Investigating a faulty earthing in our house

[Wrichik Basu]

We are facing a severe earthing problem. In our house, the potential difference (PD) between neutral and earth is $50 - 60 ~\mathrm{VAC},$ which should normally be $< 2~\mathrm{VAC}$ if earth is properly connected. I determined this with my multimeter after some appliances were giving electric shocks. And this value is approximately the same in all outlets inside our house.

Now, I am trying to figure out whether the issue is only in our flat, or throughout the building.

Here is a diagram of the main circuit board in our building:

There are three lines (phases?) (red, blue, yellow) and a neutral (black) that enter the building. I have not shown the electricity meters, as they're not required. Also, the neutral wires from each fuse (F1-6) are actually separate wires that meet at the company fuse (point D) for the neutral line (similar to the earth wires, which meet only at E).

I measured some potential differences, and the list is as below:

Multimeter probe 1 location​	Multimeter probe 2 location​	Potential Difference (in $\mathrm{VAC}$)​
Company fuse for neutral, point D	Earth, point E	$\approx 0.5 - 1.1$​
Neutral at F1	Earth, point E	$\approx 0.5 - 1.7$​
Live at F1	Earth, point E	$\approx 229$​
Live at F1	Neutral at F1	$\approx 230$​

Our fuse box (F1) is made of metal, so the earthing wire that comes down from our flat is first connected to that metal box, and thereafter connected to point E. I also checked the PD b/w this box and point E, and it was $\approx 1.5 - 2~\mathrm{VAC}.$ It shows that earthing is fine at the main board, so something is wrong in the wires between our house and the main board. We shall be calling an electrician to rectify it.

But I discovered something more. There is a three-pin socket from the common place line near the entrance of our building (it is indoors). I checked the PDs at this location, and found this:

Multimeter probe 1 location​	Multimeter probe 2 location​	Potential Difference (in $\mathrm{VAC}$)​
Live	Neutral	$230.1$​
Live	Earth	$40.6$ (?)​
Neutral	Earth	$7$ (?)​

Note that I rechecked these twice. But I didn't verify it by checking with F6, the common place fuse.

I am interested in why the value $40.6~\mathrm{VAC}$ comes up, and whether it is of any significance.

 

[anorlunda]

OMG I feel so bad for you. But it is extremely difficult for those in other countries to help. That is because there are more than 60 different wiring and grounding systems in use around the world. People give advice applicable to their own country but wrong for yours.

On the other hand, we have some extremely clever engineers here. I hope some of them can give you useful advice independent of national practice differences.

 

[hutchphd]

What are the physical locations of points D and E (and how far apart)?

 

[Wrichik Basu]

What are the physical locations of points D and E (and how far apart)?

They are on the lowest row on the wooden board, in line with all the other company fuses, and maybe around 10 cm apart. E is vertically a bit below the line of the company fuses.

 

[Baluncore]

I am interested in why the value 40.6 VAC comes up, and whether it is of any significance.

I assume you are in India, with international standard 230 V, at 50 Hz. We have a similar system in Australia. In MEN systems, the neutral is earthed throughout the distribution system, but there would be only one link between your neutral and the protective earth on your property. That link would be with your fuses or breakers, between the earth and neutral bar in the back of your distribution box. You do not show that link, which should prevent the 40.6 VAC appearing in your building.

I am surprised there is a fuse in the company's neutral distribution. Maybe it is open circuit.

The one link between earth and neutral makes it possible to use Residual Current Detection or earth leakage breakers on many of your domestic outlets.

A high impedance voltmeter will not give you a meaningful voltage reading in a floating or open circuit system because of the capacitance between conductors.

The first test I would do is to connect a 240V filament lamp between earth and neutral, then measure the voltage again.
1. If the breaker immediately cuts that circuit, then you have a good RCD breaker.
2. If the voltage then falls toward zero, you are missing your local ground to neutral link. Call an electrician to restore that link in your distribution box.
3. If the lamp glows red then wires are crossed in your vicinity, you have a problem that certainly needs an electrician to resolve the safety issue.

 

[hutchphd]

E is vertically a bit below the line of the company fuses.

And that is a ground buss well connected to a ground rod? (If that buss floats it seems to me that an internal case fault at your neighbor #3 could be bad for you) Are red yellow and blue 3 phases? I think I am agreeing with @Baluncore .

