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Location: Visitation between Wal-Mart & Home Depot
8,309 posts, read 38,774,074 times
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Quote:
Originally Posted by Barking Spider
A jumper from a neutral to the ground screw on an outlet should NEVER be done.
No no!! I'm not saying that I want to do that at all nor would I have a reason to. I just want to understand this stuff and it made me question if the GFI would see a ground fault through the "3rd Prong" as a balanced current in that particular configuration.
I'm going to do an experiment this evening to see what happens. Please alert the authorities if I do not post on the matter tomorrow.
You might be able to ground this to a nearby plumbing pipe without ripping out your walls. Probably not to code, but it works. All the ground is is an alternate route for the neutral if something happens to the neutral. In older houses they grounded the whole system to the pipes. They do nto do that anymore so it must not be allowed. Now they use a big spike that is driven 4 feet into the ground. Maybe they just switched becuase so much of the pipe is now plastic. Or maybe grounding ot the plumbing woudl electrify your faucets in the event of a short. I lived in several houses that were grounded ot the plumbing and never had any problems. But then it only takes once to make you dead. (well actaully maybe more than once, I have been shocked several times with nothing but a little brain damage ).
Location: Visitation between Wal-Mart & Home Depot
8,309 posts, read 38,774,074 times
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Quote:
Originally Posted by Coldjensens
You might be able to ground this to a nearby plumbing pipe without ripping out your walls. Probably not to code, but it works. All the ground is is an alternate route for the neutral if something happens to the neutral. In older houses they grounded the whole system to the pipes. They do nto do that anymore so it must not be allowed. Now they use a big spike that is driven 4 feet into the ground. Maybe they just switched becuase so much of the pipe is now plastic. Or maybe grounding ot the plumbing woudl electrify your faucets in the event of a short. I lived in several houses that were grounded ot the plumbing and never had any problems. But then it only takes once to make you dead. (well actaully maybe more than once, I have been shocked several times with nothing but a little brain damage ).
Have you ever noticed that you're a poor conductor when you stand on a hardwood floor in tennis shoes? I think it would take a long while to get a lethal dose of 120v by just grabbing a live lead by itself. Of course, if you are touching a water pipe at the same time or have the neutral wire in your other hand you may get the full 15A before the breaker trips. That would suck. I've accidentally tripped a GFI with my thumb and forefinger. Even a 5 mA shock is a significant psychological event.
Hang on, tho... My understanding of ground: a grounded appliance, for example, will have its casing connected to "ground" so that in the event of a short that energizes the casing, the breaker trips or the fuse blows immediately rather than waiting around for the user to grab it and get a shock.
Last edited by jimboburnsy; 05-11-2009 at 03:55 PM..
Here's a photo I took at a house a few months ago. There was a loose neutral in the panel, and the voltage traveled down the ground conductor to the water pipe. You can see where it was arcing.
Heh. Good thing that we used PEX in our current house and grounded the electrical system to a spike.
We had an old house that had almost all knob and tube wiring. We just put GFCI outlets in every box. They worked fine on the few occaisions that something shorted out (like when we spilled a cup of water into a fan). It was nice with kids, becuase we could turn off any outlet that we were not using. Better than those kid safety plug thins that you electrocute yourself trying to remove from outlets.
Jimbo. I do nto know the science of it, but I was replacing a light fixture in an old house and the fixture was hooked up as a switched neutral. I was standing on a ladder and I became the neutral. It wa a substantail shock and it burned my fingers a bit and knocked me off hte ladder (or maybe I fell). The breaker never tripped either, I do not know why. That is when I learned about switched neutrals and how dangerous they can be to workers and also learned to use a tester on every wire every time always. I have been amazed at some of the wiring things that I have seen. That same house had one place where they tied knob & tube into romex by twisting wires together and wrapping them with duct tape. THey also had one 12/2 romex line twisted together with 11 Knob and Tube wires. It was pretty much feeding the entire upstairs (where we would often run three hari dryers at the same time). I thnk that it is funny how stupid some people can be. Some mistakes are understandiable, but some are amazing.
In older houses they grounded the whole system to the pipes. They do nto do that anymore so it must not be allowed. Now they use a big spike that is driven 4 feet into the ground. Maybe they just switched becuase so much of the pipe is now plastic.
It is still required to bond the system to the pipes if they are conductive. For them to be the main grounding electrode, there must be at least 10' of conductive pipe within the ground, such as the main tap, but most utilities have changed to PVC, if not all.
