# NEMA L14-30, Purpose of neutral in circuit (4 vs 3 prong)



## g1mb

What is the purpose of the neutral circuit in a newer 240 volt electrical system?

I just bought a generator (Generac GP6500) and it has a 4 prong receptacle for the 240 volt connection.  I can't find an adapter to convert this to a standard 3 prong plug.  Is the neutral actually necessary?  Can I make a cord that is 3 prong on one end, 4 prong on the other and eliminate the neutral?


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## jharkin

The neutral is there because its a mixed 120/240 v connection. Without that neutral you cannot feed any 120v circuits.

What are you trying to power with the generator? If you are trying to feed a transfer switch the neutral will be required to break it into 120v circuits. Even many 240v appliances like dryers and ranges are actually mixed 120v and 240v and need that neutral. the "3 prong" outlets you see on such don't lack a neutral - what they lack is a separate ground. Which is why they haven't been code legal for 20 years and are only grandfathered in for existing installs.

Don't want to make assumptions but I certainly hope you are not planning to backfeed your main through a dryer outlet or something.......


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## g1mb

Eventually I will install some type of proper transfer switch.  I'm looking at a Generlink setup, a Interlockit device, as well as a standard type transfer switch with a sub panel.

In the interim, I wanted to backfeed the house through the dryer outlet to make sure the generator works before I store it away.  Buying a generator was not high on my priority list until we had 2 prolonged power outages in the last couple of months.  I bought the generator last week just to make sure I got one before they ended up on backorder again.  I haven't decided on what to do with a transfer switch or panel yet.

From what I can gather the neutral was added for the purpose of the return current on a 120 volt circuit in a 240 volt appliance.  Prior to adding the neutral, the return circuit for a 120 circuit was the ground itself.  

Shouldn't I be able to eliminate the neutral connection at the generator, as I believe it is bonded to the generator ground anyway?


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## nate379

That's what I did for mine.  Just 8/3 SJOW wire off the 4 prong.  2 hots and the ground, didn't bother with the neutral. 

I made a male male pigtail and I just use my ~100ft welder cord (8/3).  

I don't really care if backfeeding the panel is "wrong".  So is drinking crap beer and people still do that everyday too.  I'm not going to spend big $$ for a transfer switch and all that for something I might use every few years.


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## bubba3228

WOW this is not going to end good.

Nate and g1 you will not be doing any favors to yourself or linemen working on the power distribution system. I would recomend spending some bucks and getting some professional insured and bonded electrical contractor to help you with your installations. :bug:


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## nate379

What do lineman have to do with running a gen set to power MY house?  The power company owns from the meter and beyond, the rest is MINE!

Turn off the main breaker, and holy cow, I can power up my house!!  WOW!

IF and I say IF I didn't shut the main, do you think a 4K gen set could actually backfeed an entire grid?  No, it can't.  It loads the gen set too much and it stalls.  

AND in any case why is a lineman handling wires without the proper PPE and training?


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## bubba3228

Yea your right. they should not sell them fancy new fangled transfer switches because them generators will just stall out anyway.


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## nate379

We have a transfer switch at work and it's nice.  Power goes out and 15-20 secs later gen set it running, all without having to move a finger.   Of course that gen set is in a nice heated 12x14 room, 6 cylinder Detriot diesel with 150Kw 3 phase gen head.

Just a "little" bit difference than my 8hp 4Kw Generac!

The gen set at work could power my whole neighborhood with plenty to spare.


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## hemlock

The thing is - transformers work both ways.  ie  50,000VAC down to 240VAC = 240VAC up to 50,000VAC the other way.


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## g1mb

So the deal is that I could inadvertently forget to turn off my main and create a hazardous condition for someone else on the line, or someone could pull the cord from the backfed receptacle and end up with an exposed hot "male" plug in their hands.  I understand that. I intend to install a proper transfer device as soon as it is in the budget.  For the time being I just want to test the new generator and see it work before I store it.

Can I just eliminate the neutral from the 4 wire connector without causing harm to the generator?


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## hemlock

g1mb said:
			
		

> So the deal is that I could inadvertently forget to turn off my main and create a hazardous condition for someone else on the line, or someone could pull the cord from the backfed receptacle and end up with an exposed hot "male" plug in their hands.  I understand that. I intend to install a proper transfer device as soon as it is in the budget.  For the time being I just want to test the new generator and see it work before I store it.
> 
> Can I just eliminate the neutral from the 4 wire connector without causing harm to the generator?