 

[dlgoff]

I agree with @Baluncore when he mentioned:

... you have a problem that certainly needs an electrician to resolve the safety issue.

 

[Wrichik Basu]

Here are some pictures of the setup:

The first three are the fuses of the three phases. Then comes the neutral. At the bottom right of the board, you can see the point where all the earth connections from different houses are joined. This is connected to the metal pipe via the thick black wire. The metal pipe houses the three phases and the neutral wires and runs underground. In this way, the company ensures that the earth wires are actually grounded.
The fuse in the neutral line.


​

Edit: Changed second picture to a better image.

 

[Averagesupernova]

I avoid posting in threads like these because I always question the accuracy of the system as it is described. If you have little to no voltage between D and E in the first diagram but are getting shocks from appliances, the problem is like two fold or more. Likely an open earth, but it also implies something is putting voltage on this open earth wire which is common to many appliances. The three pin socket you refer to that you measure 40 volts neutral to earth is likely just another symptom of the same problem.
-
My guess is the open earth has existed for quite some time and some appliance or load has developed a fault and is now showing up.
-
How to troubleshoot it? If the voltage between the neutral and earth is able to drive a load such as a small incandescent bulb, watch this light while disconnecting various loads in the house. Watch for the light to go out.

 

[Lnewqban]

Have you checked the quality (conductivity and physical condition) of those connections?

 

[Wrichik Basu]

I avoid posting in threads like these because I always question the accuracy of the system as it is described.

I am describing what the company had described to me the last time they came for an inspection (many years back, but nothing has changed since then).

If you have little to no voltage between D and E in the first diagram but are getting shocks from appliances, the problem is like two fold or more.

It seems that the earthing wire(s) that go down from our house to the circuit board downstairs are somehow damaged or have got disconnected. As I've said, the PD b/w earth wires from our house with the neutral is very low when measured at the main board, but there's a huge difference when measured in any outlet in the house. This probably means that earthing is fine downstairs, but not upstairs, which, in turn, implies a problem somewhere in the middle.

The three pin socket you refer to that you measure 40 volts neutral to earth is likely just another symptom of the same problem.

Possible, but note that this 3-pin outlet is in our common place, and hence, the earthing wire is different from the one that comes down from our flat (though they are all joined at the location E).

How to troubleshoot it? If the voltage between the neutral and earth is able to drive a load such as a small incandescent bulb, watch this light while disconnecting various loads in the house. Watch for the light to go out.

Tried that with a 0.5 W LED bulb. If I connect the bulb b/w neutral and earth in our house, it glows (but obviously with a far lower luminosity). But I couldn't pinpoint any appliance.

Have you checked the quality (conductivity and physical condition) of those connections?

Visually, they seem to be ok.

 

[Wrichik Basu]

there would be only one link between your neutral and the protective earth on your property. That link would be with your fuses or breakers, between the earth and neutral bar in the back of your distribution box. You do not show that link, which should prevent the 40.6 VAC appearing in your building.

If you check the pictures I have posted in #8, the neutral and earth are not connected anywhere above the ground; the neutral is a separate wire while the earth is connected to the metal pipe that ascends from under the ground. Now, they should be connected under the ground, but I can't see that. The low voltage b/w the neutral fuse and point E suggests that they are definitely connected; but not above the ground.

Also, we don't have any residual current device installed on any of the lines. Only F4 is an MCB, all others are fuses.

 

[Lnewqban]

Visually, they seem to be ok.

Marginal conductivity may still exist, and can be measured with the proper tool.

Has the problem manifested itself for long or short time?
What changes could have be made to the circuit by that time?

 

[Averagesupernova]

You have already at your disposal a good tool. That is the incandescent bulb. You need to try harder to isolate the problem. Also, how much current are you able sink on the earth from the hot? That should give an indication that may point you in the right direction.

 

[Rive]

That connection to the metal pipe seem dubious, and I was very reserved with that. Try measuring 'earth' to water pipes at various points.
You can also try measuring current on 'earth' lines by an AC clamp meter (so you don't have to break the line anywhere).

I do agree with @Averagesupernova that this is likely some double fault. One is the earth being broken or weak: other is some appliance 'leaking' current to the earth instead of neutral.

In my book this clearly requires an electrician, and I bet he'll sweat buckets while solving it. Likely, he'll need to check all houses and appliances one by one...

