Portable Generators and Ground Rods

Status
Not open for further replies.
Re: Portable Generators and Ground Rods

charlie_b,

"It was their attempting to leave the vehicle afterwards, and receiving a shock when their foot touched the ground."

Agreed. This is why there needs to be a connection to earth, to help disipate the charge.
 
Re: Portable Generators and Ground Rods

Originally posted by bennie:
A portable generator is one that can be carried. A trailer mounted generator is one that can be transported.
Portable generators are small, and don't need any method for relaxing possible electrostatic charges.
Click to expand...
Where did you find your definition of portable?

How do you explain the lack of ground rod required for Vehicle-Mounted Generators?

Lets say the carnivals generator is mounted in a 10 wheel truck instead of a trailer, now without question it is a Vehicle-Mounted Generator.

I have a purpose here that has to do with generators on construction sites, I will explain later.

Bob

Really Bennie you have been missed, glad you are back.
 
Re: Portable Generators and Ground Rods

II. Power Sources
525.10 Generators. Generators shall comply with the requirements
of Article 445 and, as applicable, 250.30 or
250.34. [ROP 15?91]
 
Re: Portable Generators and Ground Rods

Bob: A vehicle generator will require a ground rod, if the premises served is not grounded, and requires grounding. 250.30.

Portable...from the latin word portare, meaning to carry.

Transportable...Means over portable, or by vehicle.
 
Re: Portable Generators and Ground Rods

2002 NEC Handbook.
Portable describes equipment that is easily carried by personnel from one location to another. Mobile describes equipment, such as vehicle-mounted generators, that is capable of being moved, on wheels or rollers.
 
Re: Portable Generators and Ground Rods

Ok I asked about the word portable because while I worked on carnival and amusement park equipment it came in two flavors, stationary or portable.

I have always thought the NEC intended this to mean the garden variety 5KW generator, but what is the cut off point, shouldn't a size be given if that's what they meant?

Or is the rule if you can carry it you don't need to ground it? ;)

[ August 25, 2003, 05:55 PM: Message edited by: iwire ]
 
Re: Portable Generators and Ground Rods

When the GC asks me

"Do those generators need to have ground rods"?

What do I tell him? :)

[ August 25, 2003, 05:57 PM: Message edited by: iwire ]
 
Re: Portable Generators and Ground Rods

I have a portable radio. I can carry it anywhere. I have a console radio, I leave it where it is.

Yea, if you can pick it up and run with it, it is portable.

Generators do not have to be grounded if the first switch, which is the service, is grounded. If the service is not grounded and should be grounded, then the bonding and grounding can be at the source for the separately derived system.
 
Re: Portable Generators and Ground Rods

charlie,
But people have been injured, and even killed, by a lightning strike on the car in which they were riding. But it was not the lightning event itself that caused the injury. It was their attempting to leave the vehicle afterwards, and receiving a shock when their foot touched the ground.
Click to expand...
Not that I don't believe you, but can you cite any documentation for that statement?
don
 
Re: Portable Generators and Ground Rods

The event described by Charlie, has happened. The automobile gets a high negative charge, the earth is positive in relation. The person shorts across the dielectric(air). This can happen long after the lightning strike.
 
Re: Portable Generators and Ground Rods

Two comments:

I thought todays' tires has a small amount of carbon in the rubber to drain-off static electricity.

My son-in-law was on a job-site where a 'portable' generator was being used. Suddenly the power tool stopped, looking toward the generator, two guys were running down the street with the generator and the generator was still running. Guess that is portable.
 
Re: Portable Generators and Ground Rods

Glenn: You are correct, tires do have a conductive material added for electrostatic balance. The impedance is high, so there is a time element before equilibrium is attained.

This is the same as a high impedance ground electrode connection to earth.
 
Re: Portable Generators and Ground Rods

My statement and question of Aug 24, 9:49PM was 'loaded' and still some of it has not been addressed.

My only carnival inspection was for a small carnival which I believe I should have spent many hours opening up all the electrical to see what connections were inside.

just some of the violations;
525.23(A). not one GFCI on site.

525.3(A).

240.4(D), 50A 45A 30A 20A single and/or double pole CB' protecting 14 AWG to the 50A 30A 20A 15A receptacle(s).

50A DP CB to 14AWG to 50A single receptacle which had 3/c plug & cord to 1500 Watt Quartz flood lights, some with-out protective lens 527.4(F). The plug & cord at the lamp location was a duplex recp with-out a box, just taped-up recp, and a 20A plug ,I guess as a disconnet at the flood light(s).

