Help! Strange voltages on old wire lighting circuit

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Jon456

Senior Member
Location
Colorado
The new owners of an estate need me to solve some electrical problems in their old wiring. Actually, most of the wiring problems seem to be in wiring that is only about 10 years old (previous owners had major renovations done to the property). Even though this is a multi-million dollar estate (and the previous owners were VERY VERY rich), the old electrical work I'm uncovering is very shoddy (which just goes to show that even when you pay a lot, you don't always get quality work). Examples of the problems I'm uncovering: white travellers not marked as hot, missing ground wires, wires breaking from fatigue due to over-stuffing a box, using un-tied (and non-adjacent) single-pole circuit breakers to feed 220VAC, badly corroded outdoor switches (behind wet location switch plates), etc. In addition to fixing problems, part of my job is to try to figure out just what some of the switches control (mystery circuits).

One problem I've found is that a lighting circuit has strange low voltages on the wires, even after the circuit breaker (subpanel in a utility room off the garage) to that branch has been shut off. It's a 3-way circuit for a hanging light in the veranda; one switch is in the living room and the other switch is in a hallway. The circuit begins in the living room where a hot 12-2 NM enters the box. The hot is spliced to the black wire of a 12-3 NM cable to the hallway box. In the hallway box, the 12-3 NM black is connected to the common terminal of a 3-way switch, and the red & white are the travelers back to the 3-way switch in the living room box. Connected to the common terminal of the living room 3-way switch is the black wire of a 12-2 NM to the fixture. When the branch is energized, the switches and light operate as expected.

If I disconnect the black wire of the 12-3 NM cable from the hot in the living room box, and I disconnect the wires from the terminals on the 3-way switches, I am still reading voltages on the individual wires of the 12-3 NM cable. This is what I'm measuring with all the wires disconnected at both ends in the living room and hallway boxes:

Branch circuit breaker #28 turned OFF
------------------------------------
12-2 NM Black wire (hot in living room box): 18.6 VAC

12-3 NM Black wire (from hot to hall common): 1.75 VAC
12-3 NM Red wire (traveler from hall switch to living room switch): 1.17 VAC
12-3 NM White wire (traveler from hall switch to living room switch): 1.28 VAC

12-2 NM Black wire (to veranda light fixture): 0 VAC
============================



Branch circuit breaker #28 turned ON
-----------------------------------
12-2 NM Black wire (hot in living room box): 122 VAC

12-3 NM Black wire (from hot to hall common): 2.1 VAC
12-3 NM Red wire (traveler from hall switch to living room switch): 1.4 VAC
12-3 NM White wire (traveler from hall switch to living room switch): 1.5 VAC

12-2 NM Black wire (to veranda light fixture): 0 VAC
============================

I measured these voltages (using a Fluke multimeter) multiple times at both ends of the wires, with the circuit breaker off and on. The voltage readings were consistant every time, so I'm confident that the readings listed above are accurate.

Another puzzler is a second 3-way switch in the same hallway box (which, by the way, is right next to a door to the veranda). That switch is fed from a circuit breaker from the main panel in the exercise room. So far, I have not been able to locate the "mating" 3-way switch for this circuit, nor have I been able to discover what this 3-way switch controls. But it too has strange voltages on it's wiring. For this switch, there is only a 12-3 NM cable entering the box with the white wire on the switch common terminal, and the red and black on the traveler terminals. Again, I disconnected all the wires from the switch terminals for the voltage measurements. This is what i found:

Branch circuit breaker #15 turned OFF
------------------------------------
12-3 NM White wire (common terminal): 0 VAC
12-3 NM Black wire (traveler terminal): 0.69 VAC
12-3 NM Red wire (traveler terminal): 0.73 VAC
============================

Branch circuit breaker #15 turned ON
------------------------------------
12-3 NM White wire (common terminal): 122 VAC
12-3 NM Black wire (traveler terminal): 38.9 VAC
12-3 NM Red wire (traveler terminal): 32.6 VAC
============================


Any ideas on any of this?
 

walkerj

Senior Member
Location
Baton Rouge
All day long;)

Try this:

Use your 'wiggy' and your digital tester at the same time on the wires.

The 'wiggy' should read nothing and the digital will read ~0.
 