 

[Wrichik Basu]

Has the problem manifested itself for long or short time?

This is something we are still pondering on. We have not been at home for around six months last year, and before that, I don't remember facing the issue. We have been at home since February this year, but detected the issue only a few weeks back when we started using our immersion water heater. It was giving a shock even when it was turned off. Initially, I had thought only that outlet was faulty, but when I measured other outlets, they too turned out to have a faulty earthing. Some outlets had nearly > 60 VAC difference b/w earth and neutral.

What changes could have be made to the circuit by that time?

House #2 (the one sharing the same phase with us) had a lot of repairing work going on for the last two years. They also got their electricity meter upgraded by the company to 63 A so that they could drive another air conditioner. (Our line, too, is 63 A, which we upgraded back in 2020, just before the COVID.) Their electrician may have messed something up, and our earthing got snapped.

That connection to the metal pipe seem dubious, and I was very reserved with that. Try measuring 'earth' to water pipes at various points.

Will check.

I do agree with @Averagesupernova that this is likely some double fault. One is the earth being broken or weak: other is some appliance 'leaking' current to the earth instead of neutral.

Possible, but, as I said in #11, I disconnected all the appliances in our house with three pins, but the bulb didn't go out.

I bet he'll sweat buckets while solving it.

I am afraid so. The first thing to do is to "restore" the earthing in our house so that the PD b/w earth and neutral lowers to acceptable levels. But how he will locate that exact junction box where the problem has occurred, is something out of my imagination.

Also, how much current are you able sink on the earth from the hot? That should give an indication that may point you in the right direction.

How do I find that (without blowing any fuse)?

 

[Averagesupernova]

How do I find that (without blowing any fuse)?

Connect a load between hot and earth.
-
This shouldn't be that difficult. If you are unable to get the voltage to go away by unplugging stuff in your house then you need to go back closer to the source and start disconnecting the hots. I assume you can do this by turning breakers off or removing fuses. If ALL of the power is off to your house and still have voltage then you have a possibility that your earth connection is shared by a neighbor and this connection is compromised. In this case the neighbor may have a faulty appliance.

 

[Lnewqban]

This is something we are still pondering on. We have not been at home for around six months last year, and before that, I don't remember facing the issue. We have been at home since February this year, but detected the issue only a few weeks back when we started using our immersion water heater. It was giving a shock even when it was turned off. Initially, I had thought only that outlet was faulty, but when I measured other outlets, they too turned out to have a faulty earthing. Some outlets had nearly > 60 VAC difference b/w earth and neutral.

House #2 (the one sharing the same phase with us) had a lot of repairing work going on for the last two years. They also got their electricity meter upgraded by the company to 63 A so that they could drive another air conditioner. (Our line, too, is 63 A, which we upgraded back in 2020, just before the COVID.) Their electrician may have messed something up, and our earthing got snapped.

It is then possible that some connection through the shared ground rather than neutral has been done next door.
Your house is powered backwards from the other house, making your ground invalid (your body has become a better ground).

For a few minutes, may you fully shut down power supply to house #2 to test that?

 

[Averagesupernova]

It is not uncommon in the USA to have current on the wire that connects the main buried water pipe when the main breaker to the house is off. I won't confuse the issue with details but I want it to be clear that troubles in a neighbor's house can show up in your own.

 

[Wrichik Basu]

If you are unable to get the voltage to go away by unplugging stuff in your house then you need to go back closer to the source and start disconnecting the hots. I assume you can do this by turning breakers off or removing fuses.

This is what I did:

Inside our house, there is an isolator (not sure whether it is SP or DP), and after this, there are separate fuses of low rating for each room (or a set of rooms, sometimes). However, as per the standards, single high current lines (> 8 A) have to be directly drawn from the main circuit board downstairs. So, the wires to the outlet for our air conditioner is directly drawn from F1 and bypasses the isolator. It has a separate 11 A switch-cum-single pole MCB (similar to this, but with lower rating than the one linked). Therefore, switching off the isolator has no action on this outlet; it can only be switched off from F1.

I put the bulb b/w live and neutral neutral and earth in this outlet, and it was glowing with low brightness, as usual. Then, I switched off the isolator. (In this situation, the whole house has no power except that outlet, and no appliance is connected to that outlet, except the bulb.) The bulb flashed bright for a second, and then became dimmer, but still continued to glow. Switching on the isolator increased its brightness to what it was initially.

