Grounding Requirements for Portable Construciton Electri

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johndickman

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Portable Generators with GFCI recpticals that are not earth grounded may not provided electrical shock protection to workers when an assured grounding program is not in place. IE if the ground wire on an extension cord (3 wire)is broken (because of lack of assured grounding) and an electrical tool is being used and the tool or chord is defective and both hot and neutral sources are exposed and come in contact with the worker. (The GFIC will not act as their is no leakage current)

What does the NEC require for these generators
 
Re: Grounding Requirements for Portable Construciton Electri

Ryan, you are correct.

A GFCI does not require a groudging connection in any way to operate properly.

If a worker is dumb enough to use the equipment described above, regardless of GFCI, he will not be long for this world!
 
Re: Grounding Requirements for Portable Construciton Electri

This construction power is a separately derived system. Ground the generator neutral to building steel or rebar.
 
Re: Grounding Requirements for Portable Construciton Electri

A portable generator by your description is not required to be earthed. Refer to 250.34
 
Re: Grounding Requirements for Portable Construciton Electri

Originally posted by websparky:
A GFCI does not require a groudging connection in any way to operate properly.
Click to expand...
Not exactly, the system has to be grounded for a GFCI to operate.
 
Re: Grounding Requirements for Portable Construciton Electri

The reason for an external logic circuit breaker,(GFP) on a generator, is because the generator usually will not produce enough fault current to trip an internal logic breaker.

The generator must be earth or building steel grounded to facilitate operation of the GFP.

This is the reason for 250.30.
 
Re: Grounding Requirements for Portable Construciton Electri

By johndickman: Portable Generators with GFCI receptacles that are not earth grounded may not provided electrical shock protection to workers
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First as was said by others a GFCI does not have to have a earth ground to work as it does compare the current between the hot and neutral to know when there is current flowing on another path to get back to the generator.

Second if there is no earth path back to generator then there is no shock hazard and if this path were to develop IE.the generator is now in a puddle after a rain, then the GFCI will trip at the 5ma that it is design to.

There is no requirement to ground or bond a portable job site generator anywhere in the NEC. as isolation is the best protection against electrical shocks.

Now for number three.
and an electrical tool is being used and the tool or chord is defective and both hot and neutral sources are exposed and come in contact with the worker
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I have to say that even if the generator was grounded and bonded the GFCI would not prevent a shock if anyone was to come into contact between a hot and neutral as the GFCI does not provide any protection or can it as it must pass the full current of the circuit on these wires or any load placed on these wires would only trip the GFCI, if the GFCI did try to protect these wires.

[ March 26, 2004, 01:03 AM: Message edited by: hurk27 ]
 
Re: Grounding Requirements for Portable Construciton Electri

The problem on a construction site is often the active line conductor makes contact with the building steel, or rebar grid. Temporary lighting is usually the culprit.

When a worker picks up a grounded drill motor, and touches the steel, or rebar, he is instantly zapped.

By connecting the generator neutral to the steel, or rebar, the GFCI will see the LG fault and trip.

Without a GFCI, an LG fault may not clear, if far away from the generator.

This scenario is not playing on a wood frame building.
 
Re: Grounding Requirements for Portable Construciton Electri

Originally posted by johndickman:
Portable Generators with GFCI receptacles that are not earth grounded may not provided electrical shock protection to workers when an assured grounding program is not in place.
Click to expand...
If the Generator is truly not grounded the only shock you can receive is a line to line shock. (hot to hot or hot to neutral)

Originally posted by johndickman:
IE if the ground wire on an extension cord (3 wire)is broken (because of lack of assured grounding) and an electrical tool is being used and the tool or chord is defective and both hot and neutral sources are exposed and come in contact with the worker. (The GFIC will not act as their is no leakage current)
Click to expand...
Correct, grounded or not grounded a GFCI will not protect a worker from a line to neutral shock. This is the same as a GFCI outlet supplied from a permanent source.

Originally posted by johndickman:
What does the NEC require for these generators
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The NEC does not require these generators to be grounded.

Your listed as a General Inspector take a look at 250.34 Portable and Vehicle-Mounted Generators.

