I live in an old house that has the old 2-slot outlets. The copper wires are romex (so at least I don’t have to deal with knob/tube). I want to upgrade my electrical system with grounded outlets. Do I need to:
a) run new 3 cable romex all over the house
b) run a single 12 guage wire to every outlet (behind base boards, etc)
c) simply hook my white wire up to the grounding screw on the new outlets.
I’d be really happy if C were correct. If it’s not, how come? The ground wire & white wire go to the same place in the breaker box…don’t they?
Legal requirements aside, I’ll answer that it depends on what you are needing the ground for.
Trouble with tieing the nuetral to gound pin is several fold:
current through the nuetral wire creates a voltage drop, if ground is also connected to neutral at outlet, that means the grounded-external case of whatever is plugged in, is no longer at ground potential, in most cases, this isn’t that big a deal but if you have a computer plugged in, and a monitor plugged in to a different outlet, the shields on the interconnecting cables may find themselves carrying current, which may either affect the proper function of actually cause damage.
safety hazard is this, if the nuetral connector ever becomes disconnected somewhere bewteen plug and main panel, then the metal parts frame of what ever grounded device is plugged in will end up at line voltage. A dangerous situation, especially if around water, or in humid enviroments, or where this is grounded metal nearby. If there is interconnected equipment, like in your computer, then the chance for damage increases greatly. To help mitigate this safety hazard, please make sure to use a Ground Fault Interupter(GFI) breaker in the panel board. In fact, unless the National Electrical Code(NEC) has changed recently, it is allowed to install a grounded outlet, without the ground wire, provided you use a GFI breaker in the panel and label the outlet saying it doesn’t have a ground. I hoping an electricain will come along and check that for me.
from an electrical noise point of view, the computer power supply produces a lot of noise. The line filter in the PC uses the ground line as a way to lessen the noise it puts back on the power line. If you tie the ground a nuetral together, then that noise stays on the power lines and ends up back at your TV, or at your amplifier, so now you get either picture or audio trouble.
In my view, and if you own the property, then bite the bullet and run the 3wire cable, it will increase resale value. If you don’t own it, then at least use the GFI breaker and hope you don’t destroy any of your electronics.
(B) will work, as long as you ground the electrical box as well as the outlet that’s in it. Check with your local codes though. It may not be legal in your area.
(A) of course is the best way to do it, and I’d be happy if I bought a house and found out that it had been done this way rather than (B).
If you’re going to run a separate ground wire, you might as well just run the 12/2 w/ground. It’s going to involve the same amount of work, and as others have pointed out, you improve the marketability of your house.
The other reason that C is bad, safety aside, is that by doing this, you are creating a ground loop. Depending on the size of the loop, it can be a very efficient antenna for EMF, which can then cause interference problems and unstable operation in many types of electronics. Yes, C is bad.
You said the house is wired with Romex is there no ground wire in the existing Romex? Check you panel. if there are grounds you may just need to change the outlets.
OK. C is bad. I knew it was too easy. But Question #2:
When I look at the guts in my breaker box, I notice that the neutral as well as the grounds (some of my circuits are “modern”) connect to the same bus bar.
Since any faults that might ground the casing of the appliance are supposed to travel to the neutral bus bar via the ground wire, why does it matter if the dislocated juice flows through the ground wire as opposed to the neutral wire? It all goes to the same place and, theoretically is all part of the same piece of metal since the ground and neutral are ALWAYS connected via the neutral bus bar.
I did “B” and it passed an inspection–luckily I didn’t think of “C” until long after that project. IMO it was way easy because it was part of a remodel that involved replacing baseboards. In this action I ran a single 12-guage wire to each outlet per circuit. I could have saved some time by hooking ALL the outlets to the same ground wire and then wrapping that wire to a water pipe–would THAT have been OK? Or would that have turned the house into a large scalar weapon?
You were doing ok until you got to the water pipe. You can’t rely on water pipes to be part of your ground system. Someone could easily come along and replace a section of pipe with something non-conductive, and there goes your ground system. On the other hand, your water pipes do have to be grounded, for safety reasons. None of your circuits can use the water pipe for grounding, but the water pipes do have to have their own ground wire run to them.
I forget exactly when it changed, but it used to be that you had to ground through your cold water pipe near where it entered the house. If you have an older home yours might be grounded this way.
The purpose of the protective ground is to provide a path to ground that carries no current, so that it is at ground potential. If you just tied the nuetral to the case then as current flowed through the wire, the case potential would rise above ground, causing a shock hazard. Sure it’s nowhere near as dangerous as touching the hot and ground at the same time, but it’s still a shock hazard. Just having the ground wire present does not provide the level of protection you seem to think it’s intended to. That requires a GFCI (ground fault circuit interruptor).
