


Sent from my iPhone using Tapatalk


----------



## dont (May 26, 2015)

NEClook up: Portable power. We had this issue when a concert came to a farmer's field. it is not temporary power from the power company. Equipment grounds between utilization equipment and the gen set are needed (three prong plug extension cords), but earth ground for the gen set is not required as it is portable power, if there is a bond to the frame of the genset.


----------



## MXer774 (Sep 1, 2014)

What good do you think a ground rod would do for that gen set and stage? Not going to help clear a fault in the event of one. Not going to bring the stage to the same potential. As mentioned above, only thing need be concerned with is verify the EGC bonded to metal frame of gen set and all metallic portions pertaining to the stage. Ground rod is cheap enough to install if you feel like it's necessary. Land it at the EGC at genny or stage.


----------



## j johnson (Jul 20, 2009)

To lower the chases of thaving touch volt being present!


----------



## MXer774 (Sep 1, 2014)

Bull


----------



## wildleg (Apr 12, 2009)

dont said:


> NEClook up: Portable power. We had this issue when a concert came to a farmer's field. it is not temporary power from the power company. Equipment grounds between utilization equipment and the gen set are needed (three prong plug extension cords), but earth ground for the gen set is not required as it is portable power, if there is a bond to the frame of the genset.


this is a separately derived system, and requires a ground rod per 250.34, unless I am missing something. (since it has a feeder it appears that it is supplying some kind of panel, not just cord and plug, and therefore does not meet the exceptions for a portable generator that say that it does not need a ground rod)


----------



## FaultCurrent (May 13, 2014)

250.34 Portable and Vehicle-Mounted Generators.

(A) Portable Generators. The frame of a portable generator
shall not be required to be connected to a grounding
electrode as defined in 250.52 for a system supplied by the
generator under the following conditions:
(1) The generator supplies only equipment mounted on the
generator, cord-and-plug-connected equipment through
receptacles mounted on the generator. or both, and
(2) The normally non-carrying metal parts of equipment
and the equipment grounding conductor terminals of
the receptacles are connected to the generator frame.

(B) Vehicle-Mounted Generators. The frame of a vehicle
shall not be required to be connected to a grounding electrode
as defined in 250.52 for a system supplied by a generator
located on this vehicle under the following conditions:
(1) The frame of the generator is bonded to the vehicle
frame, and
(2) The generator supplies only equipment located on the
vehicle or cord-and-plug-connected equipment through
receptacles mounted on the vehicle, or both equipment
located on the vehicle and cord-and-plug-connected
equipment through receptacles mounted on the vehicle
or on the generator, and
3) The normally non-current-carrying metal parts of equipment
and the equipment grounding conductor terminals of
the receptacles are connected to the generator frame.


Driving a ground rod will do nothing. If the equipment grounding conductor is installed properly from the the generator to the stage equipment all is well. Maybe if lightning strikes the generator it would have a purpose.

Some argument could be made for bonding the metal stage structure to the equipment ground.


----------



## RIVETER (Sep 26, 2009)

[email protected] said:


> Thanks for the reply. As I think this over it seems to me the EGC pictured is bonded to the stage. It would provide a low impedance path for any fault to open the OCP. Driving a ground may at best be a back up however, the ground is so dry and the impedance so high doubt it would have much effect. I'm I seeing this correctly ?
> 
> 
> Sent from my iPhone using Tapatalk


The ground is for lightning strikes. The egc is for circuit interrupting.


----------



## Electric_Light (Apr 6, 2010)

MXer774 said:


> What good do you think a ground rod would do for that gen set and stage? Not going to help clear a fault in the event of one. Not going to bring the stage to the same potential. As mentioned above, only thing need be concerned with is verify the EGC bonded to metal frame of gen set and all metallic portions pertaining to the stage. Ground rod is cheap enough to install if you feel like it's necessary. Land it at the EGC at genny or stage.





dont said:


> NEClook up: Portable power. We had this issue when a concert came to a *farmer's field*. it is not temporary power from the power company. Equipment grounds between utilization equipment and the gen set are needed (three prong plug extension cords), but earth ground for the gen set is not required as it is portable power, if there is a bond to the frame of the genset.


Anything that sticks up into the air on a large field becomes susceptible to lighting strike and lightning can source like 1.21 jigga-amps 

If the stage sits on a dry ground and the generator is sitting near a grounded item like a fence, hydrant etc with low impedance ground connection, the lightning will probably hit the frame used for banner/lighting, travel down the cable, then arc over from the generator to the hydrant and if someone happens to be standing in between the two, he's going to be BBQ'ed. 