Let me know what this means.

For a few minutes, may you fully shut down power supply to house #2 to test that?

Don't want to get killed!

Edit: Fixed mistake sighted in #24.

 

[Wrichik Basu]

For a few minutes, may you fully shut down power supply to house #2 to test that?

On second thought, I can try to do that in the following days when they are not at home. What exactly are the things I should note down? Only whether the bulb glows b/w neutral and earth (and whether it becomes dimmer or brighter)? Should I also note down multimeter readings? Anything else?

 

[Lnewqban]

On second thought, I can try to do that in the following days when they are not at home. What exactly are the things I should note down? Only whether the bulb glows b/w neutral and earth (and whether it becomes dimmer or brighter)? Should I also note down multimeter readings? Anything else?

You should not see any problem in your house if next door house is not powered, if our assumptions are correct.
Do you know any good electrician who could check the problem for you?

 

[Wrichik Basu]

Do you know any good electrician who could check the problem for you?

Ultimately, I will be calling one, but I wanted to narrow down the problem as much as possible (and learn something in the way, too!).

 

[Averagesupernova]

I put the bulb b/w live and neutral in this outlet, and it was glowing with low brightness, as usual.

Live and neutral or live and earth?

 

[Baluncore]

What exactly are the things I should note down? Only whether the bulb glows b/w neutral and earth (and whether it becomes dimmer or brighter)? Should I also note down multimeter readings?

Connect a filament lamp between Earth and Neutral.
Does the lamp glow ?
What is voltage across the lamp, before and after ?

Once you have performed that test, it will be possible to work out the next step in the search for what must be at least two faults.

 

[Wrichik Basu]

Live and neutral or live and earth?

Neutral and earth. Sorry for the confusion.

 

[Wrichik Basu]

Updates:

I tested with the neighbour's (House #2) main switch (F2) off. There was no change in the readings in our house.

---

Following the advice of @Averagesupernova, I tried harder to debug and find if there was an appliance which was faulty, as many others pointed out too. To this effect, I took some more data.

The only 3-pin appliance currently working in our house is the refrigerator.

Here is a schematic of the circuit inside our house which will help understand the data I took.

Note that I am unsure whether the isolator is SP or DP. The refrigerator is connected through the isolator.

The data is summarized in the Google Sheet below:



What I can see:

• When the compressor of the refrigerator is running, the difference between earth and neutral is greater than $10-12~\mathrm{V}$ compared to when it is not running.
• However, the PD is almost the same when the refrigerator is unplugged vs. when the refrigerator is plugged in and the compressor is not running.

Can we infer that the refrigerator is not at fault here? What other conclusions can be drawn (in addition to the fact that the earthing is faulty, and needs to be rectified by an electrician)?

 

[hutchphd]

You should not see any problem in your house if next door house is not powered, if our assumptions are correct.

No. You are ignoring the other houses at the other two phases. They can be equally culpable in backdriving, and can , in fact, be worse.
@Wrichik Basu Have you done the tests @Baluncore suggested? My working hypothesis is that the local Earthing network is not well connected to either Earth or Neutral. Then any faulty appliance in any house can create a serious problem for all.
Or spend your effort finding the best electrician you can , show him/her your diagram, and indicate you want an explanation of the problem when it figures out.

 

[Baluncore]

I am going to ignore this thread until the filament lamp test has been done.

 

[Averagesupernova]

Yes, please use the incandescent when doing tests.
-
Let's get back to the fact the that there is very little voltage between D and E in the first diagram you posted. The assumption is a poor connection in the earth conductor as you get away from what is point E in your diagram. I am going to stand by what I said in my first post about concerns whether the system exists as it is presented in the thread. No offense intended, mistakes happen. You may know that each earth pin is supposed to connect back to earth but do you really know the route? I would be familiar with how things are supposed to be done in the USA but what is the practice where you are at? In the USA the earth conductor is run in the same cable or raceway as the hot and neutral back to the source. If there is a broken earth wire in the raceway only devices downstream from that break will be affected. It's not spaghetti when done correctly. Based on your diagrams, I have to wonder about your system.
-
Troubleshooting 101: Find a place in the system where readings are correct and you understand them. Then move away from this point until the reading are incorrect.

