A little diddy I wrote a few years ago. The inspector refused to final a retirement home due th phantom/ghost voltages.
From a letter I wrote.
SUBJECT: Voltage Anomalies Phantom/Ghost Voltages
Job No. 6880
Dear Mr.:
On February 6, 2009 technicians from Mid-Atlantic Power Specialist were called to the above reference project to investigate possible stray voltage issues. In discussions with Colonial Electrical personnel it was determined the possible stray voltage issues were occurring with 120 VAC 15 amp switched receptacles. These receptacles are fed with a 14-3 with an equipment ground conductor NM cable. The only time there is an issue of concern is when the three way switch controlling the top Unit and were checked for this possible
stray voltage issue. This issue was first noted per Colonial Electric personnel when the Prince Georges County electrical inspector (Authority Having Jurisdiction- AHJ) was performing an inspection of the receptacles in the individual units.
Voltage reading were taken on the receptacles with the top (switched portion) on and off, nominal voltages were noted with the receptacle energized (top and bottom). With only the bottom of the receptacle energized and the top half off from the 3-way switches voltage readings were noted in the 42 VAC - 84 VAC range.
These readings were verified with a calibrated Fluke 187 True RMS Multimeter, a Fluke 435 Power Quality Analyzer and a Simpson Model 260 (analog meter). In addition an Ideal 61-501 Receptacle tester was utilized to try and achieve the anomaly that brought this issue to the attention of the AHJ. With the Ideal 61-501 inserted in the outlet the center light dimly lights. When a Wiggy style tester (solenoid tester) is utilized there is no indication of voltage and the neon light (if present) does not illuminate. In this instance a Knopp k60 solenoid tester was utilized.
Voltage Anomalies
Page II
During these test with the Ideal 61-501 center light dimly illuminated a 12 VDC resistive element lamp was connected to the receptacle under test (with the receptacle de-energized) the 12 VDC lamp did not light and the Ideal 61-501 was no longer illuminated. With the Fluke 187 Multimeter measuring voltage and the lamp connected the voltage reading dropped to 41 millivolts AC (this result was the same for the Simpson 260 and Fluke 435). In addition with the Ideal 61-501 dimly illuminated jumpers were installed that permitted shorting the grounded conductor (neutral) to the opposite polarity of the receptacle together and through the technician?s hands, no shock was felt and in both cases the Ideal 61-501 lamp was extinguished.
This condition, reading voltage on a de-energized conductor to neutral or ground that is part of a multiwire cable or feeder in conduit where another conductor is energized is referred to by several terms in electrical literature Fluke refers to this as ?stray or ?Ghost? voltages, NEMA (National Electrical Manufactures Association) utilizes the term ?phantom? voltages. See attached documentation from Fluke and NEMA
Stray, Ghost or Phantom voltages are a result of the test equipment utilized to perform the test. These instruments are high impedance measuring devices and the conductors in the cables are by nature of the design capacitively coupled. This issue is common and unavoidable by nature of the cables and is necessary as all conductors of a common multiwire circuit need to be routed tighter to avoid inductive heating. This issue has been known for years but seldom comes to light till such time as cases as this arise.
Ideal Industry was contacted regarding this issue and they are aware of the phenomena and its effect on their Model 61-501 receptacle and while Ideal has no documentation at present regarding this issue they do note in their application notes (attached) that this instrument is not for diagnostic work. From the application notes for the 61-501 Colum 1 Note- item 2.
NOTE:
2. Not a comprehensive diagnostic instrument, but a simple instrument to detect nearly all common
improper wiring conditions.
The Ideal applications engineer did inform me if there were any concerns we could not alleviate with our letter he would be happy to discuss this issue with Colonial Electric personnel or the AHJ regarding this issue.
To check the Ideal tester center light operation issue a test circuit was set up in our shop the results of this test is detailed in the table below. The test circuit was comprised of 50? of 10-3 NM (the only available NM in our shop). The conductors were meggered at 1000 VDC prior to the test. The NM cable was laid in a straight line on the floor and the Black and Red conductors were connected to two separate single pole circuit breakers at
208/120 VAC in a 3 phase 4 wire wye panel), the white/neutral/grounded conductor was connected to neutral termination bar in the panel and the bare grounding conductor was terminated on the grounding termination bar.
Voltage were measured and recorded and then the red conductor was removed from its circuit breaker and left in free air at both ends.
February 10, 2009
Colonial Electric Company Inc
Voltage Anomalies
Page III
In the Voltage Test Black Red Energized the Ideal 61-501 was connected with alligator jumpers to the black, white and bare conductor with correct polarity and the unit indicated CORRECT. The Ideal 61-501 was then connected with jumpers to the red, white and bare conductor with correct polarity and the unit indicated CORRECT. In the voltage test Voltage Test Black Energized, Red De-energized the Ideal 61-501 was connected with alligator jumpers to the black, white and bare conductor with correct polarity and the unit indicated CORRECT. The Ideal 61-501 was then connected with jumpers to the red (red was de-energized), white and bare conductor with correct polarity and the unit indicated center light dimly illuminated. When the red conductor was shorted to ground the center light on the Ideal 61-501 went out. This is what we expected and is what is consistent with the attached literature. The above test can be recreated with consistent results
at any location of your choosing
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