Assuming the stage is considerably taller than the generator and the two are reasonably close together, make sure the stage is earthed. 

If you earth just the generator, you have the worst of everything. The lightning will raise the potential of stage which will seek path to the grounded generator through the person, through the instruments through signal cable and vaporize everything in its path.


----------



## wildleg (Apr 12, 2009)

FaultCurrent said:


> 250.34 Portable and Vehicle-Mounted Generators.
> 
> (A) Portable Generators. The frame of a portable generator
> shall not be required to be connected to a grounding
> ...



so . . like I said, it does not meet the criteria for the exceptions to 250.34 and needs a ground rod to be NEC compliant. 

(I can only assume that since you posted that after my previous post that you did not notice the conjunction "AND" connecting the requirements for the exception (cord and plug) to not needing a ground rod ?)

I'm not saying a ground rod does anything (other than provide a path for lightning), but it appears to me to be a violation otherwise.

I agree that bonding the stage would seem to be a good idea, but I haven't done any events like that, and the only experience I have is knowing that my brother got hooked up on a mike on an outdoor event stage, and I always wonder how safe the people on those stages really are. (lightning protection, or the absence of it, also makes me wonder)


----------



## FaultCurrent (May 13, 2014)

Yes I agree that a ground rod is required when it supplies the cables as in the OP.

What if the generator had meltric or cam-lok connectors? Could that be considered as cord and plug connected equipment? Often times movie shoots use 400 amp cam-loks to feed a portable stage board using the Mole-Richardson stuff.

Lightning like never happens here in LA. If it ever strikes anything it makes the news.

The LAFD makes the temp power guys drive ground rods at all the portable carnivals, shows whatever. (maybe with the carnies with no teeth as electricians could be a crap shoot, we find the 3 foot ground rods all the time).

In the big city with nothing but asphalt and concrete can't always find a planter or median to drive a rod into. Then the LAFD makes the temp guys bond the genset to a fire hydrant.

A waste of time in my thinking, but it makes then happy. The real hazard is the out of state roadies that bring in welding cable, paddle boxes, and sister lugs to power up a concert venue. Some of the work they do leads to guys getting hooked up to guitars and mikes like your bro. Those roadies when confounded by ground loops and 60 hz hum solve the problem by cutting off the ground wires to each amp until they find the right one, then look out. I heard that those big lips of Mick Jagger were caused by him kissing the mike.


----------



## Meadow (Jan 14, 2011)

I say article 250 needs to be revised to make this clear, along with some more common sense in the CMP :thumbsup:


----------



## ampman (Apr 2, 2009)

meadow said:


> I say article 250 needs to be revised to make this clear, along with some more common sense in the CMP :thumbsup:


That sounds like a political answer are you campaigning for something


----------



## Meadow (Jan 14, 2011)

ampman said:


> That sounds like a political answer are you campaigning for something




Yes, because a single internet post will cause change bypassing all democracy 


Seriously, when you think about the terms they obfuscate. For example ground wire is not a correct term. Its not grounding that clears the fault, its bonding back to the source. The terminology is erroneous in its literal sense making it confusing. I still cant make heads or tails of 250. :blink:


----------



## Electric_Light (Apr 6, 2010)

Don't make it too complicated.










Bonding keeps things together in the box. 
Grounding keeps the box leashed.

The stage is the biggest metal object. So, if you ground the stage, the lightning will try to yank the stage out directly off the ground. The generator won't see much of it. 

If you ground the generator, the stage will simply move and the cable between the generator will try to hold it down, but mother nature will just break it off like it's a piece of string. 

The kVA capacity of generator is a drop in the bucket compared to lightning.


----------



## RIVETER (Sep 26, 2009)

meadow said:


> Yes, because a single internet post will cause change bypassing all democracy
> 
> 
> Seriously, when you think about the terms they obfuscate. For example ground wire is not a correct term. Its not grounding that clears the fault, its bonding back to the source. The terminology is erroneous in its literal sense making it confusing. I still cant make heads or tails of 250. :blink:


When you feel as though you are obfuscating again. We will help.:thumbsup:


----------



## Meadow (Jan 14, 2011)

Electric_Light said:


> Don't make it too complicated.
> 
> 
> 
> ...


If the generator is hit by lighting I doubt a ground rod would do much.


----------



## Electric_Light (Apr 6, 2010)

meadow said:


> If the generator is hit by lighting I doubt a ground rod would do much.


Realistically, the tallest part is the most susceptible to lightning strikes, which is the stage frame


----------