What I did was install a "power panel" in my utility room in the basement consisting of a few standard 120VAC receptacles, and one 240VAC receptacle all wired to a cord running to the garage that can plug into the generator outside.  For my well, I put a 240VAC plug and receptacle on the wires, and it stays "plugged in" to the normal house wiring.  In the event of a power outage, it gets unplugged and plugged into my "power panel".  The same with the freezer/fridge, and a few other smaller items.  
It's not as convenient as a hard wired set-up, because you still need a few extension cords, but it eliminates the need for transfer switches, etc.... as the home made "panel" is completely separate from the main panel.  The generator is outside, no cords going through windows, and best of all, it is fairly inexpensive.


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## jharkin

Sorry but stupid ideas like this get people *KILLED*.  Not to mention that its quite illegal.


 I don't care what your excuses are. Stop being cheap and do it the proper safe way.  If you don't understand the purpose of a neutral and ground you really have no business working on your house wiring, please hire an electrician.


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## bubba3228

The main job of the neutral(grounded conductor) is to carry the imbalanced amperes between the hots (phase conductors). The code has changed so that the installation of multi-wire circuits are not sharing neutrals without a means of disconnect. It is not a good practice to allow the bare(grounding conductor) to do the job of the neutral. The grounding conductors job is to bond metallic objects that may come in contact with the phase conductors, so they are not energized without tripping the breaker(over current protection device). Will it harm your new generator? That depends on how you wire your cord end. If you want to test your generator, plug something into it that creates a load and enjoy. If I was out of power and wanted to jerry rig a circuit or two that I wanted to temporarily energize and did not have a transfer switch I would isolate them from the panel and wire nut a cord ends on them plug them into the receptacles on the generator. I would not comfortable back feeding circuits with plugs downstream. That said, electricity will work in many different installations and you may think it is safe, however if you really do not know all the variables what are you energizing you may not want to be?


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## hemlock

jharkin said:
			
		

> Sorry but stupid ideas like this get people *KILLED*.  Not to mention that its quite illegal.
> 
> 
> I don't care what your excuses are. Stop being cheap and do it the proper safe way.  If you don't understand the purpose of a neutral and ground you really have no business working on your house wiring, please hire an electrician.



I'm not sure how my set-up is going to get anyone killed.  It's a pretty simple circuit, and isolated from the main feed.  I just bascially moved the generator plugs indoors.


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## bubba3228

I do not recall the code atrticles allowing your method for this application. Will it work? Yes - maybe ? jharkin has the correct advise.


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## willworkforwood

I wouldn't make any changes that MIGHT affect my generator.  All of the non-inverter gensets create "dirty" power, with high enough harmonic distortion to affect some motors and electronic equipment.  My generator is a typical non-inverter, and causes my wood boiler controller to be unusable.  It also changes the way our microwave runs, which in turn makes the oil burner motor change pitch.  So, brand new these gensets aren't producing great power, and chopping off the neutral prong could only potentially make things worse.  Unless someone who designs and builds generators for a living can guarantee that this cannot damage a genset, I wouldn't try it.    And +1 to not backfeeding, where there is any chance of powering into the grid.  I installed a transfer switch/sub-panel and outside receptacle 3 years ago - $300 and a good amount of work to re-route lots of wires.  But, there was NO WAY I was going to take even a .00001% chance of killing someone by backfeeding.   If you backfeed and kill a lineman who wasn't using PPE, then it's not your fault?   :bug:


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## velvetfoot

The thing is, that approach is probably just as expensive than an interlock kit, wire to the outside, and inlet box.


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## jharkin

hemlock said:
			
		

> I'm not sure how my set-up is going to get anyone killed.  It's a pretty simple circuit, and isolated from the main feed.  I just bascially moved the generator plugs indoors.



That wasn't aimed at you. It was aimed at people backfeeding a dryer outlet with a suicide cable, and using bare grounds as a neutral.


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## hemlock

jharkin said:
			
		

> hemlock said:
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> I'm not sure how my set-up is going to get anyone killed.  It's a pretty simple circuit, and isolated from the main feed.  I just bascially moved the generator plugs indoors.
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> That wasn't aimed at you. It was aimed at people backfeeding a dryer outlet with a suicide cable, and using bare grounds as a neutral.
Click to expand...


