A/C voltage and polarity - who check that?

[murali]

There have been some recent "long" threads on effects of cables and interconnects and it is not my intention to introduce more controversies here. However, another interesting issue is the correct A/C polarity to be used in connecting a power cord between a component like amplifier and the wall socket, especially with 3-prong plugs (phase, neutral and earth). Good equipment manufacturers always insist that the correct polarity should be maintained, like the phase of the wall socket should be connected to the prong meant for phase in the device also. Even if the phase and neutral are reversed, it will still work but the right connection does cause a difference in sound, in my humble experience. The best description a friend of mine gave was about hand-clapping at the end of a music which in the system connected correctly will sound like several hands clapping whereas will sound like popcorn popping in the other way round.
There are simple polarity checkers available in the market (I believe multimeters can also be used). I use a cheap van den Hul polarity checker. The equipment has to be disconnected completely from all interconnects and the power cord plugged in and switched on. The polarity checker on contact with the equipment body will show you any residual voltage there, then you reverse the plug and check again. The lowest residual voltage is the right phase-phase connection.
I wonder whether anyone else has tried this and will be kind enough to share his/her experiences.

Thanks.
murali

 

[gobble]

Polarity? What about when we use balanced power supplies?

--G0bble

 

[santhosh]

Here is small pictorial guide to check earth, polarity with a multimeter:
http://www.diyable.net/forum/viewtopic.php?f=13&t=49


Sent from my iPhone using Tapatalk

 

[anuragn]

"van den Hul polarity checker"
Won't it be an overkill for the job? (although no doubt it would still serve the purpose).
Anyway, I use a simple "line tester", the screw driver type that you get for Rs 10-15 at any electrical shop.
In case of equipment where they connect the chasis to neutral instead of ground, you get a voltage if the line & neutral are reversed in the power socket. Ideally the chasis should be connected to ground and not neutral.

 

[Thad E Ginathom]

Anyway, I use a simple "line tester", the screw driver type that you get for Rs 10-15 at any electrical shop.

I was thinking the same --- and wondering what I was missing. Electrical testing screwdriver in each hole: it lights up for the live one, it does not for the neutral one.

Reversed polarity at outlets is very dangerous. The switch works, because it breaks the circuit, but because it is switching the neutral, live supply is still available to the appliance. This should not be the case for anything, whether it is an amplifier or a lightbulb. All outlets should be checked.

Here is small pictorial guide to check earth, polarity with a multimeter:
www.DIYable.net • View topic - How to: check earthing using a multimeter

Probably a much more sophisticated method of checking the health of the wiring. I do not know what these voltage differentials mean --- but I'll have a go at understanding!

In case of equipment where they connect the chasis to neutral instead of ground...

Is that safe? Is it even legal?

 

[anuragn]

Is that safe? Is it even legal?

Of course its very unsafe.
Legal part I doubt there would be any law in India that explicitly prohibits connecting neutral to chasis. Although it is illegal for any person to operate as an electrician unless he/she is a certified (licensed) electrician.
You can be sure that chasis is connected to neutral (i.e. if at all connected), if the power cord has a 2-pin plug.
Like my old Sony CRT used to give electrical shock when I touched any of the RCA input sockets!

 

[Kannan]

In India the 220V alternating voltage, the difference between neutral and live is mostly safety.

It is correct that you can usually swap these when connecting your device. (It is anyhow impossible to tell when you connect two pin devices without a multimeter to note which pin in the device is the live part).
The device will work since we're talking alternating voltage here.
However there is a safety concern especially in wet or humid conditions or in cases where the live and neutral wires are not fused or if there is a leakage due to poor insulation.
There is a inherent risk of getting a shock even if the fuse is blown since only the neutral would have got cut and the current will continue to flow through the live wire.
So when using 2 pin devices, it is better to mark that part of the pin that connects into the devices main circuit with a color code (red is the usual standard).

It is also very important to ensure that the line is uniformly connected to the left side of the socket in all the points in the house and the neutral to the right side of the socket. Also use the same color wire through out the wiring (for eg. red for line, black for neutral and green for earth.).

Earthing is a very critical issue usually ignored in many households. Get it done professionally and let all the electrical points be properly earthed.

 

[Thad E Ginathom]

line is uniformly connected to the left side of the socket in all the points in the house and the neutral to the right side of the socket.

As seen from the back, right?

 

[Kannan]

As seen from the back, right?

Yes..
Very important clarification else...

 

[Thad E Ginathom]

It was late night, about to go to bed, and, at first I thought you'd got it reversed . Then I realised that you mean as seen when wiring the socket.

Always best to check with a tester. Anyway, one should never assume that the red cable is live: there might be a mistake upstream.