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Thread: grounding 2000W inverter generator

  1. #1
    DIY Member JAR8832's Avatar
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    Default grounding 2000W inverter generator

    I recently purchased a Honda inverter generator to power one television/DVR and two computers/internet service during a power outage. The three items (all connected to their own UPSes) are located in different areas of the house. To make connecting them to the generator convenient, I ran 12/2 NM and hardwired outlets to each location, connected to an inlet in the garage. These three outlets are not connected to the house's electrical service in any way. When the power goes out, I must unplug the UPS from the wall outlet and into the generator powered outlet.

    The one thing I am unsure of is if I need to provide any additional grounding for this setup, or if the grounding provided by the generator itself is sufficient? If it makes a difference, the television is connected to a roof mounted antenna which has its own ground rod, and the internet is provided through the cable company's connection, which is grounded to the house's copper plumbing.
    Last edited by JAR8832; 07-14-2011 at 07:24 PM.

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    If you were going to use the generator for a tool such as a saw or drill would you drive a ground rod every time and place you used the generator?

    If the generator has receptacles on the generator and the neutral is bonded to the frame then the generator is a separately derived system and would not bond to the house grounding electrode at all.

    250.34 Portable and Vehicle-Mounted Generators.
    (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 receptacles are connected to the generator frame.

  3. #3
    Licensed Electrical Contractor Speedy Petey's Avatar
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    Quote Originally Posted by DonL View Post
    Many Generators have a floating neutral. I would Ground it even if it is not required by code.

    If the generator is not grounded then it will find a path thru your equipment that is, And that would not be a good thing.


    DonL
    MOST portable generators ARE bonded.

    Let me ask you something. What do you think a ground rod will do?
    Do you think it would avoid this "path" you speak of?

  4. #4
    Licensed Electrical Contractor Speedy Petey's Avatar
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    A ground rod stuck in the dirt will do NOTHING in the case of a fault except bring up worms. The earth is not a reliable, acceptable or valid path BACK TO THE SOURCE.
    Contrary to what most folks think, voltage is NOT seeking ground. It is seeking it's source. The earth plays NO role in this.

    A bonded neutral means just that, it is bonded to the frame or case of the generator, which means the neutral and ground are bonded, just like in a main service panel. THIS is where your safety, or equipment ground, comes from.

    JW quoted the code section regarding this. Please read it carefully.

  5. #5
    Electrical Contractor/Instructor jwelectric's Avatar
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    250.4 is the criteria for connecting a system to earth or grounding if you please.
    In 250.4(A)(1) we are given the reasons for doing this connection.
    (A) Grounded Systems.
    (1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

    Bonding or the connection to the neutral at the service is what most think that grounding is supposed to accomplish
    This requirement is found in 20.104(A)(3)

    (3) Bonding of Electrical Equipment. Normally non– current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the electrical supply source in a manner that establishes an effective ground fault current path.

    For PORTABLE generators see my first post in this thread.

  6. #6
    Plumber jimbo's Avatar
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    Reallly good point by DonL: You should never run a generator in the garage. People die every year from things like that.

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    Engineer Furd's Avatar
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    Electrons still flow the same way today. The path of least resistance is where they go.
    Sorry, Don but you are WRONG! Electricity will follow ALL PATHS back to the source.The amperage and average voltage on these multiple paths will be dependent upon the resistance of each individual path. The source of electricity is NOT the ground (earth) so there is no reason why electricity would seek ground.

    The grounding electrode (ground rod) at an electrical service is for a VERY specific purpose and NOT for the clearing of fault currents OR to allow some strange flow of electricity to travel into the ground.

    Bonding of the neutral and EQUIPMENT GROUNDING conductor at the SOURCE (service panel or separately derived source, e.g. generator or inverter) is for the purpose of providing a low impedance return path that will cause a high enough current flow under fault conditions to cause the overcurrent device (fuse or circuit breaker) to open.

  8. #8
    Licensed Electrical Contractor Speedy Petey's Avatar
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    Quote Originally Posted by DonL View Post
    So You are saying that every house in the USA, Has a REQUIRED Ground Rod that will do NOTHING ?
    We are talking about a PORTABLE generator, not a system wired to the local utility. Two very different animals.



    Quote Originally Posted by DonL View Post
    I guess you took a different Electrical test than I did when I got my License.
    I bet it wasn't that different.



    Quote Originally Posted by DonL View Post
    Bonding is a completely different story. Bond all day long, But if you do not bond to a good ground, what good are you doing ??? Sometimes a fault is unpredictable. In a perfect world your path would return to the source. That may not always be the case, In a Fault condition.
    The voltage path is ALWAYS back to it's source. Sometimes it finds crazy ways to get there, but that is a FACT.
    You tell me what good a "good ground" does in the case of a fault. Please, tell me what purpose the earth does in clearing a fault. I am all ears, and not pissing.