No equipment grounding conductor ( with the circuit conductors ) to the two 100A MLO panelboards from the truck mounted 400A CB of the generator.
The common conductor to the remote panelboard(S) ID'd green.

210.21(B)(?) for some of the above.

406.5 missing recp face plates.

406.8(A), panelboard just laided up against a dual wheel truck tires. ( rain predicted for the evening).

110.14 and .14(A), Line terminal of MLO panelboard had been overheated and melted the plastic backing stand-off within the panelboard.

Did not look inside the cover at the Generator 400A CB for load side 110.14.

Did not look inside any cord connected load end(s).

Again, that is just some and the guy says "you're the first one to not give an OK ".
 
Re: Portable Generators and Ground Rods

The circus is a separately derived system, supplied by a generator as the power source. The generator does not require an equipment ground conductor. The neutral should be bonded to the stator frame at the generator, and the bonding of the neutral ground at the first switch (main service)

There is no point in an equipment ground conductor, when it will be smaller than the neutral.

Grounding of the system should be as described in 250.30.
 
Re: Portable Generators and Ground Rods

Hi bennie Glad your back.
Yes a generator does not require a equipment ground to operate, but the NEC does in 525.31
What is confusing is there is no requirment for a GE and since most of these generators are mounted on a vehical of some sorts the NEC only has a requirment for it to be bonded to the frame. Now I understand that the NEC is bare min. and lighting protection needs to be left to the pro's but one would think that with most carniviles since they would be in place more than one day that it would address this.
Also I have to agree with Don on that lightning will not travel very far down a ground wire to be effective, to me why grounding a gen-set that would be accross the field from a ride when grounding the ride it self would provide for better protection as it is the tallest mettal structure around and pose's the greatest chance of being struck, more than the generator.
Now as far as portable generator's that you are only going to use for a few hours at a time and most likely not when it's lightning I cant see a reasone to require them to have to install a ground rod.
 
Re: Portable Generators and Ground Rods

Hurk: I don't read 525.31 as requiring an equipment ground conductor be connected to the generator. It can be connected, but only needs to be connected to the system neutral at the first switch.

A generator source to a separately derived system is no difference than a utility service, from an operational and code standpoint.

The fact of the generator having a switch, to isolate the unit, does not change the definition of a service, from a practical approach.
 
Re: Portable Generators and Ground Rods

Bennie twice In this thread you called the feeders from a generator a service, in looking at article 100 definitions I would dispute that the NEC considers it that way.

Service. The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.
Click to expand...
Now I understand that the handbook is opinions, but here is the commentary under the definition of service.

The definition of service was modified for the 1999 Code to state that electric energy to a service can be supplied only by the serving utility. If electric energy is supplied by other than the serving utility, the supplied conductors and equipment are considered feeders, not a service.
Click to expand...
This is recent enough of a change that I am sure someone could verify that the handbook commentary is accurate.

I respect your opinion highly and if you tell me a large generator can develop a static charge I believe you.

The thing is I am looking for a code article that would settle this as far as the 3 examples I will repost here.

1)The steel workers drop a shipping container on the job, inside is a very nicely mounted diesel generator set, totally self contained feeding a 400 amp 120/208 panel that sends power to a bank of ten 50 amp outlets that they add extension cords to feed remote welding units.

2)The concrete cutters arrive with a self contained generator set mounted on a skid, they transport this on the back of a ramp truck with the rest of their gear. They dump this on the ground and power their equipment with cord and plugs. Again this was a professional set up. Two 200 amp panels and various sized outlets mounted to the skid, proper OCP, GFCIs where required etc.

3)The Demo contractors pull up with a trailer mounted diesel generator set and a "Brock" (essentially a small remote controlled backhoe powered by electricity) They also have proper receptacle, cord and OCP. The Brock takes 60-100 amps 480 volt 3 phase.

Which one of these need a rod and what code article could I tell the GC would mandate it.

Thanks, Bob
 
Re: Portable Generators and Ground Rods

Sorry Bob, I screwed up and used the word "service" as defined by Webster, not the NEC. ;) I forget that the NFPA creates their own definition.

An earth connection, for a generator, is not necessary. A solid connection from the X-0 to any metal that may become energized, is important.

I have seen temporary light cords make contact with rebar, and knock the daylight out of everyone, touching a power tool.
 
Re: Portable Generators and Ground Rods

Bob: We didn't have long enough ground rods. I suggested, to the National Science Foundation, to fly in a few yards of soil.

The Antarctic treaty forbids contamination by introducing foreign material, so that idea died.

When there is terra firma available we call it grounding. When only ice is available we called it(you guessed it) icing.

We drove ice rods and bonded them to form an ice electrode system.
 
Status
Not open for further replies.
Top