 

[artis]

Well @Wrichik Basu , no offense but the pictures you provided show a rather dirty fuse box and the neutral and earth connections do seem oxidized and rusted outright, that can be a problem or part of it, but to know one would need to measure the contact resistance and visually inspect them thoroughly.
I recall one late friend of mine who was an electrician once said to me:" There are only 3 problems in all of electronics, namely
1) A contact where there should be no contact
2) No contact where one should be
and
3) Searching in the wrong place

Apart from the possible ideas already said here one additional idea came to mind.
If I understood you correctly you have a earth wire in each outlet of the house besides the two wires of neutral and live.
So a 3 pin socket essentially. Now apart from the good suggestion that @Baluncore already said in post #5, my additional idea is this.
Clearly apart from bad ground appliances shouldn't leak current to chassis which is a defect in itself.

You could make a short cable with a wall type receptacle on one side and a wall type plug on the other side. Make it out of 3 wires, where you connect L to L, N to N and earth to earth, attach an ampere meter in series on each of the wires.
Then you can go around your house with all appliances disconnected and connect them to your ampmeter cable one at a time.

If truly one of your appliances is faulty itself then you should see a discrepancy between the amp readings of that appliances live and neutral.

This is the same thing a ground fault circuit interrupter does, it compares the current between live and neutral because if everything is ok those currents should exactly match, if they don't there can be only one reason and that is the device is leaking current to ground.

 

[Rive]

Erm. I think that by throwing in DIY equipment for investigating a live line voltage electric network in unclear state we are treading on thin ice here.

 

[Averagesupernova]

Erm. I think that by throwing in DIY equipment for investigating a live line voltage electric network in unclear state we are treading on thin ice here.

I think you might be surprised that the "DIY equipment" AKA the incandescent bulb is a very common tool amongst electricians. Do you have another tool in mind?

 

[Rive]

I know that and I think I would be able to dig up mine from some boxes in storage: I'm myself also fine with extension cords with patched in current measurement (though I prefer clamps instead) but we are in the open here.

 

[Wrichik Basu]

I am going to ignore this thread until the filament lamp test has been done.

Connect a filament lamp between Earth and Neutral.
Does the lamp glow ?
What is voltage across the lamp, before and after ?

Once you have performed that test, it will be possible to work out the next step in the search for what must be at least two faults.

The first test I would do is to connect a 240V filament lamp between earth and neutral, then measure the voltage again.
1. If the breaker immediately cuts that circuit, then you have a good RCD breaker.
2. If the voltage then falls toward zero, you are missing your local ground to neutral link. Call an electrician to restore that link in your distribution box.
3. If the lamp glows red then wires are crossed in your vicinity, you have a problem that certainly needs an electrician to resolve the safety issue.

I have a 15 W incandescent bulb. Connected it b/w earth and neutral. It didn't glow. (The 0.5 W LED bulb glows, however.)

PD before connecting lamp: 29.84 V
PD after connecting lamp: 30.12 V.

If you want me to get a bulb of lower rating, I will have to search for it.

 

[Wrichik Basu]

Erm. I think that by throwing in DIY equipment for investigating a live line voltage electric network in unclear state we are treading on thin ice here.

I know that and I think I would be able to dig up mine from some boxes in storage: I'm myself also fine with extension cords with patched in current measurement (though I prefer clamps instead) but we are in the open here.

Please don't report the thread for high voltage safety issue. My multimeter probes are rated for 1000 V, 10 A max. I use proper safety precautions when measuring mains voltage.

 

[Averagesupernova]

I have a 15 W incandescent bulb. Connected it b/w earth and neutral. It didn't glow. (The 0.5 W LED bulb glows, however.)

PD before connecting lamp: 29.84 V
PD after connecting lamp: 30.12 V.

If you want me to get a bulb of lower rating, I will have to search for it.

Assuming the 15 watts lamp is not defective even though it does not glow indicates there is a significant leak someplace that is partially energizing the earth conductor since you measured voltage.
-
You didn't previously mention that the 1.5 watt was an LED bulb. These are not good for this type of troubleshooting.

 

[Wrichik Basu]

You may know that each earth pin is supposed to connect back to earth but do you really know the route? I would be familiar with how things are supposed to be done in the USA but what is the practice where you are at? In the USA the earth conductor is run in the same cable or raceway as the hot and neutral back to the source. If there is a broken earth wire in the raceway only devices downstream from that break will be affected. It's not spaghetti when done correctly. Based on your diagrams, I have to wonder about your system.

