why no nutral for 240_480v load?

[Toros]

Hi,
I do not understand well why no nutral or return path of current for 240_480 loDs
Why, why

 

[iwire]

A neutral is no more or less of a 'return path' than the hot that is with it.

 

[GoldDigger]

A neutral is no more or less of a 'return path' than the hot that is with it.

And a load connected between two hots uses one conductor as the supply and the other as the return. It is a complete circuit regardless of how you name the conductors.

 

[iwire]

And a load connected between two hots uses one conductor as the supply and the other as the return. It is a complete circuit regardless of how you name the conductors.

Generally 240 and 480 circuits are AC so I try to stay away from calling individual conductors supply or return.

 

[__dan]

The supply only has the neutral bond point, system bonding jumper, GEC. The load has no effect on the neutral, it can be connected or not, the only difference is the nominal supply voltage. The load connects to the EGC but not the neutral.

 

[Smart $]

I'd like to know exactly what system configuration(s). Can't tell whether"240_480 loDs" refers to 240 or 480, or 240/480. Of the voltages by themselves, no neutral is required with typical configurations. 240/480 refers to a split phase configuration... for which any 240V load would require a neutral conductor.

In a three- or four-wire system, which all slashed configurations are either three- or four-wire, only two of the three conductors are necessary to deliver power to a single phase load. Which two is just a matter of the equipment's nominal operating voltage. Of course if the equipment is split- or three-phase, then three conductors are required for the equipment to operate.

 

[JDBrown]

Hi,
I do not understand well why no nutral or return path of current for 240_480 loDs
Why, why

You have to remember that AC stands for Alternating Current, meaning that the current flows first one way, and then the other. In a DC circuit, current flows out of the source via the "supply" conductor to the load, and from the load back to the source via the "return" conductor. But an AC circuit doesn't work that way because the current is constantly changing direction.

When you connect a line-to-neutral load (let's say L1 to N), the current flows from L1 to N, then from N to L1, then from L1 to N, etc. over and over again at 60 cycles per second.

When you connect a line-to-line load (let's say L1 to L2), the current flows from L1 to L2, then from L2 to L1, then from L1 to L2, etc. over and over again at 60 cycles per second.

So, for a 240Vor 480V single-phase load, the current leaves your source (generator, transformer secondary, PV inverter, whatever) via one "hot" leg and returns via the other "hot" leg -- but this only lasts a fraction of a second. Then the current reverses direction and flows out of the source via the second "hot" leg and returns via the first "hot" leg. This also only lasts a fraction of a second before the current reverses direction again.

I hope this made as much sense written down as it did in my head.

 

[iwire]

I hope this made as much sense written down as it did in my head.

It made sense to me.

 

[growler]

Hi,
I do not understand well why no nutral or return path of current for 240_480 loDs
Why, why

You do have a return path but a neutral is not needed with a balanced load. If you were to break either conductor the circuit would be open.


On a multi-wire branch circuit you have 240Vs (phase A to B) but the neutral only carries the unbalanced load.If I were to take those same two phases and hook them to a motor or heating element that required 240 V there would be no current on the neutral so it's not needed.

 

[Toros]

You do have a return path but a neutral is not needed with a balanced load. If you were to break either conductor the circuit would be open.


On a multi-wire branch circuit you have 240Vs (phase A to B) but the neutral only carries the unbalanced load.If I were to take those same two phases and hook them to a motor or heating element that required 240 V there would be no current on the neutral so it's not needed.

This make sense to me but 70%,
Can you explain me more in sense of "Potential difference" that neutrals create to attract currents in 120-277 volt loads.

what creates Pot. Diff. in 240-480v???

 

[ActionDave]

This make sense to me but 70%,
Can you explain me more in sense of "Potential difference" that neutrals create to attract currents in 120-277 volt loads.

what creates Pot. Diff. in 240-480v???

Check out this post from a member of this forum who dropped off the radar a few years ago; see if answers any of you questions. http://forums.mikeholt.com/showthread.php?t=89023&p=708650#post708650

If this thread takes off you may get a lot more info than you ever imagined.

 

[iwire]

This make sense to me but 70%,
Can you explain me more in sense of "Potential difference" that neutrals create to attract currents in 120-277 volt loads.

what creates Pot. Diff. in 240-480v???

A neutral does not create a 'potential difference'.


A generator or battery can create a 'difference of potential' and conductors can be used to bring that difference of potential to where we need it.

The difference of potential does not care what we choose to call the conductors.

