What could be causing electric current on my laptop case?

[Wrichik Basu]

I found something very interesting: We have one air conditioner of 1.5 ton in our house. When the above readings were taken, it was switched on. Later, after switching it off, I tested again, and the voltage b/w Earth and neutral became 23 V. Still much higher than normal, but lesser than the previous reading. When I switched on the AC again, the value climbed up to ≈ 44 V. I chose four different outlets in the house; same observation in each of them. Any idea why this fluctuation is occurring?

And another thing: the tingling doesn't go until I unplug the charger from the outlet. Simply switching off the outlet doesn't work.

 

[berkeman]

And another thing: the tingling doesn't go until I unplug the charger from the outlet. Simply switching off the outlet doesn't work.

Switching off the outlet likely just disconnects the Hot lead, not Neutral or Ground.

 

[DaveC426913]

Nope.

 

[berkeman]

Nope.

Remember to always quote what you're responding to...

If you're responding to my switch comment, some house outlets (in the US) do have wall switches that switch the Hot/Line wire to the outlet.

 

[berkeman]

some house outlets (in the US) do have wall switches that switch the Hot/Line wire to the outlet.

BTW, don't ask me how I know that...

 

[jedishrfu]

BTW, don't ask me how I know that...

Secrets of the EMT!

 

[berkeman]

Secrets of the EMT!

No, I wish. More like moving into a new place and thinking, "I wonder why this outlet doesn't work sometimes. Hey it works! Ack, it stopped working."

 

[Tom.G]

@Wrichik Basu
If the power plug is not polarized, try inserting it the other way in the wall outlet. Depending on the particular situation, that can sometimes hide the shocking problem, but doesn't fix the underlying fault.

No, I wish. More like moving into a new place and thinking, "I wonder why this outlet doesn't work sometimes. Hey it works! Ack, it stopped working."

Same situation here, very confusing until tracked down! It turns out the standards this building was wired to required either a switched overhead light or a switched outlet.

The kitchen, bath, and closets (even the pantry!) have the overhead light, the living room and bedroom have the switched outlets. Aargh!

 

[anorlunda]

No, I wish. More like moving into a new place and thinking, "I wonder why this outlet doesn't work sometimes. Hey it works! Ack, it stopped working."

That reminds me of a Steven Wright story.

I had a light switch in my house that didn't do anything. Every time I walked past, I would flip it. Last week I got a phone call. It was a woman in Germany. She said, "Cut it out."

 

[Wrichik Basu]

@Wrichik Basu
If the power plug is not polarized, try inserting it the other way in the wall outlet.

It's a 3-pin plug that has L and N written on it. Probably it's not meant to be plugged in with L and N reversed.

 

[Mark44]

If you're responding to my switch comment, some house outlets (in the US) do have wall switches that switch the Hot/Line wire to the outlet.

This is a useful feature. In our living room there is a receptacle that can be turned on by a switch. You can walk into the room and turn on a floor lamp. I've wired three outlets in my outside shop to work the same way so that three fluorescent lights turn on from a wall switch. It's also possible to wire a receptacle so that one half is switched and the other half is always hot.

It's a 3-pin plug that has L and N written on it. Probably it's not meant to be plugged in with L and N reversed.

Definitely not. Most likely L = line (or hot) and N = neutral. The third pin, all by itself would be ground or earth.
The polarity tester that @berkeman showed in post #26 is a very handy tool to have. Just plug it in, and the lights on it will show if the receptacle is wired correctly.

 

[Wrichik Basu]

The polarity tester that @berkeman showed in post #26 is a very handy tool to have. Just plug it in, and the lights on it will show if the receptacle is wired correctly.

I can buy it, but is it actually required? As pointed out by @berkeman, ~45V between Earth and neutral lines means a faulty earthing connection.

Also, I wanted to mention that yesterday I got a good shock by touching the negative pin of the laptop charger's DC jack. I have touched that terminal thousands of time in the past without any problem. But yesterday, don't know what happened. Maybe the potential difference between Earth and neutral caused that shock? Not sure. I've got a black mark on my finger.



I will have to call a certified electrician to fix the earthing, but, as almost everyone knows, the second wave of the pandemic has hit us hard, and I don't want to call anyone unless absolutely necessary because these people are just not following any COVID-19 protocols.

 

[Mark44]

I can buy it, but is it actually required?

It would be useful to check the other outlets in your house, and they are quite inexpensive. The one in your link works out to just under USD3.00.

I've had mine for about 20 years, and used it to verify that I had wired up several receptacles in a carport I converted to a garage as well as in an exterior shop that I wired myself.

As pointed out by @berkeman, ~45V between Earth and neutral lines means a faulty earthing connection.