The earth wires from the rooms are joined to each other at the nearest junction boxes inside the house. These wires then finally meet at the main junction box, from where the wires descend downstairs. As I had said in post #11,

It seems that the earthing wire(s) that go down from our house to the circuit board downstairs are somehow damaged or have got disconnected.

This is what the electrician will locate, if he concurs with my inferences.

---

You didn't say the 1.5 watt was an LED bulb. These are not good for this type of troubleshooting.

Please see post #11:

Tried that with a 0.5 W LED bulb.

 

[anorlunda]

In the USA, our answer would certainly be to leave this problem to a licensed electrician; trusting the electrician to follow codes. In India, that may be less practical.

However, I'm uncomfortable about recommending some of these DIY troubleshooting methods. I fear safety hazards. @Wrichik Basu is a valued member of PF. I would not want to see him hurt.

Is the advice given prudent?

 

[Averagesupernova]

In the USA, our answer would certainly be to leave this problem to a licensed electrician; trusting the electrician to follow codes. In India, that may be less practical.

However, I'm uncomfortable about recommending some of these DIY troubleshooting methods. I fear safety hazards. @Wrichik Basu is a valued member of PF. I would not want to see him hurt.

Is the advice given prudent?

Several things. @Wrichik Basu has been given sound advice here. Closing this thread will not likely stop him from continuing to investigate this. An electrician called in could potentially end with the electrician saying to replace the fridge, everything else is fine. You said yourself that in India getting an electrician may not be practical. That implies instead of @Wrichik Basu investigating this, someone less qualified does it.

 

[Wrichik Basu]

Well @Wrichik Basu , no offense but the pictures you provided show a rather dirty fuse box and the neutral and earth connections do seem oxidized and rusted outright, that can be a problem or part of it, but to know one would need to measure the contact resistance and visually inspect them thoroughly.

For the neutral, the company needs to be called. And they are least interested in these things. For the earth, I need to have a word with my neighbours. And I would shoot myself before trying to make them understand the issue.

You could make a short cable with a wall type receptacle on one side and a wall type plug on the other side. Make it out of 3 wires, where you connect L to L, N to N and earth to earth, attach an ampere meter in series on each of the wires.
Then you can go around your house with all appliances disconnected and connect them to your ampmeter cable one at a time.

While a good way to find the defective device, I am a bit hesitant to follow this at this moment for the following reasons:

1. My multimeter has a hall clamp (for both AC and DC), so I don't need to connect the multimeter in series. However, it's a lot of work, to be honest.
2. I want to "preserve" the fault till the electrician comes in. If I rectify it, then I will not be able to point out that the earth is faulty.
3. From my data in post #27, I believe we can rule out the refrigerator as a culprit, since there is not a lot of difference between the PD measured when it is plugged in vs. unplugged. (The fridge is also brand new, bought just a few months back…) All other appliances we own have a plastic body, so there is no chance of shock to the user (except that one immersion heater, which we unplug after use).
4. Once the earthing is done properly, if some appliance breaks down by drawing excessive current into the earth and blows a fuse, let it do so. The house is well protected by properly rated fuses at different points. And it will be easier to locate it at that time.

---

In the USA, our answer would certainly be to leave this problem to a licensed electrician; trusting the electrician to follow codes. In India, that may be less practical.

However, I'm uncomfortable about recommending some of these DIY troubleshooting methods. I fear safety hazards. @Wrichik Basu is a valued member of PF. I would not want to see him hurt.

Is the advice given prudent?

I understand and appreciate your concerns. But in India, unfortunately, there is no such thing as a licence for being an electrician, let alone codes to follow. I really wanted to document the unsafe ways they adopt in their everyday work. Following advice from experienced users in PF is a lot better than letting them tear down each and every socket, trying to find a fault. I believe doing measurements with a multimeter (with safety measures adopted) and using a bulb won't cause a lot of harm. The rest is up to the mentors to decide.

I will be calling an electrician in the next few days, and hopefully, he will be able to solve the issue. Learnt a lot through this thread. Thanks, everyone, for your time and input!

