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TW Lucas 05-07-2008 03:45 PM

Nuetral from feeder cable to main panel question?
I am trying to prepare myself for the day when a Master Electrician walks through the door. It has finally dawned on me; before I hire someone to try networking with my contractor friends to find a master Electrician who might stop by in their spare time, and size my situation up for me. Thank heaven for sites like this, and Mike Holts site. To this end over the past several days, I've been reading a lot of the related questions and answers here.
This may seem like a trivial question. I'm hoping the answer may help me better understand how the neutral and ground interact on the main panel. When the feeder cable comes into the panel the neutral wire is wrapped with white tape from the lug at the main breaker up to within about 1 !/2 inches of where the feeder enters the main panel. I thought I understood from something I read here somewhere that the neutral is supposed to be taped. Does it not have to be taped completely. Also the neutral is only supposed to contact the panel at one spot, correct, only at the neutral bar. If this 1 1/2 inches of bare neutral wire is not contacting the case; it can't be more than an 1/8 of an inch away. Am I splitting hairs here; is it a violation of code for the neutral to contact the panel at a point other than the neutral bar. does this not defeat or diminish the function of the neutral wire? If not, could you explain for my novice brain, why not?
Thanks again for helping me to more fully understand these matter. T.

Thanks for letting me bend your ear. T.:jester:

darren 05-07-2008 04:18 PM

If i am understanding your question you are looking in your house panel that is fed with two hots and a bare neutral.

I will first say I am from Canada and what I am about to explain is how we do it in Canada, it may be differnt in the US and if it is I am sure someone will correct me.

Our bare neutral neutral will come in go through a grounding bushing, if you are useing a metal raceway and then go to the neutral lug. Then we run a proper size ground wire to the street side of the meter and this grounds the panel as well as grounds the neutral wire. So your bare neutral in your panel is very common. The neutral has no potential on it and if it touches the box nothing will happen.

That is why your neutral is refered to as the grounded conductor.

If you are dealing with a panel that is being fed from another panel then the answer is totatly differnt then what i just told you.

mr500 05-07-2008 05:14 PM


Originally Posted by TW Lucas (Post 121608)
When the feeder cable comes into the panel the neutral wire is wrapped with white tape from the lug at the main breaker up to within about 1 !/2 inches of where the feeder enters the main panel.

I believe it is wrapped on BOTH ends so that the electrician will know which wire is the neutral load. Helpfully when he/she does not pull the wires and all the wires are of the same gauge. BUT I think it only has to be taped at the end where it its landed on the lugg :eek:

I think loll

TW Lucas 05-07-2008 05:52 PM

Hi Darren, Yes I was talking about the feeder cable with the two hots and the bare neutral coming in from the meter box outside. Out side the panel all three cables are covered with an outer sheath.


Our bare neutral neutral will come in go through a grounding bushing, if you are using a metal raceway and then go to the neutral lug.
In my panel the bare neutral comes through the top of the panel through a large wire nut. (perhaps with a grounding bushing ?.) It could be grounded to that large wire nut.

From there it travels down to the nut on the top end of the neutral bar; on the right side of the panel as facing.

The ground bar is on the left side as facing with two ground wires (size?) running up and out of the panel.

One ground runs through the wall going outside where the main feed comes in from the meter. The other ground wire connects to the water line on the opposite side of the house. There is also a rubber joint/ bushing where the copper water line leaves the house.

Thanks Darren, and Mr500
I think I see what you are each talking about.

Here's another one. I found a ground wire connected to a copper water line which feeds the sink in my bathroom. I suspect it was used to ground one of the old fixtures boxes in the wall or the ceiling of the bathroom.

I remember reading somewhere; a second grounding source can interfere with grounding at panel. Does that apply here in this situation?

Thanks again.

wire_twister 05-07-2008 06:18 PM

Hi TW, if the neutral in your panel comes directly from the meter, and not through a disconnect or breaker other than in the load center, then it can be connected to the neutral and ground bars in the load center, it does not have to be jacketed, and does not matter if it contacts the can on its way to the lug. On the other hand, if there is a disconnect or breaker between the meter and load center the neutral and ground will be bonded at this point and will not connect again. The neutral leaving this point must be a jacketed conductor and might have white tape on it to identify it. The ground bar in the load center will be bonded to the can and the neutral will be isolated from the can and the ground bar. hope this clears things up.