No, that would be more like a 1920s style death ray.
That would not be a good idea at all. The water pipe is not designed as a ground, and you have no way of being sure that it is an effective ground - neither now or sometime in the future when corrosion has had its way with the pipes.
The neutral and the ground are bonded together in the breaker box. That is true. The thing is, the ground wire is run separately from the neutral to continue the protection in case something is wrong with the neutral line. Tying the two together at the outlet is electrically equivalent to running a separate ground and tying it to neutral in the box - from a redundancy stand point, though, it is worlds apart. Also, since there is normally current flowing through the neutral line, it might not really be at ground potential at the outlet. Resistance in the wire (with a heavy load) will cause the neutral to be a little above ground potential at the outlet - and that “little” can be enough to cause pain or ass-toastage.
I followed this thread a bit yesterday, but I never got a chance to reply. I’ve actually wondered this exact same thing since the first time I looked into a breaker box. I have went so far as to ask two different electricians this same question and I typically get, “mumble… mumble… extra ground… double talk… it’s code… mumble… don’t ask me this stuff any more…”
First, I will agree that ‘C’ is definitely going to violate codes and just “seems” like a bad idea. However, statements like this:
fly in the face of everything that I ever learned about circuits and electronics. Granted, it has been a long time since college, but I do have a bachelor’s degree in electronic engineering.
To me, the above statement is just plain wrong. The ground wire and the neutral (white) wire are both connected to the ground lug in the breaker box. They are electrically the same point in the circuit. I guess you could say that there is a very small amount of resistance in the wire, but for a short run of copper wire, that isn’t going to cause a voltage drop that any of us are going to see with most of the equipment we own.
Now I’m not trying to pick on billy, but this statement is false for the exact same reason:
Sorry, the neutral and ground are already tied together. I have a hard time believing that you are curing any noise.
QED’s answer about a ground loop is something that I can’t refute. I would like to hear more.
I also agree that there is redundancy in having a separate neutral and ground. This should be a good thing.
So in the tradition that I’ve found here at the SD message boards, I’m asking for a cite. Thank you!
A quick skim of Leviticus reveals that the Rabbis have forbidden option C) in favor of A).
(I know kosher has entered the lexicon meaning “proper,” but there are so many better words to use. It just grates on my ears when people use it to refer to anything other than Jewish law.)
RogueRacer, read over what Mort Furd and e_c_g have said, since they pretty much answer your question without mumbling or double-talk. Both have said that yes, ground and neutral are tied to the same bus in the breaker panel and are at the same potential. It’s what could happen downstream from there that the issue of having a separate ground wire, not connected to the neutral anywhere else, becomes important, from a safety standpoint, not one of electrical potential.
Let’s take an extreme case:
Circuit at full load=16Amperes
Resistance of neutral line (including all connection lugs and such) 1 Ohm.
E=IR Where E is voltage, I is current, and R is resistance
We’ve got I and R, so E is easy to figure: 16 Volts
That is, however, RMS. The peak voltage is higher - 22Volts.
22 Volts is enough to bite you hard. If the resistance of the neutral line is higher, then the voltage will also be higher. 16 Amps is an extreme, but higher resistance at a lower current can be just as bad.
With pleasure. As others have addressed your other misinformation, I’ll just leave that be. A ground loop is what occurs when you have more than one path to ground from a given point. Here is some information as it pertains to audio eauipment, but the same principles are at work in the scenario we are discussing.
I guess I could be wrong, it’s happened before. I hope it’s not … if it is, I get paid too much at work. I design electrical power distribution systems for industrial equipment.
I’m not gonna cite anything specific because I was using general knowledge when posting but you could look at ‘IEEE1100-1999 - IEEE Recommended Practice for Powering and Grounding Electronic Equipment.’ to get a feeling for some of this. They some good info there.
Actually, I’m a little hurt. You wouldn’t tell QED he was wrong. Why can’t you trust me??? I’m taking my ball and going home.
Everything you ever learnt about circuits and electronics? You didn’t learn much then. Did you get to Ohm’s law? You know, V = I * R? You are going to have a voltage drop in the white neutral wire because it is carrying a current and because it has resistance. The protective earth wire, OTOH, does not carry a current and so is at ground potential. Furthermore, if the white, neutral, wire increases its resistance (due to a bad connection or splice, for instance) then you can have up to the full live wire voltage (110V) and using that as protective earth could be lethal. The separate PE wire is there for a reason.
