Portable generator grounding

[vince99]

A friend of mine has a 3000 watt portable generator, to be used at his house in case of power failure. The manual states the frame should be grounded to a copper rod driven into the ground. He asked me if grounding the frame to the 3rd prong in an outlet would be sufficient for safety purposes. I'm unsure what to tell him. I suspect it would be sufficient for safety purposes, but perhaps be a violation of local codes. What do you think?

Thanks

 

[templdl]

Is the neutral of the generator bonded to the frame?
Are the loads that are being supplied by the generator going to be plugged directly into the generator?

If the answer is yes then it is of my opinion that I see no reason why the manufacturer's dirction shouldn't be followed.

If the generator is to be connected to the home wiring then it's a whole different issue. Special attention must be paid to the application of the transfer scheme, the neutral, where the neutral is allowed to be grounded and the grounding conductor.

 

[vince99]

The loads will be plugged directly into the generator. Generator will not be connected to the house wiring. I assume the neutral is bonded to the frame, don't know for sure.

So his question is, is the generator just as safe with the frame connected to a 3rd prong in his garage as it would be connected to a rod driven into the ground?

I can't really see a reason why it would not be, since the 3rd prong is just as good a ground as the copper rod, and either one would trip the generator's breaker in case of a short.

 

[vince99]

In thinking about this question, it has occurred to me that, unless I am missing something here, it may actually be safer to not ground the frame to a copper rod or the 3rd prong. It someone is using a tool or other device powered by the generator and the tool has an internal short that makes the case of the device "hot", they could get a shock if the generator is connected to earth ground, and they are in contact with that ground. If the generator frame is "floating", not connected to ground, they can only be shocked in this situation if they touch the frame (or neutral).

What do you think?

 

[chipster]

Generator Ground Rod

Generator Ground Rod

A grounding electrode is not required for a portable when the receptacles on the generator are bonded to the generator frame. It is not required to be grounded if the gen. only supplies equipment or recepts. mounted on the gen. See 250.34C

 

[vince99]

OK it is pretty clear there.

Thanks

 

[wieand]

Osha

Osha

OSHA 29 CFR 1926.404(f)(3) also indicates the generator does not need to be grounded by a GEC to earth. However the argument of the ground-reference of the neutral to earth as an increased hazard does not hold water. As in then why is a grounded neutral not causing additional hazard in my house service.

Also if there is no ground then there is no return path from the actual earth that you're standing on the operate the GFCIR. The GFCI test is, per OSHA clarification, not to be tested at the end of the power cord to earth but limited to pushing the test button provided by the GFCI manufacturer. Works great at the generator.

I will continue to ground to earth with a driven rod per the generator manufacturer's instructions. And i test the GFCI at my end of the power cord.

If you don't think the 5000 watt generator is a hazard then why not just grab the engine shaft to stop it. Not so tough now are you. I can only take mA for mSec my self.

 

[don_resqcapt19]

However the argument of the ground-reference of the neutral to earth as an increased hazard does not hold water. As in then why is a grounded neutral not causing additional hazard in my house service.

On a small system like a portable generator, if there is no connection to the earth then the only way to get a shock is to touch both of the circuit conductors. This doesn't work in bigger systems as there may be enough capacitance coupling to provide a shock hazard.

Also if there is no ground then there is no return path from the actual earth that you're standing on the operate the GFCIR.

And there is no path for current to flow that would cause a shock. If for some reason there is a path that will flow more than ~5mA then the GFCI device on the generator will open.

And i test the GFCI at my end of the power cord.

And assuming that there is a neutral to frame bond at the generator and an EGC in the cord, then the GFCI device will function with or without an earth connection.
Don

 

[vince99]

OSHA 29 CFR 1926.404(f)(3) the argument of the ground-reference of the neutral to earth as an increased hazard does not hold water.

If I am operating a generator without a ground rod and come into contact with the hot conductor, I don't get a shock, there is no return path. If there is a ground rod, I can get a shock, the return path being through the earth. That sounds like an increased hazard to me.

OSHA 29 CFR 1926.404(f)(3)
If you don't think the 5000 watt generator is a hazard then why not just grab the engine shaft to stop it. Not so tough now are you. I can only take mA for mSec my self.

Not sure what you're trying to say here.

 

[templdl]

My concern with this discussion is that we're dealing with all to many variables and assumptions.
When it comes to electric shock one can never, never rely on GFCIs,a double insulated tools, etc, etc, for your safety. Electric tools should always be used as if there was a potential for electric shock at any time us have one in your hands never to assume that GFCIs, ground or no ground, and so on will protect you from your own carelessness.
To ground or not to ground? Safer or not so safe? Theory is one thing, reality is another.

Back to the basics:

Current in mA Effect to humans
1 to 5 tingling sensation
5 to 8 pain
8 to 20 involuntary muscle contraction
> 20 paralysis, can't breathe, pain
80 to 1000 ventricular and heart fibrillation
>1000 heart stoppage, burns, defibrillation

1000ma= 1a or 1ma= .001a sort of gets ones attention you would like to think.
Just think a well placed .008-.020 amperes of current could be enough to knock you off a ladder.
What will determine the current that will flow through you if you place yourself in a current path?
If a generator is grounded or not can you be assured that the minute current that is required to cause death will not be present?

 

[LarryFine]

OSHA 29 CFR 1926.404(f)(3) also indicates the generator does not need to be grounded by a GEC to earth. However the argument of the ground-reference of the neutral to earth as an increased hazard does not hold water. As in then why is a grounded neutral not causing additional hazard in my house service.

Actually, the grounded neutral in the service does increase shock hazard exactly in the same way that it does in a grounded-neutral generator supply.

