1950 wiring mess!

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  #1  
Old 10-03-01, 05:27 AM
Todd B
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Sorry this is so long... I wanted to be thorough

First a little background info>:

I just bought a home that was built in 1950. I have been upgrading the wiring a little at a time. I have been making good progress but I keep running into some strange wiring techniques in the house. I guess this comes with 1950 wiring design right? So far I have replaced the SEC (upgraded from what looked to be maybe a #6 to 4-0), relocated the meter to the outside of the house (where it should be!), replaced the fuse box with a 30 space breaker box and had the energy company upgrade the service from 60AMP to 200AMP.

Now for the latest discovery>:

I was inspecting the wiring in the garage last night and discovered that they had wired it like this:

- they tapped an outlet in a bedroom to supply energy to a pull string light in the attic above the garage.

- from the pull string light in the attic they tapped a wire for another light for the garage. In this light there is a wire going to a 2 gang box on the garage wall. In this box are two switches, one controls the garage light.

Here is where it gets weird -

PROBLEM #1:
From what I can tell, they used the power on this switch loop to wire a light on the outside of the garage. The neutral for this light is connected right to the metal gang box! This box is in a cinder block wall, it is not connected to any conduit and this circuit also doesn't have a ground. I can barely see what appears to be a bare copper wire also connected to the box. A couple of weeks ago, I was rewiring the parts of the house that are accessable via the basement. I noticed that they had bonded all of the boxes in the kitchen to the plumbing below! I guess they were trying to provide a ground? When I replaced all of this wiring, I made it a point to cut out all of these connections as it is unsafe and not to code. In addition to this mess by the kitchen I found one other wire just like this... guess where? ... right next to the garage wall, just below the gang box. It sounds like they were using the plumbing as a neutral path! This is not good right? Well, I also cut out this connection a couple weeks ago and it was about this time (I am just realizing this now) that the light stopped working! At the time I thought the bulb just burned out! But I guess it actually went out because I unknowingly cut the neutral.

PROBLEM#2:
On the other side of this 2 gang box is a three way switch that picks up power from the same circuit and the two other wires go to the other 3 way switch by my front door that controls the outside light by the front door. the lights are connected to a neutral on a completely different circuit! Is this bad? I am pretty sure it is not good but I don't understand WHY?

ONE MORE THING:
I have measured about 75 volts on various light circuits in the house when the switch is off and 120 when it is on. Any ideas on this? shouldn't there be 0 volts? when the switch is off?

Once again sorry for a long post, hopefully someone out there is just as bored as me to read this! I have been reading this board for a few months but this is my first post, hello everyone.

Thanks,
Todd.
 
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  #2  
Old 10-03-01, 06:14 AM
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Problem #1 comes about because they tapped power from a switch loop. Since a switch loop has no neutral, they were forced to use the grounding connection as the neutral. This is pretty dumb and should be corrected. The correction is pretty simple -- just run a new neutral wire from the garage light to the switch box.

As you say, using plumbing for a grounding connection isn't a particulary wise idea. And since they used the grounding connection as a neutral, the idea got considerably dumber. Apply the simple correction I noted above.

Problem #2 is pretty strange. But my guess is that this wire that looks like a neutral probably also uses the plumbing as the return path. You should understand where these wires come from before adding a new neutral. Don't use the same new neutral from above unless you're sure that the power is on the same circuit.

My recommendation on the 75 watt thing is to forget it. Induced voltages will lead you on a wild goose chase.
 
  #3  
Old 10-03-01, 07:08 AM
Todd B
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First of all, thanks for your response.

Problem #1:
I know this is wrong and I know how to correct it... What I want to know is what are the consequences of someone choosing to wire like this. What could have happened? Could this have put voltage on my plumbing? Unfortunatley, the person who made the mistake probably smiled and said "lights working!"... and yes, the light did work, probably for decades. But I am curious as to what potentially could have happened. What problems does this wiring technique present?

PROBLEM #2:
The neutral is a #12 all the way to the panel.
What I am wondering is, the positive and neutral are on seperate circuits... how bad is this, what problems can it cause? Sure, the lights work but what is happening here, why the concern... is it just a simple matter of not overloading the neutral?

Any chance you could explain induced voltages a little more? Is my meter actually picking up voltage on the neutral? sounds like this is a common thing...

Thanks again for your help.
 
  #4  
Old 10-03-01, 08:47 AM
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Consequences of stray neutral currents.

Originally posted by Todd B
First of all, thanks for your response.

