Household Wiring Question

NutBucket

Lifer
Aug 30, 2000
27,033
545
126
Alright, I'm adding another circuit specifically for my room for all my computer sh*t. Anyway, our house is circa 1940 and still has the original wiring. It only has two conductors going to each outlet; no dedicated ground. Also, we only have two-phase power; we don't need 240 for anything. So here's the thing. I'm trying to figure out what to do about grounding this circuit I'm installing. I looked at this wiring guide and it seems to me that the neutral(white) cable is connected to the same grounding point as the bare wire would be (dealking with romex). Since this is the case, why bother running two ground cables back to the same point? Am I really missing something here?
 

miniMUNCH

Diamond Member
Nov 16, 2000
4,159
0
0
Based on what you said in your post, think for your future and call a contractor...

Your house is not 2-phase. The feed to your house is probably 3 single phase feeds split off from a high power 3-phase transformer...the 3 single phase feeds are split off into different circuits of the house.

Term 'neutral' in electrical terminology is a dangerous misnomer...the neutral is hot (that is an entirely UNGROUNDED side to your circuit).

If you want a good wake up call, wire your "neutral" and your new "ground" together and grab a hold, I hope you don't lose an arm or anything.

Your neutral bus is not connected to your ground bus...it would completely screw up every piece of electronics in your house.

For routine grounding practices in residential housing, you can screw the ground wire to the junction box but it is better to run all the way back to the panel.

The best reference for electrical practice is NEC2002 (national electrical code 2002).


<---- control system engineer (does a lot of electrical)


 

Ly2n

Senior member
Dec 26, 2001
345
0
0
When dealing with romex wire ( 2 wires w/ ground) the white wire and the bare (ground) wire do indeed go to the same junction strip. It is suggested that you put them under different screws in case one of them comes loose. The junction strip is connected to the electrical ground and, usually earth ground. I have done some professional house wireing in the past, and this is what any inspector would be looking for. Lynn
 

NutBucket

Lifer
Aug 30, 2000
27,033
545
126
Well, I know for a fact that I only have two phase power going into the house. Here's a pic of the power line connection from the lines running from the pole to the lines running into the breaker box. Here's another pic of the main breaker box (I told you it was original). Its a little hard to see but you can see the white (neutral) wire running down the left side of the breaker and to the bottom of the fuse block where it is screwed to a 3 screw terminal, on the left lug. On the center lug another neutral wire runs down to the distribution panel(top is visible). On the right side another white wire is attached that not only runs into a conduit exiting the bottom left corner but is also screwed to a hardpoint where the conduit is secured to the box. Based on the fact that there is a bare wire coming off the pole and that the neutral white wire is connected to the electical boxes (this was done by a licensed elecritian years ago) and what the diagram in the pdf I linked to originally shows, for a pure 120V 2-phase setup like I've got, the ground and neutral are the same.
 

NutBucket

Lifer
Aug 30, 2000
27,033
545
126
Originally posted by: Ly2n
When dealing with romex wire ( 2 wires w/ ground) the white wire and the bare (ground) wire do indeed go to the same junction strip. It is suggested that you put them under different screws in case one of them comes loose. The junction strip is connected to the electrical ground and, usually earth ground. I have done some professional house wireing in the past, and this is what any inspector would be looking for. Lynn

That's exactly what I thought. Though, I posted above just to clarify to minimunch that I am referring to them as the same since I only have 2-phases coming into my house.
 

Squisher

Lifer
Aug 17, 2000
21,207
66
91

You do have a single phase electrical supply, but you presenty have a two wire setup. These are very different.

Yes, the both connectors are screwed to the same grounding bus(es) in the main breaker box. This would not be so in any sub boxes.

Picking up an electrical do-it-yourself book is highly recommended.

I also recommend the alt.home.repair newsgroup. Those people have helped me through many difficult wiring setups.



 

jobert

Senior member
Nov 20, 1999
714
0
0
They both eventually go to ground. (The same ground.)
The bare wire is intended to prevent your case
or any other metal object from shocking you...
if the case accidentally becomes "hot" the electrical
charge goes to ground (and blows your fuse)
instead of traveling through your body to ground.

The white (neutral) wire is kinda hot when current
is flowing. 'Never could understand why current
doesn't come back through the bare wire.
Must be because the electrical panel provides
a much better path to ground?
 

jobert

Senior member
Nov 20, 1999
714
0
0
Oops. What happened to the edit function on this board?

From the picture of your roof, it would seem that the third
wire is sitting up there, not brought in to your panel.
(But you only really need it for 240 volt circuits.)
You can get a decent 100 amp breaker panel for 100 bucks.
But even with a "real" panel, you will find that the white wire
and the bare (ground) wire end up at the same place on the panel.

 

Ornery

Lifer
Oct 9, 1999
20,022
17
81
Ground Fault Circuit Interrupter
  • In accordance with NEC Article 210-7(d), a GFCI receptacle may be used to replace an existing non-grounding 2-wire receptacle. In addition, existing non-grounding 2-wire receptacles may be replaced with grounding-type receptacles when they are supplied through a GFCI receptacle. (In this case, however, a grounding conductor should not be connected between the GFCI receptacle and those receptacles that it supplies).
 

Kwatt

Golden Member
Jan 3, 2000
1,602
12
81
Neutral is a Grounded conductor. It is the return path of the electrical circuit. It also carries the unbalanced load in a 2 or 3 phase circuit. Code requires a white or gray insulation.

Ground is a Grounding couductor. It is for safely carring a short current to ground. Code requires a green insulation or a bare conductor.

They both do tie to the same point in a panel. That is the only place they should be landed together.