If you don't think the 5000 watt generator is a hazard then why not just grab the engine shaft to stop it. Not so tough now are you. I can only take mA for mSec my self.

What does damaging your hands have to do with elecric shock? Why are you being so antagonistic? You hardly have the post count to justify such an attitude.

 

[ItsHot]

engine shaft?

engine shaft?

I have never seen a portable generator that you could access the engine shaft to grab it!

 

[tomP]

OSHA 29 CFR 1926.404(f)(3) also indicates the generator does not need to be grounded by a GEC to earth. However the argument of the ground-reference of the neutral to earth as an increased hazard does not hold water. As in then why is a grounded neutral not causing additional hazard in my house service.

Also if there is no ground then there is no return path from the actual earth that you're standing on the operate the GFCIR. The GFCI test is, per OSHA clarification, not to be tested at the end of the power cord to earth but limited to pushing the test button provided by the GFCI manufacturer. Works great at the generator.

I will continue to ground to earth with a driven rod per the generator manufacturer's instructions. And i test the GFCI at my end of the power cord.

If you don't think the 5000 watt generator is a hazard then why not just grab the engine shaft to stop it. Not so tough now are you. I can only take mA for mSec my self.

Actually, the grounded neutral in the service does increase shock hazard exactly in the same way that it does in a grounded-neutral generator supply.

What does damaging your hands have to do with elecric shock? Why are you being so antagonistic? You hardly have the post count to justify such an attitude.

How many posts must you have until you can be antagonistic? And how do you get those posts? Maybe just agree with what all the "high post people" say? ...........

Oh, by the way what does "just grab the engine shaft" that have to do with electric?............

 

[76nemo]

If I am operating a generator without a ground rod and come into contact with the hot conductor, I don't get a shock, there is no return path. If there is a ground rod, I can get a shock, the return path being through the earth. That sounds like an increased hazard to me.


Not sure what you're trying to say here.

Not sure what you are saying either. Are you saying that there is NO possibility of your body being grounded or serve as a path to ground?

 

[LarryFine]

How many posts must you have until you can be antagonistic?

I think it's 1000, but I'm not sure. Check with the Mod Squad.

And how do you get those posts? Maybe just agree with what all the "high post people" say? ...........

Hardly. I rarely agree with anyone. Have you read my signature?

 

[LarryFine]

Not sure what you are saying either. Are you saying that there is NO possibility of your body being grounded or serve as a path to ground?

No, he's saying that a current requires a circuit. Not grounding a circuit conductor of a source provides a break in the loop.

 

[wieand]

For the best and probably longest review of GFCI see
Mike Holt's Forum (http://forums.mikeholt.com/index.php)
- Grounding versus Bonding (http://forums.mikeholt.com/forumdisplay.php?f=63)
- - GFI receptacles (http://forums.mikeholt.com/showthread.php?t=88679)

However the entire discussion assumed an electrical connection between the grounded circuit conductor and the earth (piping, siding, etc.) at the service.

If we do not provide a ground for a portable generator then we have not established the earth connection.

And yes the test button will draw power from the Hot through the toroid and back to the neutral (or without a ground to ground it, is it the 'other Hot') without going through the toroid again and the sensor will initiate the GFCI to trip. But what does it do for me and the cracked case on a drill that I am using.

Also what is small when deciding to ground. As in a small generator. Contractors at job sights have installed 100 kva trailer mounted generators without a ground.

 

[wieand]

OSHA 1926.404(b)(1)(ii)

OSHA 1926.404(b)(1)(ii)

Since 1971, there has been an exception to the GFCI requirement by NEC for outlets on portable generators. In the 1999 NEC, it was Exception No. 1 to 305-6(a). In the OSHA regulation, it is found in 1926.404(b)(1)(ii). It reads:

"Receptacles on a two-wire, single-phase portable or vehicle-mounted generator rated not more than 5 kW, where the circuit conductors of the generator are insulated from the generator frame and all other grounded surfaces, need not be protected with ground-fault circuit interrupters."

This exception has been removed from the 2002 edition of the NEC. The reasoning is that Article 250 requires that 120-volt generators have one wire of the generator winding connected to the generator frame (grounded). The generator described in 1926.404(b)(1)(ii) is commonly referred to as an "isolated winding" generator. The NEC, and specifically Article 250, does not permit such a generator.

at www.oshazone.com.

by Thomas and Michael Kovac ()

My point is if you do not connect a GEC from the generator XO (and frame) to a ground rod you have created an isolated (floating) neutral. However, no one is limiting the created floating neutral generator size to not more than 5000 watt. And I have seen some very large generators without a 'ground'.

 

[weressl]

A friend of mine has a 3000 watt portable generator, to be used at his house in case of power failure. The manual states the frame should be grounded to a copper rod driven into the ground. He asked me if grounding the frame to the 3rd prong in an outlet would be sufficient for safety purposes. I'm unsure what to tell him. I suspect it would be sufficient for safety purposes, but perhaps be a violation of local codes. What do you think?

Thanks

IMO opinion - and verbally confirmed by UL and NFPA engineers - the generator should be installed as a grounded system. All the exceptions exist because of industry pressure as both engineers I've spoken to acknowledged it. Of course they would not confirm it in writing as it was their personal belief contrary to excemptions in the Code.

If you want to be safe, ground it. The closer do you ground to the 'system' the less potential is there to expose wiring to failure where the fault current would bypass your protective device.

 

[roger]

The following link is a very good thread on this issue, be sure to read the whole thread.

IMO, it is safer not to earth a portable generator used in this manner.


I'll fix this shortly.

Copy and paste the following link into your address window

http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=7;t=000351;p=1

Roger