Jon456

Senior Member
Location
Colorado
Ok thanks. Now I still need to figure out where the mating 3-way switch is for that second circuit. And what it's supposed to be controlling.

Another oddity: not far outside from the hallway door to the veranda, is a piece of 1/2" PVC conduit is protruding about 8" from the soil of the garden. just coming out from the open end of the conduit is the end of an extension cord (with the original factory-molded 3-prong female receptical... face-up to catch the rain of course). I haven't found any voltages on that yet; maybe it was intended for low-voltage Christmas lights. But it's disturbing nonetheless.
 

glene77is

Senior Member
Location
Memphis, TN
Another oddity:

Jon,
Please put a FS box on the conduit and tape it closed.

Makes me tingle all over
just thinking about someone touching it. :)

I have a AT4000 which will allow me to trace it back to the other end
for both dead and live circuits.
For years I used a data-comm toner & receiver for this purpose
(provided the line is truly dead).
These methods are something you might look into.
:)
 

growler

Senior Member
Location
Atlanta,GA
The new owners of an estate need me to solve some electrical problems in their old wiring.
Any ideas on any of this?


Stay there and trouble-shoot and do repairs as long as they are willing to pay.

A lot of older homes need lots of repairs ( it happens ).

Keep a list of what you find and any repairs made and also of any repairs that they may not want you to do.
 

JdoubleU

Senior Member
All day long;)

Try this:

Use your 'wiggy' and your digital tester at the same time on the wires.

The 'wiggy' should read nothing and the digital will read ~0.

Is the wiggy a glow stick? If so how does it cancel out the 18 volt reading?
 

hurk27

Senior Member
I agree with all the above on the phantom voltage, but as for the 3-ways, remember it was and still is common to have outside lights switched from multiple places in the home so if a noise is heard they can switch on these outside lights from just about anywhere, now after a few years maybe the lights were eliminated and sided over? either way, investment in a good circuit tracer is a good choice for this types of service calls, just remember you get what you pay for, I have a couple Green Lee ones that I cant live without, but there are other less costly ones out there. get the right tools and jobs like this are a breeze.
 

hurk27

Senior Member
Is the wiggy a glow stick? If so how does it cancel out the 18 volt reading?

A wiggy, is a brand name for a Square D solenoid type voltage tester, IDEAL calls there one a VOLT-CON, which also has a continuity tester built in, so the later is what I use, these tester have a solenoid coil that loads the circuit at the same time it is measuring the voltage, there are now DVM's that have this feature and can do other functions also, some even also allow the loading part to be turned off, to take regular high impedance measurements, but the price goes up for these and you can get a VOLT-CON for less then $40.00 at the big box stores.
 

glene77is

Senior Member
Location
Memphis, TN
A wiggy, is a brand name for a Square D solenoid type voltage tester,

Hurk,

My selenoid tester has a 4K Ohm coil, passes about 40mA,
which draws down the usual phantom voltage.
(It is in the van, an old off-brand)
Measure yours sometime, for comparison.

I took one of my little 3 pin neon bulb plug-in testers and cross-loaded the poles in a similar fashion with a resistor so that it draws current and pulls down the phantom voltage. Works better.

I still like making things. :)
 
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glene77is

Senior Member
Location
Memphis, TN
My dad was old school. He never really trusted the DMM's. Always prefered a good ole Simpson 260. I keep one with me, along with my Fluke 87.

My old Simpson had a 50,000 Ohm system.
That pulled 2.5mA, and still tried to display phantom voltage sometimes.
Phantom voltage varies, depending on the coupling between the cables.
I have read as high as 105 VAC in an old dwelling with 40's Romex cables.

There were different Simpson models with different sensitivities.
I don't think any of them got up to 1 MegOhm or 10 MegOhm
like the high impedance digital ones nowadays.

You might do well to see if your Simpson
actually draws down some phantom voltage.
A little comparison test would do it.

Perhaps a 'wiggy' thing would be a good addition to your tools.

I used to carry a 100Watt light bulbs in a festoon socket (with leads),
but the glass bulb kept breaking. :)
So, I started using the 'wiggy' thing with the 4000 Ohm load
and by comarison tests I find it works very well, just pulling 3.5 mA.
 
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