Voltage downstream of a contactor - Home Brew Forums
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Old 11-30-2013, 11:42 PM   #1
stevehaun
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I did some rewiring in my control panel and then tested it with my multimeter. At my two 240 vac outlets, I found 235 vac (on) and 0.25 vac (off) and 235 vac (on) and 1.1 vac (off). I was expecting 0.0 vac with the contactors off. I then tested upstream (236 vac) and downstream (0.85 vac)of my main contactor when it was off. Is this kosher or do I have something wrong?



 
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Old 11-30-2013, 11:46 PM   #2
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It may just be the meter. What does it read across your index fingers? Then with the probes shorted? And open air?



 
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Old 11-30-2013, 11:55 PM   #3
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index finger 0.0
shorted 0.0
air 0.01-0.02

 
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Old 11-30-2013, 11:59 PM   #4
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Even when a contactor is open some current can flow between the open contacts via because of the capacitance between them. As this current is at right angles to the voltage no energy is transferred across an open contactor but if the meter is high impedance (as modern meters are) it may register a small voltage. This is a possible, but not necessarily the, explanation for what you are seeing.

 
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Old 12-01-2013, 12:21 AM   #5
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Are you going across an SSR by any chance?
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Old 12-01-2013, 01:30 AM   #6
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No. The SSR is between the main contactor and the contactors that control the elements.

 
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Old 12-01-2013, 01:40 AM   #7
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I wouldn't worry about a volt or fraction thereof. It is probably some phenomenon like AJ described. I dislike my digital meter and usually use an old analog one if I am only checking for power and continuity. Watch for auto range too. I scratched my head a few times not realizing my meter was displaying mV.

 
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Old 12-01-2013, 02:08 AM   #8
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You should not get any leakage through a contactor. I suspect you're reading your own aura. You might be a lightning attractor... be careful out there.

j/k. If you are downstream of the contactor, it might be something simple like a seebeck effect from dissimilar metals. I wouldn't worry about a volt.

AC voltage? Might be what you're picking up from the walls.


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