Code will tell you that your neutral wire is to be bonded to the ground at the first means of disconnect. This bond makes the one and only place that makes your neutral stable. If you lose this bond, you will end up with what's called a floating neutral. Under normal conditions, the neutral wire carries voltage. The ground does not. The ground, or bare wire is there for SAFETY only. It is not integral to the voltage system. It only meets the system at the bonding point for convenience. If you didn't have that bond you'd need to run the neutral (or common) somewhere to bond to ground. (Most likely to the ground rod.) Here's an example. If you have a three wire from your panel , black wire to A phase , red wire to B phase sharing the one common (or neutral wire.) The load on A phase is 10amps. The load on B phase is 5amps, your common, or neutral wire will be carrying a load of 5amps. If you removed the bond to ground, the system wouldn't appear any different (at first) Your floating neutral will attempt to stabilize A&B phases by , rather than having a stable voltage and carrying the unbalance load, your system will work only by fluctuating the voltage to equalize the system. Now, you could, for testing purposes only, use your ground wire as a neutral and your neutral wire as a ground. For metering out your system, this is perfectly fine. In an emergency/temporary situation, it's safe to use your neutral wire as a ground. But since your active neutral is carrying both voltage and amperage, NEVER try using a bare ground wire as a neutral.
Is the setup you describd with black and red wires powering different circuits very common? Excluding situations like that, if you've got a regular circuit with black hot and a white neutral, if there were no ground as we currently understand it and the white core were connected to the ground spike outside, would it be functionally different to what we have now? There would be no need to fluctuate voltage to equalize two circuits. ETA: The reason I ask is because when I was testing my sockets to make sure they were wired correctly, with a view to fixing up anything that was badly wrong, I found a lot that had open ground (largely expected, given they were two-prong sockets), a few that had grounding pins but still had open grounds (I subsequently found the ground bent back as I described earlier), and some that appeared to be correctly grounded but were fed by cables that looked old enough to lack a ground. I opened one up and found a strap between the ground and the neutral, and hence got to wondering if there was a reason that couldn't be done as a matter of routine.
It's quite common to use a three wire system. Efficiency being the motivator. Example: The distribution panel is in the garage on the east side of the house. You have two bedrooms on the west side and you want each bedroom to have its own circuit. Will you spend the time(and expense) of installing two 12/2 wires, or a single 12/3 and split the three wire in a junction box in one of the bedrooms? Same in your kitchen. You have a refrigerator that requires its own circuit, and a microwave next to it that also requires its own circuit. Will you run two 12/2 to them, or one 12/3 to the microwave, and tap into the outlet box with a 12/2 to run over to the refrigerator? (Simply requires a color change of red to black at the microwave box) I would like for you to stop thinking of bonding neutral and ground wires at a device. Neutral wires are part of a live electrical system. It carries voltage. The ground wire is meant for safety ONLY. Used as a bond for the metal housing of a device. If something goes wrong with a circuit and voltage leaks to the housing of the device, the ground wire absorbs and takes that voltage to earth ground. Under normal conditions, the ground wires remain idle and not energized . Bonding at the fist means of disconnect is the ONLY place the ground wire should be attached to the electrical system and that simply allows the neutral wire a path to earth ground. Other than that ONE point the ground and neutral wire should remain separated.
We had a hail storm about a month ago north of me that broke a lot of people’s house windows and tore up siding. Never seen that before.
If you wire it this way don't you lose power to both circuits if one of them trips the breaker? Obviously in an ideal world it doesn't happen but if the microwave develops a fault and trips the breaker I'd rather not lose the fridge as well. Would code permit having the two live cores of 12/3 connected to two different breakers, such that one tripping wouldn't cause the other to trip? I can see the cost savings given that 12/3 is less than twice the price of 12/2. It's not something I'm planning on doing, I'm just trying to understand the practical implications of why it might work or not work. I get that's what code requires and since I don't get to rewrite the code I comply with it. I'm just trying to understand what practical difference it would make if one wire were used for both neutral and ground, even if only in the context of a simple 2-core circuit. I asked the guy who fitted my new breaker panel and he thought for a minute and couldn't tell me, so I still don't know the answer.
Using the 12/3 wiring, YES, you will wire to two different breakers. As long as those breakers use both A&B phases. (Black wire to breaker on A phase, red wire to breaker on B phase. Both sharing the one neutral cable. By properly using the three wire system, the neutral wire will carry a load of the differences in amperage of the two circuits. If A phase has a load of 10 amps, and B phase has a load of 5amps, the neutral wire will carry a load of 5amps.. In the same respect, if each A&B phase have a load of 10amps each, the neutral wire will have -0- amps. The issue of bonding the neutral and the ground together at the device is that you're doing nothing but ending up with two parallel neutrals. Both are current carrying. The danger in that is you've lost the ground wire. Rather than protecting the device (and you) is that if you have a ground fault in the neutral you'll not know it UNTIL...you've received a shock. Voltage takes the shortest, most reliable path to ground. Scenario; You have a microwave plugged into an outlet that has the neutral and ground bonded together. The microwave is three pronged plug. Hot, neutral, ground. (Well, it used to be a ground. Now it's a parallel neutral. Which means the housing of the microwave (which is also bonded with what used to be the ground, is now part of the circuit also. If you should be running water in the sink, (next to the microwave) and you reach over and touch the housing while the microwave is on, there may be a good chance that YOU ARE THE SHORTEST PATH TO GROUND! Yes OUCH!! In a standard 110V circuit you only have (and want) two energized wires. One hot, one neutral. The ground wire is running with the two in the cable FOR CONVENIENCE ONLY. IT IS NEVER MEANT TO BE A PART OF THE ENERGIZED CIRCUIT! The bonding at the first means of disconnect is also for convenience. You could just as well eliminate that bond and continue each separately to the ground rod outside. And bond them there. They are both searching for EARTH GROUND. To carry it to extremes. They NEVER need to be bonded. You could have two ground rods. One for the ground, one for the neutral. (I've even done that when there's sensitive electronics involved. Eliminating harmonics) So, install an electrical service. Bond the neutral at the first means of disconnect, AND NEVER LET THEM TOUCH EACH OTHER AGAIN.
