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E Z Peaces

wrote:
On Fri, 07 Nov 2008 23:10:33 -0500, E Z Peaces
wrote:

E Z Peaces wrote:
Smitty Two wrote:
So the g.f. and I are chipping in on a newly remodeled investment
house in her city, 300 miles from me. Home inspector sent a report
that included a notation that the outlet intended for the refrigerator
is giving an odd indication on the 3-LED tester: All three lights
illuminate.
Any speculation on what could cause this unlisted and presumably
improbable test result?
Each terminal of an outlet can be hot, open, or grounded. That makes 27
possible combinations.

With the tester I know you don't get all three lights unless the hot
terminal is grounded and neither other terminal is grounded. Both the
neutral and ground may be hot, or one may be open.
In order to detect each of 27 possibilities, this kind of tester uses
capacitive coupling to the person's hand as a ground reference. If the
person's hand is at or near line voltage, a properly wired outlet will
show three lights.

I wonder if the inspector was picking up leakage from something he was
touching, such as the refrigerator. If he was insulted from ground he
wouldn't feel it. The impedance may be to high to be hazardous.

Neon or LED tester? The old neon testers could do this - but the led
testers are NOT capacitively linked and can not display this anomoly.
Don't think the neon 3 lamp tester has been sold in Canada or the USA
in the last 10 or more years.

The one I have in mind was made by Communications Technology Corporation
in the 1970s. CTC still has offices in several cities, so their tester
may still be on the market. Richard R. Spear, who passed away this
year, invented it.

The lights are two neon lamps (white and amber) and a red LED. The
tester also uses a momentary switch, a relay, a transformer, a circuit
breaker, and lots of diodes. It uses a power cord.

If an outlet is wired properly, you get red and white when you plug in
the cord and white alone when you press the button. A buzzer will tell
you if impedance at the ground terminal is above a set threshold.

In each of 12 possible faults where hot and ground are present, the
pattern of lights will tell you what's what. That makes 13 situations
the lights can identify.

With 120VAC, a simpler tester's lights can show only 6 possibilities.
That could be deadly if for example the hot terminal were grounded and
the other two were hot. The simpler tester would say it was okay.

With 120VAC, there are 14 possible faults where a hot and a ground won't
be present. Neither kind of tester will show any lights, so neither
will specify what's wrong.