portable generator
- Thread starter domnic
- Start date
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- Location
- New Jersey
- Occupation
- Journeyman Electrician
Not much. If you're not switching the neutral with a transfer switch the generator is not a separately derived system and will use the grounding electrode system of the building.
- Location
- Illinois
- Occupation
- retired electrician
While it does no good, it is still my opinion that you must do it if the generator is supplying premises wiring. Few agree with my position on this issue, but in my opinion the change in the definition of grounded for the 2008 code results in a requirement to provide a grounding electrode for any generator that supplies premises wiring.
Here's the way I look at it:
Usually the neutral of a portable home generator I bonded to the frame then the 2 lines, neutral and grounding conductor (EGC) are brought to the plugs.
The EGC provides a circuit back to the generator should a line fault to anything that is grounded with the EGC which provides a means to trip an OCPD.
Driving a ground rod doesn't bring anything to the party for ground fault protection. If you were to do so and drove another ground rod in another location and connected a line conductor to it I doubt very much if enough current would flow back to the source to trip the OCPD. Think of the ground rod as being used for lightening protection which certainly shouldn?t be an issue with portable home type generators.
One thing that should never be over looked is one attempts to use the generator to power a home through its distribution system. If not don't correctly the neutral could be grounded at the service entrance as well as back at the generator which is a code violation.
Usually the neutral of a portable home generator I bonded to the frame then the 2 lines, neutral and grounding conductor (EGC) are brought to the plugs.
The EGC provides a circuit back to the generator should a line fault to anything that is grounded with the EGC which provides a means to trip an OCPD.
Driving a ground rod doesn't bring anything to the party for ground fault protection. If you were to do so and drove another ground rod in another location and connected a line conductor to it I doubt very much if enough current would flow back to the source to trip the OCPD. Think of the ground rod as being used for lightening protection which certainly shouldn?t be an issue with portable home type generators.
One thing that should never be over looked is one attempts to use the generator to power a home through its distribution system. If not don't correctly the neutral could be grounded at the service entrance as well as back at the generator which is a code violation.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I would think that, whether the neutral and generator frame are bonded or not, the connection cord EGC ties the frame to the existing building GEC system. A new rod would have to be bonded to an existing one anyway, right?
SG-1
Senior Member
- Location
- Ware Shoals, South Carolina
If you are just using cord connected power tools then a ground rod makes the situation more dangerous, by providing a high impedance path for ground fault current where none may have existed before. If the generator is sitting on a truck or is insulated from ground by some means, then no ground fault path exists for you to complete.
Some more thoughts:
The earth can not provide a reliable path for ground fault current.
Considering the resistance of a "made electrode" is to be 25 ohms or less the voltage drop through the ground path would be so great as to limit the fault current an not very likely to trip a breaker instantaneously.
Also, the neutral can only be grounded at on point. Should the neutral be grounded at another point, that is not only at the service entrance but also at the generator that would permit neutral currents to be conducted on the grounding conductor, "objectionable current."
Please remember that the neutral is with almost all certainty on the common residential generator is bonded to the frame of that generator. Should that generator be used to provide power directly to a home it must be understood that the neutral will be bonded both to the ground at the service entrance and as well as bonded to the grounding conductor at the generator. Doing so will turn neutral currents loose on the grounding conductor and anything that the grounding conductor is supposed to be grounding.
So please don?t forget home a residential generator is intended to be use and how the can be applied incorrectly.
Your point of view would be appreciated on this subject also.
The earth can not provide a reliable path for ground fault current.
Considering the resistance of a "made electrode" is to be 25 ohms or less the voltage drop through the ground path would be so great as to limit the fault current an not very likely to trip a breaker instantaneously.
Also, the neutral can only be grounded at on point. Should the neutral be grounded at another point, that is not only at the service entrance but also at the generator that would permit neutral currents to be conducted on the grounding conductor, "objectionable current."
Please remember that the neutral is with almost all certainty on the common residential generator is bonded to the frame of that generator. Should that generator be used to provide power directly to a home it must be understood that the neutral will be bonded both to the ground at the service entrance and as well as bonded to the grounding conductor at the generator. Doing so will turn neutral currents loose on the grounding conductor and anything that the grounding conductor is supposed to be grounding.
