Non contact pen picking up current on my water pipes. I've turned off the boiler but it's not that. Found that it's the down stairs lighting. I'm starting out on electrics so medium to low experience. Is this a normal thing?
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Thank you for your reply. To add more info my clamp meter reads AC 0.021V and on another pipe next to it it reads AC 0.010V. if this is normal how do you spot the difference in future between a fault or something normal? And also why do you get a reading for pipes? Does it have to do with the live wires around the pipes under the floor bords creating a kind of magnetic field?Non contact pens will light up if you rub them on your trousers fast enough.
It may well be a perfectly normal thing or it could be a sign of trouble, impossible to tell without some proper testing.
Also what you are detecting, if anything, will be voltage and not current. If you are just starting out it is especially important to learn what these two things are and how they relate to each other. This is fundamental knowledge that will make a lot of other theory easier to understand if you can get them right now. It's surprising how many fully qualified electricians don't actually understand what voltage and current are!
This is the reason for spurious volt readings in most cases.Does it have to do with the live wires around the pipes under the floor bords creating a kind of magnetic field
Voltage is always measured between two points, but you have not identified what the other point is, so the numbers are meaningless. A statement such as 'I measured 0.021V between the pipe and the main earthing terminal' conveys information. Voltages like these, down in the tens of millivolts, can be completely insignificant or moderately interesting depending on what exactly you are trying to discover.my clamp meter reads AC 0.021V and on another pipe next to it it reads AC 0.010V
Amazing reply. Thank you very much.Non-contact voltage detectors are versatile and useful but their behaviour is more subtle and complex than might appear at first glance. Their indications can be easily misinterpreted unless you understand about electric fields, which is perhaps why some people say they are unpredictable and useless because they don't fully grasp what the detector is telling them. As a newcomer, I'd suggest putting the non-contact detector aside for now and getting used to taking measurements with conventional test equipment. Return to it and discover its unique advantages once you are familiar and competent at using the MFT and multimeter.
Voltage is always measured between two points, but you have not identified what the other point is, so the numbers are meaningless. A statement such as 'I measured 0.021V between the pipe and the main earthing terminal' conveys information. Voltages like these, down in the tens of millivolts, can be completely insignificant or moderately interesting depending on what exactly you are trying to discover.
Further, if you use a regular multimeter: these are very high impedance and will(can) also display spurious voltages as the result of induction from wiring.Amazing reply. Thank you very much.
Most water and heating pipes are either earthed, or have a relatively low resistance and high capacitance to earth. It's unusual, although not impossible, for them to float up to significant voltage w.r.t. earth. We need to be careful not to confuse the OP, who is not experienced with making electrical measurements, with all the possibilities unless we are absolutely certain of their cause.No, you are picking up induced voltages.
You would expect that. Many fabrics are triboelectric and can be charged to a high voltage by friction, which the non-contact detector correctly detects. It's handy to be able to detect such small amounts of charge, provided one understands the significance.I have one of those and it lights up if I rub it on my knickers. I don't think I am electrified....
It's entirely possible that your (copper?) pipe is effectively a floating conductor, as above. All it takes is some plumber to fit a plastic joint or two.The voltage sensed e.g. on a disconnected a.k.a. floating conductor that has significant capacitive coupling to a live one, is a real voltage. It's not unknown to read 50-100V on a long 'dead' circuit lying amongst live cables.
As I've posted before, I have experience of this as well.. In theory, if one were in a well defined equipotential zone with lots of conductive structures connected to the MET downstream of the PEN break, it is possible that the mean capacitive reference could be above ground potential and the sensitivity of the device reduced. In the extreme case where the user is significantly capacitively coupled to a high potential, the device could light up when probing earthed metal.
Extremely important to know the difference between a non-contact voltage deathstick and a CONTACT voltage indicated, used to investigate phenolic degradation.I think GN3 recommends using a voltage stick type of tester for when investigating a broken PEN conductor , as a 2 pole tester wont work without an earth reference .
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