[ March 26, 2004, 04:50 AM: Message edited by: iwire ]
 
Re: Grounding Requirements for Portable Construciton Electri

Getting caught between the neutral and hot conductor is the same as being a load and the OCPD will open for an overload condition - which a person will not likely cause.

The GFCI monitors the flow of 'current in'(hot conductor) and the 'current back' (in the case of the generator, the white wire going back). If there is a chance that current will flow outside of this normal path, the GFCI will open if more than 5 miliamps of current finds this alternate path. An equipment grounding conductor/grounded connection is not necessary for the GFCI receptacle to operate.
I think that Ryan, Dave, Wayne and Bob have covered this very well.

Pierre
 
Re: Grounding Requirements for Portable Construciton Electri

Concernig small portable job site generators.. When a cord is plugged into a generator GFCI it cannot have another GFCI in the circuit. I know that I have tried using "strings" (one plugged into another into another etc) of GFCIs trying to get them to trip on their own but it will not happen as long as they are plugged into utility power. However if a GFCI is plugged into the generators GFCI one will immediately trip. The only way around this is to open the end bell on a generator and lift the ground wire from the generator to its frame. I have never come up with an explanation for this phenomena but one or the other GFCI will trip even when the ground screw is lifted when there is the prerequisite leakage. Any one with any thoughts about this?
 
Re: Grounding Requirements for Portable Construciton Electri

Originally posted by j7david:
Concerning small portable job site generators.. When a cord is plugged into a generator GFCI it cannot have another GFCI in the circuit. I know that I have tried using "strings" (one plugged into another into another etc.) of GFCIs trying to get them to trip on their own but it will not happen as long as they are plugged into utility power. However if a GFCI is plugged into the generators GFCI one will immediately trip. The only way around this is to open the end bell on a generator and lift the ground wire from the generator to its frame. I have never come up with an explanation for this phenomena but one or the other GFCI will trip even when the ground screw is lifted when there is the prerequisite leakage. Any one with any thoughts about this?
Click to expand...
Have you had this on several different generators? I have only had it something like it on one Onan set that was used as a permanently installed auxiliary supply. I never did figure out why but I suspected that I had a fault on the neutral of the circuit into which I was plugging the portable GFCI and some how current was flowing through the ground of the supplied equipment.
--
Tom H
 
Re: Grounding Requirements for Portable Construciton Electri

Just trying to re-hash some talk about generators
I've been on tons of jobsites in N.C. and have been required by certain inspectors to use diff-erent bonding and grounded requirements, where there is a distribution pnl.in the job trailor being fed from a generator. What are the requirements??
 
Re: Grounding Requirements for Portable Construciton Electri

You asking about two separate issues here, generator requirements and the feed to a job trailer.

A standalone generator must have the neutral bonded to the frame of the generator, anything down line from that will need the neutral isolated from the grounding conductor.

Your job trailer panel should already have an isolated neutral bar and the equipment grounding conductor should be bonded to the trailer frame, if this is a factory made job trailer this should already be done.

Now the ground rods, if everything is simply cord and plug connected to the generator you are not required to put a ground rod at the generator or the trailer.

If it is hardwired you will need to ground the generator as a service and then the trailer will need a ground rod as a separate structure fed from a common service.

At least that is how I see it and I may be wrong. :eek:

You can not go wrong with the installation of the ground rods even if they will not help at the voltages likely to be imposed on them. :p
 
Re: Grounding Requirements for Portable Construciton Electri

hornetd

Tom Yes I?ve tried it many times. Actually the way I was first made aware of this problem was by the Honda rep telling me about the problem and the solution. I flat out told him he was wrong and set out to prove it. Well turns out he was right and the problem is not limited to Hondas. It still doesn't make any sense to me.
 
Re: Grounding Requirements for Portable Construciton Electri

I have had this happen if you accidentially hook up two gfi to one circuit, or try to hook up a 2 pole gfi to two single circuits. I think it may have to do with the current running through the two systems, causing a slight imbalance. BUt that is just a wasg and have no info on it.
 
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