Jump to content

Do small generators require a ground rod?


Recommended Posts

  • Members

Thats not quite true..from the nec:

 

250.34 Generators-Portable and Vehicle-Mounted

(A) Portable Generators. The frame of a portable generator is not be required to be grounded to the earth if:

(1) The generator only supplies equipment or cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and

(2) The metal parts of generator and the grounding terminals of the receptacles are bonded to the generator frame.

 

(B) Vehicle-Mounted Generators. The frame of a portable generator is not required to be grounded to the earth if:

(1) The generator frame is bonded to the vehicle frame.

(2) The generator only supplies equipment or cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and

(3) The metal parts of generator and the grounding terminals of the receptacles are bonded to the generator frame.

 

I interpret this to mean that if a distro is used, the genset must be grounded.

Link to comment
Share on other sites

  • Members

I interpret this to mean that if a distro is used, the genset must be grounded.

The question there is "what is a distro?". Does a range plug distro need one but a breaker protected power strip not? Is there any real difference between them legally? Does every single piece of equipment have to be plugged into the generator's outlets separately to get away without a ground rod?

 

:confused:

Link to comment
Share on other sites

  • Members

 

The question there is "what is a distro?".

 

Let's put it to the test:

 

 

(1) The generator only supplies equipment or cord-and-plug-connected equipment through receptacles mounted on the generator, or both,
and

(2) The metal parts of generator and the grounding terminals of the receptacles are bonded to the generator frame.

 

 

If I'm reading this right, it seems like a power strip or a distro would require a generator earth ground.

Link to comment
Share on other sites

  • Members

Hmm... Looks like AH hasn't been around for a few days - I'm looking forward to his opinion. Gotta say that handing a mic to a singer standing barefoot on the grass that's tied to the genny frame via the cable shield with no ground rod seems like a bad idea to me?

 

Oh, and do yous guys call digsafe before you drive a rod?

Link to comment
Share on other sites

  • Members

 

Hmm... Looks like AH hasn't been around for a few days - I'm looking forward to his opinion. Gotta say that handing a mic to a singer standing barefoot on the grass that's tied to the genny frame via the cable shield with no ground rod seems like a bad idea to me?


Oh, and do yous guys call digsafe before you drive a rod?

 

 

Almost all my events that I use a genny for are pretty remote & outside city limits, so I don't.

 

I basically always would err on driving a rod, and keep some large auger type rill bits in order to get the hole started.

Link to comment
Share on other sites

  • Members

 

Hmm... Looks like AH hasn't been around for a few days - I'm looking forward to his opinion. Gotta say that handing a mic to a singer standing barefoot on the grass that's tied to the genny frame via the cable shield with no ground rod seems like a bad idea to me?


Oh, and do yous guys call digsafe before you drive a rod?

 

 

Andy is at the state fair. He has setups at the livestock areas plus he's putting on a horse show. I will try to scan and put up a link to a article about him. It's a busy couple of weeks for him.

Link to comment
Share on other sites

  • Members

I can already see the shoes being thrown at me, but.....

 

The ground rod is simply to bring your separately derived system to the same potential as the earth, so you don't have potential between the earth and ground. It is not designed to make a breaker trip, nor is it designed to allow fault current to travel to ground in sufficient quantity to make it trip. You must have at least 25 ohms to ground per NEC, or you are required to drive a second. If you don't get your 25 ohms after that, the code basically says, "oh well, you tried".

 

If the ground rod is 25 ohms to ground of the ground rod, and you apply 120 volts to it, ohms law says you are only gonna get 4.8 amps on that bad boy, not enough to make a breaker trip.

 

So should you drive one. Absolutely. 8 feet into the ground, and leave it there, otherwise it's useless, gotta hit wet soil. Would I on a Eu 3000? Depends on a few things I guess.

 

What is it serving? For a small park gig, I probably wouldn't if it was just a few extension cords. If it was anything bigger, I'd probably have a gen set that required camlok tails, so I would most def drive one. But thats a whole nother beast.

 

Then again, if it was a barefoot singer on the wet grass in the park, I probably wouldn't wanna own the liability with or without ground rods.

Link to comment
Share on other sites

  • Members
Then again, if it was a barefoot singer on the wet grass in the park, I probably wouldn't wanna own the liability with or without ground rods.

Good point. I do carry GFCI's for outdoor shows and I think they provide better protection in a situation like this than a ground rod would :) . My biggest system is only 5.5kw into FOH so I'll never be needing camlocks :) .

Link to comment
Share on other sites

  • CMS Author

You must have at least 25 ohms to ground per NEC, or you are required to drive a second. If you don't get your 25 ohms after that, the code basically says, "oh well, you tried".


If the ground rod is 25 ohms to ground of the ground rod, and you apply 120 volts to it, ohms law says you are only gonna get 4.8 amps on that bad boy, not enough to make a breaker trip.

 

Hang on a sec. Your wording is a bit off. NEC [250.56] states that resistance after driving a rod should be no MORE than 25 ohms, not at least 25 ohms. You want as little resistance as possible, and the second rod is intended to lower resistance to ground.

 

Having said that, only a qualified electrician is going to have the proper metering gear to do a ground resistance test, as you can't simply stick your meter probe into the dirt and get an accurate read. Even the AHJ's I've encountered have no metering setup, and simply look at the installation, assume the rod is 8 feet long, and sign off or not based on how you look.

 

Oh, and this is a good time to mention the old trick for driving a rod easily, in case you do so. Simply get a disposable cup, dig out a little cupsized hole, and put it in the hole. Fill with water, and drive the rod through the bottom. Keep filling the cup as you drive. Unless you hit rocks, of course, it'll go in way easier. As always, lubrication is the key ;)

Link to comment
Share on other sites

  • Members

 

Andy is at the state fair. He has setups at the livestock areas plus he's putting on a horse show. I will try to scan and put up a link to a article about him. It's a busy couple of weeks for him.

