Portable Generator Grounding - are ground rods required

[tom baker]

About ten years ago I wrote a series of articles for a traffic signal magazine. Often some one will contact me after doing extensive and exhaustive research (google) about one of the articles.
Here is one email I recently received:

"Tom- I saw your email at the bottom of an article about generators and ground rods. I am in need of help to understand when and if ground rods are needed in my business. I have a company that uses small portable generators, that are neutrally bonded to the frame to run inflatable bounce houses and small mechanical rides.
Question- If I build a "drop" that takes the 220v plug on the generator (L1430 outlet) see attached picture, would you require a ground rod? We only use these drops to operate fans (110v) that inflate the bouncy houses and slides. Thanks for your time"
Later he added
"Each inspector asks and wants different things done at events. I was hoping you could point me in the right direction. The county does cite NEC code 2005 250.52 in relation to ground rods, but are very inconsistent at each event on what is needed. Please let me know what safety issues you see with the box."

See attached picture...
Later I will let you know how I answered.

 

[GoldDigger]

Two wire twist-lock means no EGC.
For new construction the GFCI receptacles do not make up for that.

 

[Hacks]

Two wire twistlock? That's an L14-30 with 4 prongs.

 

[ActionDave]

I can't think of any reason a small, portable generator used as described can ever be required to have a ground rod. 250.34 excludes them.

I never drive a ground rod when we use our 5kw generator.

 

[don_resqcapt19]

I can't think of any reason a small, portable generator used as described can ever be required to have a ground rod. 250.34 excludes them.

I never drive a ground rod when we use our 5kw generator.

While 250.34 says you don't need a grounding electrode, 250.20 says that for most common portable generator system voltages, you must have a "grounded system". This applies anytime the generator supplies "premises wiring". The definition of premises wiring is very broad.
This was not a problem when the definition of "grounded" was this.

Grounded. Connected to earth or some conducting body that serves in place of the earth

With that definition you could have a grounded system from a generator by bonding the neutral to the generator frame.
A couple of cycles the definition of "grounded" was changed to this.

Grounded (Grounding). Connected (connecting) to ground or to a conductive body that extends the ground connection.

It is my opinion, that if the generator is supplying premises wiring and if the voltage is such that it is required to be grounded system, then the generator needs a connection to a grounding electrode.

I don't think that this was the intent when the words "or some conductive body that serves in place of the earth" were removed from the definition of "grounded".

I don't see any real need to use a grounding electrode for a generator and believe this is just "collateral damage" from changing the definition of "grounded".

Note, many if not most code readers read 250.34 as being the only rule that covers the connection of a generator to a grounding electrode, but I don't see how that section changes 250.20 and the definition of grounded.

 

[3goofballs]

250.30(B)(2) also speaks to grounding portable and vehicle mounted generators, also Article 702 covers Optional Standby Systems.

 

[mbrooke]

Grounds rods for a generator as about as useful as a 401k to a dog.

 

[suemarkp]

Isn't the L14-30 with 20A receptacles a larger problem? To do that correctly requires a breaker enclosure to limit the current to the receptacles to 20A. That in turn makes the L14-30 a feeder, and is that feeder connecting to a structure? Hopefully, this just just electrical equipment on a branch circuit or feeder, temporarily laid on the grass to feed a bounce house

 

[ActionDave]

While 250.34 says you don't need a grounding electrode, 250.20 says that for most common portable generator system voltages, you must have a "grounded system". This applies anytime the generator supplies "premises wiring". The definition of premises wiring is very broad.
This was not a problem when the definition of "grounded" was this.

With that definition you could have a grounded system from a generator by bonding the neutral to the generator frame.
A couple of cycles the definition of "grounded" was changed to this.

It is my opinion, that if the generator is supplying premises wiring and if the voltage is such that it is required to be grounded system, then the generator needs a connection to a grounding electrode.

I don't think that this was the intent when the words "or some conductive body that serves in place of the earth" were removed from the definition of "grounded".

I don't see any real need to use a grounding electrode for a generator and believe this is just "collateral damage" from changing the definition of "grounded".

Note, many if not most code readers read 250.34 as being the only rule that covers the connection of a generator to a grounding electrode, but I don't see how that section changes 250.20 and the definition of grounded.

That's taking code interpretation and enforcement to the level of Biblical scholarship. Bless them for being pure of heart, but I don't think the CMP's members are that smart or thoughtful.

Open the good book up to 250.34, read, go out and pull the cord to start the generator, fiddle with the choke, pull again, repeat till the generator starts, use the power from it for whatever you want.....plug in a hammer drill and drive a ground rod if you want, but you only if that is your heart's desire, using the power for something else, that's okay too.

 

[don_resqcapt19]

...
Open the good book up to 250.34, read, go out and pull the cord to start the generator, fiddle with the choke, pull again, repeat till the generator starts, use the power from it for whatever you want.....plug in a hammer drill and drive a ground rod if you want, but you only if that is your heart's desire, using the power for something else, that's okay too.

I stand by my statement that if the generator is supplying premises wiring as defined in Article 100 and if the output voltage of the generator is one that is required to be a grounded voltage system by 250.20, you are required to have a grounding electrode.

250.34 does not change the other rules. Sure, there are many cases where the generator will not be supplying premises wiring, and would not require a grounding electrode, but the Article 100 definition of premises wiring is very broad.

 

[Pierre C Belarge]

2014 NEC

250.34(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-current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacle are connected to the generator frame.

 

[don_resqcapt19]

2014 NEC

250.34(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-current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacle are connected to the generator frame.

I am well aware of that section, but that does not have any effect on the rule in 250.20 that requires you to have a grounded system. CMP 5 did not change 250.34 when the definition of grounded was changed in Article 100. As a result of the Article 100 definition the rule in 250.34 is in conflict with the definition of grounded. Until CMP 5 clears up this conflict, I stand by my statement that a grounding electrode is required for any generator where the output of that generator is used to supply premises wiring. (note that the definition of premises wiring in Article 100 is very broad)

250.34 was fine when the definition of grounded said "connected to the earth or some conductive body that serves in place of the earth". With that definition the generator frame was the conductive body that served in place of the earth. When the words "or some conductive body that serves in place of the earth" were removed from the definition of grounded, there was no longer a way to supply a grounded system from a generator unless you used a grounding electrode.

Now would a grounding electrode serve any real purpose when connected to the generator...no it would not. My point is that the correlation committee missed the conflict when the definition of grounded was changed and 250.34 was not changed.