So please don?t forget home a residential generator is intended to be use and how the can be applied incorrectly.
Your point of view would be appreciated on this subject also.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Is this true even of a portable generator as mentioned in the OP?
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
100222-2220 EST
If you have a portable Honda generator like mine, then it includes a GFCI.
If the generators frame is not isolated from ground, then if there is leakage current the GFCI trips. There is a jumper that has to be removed if you connect this to a system that is grounded to earth.
So yes, if this is used to supply portable tools the generator frame should be grounded and should provide protection to workers with portable power tools. A ground rod to the generator would make a slightly better ground connection. This has nothing to do with ground fault currents tripping the line current breaker.
I am not sure of the internal circuitry in the Honda. But logic would seem to imply that with the jumper removed and an earth ground connection from the frame existed, then a leakage current from the generator or circuitry preceeding the GFCI to the frame and to earth would cause the GFCI to trip.
.
If you have a portable Honda generator like mine, then it includes a GFCI.
If the generators frame is not isolated from ground, then if there is leakage current the GFCI trips. There is a jumper that has to be removed if you connect this to a system that is grounded to earth.
So yes, if this is used to supply portable tools the generator frame should be grounded and should provide protection to workers with portable power tools. A ground rod to the generator would make a slightly better ground connection. This has nothing to do with ground fault currents tripping the line current breaker.
I am not sure of the internal circuitry in the Honda. But logic would seem to imply that with the jumper removed and an earth ground connection from the frame existed, then a leakage current from the generator or circuitry preceeding the GFCI to the frame and to earth would cause the GFCI to trip.
.
One-eyed Jack
Senior Member
- Location
- Scotland Neck, NC
How is this any different from being grounded at the service disconnect and at the POCO transfomer? The grounded conductor is tied to a GES at the service disco and to a separate ground rod at the POCO trans. Sub the gen for the POCO. Same thing.
But the POCO doesn't have to play be the NECs rules.
Come to think of it have you ever heard of stray currents?
I think the following paper will illustrate what I'm talking about which is excellent:
Dangers of Stray Voltage and Stray Current
http://www.mikeholt.com/documents/strayvoltage/word/DangersofStrayVoltageandCurrent.doc
Come to think of it have you ever heard of stray currents?
I think the following paper will illustrate what I'm talking about which is excellent:
Dangers of Stray Voltage and Stray Current
http://www.mikeholt.com/documents/strayvoltage/word/DangersofStrayVoltageandCurrent.doc
- Location
- Illinois
- Occupation
- retired electrician
A few years ago, I would have agreed with this statement. Now there a lot of the common portable generators have the neutral floated. It is not connected to anything other than the neutral side of the receptacles on the generator. Even within the same brand, some models have the neutral bonded to the frame and others have it floated.
It is my opinion that a generator with a floated neutral cannot be used to supply premises wiring.
One-eyed Jack
Senior Member
- Location
- Scotland Neck, NC
This is true. This does not change the fact that the two scenarios; Poco/gen are the same regards ground rods in two remote locations. I won't say that the stray voltage does not exist,just that the powers that be have done nothing to eliminate it. Do we go to the Poco trans pole and disconnect the butt grd. If so how many poles do we have to disconnect before this problem no longer exist?
Don, the answer may be as plain as the nose on my face and just alluding me, but why ? Once it's wired to the premises wiring it has grounding electrodes, reference point, etc.
- Location
- Illinois
- Occupation
- retired electrician
Gus,
You can read the Article 100 definition of premises wiring as including extension cords. Generators are often used when they are not connected to building wiring systems.
You can read the Article 100 definition of premises wiring as including extension cords. Generators are often used when they are not connected to building wiring systems.
Don,
Interesting. If you said was true, that the neutral may not be bonded to the frame of the generator then what about the EGC? Would it be possible for the EGC and the neutral conductor to be bonded to each other but not bonded to the enclosure which would be add I would think?
If the EGC is not bonded to the neutral the EGC is basically useless.
Interesting. If you said was true, that the neutral may not be bonded to the frame of the generator then what about the EGC? Would it be possible for the EGC and the neutral conductor to be bonded to each other but not bonded to the enclosure which would be add I would think?
If the EGC is not bonded to the neutral the EGC is basically useless.
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