 

[Averagesupernova]

From my data in post #27, I believe we can rule out the refrigerator as a culprit, since there is not a lot of difference between the PD measured when it is plugged in vs. unplugged. (The fridge is also brand new, bought just a few months back…) All other appliances we own have a plastic body, so there is no chance of shock to the user (except that one immersion heater, which we unplug after use).

I disagree here. If the appliance puts voltage on the earth conductor it should be considered defective. However, you may measure voltage that is capacitively coupled onto the earth conductor if it is not properly connected to earth. The same thing could happen if you toss a length of wire on the floor and measure the voltage on it relative to earth. BUT, that does not mean it can source any current. If it cannot source current, that means it won't shock you. Since you are getting shocked, something somewhere is defective. Having the bulb connected when doing the measurements indicated a voltage which means current can be sourced.

 

[Rive]

Please don't report the thread for high voltage safety issue.

I won't, but since we are in the open too many DIY ideas might leave no room for consideration for mentors.

If the appliance puts voltage on the earth conductor it should be considered defective.

Well, actually...

Many electronic appliances starting with an EMI filter like this:

With a broken PE connection this kind of filter will provide ~ half line voltage on the PE pin (and, consequently: on the chassis). Most common case is a PC hanging on a cheap, inconsiderately chosen extension cord, giving pricking sensation for any light touch.

With several appliances (on different phases) hanging on a common (broken) PE the voltage measured on the PE may be ... interesting.

I would prefer having a voltage measured between PE and water tap (if there are metal pipes for water there). With and without a (filament) bulb connected between them.

 

[Averagesupernova]

I would prefer having a voltage measured between PE and water tap (if there are metal pipes for water there). With and without a (filament) bulb connected between them.

Let's not confuse this any farther. Measure the voltage between the points we know are not supposed to have voltage between them. I don't know if anyone here knows if plumbing is connected in any way in India or not. At least I don't.

 

[Rive]

I don't know if anyone here knows if plumbing is connected in any way in India or not.

Old style (metal) water pipes usually works as reference. And with the official PE-ground connection in that shape (and without proper equipment) I see no other way to get an indication (not measurement! just indication) for the quality of the actual PE<>ground relations.

Ps.: honestly, based on the pictures, I feel like the pipes might be the most reliable stuff there

 

[DaveE]

I avoid posting in threads like these because I always question the accuracy of the system as it is described.

I am describing what the company had described to me the last time they came for an inspection (many years back, but nothing has changed since then).

Yes, but how do you really know that either they were correct or that nothing has changed? You (someone) needs to verify what's really there first.

I was an R&D EE at a company that made some complex high power electronic instruments. Occasionally I'd be asked to help troubleshoot systems on the manufacturing floor. They always fixed the simple stuff themselves, of course. I always started by asking them what was happening, what did they think, etc. Then I mostly ignored their observations and remeasured everything from the beginning. Almost always, they were assuming something that wasn't actually true, even though it should have been. Often the problem was simple once you got past the otherwise reasonable assumptions.

PS: sorry, I know that's what you are doing. But keep in mind the problem isn't so much the fix, the problem is understanding what to fix. It is so easy to lose sight of that. It was a frequent problem for me in the lab troubleshooting my own designs too.

 

[Averagesupernova]

Almost always, they were assuming something that wasn't actually true, even though it should have been.

Ding ding ding ding ding!
-
This is why we start troubleshooting at the place where measurements and function is working correctly and makes sense.

 

[Baluncore]

When hot, the current through a 15 watt, 240 volt filament will be about 15 / 240 = 0.0625 amp. When cold, the resistance will be one tenth, so the current will be 0.625 amp. The cold filament resistance will then be about 240 / 0.625 = 384 ohms.

When Earth and Neutral are connected by the cold filament of 384 ohms, the voltage RISES from 29.84 V to 30.12 V. That is an increase of 0.28 volt.

I would immediately check the series connections in the Neutral supply.
How much of the E-N fault voltage appears across the Neutral fuse, and its poor connections?

 

[Averagesupernova]

When Earth and Neutral are connected by the cold filament of 384 ohms, the voltage RISES from 29.84 V to 30.12 V. That is an increase of 0.28 volt.

Hmmm. I at first read this the opposite. But that does indicate a weak neutral. Unless @Wrichik Basu accidentally reported the readings to us reversed. I'd like a verification there.

 

[Baluncore]

I'd like a verification there.

If it was a half volt drop, would it change the analysis?