TW Lucas 05-07-2008 09:46 PM

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Am I right in that the sub panel in this picture would be called a Multiwire branch circuit. Even though there is no breaker for the sub on the Siemens 150amp main panel; when I shut off the main breaker, on the main panel, the 50amp breaker on the branch panel shut down. I suppose that is because they are sharing the same neutral and ground. There also appeared to be a bit of a spark from the main panel breaker when I shut it down.

The meter on the multiwire panel shows that it has used 300kw hours over the past three years. I suppose that might be about 10 or 20 dollars a month. It feeds two large sheds.
I just found out today; the first shed has a 70 amp breaker panel with a 70 amp main breaker, a 50 amp breaker, two 20 amp breakers, and a couple of 15 amp breakers; the second shed has a 60 amp breaker in its panel, along with a couple of twenties and 15 amps.
I hate to shut his power off, I mean he lives a couple miles away; and has no other way to get power to his sheds, which he uses to store his tools for work.
It does make it a little difficult to figure the actual load on my main panel.

He told me again today he only uses the power for lights; as well as possably a welder sometimes. I suppose a welder could pull quite a few amps.

mr500 05-07-2008 10:50 PM

Umm. In the pic, is that 2 hots and 2 nuetrals landed on the same main lugg? Is that code/safe?????????? First time I ever seen that one


TW Lucas 05-07-2008 11:51 PM

Thanks for the reply Twister,
I follow the second part of your post.
I imagine the first part refers to a type of scenario of which I am not to familiar.

if the neutral in your panel comes directly from the meter, and not through a disconnect or breaker other than in the load center, then it can be connected to the neutral and ground bars in the load center, it does not have to be jacketed, and does not matter if it contacts the can on its way to the lug.
Your right Mike, the fact that it's not feeding off a breaker on the main panel is what made me wonder. I do remember that the home inspector looked right at it while I was with him; and didn't say anything about it. I didn't know enough to question it at the time.
Perhaps that is why it arched a little when I turned off the main breaker. :(

Stubbie 05-08-2008 06:26 AM

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Hello Lucas

In regards to your question about the neutral and ground and this panel of which you posted a picture. What you have shown may lead to a rather interesting discussion.

For orientation purposes the "main panel" is the panel on the right then the sub-panel is to the left. You do not have a multiwire branch circuit in those terms but a sub-panel 4 wire feeder which is tapped to the incoming line terminal lugs of the main panel. that "main" panel is being fed by SEU entrance cable with a braided concentric neutral. It has been wrapped in white tape which is not required but is not a violation to do so. It's one of the few times I've ever seen the neutral of SEU taped.

It appears since you have two meters that the outbuildings (sheds) are being sub-metered as evidenced by the meter on the load side of the sub-panel. And it also appears that the meter is in a backfed configuration. I am assuming that the owner of the sheds is just trying to see what his kilowatt usage is for his outbuildings and the utility is reading the meter on the line side of the main panel for total kilowatt usage of the dwelling and outbuildings.

The spark or arcing you saw at the main breaker was because you shut it off under load. Had you had the branch breakers off you would most likely not have seen any arc at the main breaker. Sharing the neutral and ground has nothing to do with the main breaker sparking.

As previously mentioned the neutral and ground are bonded at the main panel only. You seem to not quite understand why this is required and it is probably because you are confused between ground and neutral. the white taped neutral in your panel is the service neutral or commonly called the service grounded conductor. Grounded means intentionally connected to earth which is given a Zero (potential). So any voltage measurements from an ungrounded (hot) wire to the service neutral will be some voltage above zero. Typically 120 volts in US residential dwellings.

To simply explain the difference between ground and neutral is a rather long journey. So I'll try to summurize. Neutral is a wire that carries current and is almost always the unbalanced current between two or more hot wires or ungrounded wires. In your main panel the neutral is carrying the current returning to the source (transformer center tap) between the red and black of your service entrance SEU. The unbalanced meaning because of the red and black feeding the two columns of breakers in the panel and due to the fact that the red and black are on different or opposite legs neutral current will cancel and only the difference between the two will be flowing on the service neutral. So if the red is drawing 40 amps and the black is drawing 30 amps only 10 amps will flow on the service neutral. but understand that the neutral is just as dangerous as the hot carries current and should be treated as such.

