I read that appliance at certain times in the U.S. (for example stoves) were grounded through the neutral wire. Since the neutral wire carries current does this means the case of the stove itself is carrying current. Why didn't homeowners get electrocuted with such a setup? Is it because as long as the neutral is connected/grounded properly the current is going to "chose" to take that path (least resistance) instead of the homeowner (much resistance)?
Electrical – Why didn’t homeowners get electrocuted when appliances were grounded through the neutral
electricalgrounding-and-bonding
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In this case, you would simply not hook up the neutral wire. Instead you can just put a wirenut on it and tuck it neatly into the electrical box.
Typically 240V appliances require the neutral wire so that they can run the electronics at 120v or provide a plug on the appliance. In this case, these devices are hooked up to one leg of the hot and the neutral, giving 120V.
If no neutral is required, then the device can only operate on 240V/208V, though at 208V you should expect the oven to take longer to heat up.
What it means by "Connect only to a 3-wire, 120/240-volt power supply; the neutral conductor is not required for the operation of the appliance," is that the 240V needs to come from two legs of 120V service; this device won't function on 240V mains like you'd find in Europe.
This is a bigger can of worms than meets the eye. There are huge arguments over all this.
This is a coax grounding block:
This is a grounding bar:
This is a grounding bridge, your cable company or telephone company probably has one on the outside of the house at the electrical service entrance:
What I'd do:
- Run a ground cable from your frame to the grounding bridge. Use the biggest cable that will fit properly in the bridge. Don't use A-D above.
- Install a grounding bar that will handle that wire, at your frame in the basement.
- Run a ground wire from your metal patch panel rack to the grounding bar, use grounding lugs on the rack. Probably not necessary, but use Noalox between the lug and the rack. Remove paint if you want to go all in.
- Install and ground coax grounding blocks for your antenna and CATV service.
- Use good quality surge strips, at the frame and through the house, and check your outlets with a receptacle tester to make sure they have ground wires - surge strips generally don't work without a good ground.
- If any of your equipment has a grounding lug on the back, ground it. (For example, many of the Netgear metal cased switches have a ground lug on them.) AFAIK only necessary on equipment with a two wire power plug.
- Remember, holy wars over all this - some will say this is all totally wrong. This is what I would do though after following all the arguments.
Edit:
There is a good chance your patch panel doesn't ground the coax that goes through the house. However if you use surge strips that have a coax port in those places, and the coax has been terminated properly so the body of the plugs are bonded well to the shiled, and the outlets those surge strips plug into have a good ground, you should be fine.
One last thing - this whole thing hinges on good grounding of your electrical system. If you want to be really careful there, have an electrician check the grounding and bonding and if possible ground resistance. This is IMO worth doing in general.
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Best Answer
The US distribution system uses a neutral conductor which is grounded at the service entrance of each house/building. The neutral conductor and the ground conductor are physically and electrically bonded at the main service entrance, and tied to actual earth ground via rods and/or metallic water pipes as well.
The devices which were commonly "grounded via neutral" were exclusively 240V primary loads. In the US system those loads are fed by two hot conductors, each 120V away (in opposing directions) from ground/neutral. No current flows in the neutral conductor from one of these loads (generally, they are not even connected to it.) If there was any 120V power used in these items, it was a minor load such as a clock motor. The neutral conductor, however, was full-sized for rated load of the appliance - 30A for a typical dryer, 50 A for a typical stove. So any 120V load that would actually cause current to flow in the neutral conductor would cause a small current to flow in a large wire that was grounded at the far end. As such, no appreciable voltage would ever arise on the neutral conductor.
The move to a 4-wire system with separate ground conductor is, notably, not one where the powers that be decreed that all your old devices needed to be ripped out and replaced since they were scary and hazardous to own; new devices need to meet the new standard. How much "real improvement in safety" there may be is, frankly, debatable; but that debate is somewhat pointless (4-wire is a done deal) and probably also off-topic.
In general, even a current-carrying neutral on a fully-loaded 120V circuit should not have sufficient voltage above ground to cause a shock. Correctly sized wires should limit the total voltage drop in the wiring to 3%, or 3.6 volts, 1/2 of which will lower the hot voltage and 1/2 of which (1.8 volts) will appear as a difference between neutral and ground.