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#45775 - 09/22/03 07:37 AM 60 Volts across Switch wires?????
Jack2002 Offline
first timer

Registered: 10/30/02
Posts: 11
Loc: FL
Ran new 15 amp circuit for new kitchen lights then and at a junction box in the attic, tied together all white and ground wires and then ran appropriate wires to the switch box in wall.
With the power on, took a reading on the white and black wire for the light switch and got 60 volts. Also got reading of 120 volts across the white and ground wire, and no voltage across the ground and black wire.
However as soon as I tie together the white and black wires (representing a closed switch) and take a reading at the end of the white and black wires where I am going to have a recpetacle for the light - everything is fine. I get 120 volts across the white and black wire, and 120 volts across the black and ground wire, and no volts across the white and ground wire.
I also checked an existing wall switch that comes after the light on that particular run, and it too has about 40 volts across the black & white wire, when no load or light is attached at the end.
I asked a local electrician and he said that since our panel box is really old (25-30 years - Sylvania) they are known for a bleeding effect, and that is why I'm getting that 60 volt reading, but it was OK.
Does this make sense?

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#45776 - 09/22/03 07:40 AM Re: 60 Volts across Switch wires?????
ernietempleton Offline
Denis B

Registered: 06/15/03
Posts: 964
hi

We get these sorts of readings either due to wiring errors wiring loads in series that divides up the voltage.

THIS OFTEN HAPPENS WHEN WE MISTAKINGLY WIRE INTO A SWITCH LOOP--up in the attic ------- where the white is NOT a neutrall!!

Or what is called phantom or ghost voltages that is really no useful voltage at all,and is isiully from using digital meters AND THE CIRCUIT IS open .

This is the only type tester that is acceptable for solid circuit testing.
http://www.mytoolstore.com/klein/69115.html
It is a SOLENOID type tester and is made by several companies.
Digital and analog meters are really for electronic projects and low voltage trouble shooting .

120v and 240v are "LINE VOLTAGES"



ernie
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#45777 - 09/22/03 07:47 AM Re: 60 Volts across Switch wires?????
Arnold Offline
Helpful Electrician

Registered: 07/09/02
Posts: 5000
Loc: United States
I think most DIYers would be better off if they didn't own a voltmeter at all, but merely had one of those $2 neon circuit testers. Voltmeters too often lead people on a wild goose chase of a phantom problem. The only really useful thing I see with a voltmeter in residential wiring is to tell the difference between 120 and 240 volts.

"bleeding effect"??? Give me a break. That electrician was either nuts, or there was some serious communication breakdown between you two.
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_____________________________________________ Start every day off with a smile and get it over with

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#45778 - 09/22/03 08:38 AM Re: 60 Volts across Switch wires?????
ernietempleton Offline
Denis B

Registered: 06/15/03
Posts: 964
In reply to:

I asked a local electrician and he said that since our panel box is really old (25-30 years - Sylvania) they are known for a bleeding effect, and that is why I'm getting that 60 volt reading, but it was OK.
Does this make sense?





Some so-called electricians are only handymen and have limited exposure to practical theory.

Others will also try and put things in 'laymans terms' to be helpful,and this is valid.

But this particular project indicates an issue ----AWAY---- from the panel.

Panels are usually innocent of any bad reputation when it comes to 'bleeding'.

'Bleeding', can mean
a fault leakage to ground or another wire.

Capactive coupling to another wire or ground.
Inductive coupling to another wire or ground.

Or just about anywhere that the current is not supposed to go.

There is little opportunity for any of these in most panels.
Bleeding sounds like advice from someone where you did not pay.

Was this a opinion over the telephone?
Were they in a hurry?

When paying for a repair or advice ,dont accept something so simple!
----in laymans terms.


P.S.

A loose connection somewhere in a circuit will have the same effect as wiring loads in SERIES and will cause a reduced reading at both the loose connection and at the load, when the load is connected and switch is on and the circuit is HOT.

Loose does not mean totally OPEN!--and it can mean corroded.

Never forget that a circuit that has a loose connection [or corroded] will ALWAYS read a good circuit voltage ,like 120v for example, across the load connection,with the load,like a light bulb removed and laying on the table.
This is called 'OPEN CIRCUIT' voltage and is always true.

Screw the bulb back in and you will read lower voltage across the load leads [screws] --- if ----you have a problem like ,a loose lumped high resistance connection or lots of distributed voltage drop along the length of a long circuit.


Draw it out on paper and let a resistor symbolize the loose connection and also the load in series and see how the voltage will divy up among the resistances ..that are now really loads. ..in series !!!

ernie
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#45779 - 09/22/03 09:24 AM Re: 60 Volts across Switch wires?????
ernietempleton Offline
Denis B

Registered: 06/15/03
Posts: 964
to be helpful:

http://www.physics.uoguelph.ca/tutorials/ohm/Q.ohm.intro.series.html
let the battery mean 120v AC

more:
http://farside.ph.utexas.edu/~rfitzp/teaching/302l/lectures/node44.html

http://www.physics.isu.edu/physdemos/electric/seripara.htm


this last one demonstrates the affect of wiring 3 lamps of equal wattage, in series and all 3 will have 120v divided by 3 across them ..[40v?]

Just think of one or two of them as a loose connection or corrosion or load in series!
The sum of all the voltages across loose connections and loads will always equal the source voltage 120v.

Remove any one of these lights amd read across its terminals will read 120v!

http://www.physics.montana.edu/demonstrations/video/e&m/demos/seriesparallellightbulbs.html


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