Using either for both can lead to annoying interference to electrical devices.
Or to an even more annoying fire in your house. Usually while your asleep.

For a circuit for a computer I use an Isolated Ground that is a ground that is not sharred with any other device or outlet.



You have a single phase service in your house.(only very rarely does a house have a 3 phase service and then only a really,really,really big house. it is very expensive)

A single phase service has 2 hot phases and a netural.
A three phase service has 3 hot phases and a netural.

The ground is provided at the panel by driving ground rods or connecting to the cold water plumbing system.

Note:connecting to the cold water plumbing system is not usually used or approved for use any longer because modern plumbing is plastic pipe.(it is a poor conductor:))


Kwatt

Edit: After looking at the pics it appears you only have 1 phase and a netural coming into your house.
 

amdskip

Lifer
Jan 6, 2001
22,530
13
81
I would highly recommend replacing that main breaker box and just doing a general upgrade of your whole electrical system. It's not cheap but if you just replace the main breaker box and just hook up the existing wiring and then add your new curcuit, it shouldn't be too bad and it's a lot cheaper than having to replace your home due to an electrical fire. You can always upgrade the rest of the wiring when you get more time and funds.
 

NutBucket

Lifer
Aug 30, 2000
27,033
545
126
Ok, that makes more sense (the difference between the neutral and ground). Never did quite understand it. Yeah, I know the house needs work. It needs to be rewired yada yada. Truth is, the wiring in the walls is fine, the insulation is in tact. I actually just mentioned to my dad just replacing the panel. His always goes by don't fix what isn't broke (don't have to quote it that way:p). I believe all the wiring is 10 guage and we only have 15 amp breakers installed when I suppose I can safely use 20.

But really, I knew I wasn't nuts when I saw that diagram and stated what I did. I didn't realize that one could use a GFCI in place of a seperate ground. I think I'll have to replace a few outlets around the house now, just to be safe.

Note:connecting to the cold water plumbing system is not usually used or approved for use any longer because modern plumbing is plastic pipe.
No problem there, still have galvanized/copper supply lines.

 

NutBucket

Lifer
Aug 30, 2000
27,033
545
126
And just to make sure. So since I'm wiring in a new circuit back to the panel, it would be acceptable to connect the ground wire to the panel, right?
 

Kwatt

Golden Member
Jan 3, 2000
1,602
12
81

----------------------------------------------------------------------
And just to make sure. So since I'm wiring in a new circuit back to the panel, it would be acceptable to connect the ground wire to the panel, right?
----------------------------------------------------------------------


If you have a bare wire in the panel that should be your panel ground.
You should connect your new circuit ground to the same terminal block as the panel ground.
Try to connect it without lifting or even loseing the panel ground.
If you have any fluorescent ballest type lighting in the house they could be leaking and you could recieve a shock!

What you are doing is dangerous!
People are injured and killed almost every day doing electrical work.

Is there anyone you know that can safely do the connections for you?
If not call an electrical contractor.
I know it can be expensive but the charge for the 1 day I spent in the hospital emergency room last year was $1600.00.My Insurance paid 90% but I would rather have paid someone the $160.00 and stayed at home.:D(and no it wasn't electrical related:))


Kwatt



 

NutBucket

Lifer
Aug 30, 2000
27,033
545
126
I rewired our garage. No problem with that. I've done stuff like this, adding lights w/ wall switches etc. I'm just making sure I'm gonna be making the right connections with this project. The most aggravating part so far is getting the wire into the wall I'm adding outlets. That damned wall just had to be directly on top of one of the floor joists.

Besides, I'm an EE major and as part of my engineer training I have to start doing all repairs/projects w/o hiring anyone;)
 

jobert

Senior member
Nov 20, 1999
714
0
0
>>I didn't realize that one could use a GFCI in place of a seperate ground. <<

Whoa. Hold it. Stop.

EVERY GFCI outlet in the world uses the bare ground wire.
There is NO change in the way you wire your house
when you add a GFCI protected circuit.
You just get added protection from stray current
running through you (or something else) to ground.

 

Ornery

Lifer
Oct 9, 1999
20,022
17
81
If he's running a whole new circuit, he might as well use 12/2 with ground. If he wants to make due with an existing circuit, he could use the GFCI with the existing wiring per NEC Article 210-7(d):
  • ...a GFCI receptacle may be used to replace an existing non-grounding 2-wire receptacle. In addition, existing non-grounding 2-wire receptacles may be replaced with grounding-type receptacles when they are supplied through a GFCI receptacle. (In this case, however, a grounding conductor should not be connected between the GFCI receptacle and those receptacles that it supplies).
If the wiring is that old, there's a good chance it's already carrying more power than it was designed for. One outlet for a PC won't tax it too bad, but any more than that would probably call for a higher rated service. When you go that route, you'll probably want to upgrade the whole house.
 

NutBucket

Lifer
Aug 30, 2000
27,033
545
126
Originally posted by: jobert
>>I didn't realize that one could use a GFCI in place of a seperate ground. <<

Whoa. Hold it. Stop.

EVERY GFCI outlet in the world uses the bare ground wire.
There is NO change in the way you wire your house
when you add a GFCI protected circuit.
You just get added protection from stray current
running through you (or something else) to ground.

I meant instead of running grounds to existing outlets. If I'm doing new wiring why would I not use the included ground in the romex?

All the wiring in the house is actually 14 or possibly 12 guage I believe. All the circuits have 15 amp breakers on them and we've tripped one maybe once in the last 2 or 3 years. We're definitely not taxing the wiring. I just have so much junk with cords on it that I wanted to add another circuit, properly grounded, for my own piece of mind.