If you put them on two different breakers how would you go about marking them so that anyone working on the panel in the future would know not to separate them? I know if you see a red wire running to a breaker it doesn't take a huge leap of reasoning to figure there's probably an associated black wire running to another breaker, but then I'd have thought it was obvious that seeing white wires connected to black wires in the context of a lighting circuit means you've got a switch loop, and yet code talks of putting a black mark on the white cable to indicate it's being used as a live wire (in the UK I called it switched live") If you've got a microwave with a metal box and a loose live wire touches the box, the current goes through the ground wire and trips the breaker, so you pop a breaker rather than popping the poor unfortunate who touches the microwave. If instead of having the socket properly grounded you've just connected the ground to the neutral within the socket, doesn't the same happen? Wouldn't the errant live wire touch the metal case, allow the current to go to ground via the neutral wire and trip the breaker anyway? I'm probably missing something here, just trying to get my head around this bit. It may only be of theoretical interest but, you know.....
Yes, an arrant hot wire coming in contact with a neutral wire will cause a direct short and trip the breaker. An arrant hot wire coming in contact with a ground wire will trip the breaker. It's a ground FAULT . The goal is to keep th ground and neutral separated because the have two very different functions. The neutral is the second half of a completed ENERGIZED circuit. Ground wire is in place to protect. By bonding the metal housing of the microwave, you're making that housing a part of the grounding system. If there is a problem and the hot wire becomes loose and accidentally touches the housing of the microwave, the housing will only be "energized " for that split second before the breaker trips. It has performed it's function, to be available to trip the breaker during a circuit fault. BUT if you bond the neutral and the ground together, the ground is no longer the ground waiting idly by waiting for a fault to happen, it is now a parallel neutral and the ground wire becomes energized just as the neutral does when you supply power to your device, and anything else that ground/neutral is attached or bonded to (microwave housing) Do you really want the housing of your microwave carrying voltage every time you turn it on? You'll never know the difference until that faithful day when you have your right hand on the sink faucet and touch you left hand on the microwave when it's running and you become the shorter distance to ground. At best you'll feel a tingling. Might even notice what would appear to be a static spark. Trust me, there'll be nothing static about it.
Let me check I'm understanding this right. With a ground correctly wired the circuit works as normal and an errant live wire touching the metal case of my properly grounded microwave causes a short circuit (or as near as makes no difference), the breaker trips and the system remains safe. If I do away with the ground wire and simply connect the ground terminal to the neutral terminal the metal case of my microwave carries current whenever the microwave is turned on, that could give me a nasty shock any time I touch the microwave and something grounded. If I have no ground wire and don't connect the ground terminal to the neutral terminal then an errant live wire touching my metal case could cause a shock because there is no ground to take the current away safely but absent an errant live wire everything remains safe. Therefore, if something is wired with a two-core cable with no ground wire it makes it less safe to kludge a ground by connecting the ground terminal to the neutral terminal?
Year-end trip with my son's class today, followed by heading out to join the overnight year-end camping with my daughter's class. Fortunately yesterday's storms appear to have past and the sun is shining again.
Excellent, it makes sense now. Thanks for explaining it I have one socket in the basement where the ground terminal is linked to the neutral. I think that's the only one left with that setup, I noticed it because my socket tester reported it as correctly grounded but it looked like it was wired with old two-core cable. It would be a huge stretch to touch the freezer and something earthed at the same time but maybe I'll just take that link out pending replacing the entire length of cable.
I suspect the forum might as well be called the "Tango Breaks His House And Tries To Put It Back Together Again" forum
Agreed. The best safety feature in your home is your knowledge. The socket you mentioned in your basement. Treat it as you would a two pin socket (no ground) it's perfectly safe to use any device that has a two prong male plug. (Electric drill, trouble light, table lamp) The electric drill is double insulated(I'm sure you've seen the stickers) which simply means that no exposed metal parts are bonded to ground, or voltage system. Not to say they are going to be 100% safe,100% of the time, but risk factor under normal conditions are minimal.
That socket in the basement powers the chest freezer and nothing else. My understanding is that because it powers a single fixed piece of equipment it doesn't even need to be a GFCI despite being below grade. When I get to rewiring it I'm debating whether to run a piece of 14/2 to it and figure that because the circuit serves a single purpose (i.e. powering the chest freezer) it doesn't need 12/2, or run 12/2 anyway and figure I've got a bit of extra capacity in case I do want to run something else in there. Most of my power tools are battery powered because much of what I've been doing involves working in spaces where there may not be power within reach. It's hard to see what else I might need to power in that room but you never know. I agree entirely with what you say about knowledge being a good safety feature. The best safety device in most situations is the squishy gray bit usually stored between the ears
Now you've opened another can of worms. GFCI- Ground Fault Circuit Interrupter. Monitors the outlet for a ground fault from either the hot OR NEUTRAL to the device. Used primarily for damp or wet locations. By code, any outlet within 3' of a sink or water source, or outdoor outlet, or even the garage, must be GFCI protected. (That would have applied to the microwave next to the kitchen faucet. My bad for not applying that at the time, but I wanted to keep it simple. The number of devices, or whether it's below ground has nothing to do with it's requirements. Simple condensation buildup in the box containing the GFCI outlet (bathroom shower steam) is most of the time enough to show a ground fault.