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what's the difference between 'hot' and 'neutral' in 240v AC power?

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Posted on June 19, 2011 at 18:52:26
Tom Schuman
Audiophile

Posts: 2632
Location: Bremen
Joined: October 22, 2003
 Why would it be bad to reverse the 'hot' and 'neutral' leads to an electrical outlet?

The reason I ask is the following:

I have just moved to New Zealand where there is 240 volts coming out of the wall, but unlike in Europe, you do not have a choice as to which direction the plug goes into the wall.

In Europe, there is also 240v, but which way to plug an applicance in is not crucial, i.e., the appliance works either way.

Here in NZ, I'm using a NZ power cord to a EU power strip with an IEC outlet, and all my European equipment plugged into the power strip.

Why is there a distinction between 'hot' and 'neutral' when the appliances'/audio equipment transformers seem not to really care?

I'm aware that there is a method for getting the phase right when plugging in audio equipment, that it has to do with lowered potentials from the return signal path to ground, and that supposedly correctly plugging in an audio component makes it sound better. But I have yet to prove to my own ears that this is true. ANd I have yet to use any electrical appliance that didn't work either way.

So, what IS the difference between 'hot' and 'neutral' when using 240 volt AC power, and when does it matter?

 

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No difference only the voltage and frequency have changed, posted on June 21, 2011 at 21:16:36
Tweekeng
Audiophile

Posts: 2093
Joined: September 9, 2005
 I took a quick look at NZ electrical codes and found a few things that migh help.

Wiring colors are Brown=Hot Blue=Neutral Green/yellow=Earth

Older wiring and cords might have Red=Hot Black=Neutral Green=Earth

From the drawings the A or P terminal is HOT and should be on the left.

You can always determine the hot neutral with a volt meter by measuring from the earth terminal. The hot should read 230V to ground and the neutral should read zero.

 

RE: No difference only the voltage and frequency have changed, posted on September 9, 2011 at 15:47:55
coffee-phil
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Posts: 1444
Location: Shingle Springs CA
Joined: January 7, 2010
 I can only speek with any sort of authority about US power. I assume it is similar in New Zealand. In the US most residences get 120 Volts for lighting and most appliances, and 240 Volts for large loads such as clothes dryers, ovens, and air conditioning compressors.

The house is fed from the secondary winding of a transformer. This winding is center tapped with 240 volts from end to end. From either end to the center is 120 volts. The center is connected to Earth. All three leads are fed to the house. The center lead is called neutral because it is connected to earth. This means that there is little (ideally 0) voltage between it and earth. The other leads are 120 volts from the neutral and are called hot. If you were to touch one of them and something connected to earth you would agree that the name is appropriate. The 120 volt loads in the house are pretty much equally divided between the two hots and neutral. 240 Volt loads are connected between the two "hot" leads. Knowing which lead is hot is useful for safety.

Since you don't have 120 volts, I'm guessing that one side of a 240 volt winding is connected to earth and called neutral and the other side is hot. Again this is useful for safety.

Phil

 

RE: No difference only the voltage and frequency have changed, posted on September 29, 2012 at 11:07:03
Mushroom Soup
Audiophile

Posts: 310
Location: Western New York State
Joined: November 1, 2003
 That assumes that they have the same line voltages that the US has, which I don't think you can assume.

 

RE: No difference only the voltage and frequency have changed, posted on June 22, 2011 at 00:19:29
Tom Schuman
Audiophile

Posts: 2632
Location: Bremen
Joined: October 22, 2003
 Thanks for the link. In NZ, the 'live' lead is on the left as you look at the wall plug.
My question was more what difference it makes to have equipment plugged in the 'wrong' way around...it looks like I should pay attention to the phase in my installation even when using European gear.

Out comes the multimeter to determine the phase of my equipment. I think the computers all have switch mode supplies where I suspect it doesn't matter at all.

Thanks and cheers.

 

RE: No difference only the voltage and frequency have changed, posted on June 22, 2011 at 07:08:38
jea48
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Posts: 6770
Joined: January 5, 2005
 >>

 

RE: what's the difference between 'hot' and 'neutral' in 240v AC power?, posted on June 21, 2011 at 21:15:19
jea48
Audiophile

Posts: 6770
Joined: January 5, 2005
 Here is a Post of Charles Hansen's on the subject....

 

thanks that's just what I was looking for. nt, posted on June 22, 2011 at 00:15:48
Tom Schuman
Audiophile

Posts: 2632
Location: Bremen
Joined: October 22, 2003
 cheers

 

RE: what's the difference between 'hot' and 'neutral' in 240v AC power?, posted on June 21, 2011 at 09:53:27
6bq5
Audiophile

Posts: 4387
Location: SF Bay
Joined: August 16, 2001
 AC Mains power is delivered via one hot and one neutral wire. the power is available when a load (such as a motor)is connected across the potential - or both wires are connected to the load. Most AC (Alternating Current) appliances and not overly sensitive to the phase of the mains; however in some instances the reversing of the phase (hot for neutral) can cause or potentially cause a problem - mostly when there is only a switch on the intended HOT leg. An AC volt meter can be used to identify the HOT leg: setting the voltage to the correct range (so as to not overload the meter) the voltage potential should be the same between the HOT leg and the neutral and the Hot leg and one of the mounting screws for the faceplate.
If this does not make sense to you there should be a device sold in a local hardware store that can 'diagnose' your phase, and there are single probe units that can distinguish Hot from Neutral. see attached links:

Failing all the above, Locate the breaker and turn off the power to the plug in question, then remove the face plate the HOT wire SHOULD bee either Black or Red in colour.
If you don't feel comfortable with this, call an electrician.

Happy Listening.
Happy Listening

 

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