What is a neutral wire on a 240 wire?

Answer 1

Answer for USA, Canada and countries running a 60 Hz supply service.In countries running 60Hz services the electricity utility powerlines going to residential streets and roads are operated at nominal voltages going from 2400 up to 7,200 and even 14,400 volts relative to ground. To provide 240 volts to the buildings, pole Transformers are used having step-down ratios going from 10-to-1 up to 60-to-1.

For each 240 volt phase the pole transformer has a center-tap so that +120 volts can be supplied from the half-winding on one side of the center tap whenever -120 volts is being supplied from the other half-winding. (It is important to remember that in fact the voltages in the two half-windings or "legs" always alternate from +120 volts to zero to -120 volts 60 times per second.) The center point tap between the two "legs" - known as the "neutral" connection - is also a convenient point to make the safety grounding connection for the transformer.

The actual measured voltage in your house branch circuits (to which its 120 volt receptacle outlets and lamps are connected) will normally be around 120 volts. However all lamps and appliances are rated for the maximum operating voltage (usually 120 volts and 240 volts), thus there is much confusion about the actual level of the supply voltages.

However, all that was just a necessary preamble to the actual answer to this question! Here comes the answer:

An appliance that is designed to be connected to strictly 240 volts 60 Hz is connected with only a two wire cable plus a safety ground wire. (For example 240 volt 60 Hz base board heaters use that.)

Most big appliances such as air conditioners, dryers, some kitchen ranges, etc., which need to draw high power, are nowadays supplied not from a 120 volt "leg" but at a full 240 volts by connecting them to both of the legs, "+120" and "-120", which come from the pole transformer as was described above.

However many of these appliances also need a 120 volt feed for such things as lamps, time-clocks, program control circuits, etc. To get that 120 volts they must use the neutral wire which comes from the center tap of the pole transformer.

Thus an appliance designed to run on a 240/120 volt 60 Hz supply can have up to 4 wires altogether:

• two 120 volt 60 Hz live "hot legs" which run in opposing phase to one another: when one hot leg goes "+" (120 volts positive) the other leg goes "-" (120 volts negative);
• a neutral wired as a "central" common current return conductor:
• a safety "ground" wire but this is not required if the appliance is of the type known as "double insulated"..

One of the two hot wires feeds a 120 volt alternating voltage from the power station to the 120 volt load - the clock or programmer - and, because the voltage is alternating, that load draws an alternating current. Then the neutral wire returns the current to the power station to complete the circuit.

<><><>

Different voltage levels are used in different countries around the world. The reason to use a higher voltage is that it is more economical: the current is less, so the wires can be smaller. On the other hand, the reason why lower voltages are still used in homes and offices for supplying small appliances, lighting, etc. is safety: "The lower the voltage, the safer it must be".

<><><>

Important Note:

Do not confuse a Neutral with a Safety Ground (or Earth) connection.

For more information on that topic please read the answer to the Related Question which is shown below as:

"What is the purpose of the ground wire on an appliance or in a house branch circuit?"

Answer for countries in Europe and other world areas running a 50 Hz supply service.In countries running 50Hz services the electricity utility powerlines going to residential streets and roads are typically operated at many thousands of volts. Pole or street-level sub-station transformers are used which have the necessary step-down ratio to provide 230 volts to the buildings. The "live" wire comes from one end of the transformer's secondary winding and the "neutral" wire comes from the other end, which is also a convenient point to make the safety grounding connection for the transformer.

The split-phase type of service, as is commonly used for 60Hz systems, is not used for 50Hz systems because all appliances, lamps, socket outlets, etc. run at 230 volts.

So a neutral wire is always needed as the return path back to the power station for any 230V 50Hz single-phase circuit in which only one live wire feeds alternating current into the connected load.

<><><>

Important Note:

Do not confuse a Neutral with a Safety Ground (or Earth) connection.

For more information on that topic please read the answer to the Related Question which is shown below as:

"What is the purpose of the ground wire on an appliance or in a house branch circuit?"

<><><>

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

Answer 2

You have three feed wires on US residential service: 2 hots and neutral. These wires are connected to a 240V center tapped transformer with the neutral connected to the center tap. So, you have 120V between either hot and neutral and 240V between the hots. There is no neutral in this circuit because the load doesn't require 120V, it draws 240V directly from both hots.

Answer 3

Answer for USA, Canada and countries running a 60 Hz supply service.

In many 240v appliances there are components that use only 120v and therefore must have a neutral. Examples would be lights or the clock of an electric range or the timer and motor of an electric clothes dryer. Years ago this was not the case and in situations where it were the case the ground was used as a neutral. This is no longer allowed so any appliance that uses 240v for the primary component and 120v for others must have separate ground and neutral wires feeding it.

<><><>

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

Answer 4

In the UK, the neutral and live are the two wires that carry the current to the appliance, so a neutral is needed.

<<>>

In North America there is no neutral conductor needed on a three wire single phase system when the load is strictly 240 volts. Both of the two live conductors are "hot" to ground and to the centre tap neutral. On appliances that have additional 120 volt loads, the neutral conductor needs to be used. This would be in cases like timers on dryers, clocks on ovens and range tops. Resistive heating loads and hot water tanks only need a two wire cable at 240 volts to operate the devices. The 240 volts is supplied from two adjacent breakers from the home distribution panel.

Answer 5

In the UK, the standard wire colours are:

Brown is the positive wire.

Blue is the negative wire.

Green and yellow striped wire is the ground or earth wire.

Answer 6

it is a return of the elec.

Answer 7

To complete the circuit