A ground rod is a supplemental electrode if the pipes are your primary grounding electrode.
If you do not have conductive water pipes, you can only use one ground rod as the primary electrode if the resistance is less than 25 ohms. If not, you are required to use two ground rods spaced no closer than 6' apart (to clear the 36" step-potential ring). Because getting less than 25ohms is rare, we always install two, and to save the time of having to perform the test in the presence of an inspector (although its never checked by any inspectors I work with). In very loose or sandy soils, we'll install multiple rods.
Ground rods are 5/8" x 8' and must be driven fully underground. If you hit a rock or any material that cannot be driven through, you have to bury it in a trench (i cannot remember the minimum off the top of my head; its either 24" or 36").
Also, even if your conductive water pipes are not being used as the primary grounding electrode, they still have to be bonded to the service.
Location: Visitation between Wal-Mart & Home Depot
8,309 posts, read 38,774,074 times
Reputation: 7185
Quote:
Originally Posted by Coldjensens
Jimbo. I do nto know the science of it, but I was replacing a light fixture in an old house and the fixture was hooked up as a switched neutral. I was standing on a ladder and I became the neutral. It wa a substantail shock and it burned my fingers a bit and knocked me off hte ladder (or maybe I fell). The breaker never tripped either, I do not know why. That is when I learned about switched neutrals and how dangerous they can be to workers and also learned to use a tester on every wire every time always. I have been amazed at some of the wiring things that I have seen. That same house had one place where they tied knob & tube into romex by twisting wires together and wrapping them with duct tape. THey also had one 12/2 romex line twisted together with 11 Knob and Tube wires. It was pretty much feeding the entire upstairs (where we would often run three hari dryers at the same time). I thnk that it is funny how stupid some people can be. Some mistakes are understandiable, but some are amazing.
Help me with my understanding of switched neutrals...
A switched neutral is basically a way to bootleg a 3-way connection by using two single-pole switches to control a single fixture, right?
You would have a hot and a neutral connected to both toggles that operate the fixture and a single wire running between them, right so far?
The problem being that in half of the "fixture off" toggle configurations you still have a potential at the fixture but the neutral is open so the fixture is inactive.
I have only seen one and it was in my master bedroom. I was in the process of installing a ceiling fan and it was really pickling my noodle to see the neutral wires clipped at the Romex connectors.
Was that ever an approved practice or is that usually the result of ninjas?
The reason they no longer use pipes to ground outlets is because it will cause a ground loop that can cause a lot of problems with the equipment on your electrical system. They used to do this before they fully understood the phenomena.
The only proper way to add a 3rd wire to an electrical system is by a connection at the breaker box. There is supposed to be a 6ft or more copper rod driven into the ground where the power comes into the house. Both the neutral wire and the ground wire are connected at this point to the rod. (can be in the breaker box also) The ground wire should not be connected to earth anywhere else in the house. If you make connections elsewhere, you will most likely end up with a ground loop which can mess up your voltage.
Unfortunately there really isn't a cheap way to fix this.
A switched neutral is where the light fixture is wired to the hot wire and the neutral is switched. When you turn off the light, the circuit completion is broken and the light goes off, but the light fixture is still hot. Having no idea that there was such a thing as a switched neutral I turned the switch off. removed the light fixture and then while installing the new fixture touched the hout (whoich should have been diconnected by the switch). Zap!. Stupid person who forgot to check the hot just in case laying on the floor wondering what happened. We were able to correct this by simply cutting the wires and switching them and putting in a new junction box underneath the house. That normally would be bad because your white wire would now be hot, but this house had Knob & tube wiring, so both wires were the same color.
The reason they no longer use pipes to ground outlets is because it will cause a ground loop that can cause a lot of problems with the equipment on your electrical system. They used to do this before they fully understood the phenomena.
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I read on here about a ground loop from grounding to pipe, but I never understood what that is and still don't. Never had any problem in any house that I lived in that was grounded to the pipes. What equipment has problems? What is the problem? Is it a problem that has manifested itself or a therotical problem? What are the manifestations of the problem (what happnes/how do I know if it occurs?)
If you have a ground for your main house and a seperate ground for the carriage house that runs on a subpanel will you get this problem? I am not sure whether the carriage house is seperately grounded. It does have a 100 amp subpanel.
It your neighbor's grounding rod is really close to yours, will the problem occur?
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