Agreed if the resistance is very low, but in this case it seems to be very high. I'd like to know the DC-resistance to rule out a possibility I'm thinking about.
I would not put a meter showing current between neutral and ground. Currents could be extremely high if things are miswired, like tens of amps. Even if you throw the mains breaker you could be in for a surprise. If the neutral has not been connected at the meter or main panel as it should, and neighbors also have not done this, you could be in for quite the surprise. Neutral is not broken from the power company when you throw the breaker off, only the hot. I'm not even sure neutral is broken when the meter is pulled, although I'd hope so to protect power company service people.
I'm not talking about measuring current between N and E, but resistance.
If I'm understanding the split phase system correctly, it is no different from our three-phase system in that neutral and earth are interconnected at the transformer end and and again at the main panel end. Only at the house side of the wiring do neutral and earth split for their respective functions: normal current return path and ground fault current return path.
Obviously all devices should be disconnected before making the resistance measurement. With all devices disconnected there also should not be a voltage differential between N and E. This is why I think that there's possibly more than one problem.
If I'm understanding the split phase system correctly, it is no different from our three-phase system in that neutral and earth are interconnected at the transformer end and and again at the main panel end. Only at the house side of the wiring do neutral and earth split for their respective functions: normal current return path and ground fault current return path.
Obviously all devices should be disconnected before making the resistance measurement. With all devices disconnected there also should not be a voltage differential between N and E. This is why I think that there's possibly more than one problem.
This is likely to give an erroneous reading if there is any voltage measured between N and E. That is true even if the voltage is coming in from the power company drop.
Also, giving the OP instructions for troubleshooting procedures has not proven effective with this particular OP.
What an electrician would probably do is inspect the panel visually and tighten all connections including neutrals and grounds, and similarly inspect the ground rod and tighten its connection. Then measure voltages to see if things look more correct. Measuring resistance is not usually required to fix such problems.
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When it comes to measuring anything on power, I stick to voltage only. I look at the socket as a black box, and I've no idea what is connected in the black box, and it is a black box with essentially zero impedance wires connecting up the pieces in the box. The big ticket items we are not sure of are, is the poster's gnd/neutral connected in the main fuse box/meter? Are all the other services on the transformer connected at their respective fuse boxes. Are the other services connected in a star (with all services going from transformer to service directly) or some sort of tree arrangement where a service drop goes to residence 1, then off to 2 etc. If gnd/neutral is not connected it is possible you will be diverting some current to your ground rod if you short gnd and neutral even if all your breakers are off. When it comes to power, I am very very careful. It can be deadly. And it is not like I don't work on power stuff. I've built my own pool controller controlling 240V pumps, have a way to run the pumps via a generator in case of an outage in cold weather, mucked with the furnace, mucked with the AC, ... I work on power, and have great respect for it's ability to end me.
It is how I found missing earth connections on sockets in part of my house, but I agree that it's not going to work if there's any voltage present.
I would prefer the whole system to be switched off, but that would make the measurement impossible if the circuit breakers are 2 pole types.
Its common for electricians to use clamp-on amp meters when needed. However, 100mA is usually way at the low end of the most sensitive range. Thus it is likely to be unreliable. Its may be possible to wind a few or several turns through the clamp to multiply sensitivity, but that isn't something electricians would normally do.
An electrician can do it, but usually its not needed. Shutting off all the breakers would be the first thing to do. The other procedures I will not describe here as they involve working live circuits.
In addition to tightening all the panel connections, an electrician would probably pull all the wall sockets out for visual inspection and tightening of all the connections. Bad connection problems are something every electrician sees. Try the easy and common things that usually work first, before deciding to go into analytical mode. In most cases that leads to the quickest resolution of the problem.
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Yeah, that 100 mA is what bugs me. It could be displayed as 0.1 A on the meter which means it's quite useless as it could be way less.
I called an electrician He came and checked all the wiring and said the resistance of the earth is high by about 8.5 ohms. (He showed me) .The earthing well is dry and the earth wire at the junction where the rod drilled to the ground is completely sulfated (He said). The reason why the measured ampere is about 100 mA is that the junctions create a big resistance and the open loop voltage is high while the measured current is low. In summary, the earthing is not connected correctly.
Did the electrician check your equipment/appliances so see if any had high leakage currents? I ask because that's the other thing that should be checked.
The thing is that even if your ground resistance was high by 8.5 ohms, there is still the matter of 80VAC across that resistance as measured at some location in the house.
The thing is that even if your ground resistance was high by 8.5 ohms, there is still the matter of 80VAC across that resistance as measured at some location in the house.
My personal experience of electricians (worked with lots, worked for one, a Master Electrician) is that they know their business and know the Code and the rules, but don't necessarily know a lot about electricity. It's not required to do the job. More important is that each soldier knows and obeys Code and the rules. Anything else may be problematical. You have a potential safety issue, but the available experts are unreliable. Sounds like modern politics.
All good fortune,
Chris
All good fortune,
Chris
That 100 mA you mention, you wrote you measured it using a clamp meter. I'm wondering, how did you read this value on the display? Did it display "0.1" or "100"?
uni-T has a clamp on meter sensitive in the mA range, used for earth leakage measurement. UT251 ranges from uA's to amps. Very convenient, clamp it on a L+N cable and you see how much is leaking away. That can be a capacitive current, for example a set of solar panels; having enough of those plus some rain and you will exceed 30mA.
To OP: would you care to answer our questions? I'd like to know more as some of the measured values indicate either more than just an earthing problem or a measurement issue.
jitter
Hey everyone. I said the voltage between my body and the PC (desktop) case when I touched the floor of my room was 80 V AC. That was a kind of inductive voltage that my body absorbed and the reason was a bad grounding. It doesn't mean that the voltage when I went far from the PC had the same value. Actually, the PC case induced voltage in my body .
What I think you measured was leakage current in the µA range through a MΩ resistor (your body).
This could be caused by X or Y class caps used for RFI suppression in the wall wart or PC PSU. This is normal and in a low impedance path would not elevate the measured voltage appreciably.
If I power my laptop from its wall wart from an unearthed socket, I measure about 36 V between the case and my body which drops to less than 0.5 V when connected to an earthed socket. You can imagine that this voltage would be a good source to feed a very noisy groundloop should you indtroduce one.
This could be caused by X or Y class caps used for RFI suppression in the wall wart or PC PSU. This is normal and in a low impedance path would not elevate the measured voltage appreciably.
If I power my laptop from its wall wart from an unearthed socket, I measure about 36 V between the case and my body which drops to less than 0.5 V when connected to an earthed socket. You can imagine that this voltage would be a good source to feed a very noisy groundloop should you indtroduce one.