Or maybe a short between the hot wire and neutral. Whatever, the tester has several lights on it that can pinpoint exactly which wires aren't wired correctly.

 

[berkeman]

Also, I wanted to mention that yesterday I got a good shock by touching the negative pin of the laptop charger's DC jack.

With the charger unplugged from the wall, what do you get for the resistance from each of the 3 pins of the plug to the outer and inner barrels of that charger?

 

[pbuk]

It's also possible to wire a receptacle so that one half is switched and the other half is always hot.

This may be true in the US but is certainly not true everywhere.

Definitely not. Most likely L = line (or hot) and N = neutral.

No, in India (as well as the UK and most of the rest of the world except the US), 'L' stands for 'Live'. You should appreciate that the US 120V dual phase system means that things work very differently in the US (and the few other countries with similar systems).

~45V between Earth and neutral lines means a faulty earthing connection.

No, ~45V between Earth and neutral means a faulty or overloaded neutral path anywhere in the system.

Also, I wanted to mention that yesterday I got a good shock by touching the negative pin of the laptop charger's DC jack. I have touched that terminal thousands of time in the past without any problem. But yesterday, don't know what happened. Maybe the potential difference between Earth and neutral caused that shock? Not sure. I've got a black mark on my finger.

This is exceedingly dangerous: you must get this fixed immediately. Ideally, in order to protect against this you should install a Residual Current Device(s): in fact Wikipedia suggests that in India you should already have this. Clearly if you do then it is not working properly (it should trip when any current over a tiny threshold which is not enough to burn you flows to Earth except via the Neutral wire).

I will have to call a certified electrician to fix the earthing, but, as almost everyone knows, the second wave of the pandemic has hit us hard, and I don't want to call anyone unless absolutely necessary because these people are just not following any COVID-19 protocols.

Do not confuse earthing (i.e. connection to Earth of the Earth wire - this is not what is wrong) with grounding or bonding of the Neutral return path).

Or maybe a short between the hot wire and neutral.

No, that would blow the fuse or trip the overcurrent device (or melt the wiring if the fuse is overrated).

I found something very interesting: We have one air conditioner of 1.5 ton in our house. When the above readings were taken, it was switched on. Later, after switching it off, I tested again, and the voltage b/w Earth and neutral became 23 V. Still much higher than normal, but lesser than the previous reading. When I switched on the AC again, the value climbed up to ≈ 44 V. I chose four different outlets in the house; same observation in each of them. Any idea why this fluctuation is occurring?

Yes, the neutral return path is faulty or underrated. As you have discovered, 45V is sufficient to cause a nasty shock: if the current passes through the chest it could cause cardiac arrest. Depending on the cause, this could also cause a fire.

The cause could be a connection that has become unreliable, a new load that has been attached or a fault in your ACU. If your neutral bonding is shared with another home or homes (illegal in many areas) the fault may be nothing to do with you, but it is you that it could kill.

 

[berkeman]

'L' stands for 'Live'

Well, "Live" and "Line" basically mean the same thing.

 

[Wrichik Basu]

With the charger unplugged from the wall, what do you get for the resistance from each of the 3 pins of the plug to the outer and inner barrels of that charger?

My multimeter shows 0.L when the two leads are separated, so that means open circuit, or infinite resistance. Keeping that in mind,

​

Terminal 1 (in plug)​	Terminal 2 (barrel in DC jack)​	Value (in Ω)​
Live​	Outer​	∞​
Neutral​	Outer​	∞​
Earth​	Outer​	1.011k​
Live​	Inner​	∞​
Neutral​	Inner​	∞​
Earth​	Inner​	2.093k​

the tester has several lights on it that can pinpoint exactly which wires aren't wired correctly.

Okay then, I will buy one.

No, ~45V between Earth and neutral means a faulty or overloaded neutral path anywhere in the system.

Okay, that explains it.

The cause could be a connection that has become unreliable, a new load that has been attached or a fault in your ACU. If your neutral bonding is shared with another home or homes (illegal in many areas) the fault may be nothing to do with you

In that case, our "regular" electrician won't be able to find the fault perhaps, and I have to call the power supply company. This just got a lot complicated.

 

[Wrichik Basu]

Ideally, in order to protect against this you should install a Residual Current Device(s): in fact Wikipedia suggests that in India you should already have this.

Nope, we don't have a RCCB. Our main circuit breaker is a simple 20A fuse. It was supposed to be replaced by a 64A C-curve DP MCB last year, but then lockdown started and the work hasn't been done.

 

[pbuk]

In that case, our "regular" electrician won't be able to find the fault perhaps, and I have to call the power supply company. This just got a lot complicated.

Perhaps, although the fact that your ACU which I'd guess draws about 10A accounts for about half the neutral return voltage indicates that the problem is fairly local.