I own a "Circuit Alert" made by GB Instruments. (had it for over 6 years,
has new batteries). These are the probes that you place in the vicinity of
a live circuit and the instrument 'chirps' in response.

I just discovered that it does not detect current, or voltage, when you wave
it around a 240 volt cable. While it 'chirps' happily within 3-4 inches of
a 120 volt wire or cable, it will not do so for 240 volts. Won't detect my
main house service (6 gauge, bundled in sheathing), air conditioning feed
(10 gauge, bundled in sheathing) or any other 240 volt bundled source. Of
course, if you go to the end of the feed and wave the tool near either of
the 120 volt legs, it shows positive.

I'm doing a lot of demolition work around the house and am quite surprised
by the above results. I suppose one leg of the 240 feed is out of phase
with the other and they cancel each other? Any comments.

Be careful our there.

Ivan Vegvary

Subject should have said probe, note porve.

Sorry,

Ivan Vegvary

Ivan Vegvary wrote:

I own a "Circuit Alert" made by GB Instruments. (had it for over 6 years,
has new batteries). These are the probes that you place in the vicinity of
a live circuit and the instrument 'chirps' in response.

(...)
I'm doing a lot of demolition work around the house and am quite surprised
by the above results. I suppose one leg of the 240 feed is out of phase
with the other and they cancel each other? Any comments.

Be careful our there.

Ivan Vegvary

I think that is correct. Phase cancellation, but also proximity to the
ground conductor would limit the electric field in that situation.

http://www.circuitalert.com/pdfs/SDT-3_manual.pdf

Mfr states the only gotcha is conductors shielded by conduit
or equivalent.

I wonder if you can get a reading by repositioning/rotating the
tool near a split phase bundled conductor to pick off the portion
of the electric field that leaks?

--Winston

Yep, noticed the same issue. A probe that goes crazy when working within
a couple feet of knob and tube wiring is sensitive within 6" of a 120 NM
cable but is insensitive to 240 line with no neutral.

Ivan Vegvary wrote:
I own a "Circuit Alert" made by GB Instruments. (had it for over 6 years,
has new batteries). These are the probes that you place in the vicinity of
a live circuit and the instrument 'chirps' in response.

I just discovered that it does not detect current, or voltage, when you wave
it around a 240 volt cable. While it 'chirps' happily within 3-4 inches of
a 120 volt wire or cable, it will not do so for 240 volts. Won't detect my
main house service (6 gauge, bundled in sheathing), air conditioning feed
(10 gauge, bundled in sheathing) or any other 240 volt bundled source. Of
course, if you go to the end of the feed and wave the tool near either of
the 120 volt legs, it shows positive.

I'm doing a lot of demolition work around the house and am quite surprised
by the above results. I suppose one leg of the 240 feed is out of phase
with the other and they cancel each other? Any comments.

Be careful our there.

Ivan Vegvary

In article G1osk.668$Ro1.545@trnddc04,
"Ivan Vegvary" wrote:

I own a "Circuit Alert" made by GB Instruments. (had it for over 6 years,
has new batteries). These are the probes that you place in the vicinity of
a live circuit and the instrument 'chirps' in response.

I just discovered that it does not detect current, or voltage, when you wave
it around a 240 volt cable. While it 'chirps' happily within 3-4 inches of
a 120 volt wire or cable, it will not do so for 240 volts. Won't detect my
main house service (6 gauge, bundled in sheathing), air conditioning feed
(10 gauge, bundled in sheathing) or any other 240 volt bundled source. Of
course, if you go to the end of the feed and wave the tool near either of
the 120 volt legs, it shows positive.

I'm doing a lot of demolition work around the house and am quite surprised
by the above results. I suppose one leg of the 240 feed is out of phase
with the other and they cancel each other? Any comments.

You hit the nail on the head. Typical 240 volt single-phase service has
one wire going positive while the other goes negative, the average
always being zero. The voltage from either wire to ground is 120.

I bet a 3-phase feeder will also escape notice by this circuit alert.

The Circuit Alert gadget sounds dangerous.

Joe Gwinn

In article G1osk.668$Ro1.545@trnddc04,
"Ivan Vegvary" wrote:

I own a "Circuit Alert" made by GB Instruments. (had it for over 6 years,
has new batteries). These are the probes that you place in the vicinity of
a live circuit and the instrument 'chirps' in response.

I just discovered that it does not detect current, or voltage, when you wave
it around a 240 volt cable. While it 'chirps' happily within 3-4 inches of
a 120 volt wire or cable, it will not do so for 240 volts. Won't detect my
main house service (6 gauge, bundled in sheathing), air conditioning feed
(10 gauge, bundled in sheathing) or any other 240 volt bundled source. Of
course, if you go to the end of the feed and wave the tool near either of
the 120 volt legs, it shows positive.

I'm doing a lot of demolition work around the house and am quite surprised
by the above results. I suppose one leg of the 240 feed is out of phase
with the other and they cancel each other? Any comments.

Be careful our there.

Ivan Vegvary

I discovered the same thing with a Greenlee detector while cutting out
some old dead wires. Well, one of them wasn't so dead. 220v worth of
excitement!

--
Jedd Haas - Artist - New Orleans, LA
http://www.gallerytungsten.com

On Mon, 25 Aug 2008 01:37:42 GMT, "Ivan Vegvary"
wrote:

I own a "Circuit Alert" made by GB Instruments. (had it for over 6 years,
has new batteries). These are the probes that you place in the vicinity of
a live circuit and the instrument 'chirps' in response.

I just discovered that it does not detect current, or voltage, when you wave
it around a 240 volt cable. While it 'chirps' happily within 3-4 inches of
a 120 volt wire or cable, it will not do so for 240 volts. Won't detect my
main house service (6 gauge, bundled in sheathing), air conditioning feed
(10 gauge, bundled in sheathing) or any other 240 volt bundled source. Of
course, if you go to the end of the feed and wave the tool near either of
the 120 volt legs, it shows positive.

I'm doing a lot of demolition work around the house and am quite surprised
by the above results. I suppose one leg of the 240 feed is out of phase
with the other and they cancel each other? Any comments.

Be careful our there.

Ivan Vegvary

Odd...my several do read 240/480


"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

On Aug 24, 3:37*pm, "Ivan Vegvary" wrote:
I own a "Circuit Alert" made by GB Instruments. *(had it for over 6 years,
has new batteries). *These are the probes that you place in the vicinity of
a live circuit and the instrument 'chirps' in response.

I just discovered that it does not detect current, or voltage, when you wave
it around a 240 volt cable. *While it 'chirps' happily within 3-4 inches of
a 120 volt wire or cable, it will not do so for 240 volts. *Won't detect my
main house service (6 gauge, bundled in sheathing), air conditioning feed
(10 gauge, bundled in sheathing) or any other 240 volt bundled source. *Of
course, if you go to the end of the feed and wave the tool near either of
the 120 volt legs, it shows positive.

I'm doing a lot of demolition work around the house and am quite surprised
by the above results. *I suppose one leg of the 240 feed is out of phase
with the other and they cancel each other? *Any comments.

Be careful our there.

Ivan Vegvary

I'm going to have to check mine.
Thanks for the heads up.
Karl