Where is the electricity coming from?!
Hisham Abboud
I hope that someone can help. I'm moving some
switches around as part of our house remodel.
I moved the first 3 switches without any problem.
But now, I moved 2 other switches. With the
switch in the ON position, I can detect 120 volts
where the light will be installed. With the
switch in the OFF position, I detect 50 volts
instead of zero!!
In trying to isolate the problem, I removed the
switch entirely and disconnected everything in
that junction box. The junction box has 2
wires coming into it, one white/neutral and
one black/hot. The metal conduit is used as
ground.
Leaving the junction box is another conduit
containing 2 wires destined for the eventual
light fixture.
Now here's the intriguing part: these 2 wires
are not connected to anything on either end,
nor to each other. If I measure the AC voltage
between the black/hot wire and either of these
2 unconnected light fixture wires, the
voltmeter reads about 50 volts!
I have ran in circles for a few hours now,
searched DejaNews, and read the FAQs. Maybe
I'm missing something obvious, but I cannot
figure it out. Where the heck are those
50 volts coming from?!!
I'd very much appreciate any hints.
Thanks in advance,
Hisham.
Joseph Meehan
measure the voltage? Try a light across the voltage. 50V (if it has normal
amps) should at least glow the bulb. If it does not, it is likely your
tester is too sensitive.
--
Joe M
26 + 6 = 1 It's Irish math
Greenlight
simply disappear when you put a load (light bulb) in the circuit. The house
wire is positioned to pick up stay electricity like a radio antenna.
Joseph Meehan <jme...@columbus.rr.com> wrote in message
news:t2K_4.14638$0T2.2...@typhoon.columbus.rr.com...
Hisham Abboud
On Mon, 05 Jun 2000 09:04:25 GMT, "Joseph Meehan"
<jme...@columbus.rr.com> wrote:
> You could be picking up induction voltage. What are you using to
> measure the voltage? Try a light across the voltage. 50V (if it
> has normal amps) should at least glow the bulb. If it does not, it
> is likely your tester is too sensitive.
It turns out you are right. When I used a light bulb,
it didn't glow when the power was off.
Originally, I used a circuit tester that looks like
a pen. I thought that maybe it's induction voltage
indeed. But then I also used a digital voltmeter
and it read 50V. I am surprised that a voltmeter
(with leads actually touching the wires rather than
a pen that is simply close to the wires) got tripped
by induction voltage.
Live and learn... Thank you VERY MUCH for your
help. I truly appreciate it.
Hisham.
Don Klipstein
: It turns out you are right. When I used a light bulb,
: it didn't glow when the power was off.
:
: Originally, I used a circuit tester that looks like
: a pen. I thought that maybe it's induction voltage
: indeed. But then I also used a digital voltmeter
: and it read 50V. I am surprised that a voltmeter
: (with leads actually touching the wires rather than
: a pen that is simply close to the wires) got tripped
: by induction voltage.
I don't think of it as induction voltage, but capacitively coupled. AC
current can flow through insulators and even air in small quantities this
way, and big long open wires can pick up enough of this to supply several
millionths of an amp, which is enough to give a reading on even analog
meters as well as digital ones. Don't be surprised to get 50 volts at
maybe a goodly fraction of a milliamp from an open wire that is next to
another one that is in use.
- Don Klipstein (d...@misty.com)
Calvin Henry-Cotnam
>
>But now, I moved 2 other switches. With the
>switch in the ON position, I can detect 120 volts
>where the light will be installed. With the
>switch in the OFF position, I detect 50 volts
>instead of zero!!
Are you using a volt meter with a very high impedance?
If so, you will likely see this. Alternating current
can pass through a capacitance, which would effectively
be what exists in an open switch. Such capacitance would
be very low, and therefore the impedance of it would
be very high.
If the impedance of your meter were similar to the
impedance of the capacitance of the open switch, you
could easily measure 50-60 volts with the switch off.
Try measuring the voltage with a small load attached.
--
Calvin Henry-Cotnam | "Nothing quite livens up a suburban
DAXaCK associates | neighbourhood like a driveway boasting
Scarborough, Ontario, Canada | plastic milk crates loaded with crap."
http://home.ica.net/~calvinhc | -- John Oakley, radio talk-show host
----------------------------------------------------------------------------
NOTE: if replying by email, remove the '*' - it's there to block junk email!
Hisham Abboud
Henry-Cotnam) wrote:
>Are you using a volt meter with a very high impedance?
>If so, you will likely see this. Alternating current
>can pass through a capacitance, which would effectively
>be what exists in an open switch. Such capacitance would
>be very low, and therefore the impedance of it would
>be very high.
>
>If the impedance of your meter were similar to the
>impedance of the capacitance of the open switch, you
>could easily measure 50-60 volts with the switch off.
It's probably a very high impedance voltmeter, but
I don't know for sure. It doesn't say, and I
don't have the manual that came with it. I've
had this voltmeter for over 18 years, before
I even came to this country! Before this
week, I've used it almost exclusively in low voltage
applications.
Thanks for the help.
Hisham.