Problem #1:
I know this is wrong and I know how to correct it... What I want to know is what are the consequences of someone choosing to wire like this. What could have happened? Could this have put voltage on my plumbing? Unfortunatley, the person who made the mistake probably smiled and said "lights working!"... and yes, the light did work, probably for decades. But I am curious as to what potentially could have happened. What problems does this wiring technique present?
If the light were on and plumbing work were undertaken the person working on the plumbing could be killed when the piping was disconnected. The voltage on the part of the piping still connected to one terminal of the fixture would rise to the circuit voltage of 120 volts. When the plumber tried to separate or align the piping with one hand on each part of the plumbing he/she would have had 120 volts across their chest cavity. Since the current would only be limited by the light bulb serious injury or death could ensue. A 60 amp bulb will flow 50 miliamperes. It only takes ten miliampers to kill.

PROBLEM #2:
The neutral is a #12 all the way to the panel.
What I am wondering is, the positive and neutral are on seperate circuits... how bad is this, what problems can it cause? Sure, the lights work but what is happening here, why the concern... is it just a simple matter of not overloading the neutral?

Any chance you could explain induced voltages a little more? Is my meter actually picking up voltage on the neutral? sounds like this is a common thing...

Thanks again for your help.
In AC circuits when a balanced circuit, with all the current flowing through the same raceway or cable, passes through or past a metallic object the currents induced into the metallic object are self canceling. If only one conductor of the circuit passes through a metallic object then an induced current is generated and the metallic object will heat. How much heating will occur is the result of too many factors to enumerate hear but under the wrong circumstances the heating can cause changes in combustibles that will lead to ignition. The induced current can also cause arcing between the object in which it is induced and other nearby metallic objects. Under the wrong circumstances this arcing may generate enough heat to ignite adjacent combustibles.

Additionally the presence of a back fed neutral in the one circuit could subject anyone working on that circuit to the same risk as the plumber in example number one.

By changing only the connections and without running new cable you can have the outside garage light come on and off with the front porch light and leave the other switch in the garage to control the interior light. I am guessing that there are only two insulated conductors between the garage box and the front porch box.
--
Tom
 
  #5  
Old 10-03-01, 09:49 AM
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Slight correction, and I don't even know why I'm making it, but I guess I don't have enough to do today.
A 60 amp bulb will flow 50 miliamperes.
Make that 500 milliamps.
 
  #6  
Old 10-03-01, 11:04 AM
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Todd,

A couple thoughts. First of all, today's NEC forbids grounding to any plumbing in your house EXCEPT within 5 feet from the water main's point of entrance to the building, ans should always be on the street side of the meter unless the meter has a #6 copper jumper across it. Yes you can introduce current onto your plumbing, and John Nelson's example of a plumber separating the pipes is an excellent one. Among the other things that could happen happened to me when I bought my wiring mess. I happened to turn on my bathroom sink faucet and open the (lighted) metallic medicine cabinet simultaneously and got sufficiently juiced. The idiot before me did as the idiot before you did.

It sounds like you're more knowledgeable in general wiring than the average bear, and more willing than many to attack some of these issues. And it sounds like you have a fine sense of doing the responsible thing. My advice is usually to replace botched wiring with a whole new run where possible. And the first skill you need in an older house that has serious wiring boo-boos is drywall repair. That's right, I said drywall repair.

When I bought my house I discovered nightmares in wiring. All over the house. The previous owner had no idea about safe wiring, let alone codes, but had a million "clever" remodeling ideas that involved funky lighting and adding receptacles. I reckon his attitude was if he flipped the switch and the light went on it must be done correctly.

Fortunately for me, he also ruined many of the walls, ripping out the plaster & lathe and installing firring strips badly with cheap paneling over it. I have very good drywall skills, and knowing the walls need replacing anyway I routinely cut holes in the them when rewiring with no fear or regret. I'm simply not afraid of making a mess. Many folks live in houses with bad or botched wiring but have nice walls, which is a major stumbling block to upgrading circuits.

Two things I'd recommend if you're going to keep at this electrical stuff: Get a multimeter if you don't already have one. Don't rely on those little handy testers, they don't give enough info or have a wide range of testing capabilities. Home Depot sells an analogue multimeter by A.W.Sperry, a top name in instruments, for $9.94, model SP-5A. This little meter will do dang near anything you need it to. For $29.93 they sell a Sperry "Pocket Pro" DMZA. The digitals are nice, easier to read, do everything you'll need in home wiring, and they are even great at testing AA, C, D, 9V and other batteries to 3 decimal places.

The second thing is pick up a wiring book. I'm not a hege fan of Sunset Books, found at the Depot and many other home centers, but they do publish a decent a couple of home wiring books: "Basic Home Wiring", $11.65, and "Complete Home Wiring", $17.95. There are illustrations and instructions which make some of these techniques pretty straight-forward to do.

So, keep up the mission and good luck. You'll get there. And we'll be around when you run into a snag.

Juice
 
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