 

[K8MHZ]

I'd like to know exactly what system configuration(s). Can't tell whether"240_480 loDs" refers to 240 or 480, or 240/480. Of the voltages by themselves, no neutral is required with typical configurations. 240/480 refers to a split phase configuration... for which any 240V load would require a neutral conductor.

In a three- or four-wire system, which all slashed configurations are either three- or four-wire, only two of the three conductors are necessary to deliver power to a single phase load. Which two is just a matter of the equipment's nominal operating voltage. Of course if the equipment is split- or three-phase, then three conductors are required for the equipment to operate.

I think the OP was asking why there are no neutrals for 240 or 480 volt 'loads'.

 

[iwire]

I think the OP was asking why there are no neutrals for 240 or 480 volt 'loads'.

I agree, I think Mr Smart likes to complicate things for his own reasons.

 

[Smart $]

I think the OP was asking why there are no neutrals for 240 or 480 volt 'loads'.

I agree, I think Mr Smart likes to complicate things for his own reasons.

No, I don't. I actually like to simplify as much as possible. But the ambiguity of the OP begs for clarity. A 480V split phase system (240/480V 1? 3W), or a 480V 3? system with center tap (480/240V 3? 4W) does require a neutral for 240V loads.

 

[K8MHZ]

No, I don't. I actually like to simplify as much as possible. But the ambiguity of the OP begs for clarity. A 480V split phase system (240/480V 1? 3W), or a 480V 3? system with center tap (480/240V 3? 4W) does require a neutral for 240V loads.

I have a feeling he wasn't asking why the systems that do require a neutral don't have them.

 

[iwire]

No, I don't. I actually like to simplify as much as possible.

Hey, give us a warning before saying such things, I almost chocked on my coffee.

 

[templdl]

I have a feeling he wasn't asking why the systems that do require a neutral don't have them.

Another guess at what the OP is asking. It is obvious that he is just looking at the voltages and the simple fact that a basic knowledge of very basic electric systems is lacking. Smart$ did make a good point. There is a big difference from those who can do a most excellent code installating from this who actually have an understanding as to why they are doing it. Hense the question "Why isn't there any neutral?" which is a bit scary. It is commonly understood the a 'neutral' is commonly grounded but a conductor when it is grounded is not necessarily a neutral. And where does a neutral come from? May it be from how a transformer is wound, tapped and its secondary connections and/or how it is connected to?
On the positive note at least the OPs are asking questions and feel comfortable to do so on this forum.

 

[Smart $]

Hey, give us a warning before saying such things, I almost chocked on my coffee.

Well if you didn't make the assumptions you do, there'd be no need.

Doubt that'll change anything either way, though... :happysad:

 

[Smart $]

This make sense to me but 70%,
Can you explain me more in sense of "Potential difference" that neutrals create to attract currents in 120-277 volt loads.

what creates Pot. Diff. in 240-480v???

To what others have stated, I will add this...

Voltage is a measure of potential. Its the ooomph of the circuit. It can be likened to say a AA battery. It has essentially the same ooomph, sitting on the shelf in the store as it does installed in a flashlight (when still fully charged).

When you have multiple voltages in a system, it's like having more than one battery connected end-to end. Using a AA battery as an example, each has 1.5V potential. Connected together in series (the positive of one butted to the negative of the second), both together have a potential of 3.0V from the negative terminal of the first to the positive terminal of the second. Yet each battery still has 1.5V potential between its own terminals.

Potential difference, or rather difference in potential, doesn't really enter the picture until there are three points from which to make potential (voltage) measurements. If in the two battery example we choose to reference our measurements to the negative terminal of the first, this is saying that one of our meter leads (typically the black or negative lead) will probe this negative terminal for all measurements. Since there are only two other points (butt and second battery positive terminal) to make a measurement, we get measures of 1.5V and 3.0V respectively. Using these values, we can surmise the potential between the two points by taking the difference in potentials... 3.0V ? 1.5V = 1.5V.

While the preceding example is regarding DC voltage, split phase AC systems such as 120/240V and 240/480V exhibit basically the same relative RMS voltage measurement (though there will be no minus voltage measurement if you connect your meter leads backwards).

With 3? 4-wire systems, or 3-wire systems originating from them, the measurements will give different relative measures because the AC voltages are not aligned, i.e. they are out of phase. 208/120V 3? 4W, 120/208V 1? 3W, 480/277V 3? 4W, and 277/480V 1? 3W are common examples.