    Since you are obviously also a licensed electrician, please tell me what 250.34 means to you.


    Quote Originally Posted by DonL View Post
    Sorry that you were misinformed... I want to be corrected if I am wrong.
    I was not misinformed, and I am trying


    Please tell us specifically what you think sticking a rod in the ground will do. I am very curious as to what you think the significance of it is.

  9. #9
    Licensed Electrical Contractor Speedy Petey's Avatar
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    Quote Originally Posted by DonL View Post
    No comment, You must know it all.

    I must have spoken out of line, in your eyes.

    A person should do what the manufacture recommends.

    I guess you are smarter than the manufacture. I am not, nor do I pretend that I am.


    Be careful playing with electricity...
    Oh well, we went from a professional adult discussion to insults and sarcasm. I guess that's what happens when you have no other constructive replies.

    I expected more from a fellow ham. You must be one of those holier-than-thou Extras, huh?

  10. #10
    Engineer Furd's Avatar
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    Let it go, Pete. Sometimes it is the hardest thing in the world for a person to admit they were wrong, this is often the case when they find out their thinking has been wrong for several years. All we can do is try to properly inform others if Don continues to profess inaccurate information via this forum.

    Don, it is no shame to be wrong. What IS a shame is when you cannot admit to being wrong.

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    Engineer Furd's Avatar
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    JAR8832, I do not know how the Honda generator is wired but my Yamaha does not have the neutral and equipment ground conductors bonded together in the generator.

    An equipment ground, especially when on the input of an UPS is to provide for a low impedance return to the SOURCE of electricity to facilitate the tripping of any overcurrent device (fuse or circuit breaker) in the case of a fault from the "hot" lead to the case of the equipment. If your Honda generator has the neutral and equipment ground bonded then nothing more needs to be done. If your gennie doe NOT have such a bond then one needs to be added. An external grounding electrode (ground rod) does nothing in this case.

  12. #12
    DIY Member JAR8832's Avatar
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    Thanks for all of the replies. The manual states: "The generator ground terminal is connected to the frame of the generator, the metal non-current-carrying parts of the generator, and the ground terminals of each receptacle. Before using the ground terminal consult a qualified electrician."

    Later, it reads: "Honda portable generators have a system ground that connects the generator frame components to the ground terminals in the AC output recepticles. The system ground is not connected to the AC neutral wire."

    How would I go about bonding the ground and the neutral in the generator? Thanks.

  13. #13
    Licensed Electrical Contractor Speedy Petey's Avatar
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    For giggles I just looked at the manual for this genset. I read the same thing. NO WHERE does it state that a grounding electrode must be used for portable operation.

    Since it says nothing about a grounding electrode, and it states to consult a qualified electrician, I think 250.34 says it all. If you are only using portable cords plugged right into the genny you need to do nothing else. Sticking a rod in the dirt will not add any safety measure at all.


    250.34 Portable and Vehicle-Mounted Generators.

    (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 receptacles are connected to the generator frame.

  14. #14
    Engineer Furd's Avatar
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    How would I go about bonding the ground and the neutral in the generator? Thanks.
    At the generator inlet connection that you have installed in the garage you would connect the neutral and equipment ground terminals together. While this is normally NOT in accordance with either good practice or the electrical codes the FACT that your generator is a "separately derived source" makes it acceptable.

    Please note that this "grounding connection" ONLY protects against a "line-to-ground fault" and serves no other purpose. If you keep the interconnect between the generator and the inlet connector physically protected (don't drive over it with the car) and the ensuing wiring from the inlet connector to the UPS is likewise protected from damage the only point of failure will be a line-to-case fault on the UPS or perhaps the end equipment.

    Adding the external ground rod connected to the generator frame MIGHT serve as some limited protection from lightning or other static charge but it will offer NO protection from line-to-"ground" faults.

    One more thing. ALL your "ground" rods, the one(s) on the electrical service, the one on the television (or other) antenna, the one on the telephone (land line) network interface and the one on the cable television system need to be BONDED together into one grounding electrode system. Failure to do so (with wire of sufficient size) WILL create an unbalanced voltage among the various parts under some atmospheric conditions such as lightning.
    Last edited by Furd; 07-16-2011 at 07:52 PM.

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    Engineer Furd's Avatar
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    Quote Originally Posted by DonL View Post
    I know when I am wrong.

    How about U ???
    What doe "U" mean? Do you have a problem writing with REAL words?

    Show me where I am wrong and I will admit to the mistake. If you can't show me where I am wrong then you have no argument.

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