 

 

Hahaha, Andy is at the State Fair? That cracks me up. Such a small world it is. I'm sure my girlfriend has ooooh'd and aaaaah'd at his horses then.

 

I heard the Crest is up for sale? Is that the same Crest that Andy works at?

Link to comment
Share on other sites

  • CMS Author

 

Hahaha, Andy is at the State Fair? That cracks me up. Such a small world it is. I'm sure my girlfriend has ooooh'd and aaaaah'd at his horses then.


I heard the Crest is up for sale? Is that the same Crest that Andy works at?

 

 

If it's the Crest in Sacramento, then I'd say "yes".

 

Probably not worth the amount of time/money it takes to keep such a place going. But geez, it sure do look perty.

Link to comment
Share on other sites

  • Members

I am an electrical contractor. If you use the outlets on the generator, you do not need a ground rod. The ground rod requirement is for larger units equipped with lugs to hard wire a distro, transfer switch etc. to.

 

I always use ground fault pigtails at the generator. They protect everything downstream. If you don't you are asking for trouble.

 

Most people do not understand what a ground fault is. On an outlet, the two vertical slots are a hot and a neutral, in laymens terms, a supply and a return. A GFI monitors each of those wires, for the device to operate, they need to be balanced. What comes out of the hot wire needs to return on the neutral or it's going someplace astray, ie: your old Fender amp is frying you through the guitar strings cause you are barefoot and standing in a puddle of beer. There is also a monitor on the ground prong that will trip at 4-5 milliamps if I remember correctly.

 

I'm sure there are citys and towns here and there that will want one but 99% of all portable and temporary installations do need require one if you use the outlets provided on the generator.

Link to comment
Share on other sites

  • Members

I use the standard L5-30 twistlock on the genny (Honda EU3000, 120 volts, 23.5 amps) and run 40ft of 10/3 to a quad box that powers everything. I am under the impression that the ground rod is not required for that, but thought I would ask Start Tool since he IS an electrician.

Link to comment
Share on other sites

  • Members

 

I am an electrical contractor. If you use the outlets on the generator, you do not need a ground rod. The ground rod requirement is for larger units equipped with lugs to hard wire a distro, transfer switch etc. to.


I always use ground fault pigtails at the generator. They protect everything downstream. If you don't you are asking for trouble.


Most people do not understand what a ground fault is. On an outlet, the two vertical slots are a hot and a neutral, in laymens terms, a supply and a return. A GFI monitors each of those wires, for the device to operate, they need to be balanced. What comes out of the hot wire needs to return on the neutral or it's going someplace astray, ie: your old Fender amp is frying you through the guitar strings cause you are barefoot and standing in a puddle of beer. There is also a monitor on the ground prong that will trip at 4-5 milliamps if I remember correctly.


I'm sure there are citys and towns here and there that will want one but 99% of all portable and temporary installations do need require one if you use the outlets provided on the generator.

 

 

This may be a dumb question, but what if you connect a power strip TO the outlets on the generator? Does that still count? Or are you meaning you can only use the outlets provided to power one device each?

Link to comment
Share on other sites

  • CMS Author

 

No its just one Crest, and yes its being sold. Thats a shame.

 

 

Hopefully Andy and his partners find a good steward for the old gal. They did a helluva job restoring it, and it would be a shame to see it become a Best Buy or Starbucks parking lot. Though IIRC the building may be registered as a historical site and protected from such rape.

Link to comment
Share on other sites

  • CMS Author

 

I am an electrical contractor. If you use the outlets on the generator, you do not need a ground rod. The ground rod requirement is for larger units equipped with lugs to hard wire a distro, transfer switch etc. to.


I always use ground fault pigtails at the generator. They protect everything downstream. If you don't you are asking for trouble.


Most people do not understand what a ground fault is. On an outlet, the two vertical slots are a hot and a neutral, in laymens terms, a supply and a return. A GFI monitors each of those wires, for the device to operate, they need to be balanced. What comes out of the hot wire needs to return on the neutral or it's going someplace astray, ie: your old Fender amp is frying you through the guitar strings cause you are barefoot and standing in a puddle of beer. There is also a monitor on the ground prong that will trip at 4-5 milliamps if I remember correctly.


I'm sure there are citys and towns here and there that will want one but 99% of all portable and temporary installations do need require one if you use the outlets provided on the generator.

 

 

I'll add the other little-known fact that a GFCI does NOT require a working grounding system to function 100%.

Link to comment
Share on other sites

  • CMS Author

 

This may be a dumb question, but what if you connect a power strip TO the outlets on the generator? Does that still count? Or are you meaning you can only use the outlets provided to power one device each?

 

 

Excellent question, and it should be fine. "Cord and plug connected equipment" means your mixer plugged into a quad box or extension cord, as opposed to a camlock (separate conductors) distro wired to the genset. NEC is satisfied that a grounded extension cord is going to maintain a good ground connection to the genset, whereas a camlock install would be relatively easy to have no ground cable connected, having separate conductors and all...

Link to comment
Share on other sites

  • Members

 


 

 

 

D'OH! Thats what I get for typing in bed. You are correct, 25 ohms or LESS to ground. My bad. And yes, almost no one has a meggar to test resistance to ground. Thats why after two, they consider it all good for a service. Little suggestion about being 8 feet long. A good AHJ always knows when a rods been cut. They generally know the soil conditions in their area, and most people drive in the rod as far as it goes, and cut off the excess. All the UL listing info is at the top of the rod, so if they dig up a little dirt and can't read anything, they know its cut. So if you hit rocky soil, be aware a good inspector will know you cheated.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...