In you panel you have what is called a split neutral both bars are neutral and ground bars and are bonded together by the metal strap you see between them at the bottom of the panel. Then you will find a green screw that goes through one of those bars and threads into the metal of the panel enclosure and bonds that metal to the neutral bar(s) and ultimately the service neutral. So grounds and neutral(s) or grounded legs can connect to both of these bars at the main panel. It needs to be said at this point that all your 120 volts circuits do not utilize neutrals, the white wire is a grounded leg (not a neutral) meaning it serves to facilitate for the return of all current from one hot wire and is bonded at the neutral bar with the service neutral. Then all unbalanced current flows on the service neutral (grounded conductor) back to the transformer center tap. An example of a branch circuit that does utilize a neutral would be a 120/240 volt range (stove) circuit, which of course has two hot wires and a neutral to carry the unbalanced current utilized by the 120 volt loads of the range.

As for ground there are two concepts the equipment ground (human safety)which is the bare or green or metal conduit of a branch circuit or feeder. Then there is the grounding electrode system (property protection). The two big copper wires you see connected to that lug on one of your neutral bars are going to grounding electrodes. One is likely going your water pipe and the other one is going to a ground rod. This is for huge voltage events like lightning and sends the current (pushed by massive voltage) to earth to try to keep it from destroying your equipment and Dwelling wiring.

The equipment grounds (bare or green) you see at your receptacles and switches and light fixtures etc... are present to facilitate the opening of a circuit breaker in the event of a ground fault or other fault. The equipment ground only carries current in the event of a fault.The equipment grounds of all branch circuits and feeders are bonded to the grounded conductor (service neutral) at the main panel via the neutral bars, that metal strap and the neutral lug where the grounded conductor is connected.

Equipment ground and neutrals and grounded legs join up at the service equipment (main panel in your case) because both must use the service neutral for their currents to get back to the center tap of the transformer. In other words in your case you have a two lane road merging at the neutral bar(s) of the service equipment and then a one lane road (service neutral) that they both share to return to the source center tap.

The "main" panel in your case is more appropriately the service equipment. The service equipment is where the first means of disconnect for all power to the dwelling is located. In your case the panel on the right in the photo because this is where the main breaker (disconnect) is located.

Below is a drawing of how the equipment ground would provide the path for fault current back to the source so a breaker will open in the event of a short to the metal of an electrical box.

Stubbie 05-08-2008 06:43 AM

As a side note it is very likely that the two wires under those lugs in the main panel is a code violation in that those lugs are not rated for two conductors. I suspect this was done because there wasn't any more room in the main panel for a breaker to feed the sub.

The big issue here is you have no overcurrent protection for the feeder to the sub-panel.

An electrical inspector would have caught this violation but homes inspectors likely would not have noticed.

Silk 05-08-2008 07:21 AM

Hey Stubbie, did you notice that a plumber installed the meter!

Stubbie 05-08-2008 09:24 AM

Yes I did......:)

I was letting someone else bring that up as my fingers were tired of typing...I've seen that before, people can get darn right resourceful at times.

jbfan 05-08-2008 11:11 AM

I eyes may be deceiving me, but the outlets on the bottom of the main panel appear to have a hot and ground wire only.

TW Lucas 05-08-2008 11:22 AM

Hello Stubbie,
Thanks for the reply, and the clear lesson on bonded conductors. Iíd previously read several articles on bonded conductors at Mike Holtís site, but I always failed to grasp how all the parts work together as a system. I now feel better prepared to understanding the relationship between ground wires and bonded conductors; thanks to your post, and the linked diagram; which Iím now using as my desk top background.
The issue of lack of over current protection sounds like a serious matter. I personally believe there are more breakers on the main panel than this house needs. I wonít know for certain until I finish tracing out every single fixture and receptacle in the house.

I was considering allowing the sheds owner to continue using the sub panel. Now considering (as you note) the lack of overcurrent protection; I think it best to have an electrician move the subs feeder to a smaller breaker perhaps a 30 amp breaker on the main panel. I imagine that is going to add to my cost of updating the other half of the wiring in this house; i.e. the half they didn't do when they did the job the first time.

Silk, there is no telling who installed the meter.
The owner of the Sheds is some type of handyman himself. In a brief conversation with him at the meter yesterday; he mentioned that the meter had been inspected; (by someone). Iíve seen those green stickers many times here in Md. at new residential construction sites. Iíve always associated them with inspections of the plumbers newly installed water laterals.
Apparently there was an undisclosed fire in the house in 95 and the poco had to come out and remove the meter; and I presume the fire marshal had to inspect the repairs. I suspect somewhere within this process; before the meter was reinstalled, is when the sub panels were installed.

TW Lucas 05-08-2008 11:33 AM

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Hi JB,
those outlets do have neutral wires they are just out of focus in the picture.

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