I don't know if the sound of snoring would have the same effect on the mind as a mechanical noise.
Are the plugs 15A? And no fuses in them?
The subway can cause ground currents, it is often found that metal water pipes corrode more quickly near an electric train line, especially if it travels around an area (sort of U shape)
You can of course make the bulb light up by putting the switch in either line, but if you put it in the neutral line, it means the live to the light socket is always live, which is dangerous, and will also make worse the problem you want to cure.
On trains, we lived in an area where the main road dropped 1000ft in 5 miles, obviously the trains could not follow that route, but they still had a fairly steep descent, and we used to get a very distorted sine wave when they were going downhill, they use regeneration as one method or braking. They were also on a mainly separate system, but it had to be tied into the grid at points to get power.
Sorry, what I meant was do the plugs have fuses in them?
I think you use the same round 3 pin 15A plug as South Africa does, that used to be used in the UK (supposedly they set the original standards for both SA and India)
If it is, you almost certainly do not have a ring system.
What you need is a "neon" screwdriver (most are LCD now) which will glow when you touch the live, but not the neutral (unless it is faulty) that way you can see if the live or neutral is switched
I think that I can explain this phenomenon quite adequately.
If I understand the situation correctly:
There is a light fitting with a metal body/framework which is not connected to earth
The light works normally.
Measuring from the frame to a known good earth, there is some random voltage.
The voltage on the frame is due to the small (parasitic) capacitance between the mains wiring and the frame of the light.
The capacitance is only a few pico farads and so is a very high impedance at 50hz.
Measuring this stray voltage is possible with a high impedance voltmeter, the higher the impedance the higher will be the measured voltage.
If a low impedance meter* were to be used, then there would hardly be any voltage indicated on the meter.
* Something like an old AVO model 7, 500 Ohms per Volt sensitivity.
Is the stray voltage a problem?
Probably not, but will be very dangerous in the case of a low impedance fault between the live wire and the body of the lamp.
Is it bad practice to have an un-earthed metal case?
Yes.
JimB
you asked...........................do i need to locate a separate earth point like the waterpipe? isnt the busbar panel frame good enough for an earth?
Not easy to answer that, as we can't see it. If the busbar panel is properly earthed, probably not.
However, any metal water pipes and other metal in the house should be bonded to the supply earth for safety reasons. If the supply earth goes above ground because of a fault or bad wiring, and metalwork is not bonded, there could be a fatal difference between the two.
We also don't know the quality of your electricians and normal wiring practices. In South Africa and the UK standards for both are very high, with people doing it commercially having to be qualified and registered, and set down wiring standards. In the Philippines for example, quite often anyone with a hammer is a carpenter, and anyone with a screwdriver is an electrician, and standards, if they exist, are not followed (ie electric showers with a wall socket next to the shower unit, or the earth wire hanging down loose from the shower unit, in hotels!!).
I also really believe that the voltages you describe are insignificant, bit like chasing ghosts. The radiation round your house consists of a broad spectrum of frequencies, and RF has a far higher "transfer efficiency" to the human body than low frequencies, as shown by the danger of a leaking microwave and the relative safety of an induction hob.
I just took a Fluke meter, held onto one probe, and dangled the other lead in front of the laptop screen, and it shows 5V5, touch it on the metal of the RS232 port and it shows 36V8. It is fed from a power pack where the input is isolated from the output, though it probably has low value capacitors across both to ground to prevent RFI.
If what we hear on the TV is correct (and it is often not) water supply is a problem there, with some people not getting any because others are sucking it out of the system with pumps, and often the pumps compete with each other and the supply dries up. Maybe the stresses of water supply are what causes people to wake up at the sound of pumps. I can't help feeling the cause of sleep problems is more tangible than a little stray voltage on light fittings. Maybe that combined with your worry about the house wiring.
At the same time, it is important to make the house safe, if the light fittings can be touched, they should be earthed.
Hi,
I think JimB came up with a similar idea to this one...
It dawned on me that we should probably be using an analog meter not a digital, i assume you are using one too. The problem with a digital here is that the input impedance is so high that even the slightest inductive or capacitive coupling would cause a reading to show up as a voltage. and the voltage would depend on many very unusual factors like how much switch leakage, how close the wires are to each other, stuff like that, and the switch leakage may be only 0.1 microamp to show a significant reading on the digital meter. The analog meter would not show so much.
For example, even a 10pf capacitive coupling could cause a (very roughly computed) 5 volt ac reading on the meter, and that's not much capacitance which can be had with just two wires close to each other.
I too measure this in the bath and when i touch my finger to the meter probe and one to the light fixture metal case, i still see a voltage reading of around 40 vac on the meter but dont get a shock. So the current has got to be very light, just enough for a voltage reading but not enough to make any serious power. For example, this would never run an LED bulb (with rectifier diode) it would just "short out" the 10pf or whatever capacitance.
I could have done one more test:
Use my body as a conductor and measure the voltage developed across the body. I would bet it is very small because the human body would act as a 'load' which would overload the 'power supply' which is the 120vac coupled signal. So it's like shorting out a power supply...the voltage goes to zero or close.
So to model this, say we have a voltage source of 120vac and that is connected in series with 100pf capacitor, and we want to know what kind of power output we can get from this circuit with a human body load. I think it would be negligible. Same with inductive coupling, where the two mutual inductance coils would be so far apart there would be hardly any power transfer. Dangerous? I dont think so, but i would not be sure about a person with a pacemaker.
that 40VAC could be an issue if its in your sleeping area night after night. specially if you've got over voltage issues at night. grounding is a good idea.
As it's pretty well an imaginary value, and it's not connected via wires to your body, why would it be of any concern?.
that imaginary value goes to 0VAC when you earth it. its of concern in a sleeping area because your body is repairing itself where all signals are going through the body electrically (via the nervous system), an artificial electric field even of that low value could disrupt the bodies repair.
Whatsha smoking dude ??
Can I have some too??
As Always
tvtech
that imaginary value goes to 0VAC when you earth it. its of concern in a sleeping area because your body is repairing itself where all signals are going through the body electrically (via the nervous system), an artificial electric field even of that low value could disrupt the bodies repair.
it is a relatively new installation around 5 years old but done by amateurs who were pretending to be professional unfortunately. but you're right this is with the lamp on.. incandescent bulb on E27 type.
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