Sorry.


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## jharkin

g1mb said:
			
		

> From what I can gather the neutral was added for the purpose of the return current on a 120 volt circuit in a 240 volt appliance.  Prior to adding the neutral, the return circuit for a 120 circuit was the ground itself.
> 
> Shouldn't I be able to eliminate the neutral connection at the generator, as I believe it is bonded to the generator ground anyway?



Incorrect... ground was never a current carrying conductor in a 120v circuit EVER.  Old 2 prong 120v outlets were ungrounded - neutral was always a dedicated, insulated conductor even in the knob and tube days.

A ground is a safety feature ONLY. It is a path for fault circuit current to go to the ground and not into a human. Its there to insure that a short circuit trips a circuit breaker.   When you try to make a ground do double duty as a neutral, any wiring fault in the panel could potentially turn that ground and the metal frame of grounded appliance hot with line voltage. bad bad bad bad bad! 


3 prong dryer outlets were a special exception allowed starting in WW2 to deal with a copper shortage. The third wire was officially a neutral, but allowed to do double duty as ground in this one application only. To be legal it had to be SE or large appliance cable with a braided full size neutral. Junctions and splices were generally not allowed. That exception was discontinued in 1993, and existing installs are only grandfathered in if they are not modified in any way - which is why you cannot buy 3 prong 240/120 outlets or adapters.  The only thing you can still buy in 3 prong is the appliance cord to plug a new appliance into an old outlet.

I'm sure I'm coming off as judgmental but this is seriously risking somebody getting seriously hurt.  Please be safe!!


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## jharkin

hemlock said:
			
		

> jharkin said:
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> hemlock said:
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> I'm not sure how my set-up is going to get anyone killed.  It's a pretty simple circuit, and isolated from the main feed.  I just bascially moved the generator plugs indoors.
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> That wasn't aimed at you. It was aimed at people backfeeding a dryer outlet with a suicide cable, and using bare grounds as a neutral.
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> Click to expand...
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> Sorry.
Click to expand...


not necessary... I didn't make clear what I was addressing so my apologies for confusion.


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## oldspark

These posts make for some fun reading, I dont have a transfer swithch but ya gotta know what you are doing, there are ways to isolate from the grid and I get the impression Nate is doing that and said as such, I have a fuse block I remove. Anyone hooking in a gen. and not isolating from the grid (usually easy to do) is asking for a law suit. I agree with comment about if you dont understand neutral and ground facts than you are in over your head.


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## g1mb

Maybe I worded my post poorly.

I was referring to a 240 volt appliance, with the 120 volt portion of the appliance (eg.light bulb in dryer) using the ground (neutral) of the 240 circuit as it's return.  I didn't mean that the ground (bare wire) was ever used as a conductor.

I'm not likely to back feed this outlet anyway at this point, but it uses a 10/3 wire, all of the circuits are insulated, my neutral and ground are bonded in the generator, and my neutral and ground are bonded in my main panel.

My concern was in causing harm to the generator while checking to make the 240 outlet worked, as I have nothing that is wired for a newer type 120/240 receptacle to test it with.


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## oldspark

Oh boy now I am confused, a neutral is a conductor and it is not the same thing as a ground what so ever.


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## nate379

No point in continuing on with this thread.  I'm still going to do it, no matter what anyone says.  I know the "risks" which are all extinguished but simply turning off a breaker.

AND yes you certainly can still buy 3 prong 240v outlets.  Most 240v equipment outside home appliances like dryers and ovens have no use for a neutral.


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## burnham

NATE379 said:
			
		

> What do lineman have to do with running a gen set to power MY house?  The power company owns from the meter and beyond, the rest is MINE!
> 
> Turn off the main breaker, and holy cow, I can power up my house!!  WOW!
> 
> IF and I say IF I didn't shut the main, do you think a 4K gen set could actually backfeed an entire grid?  No, it can't.  It loads the gen set too much and it stalls.
> 
> *AND in any case why is a lineman handling wires without the proper PPE and training?*



 I am a lineman and a master electrician.  Your 4k generator could excite the coil in a transformer and send primary voltage out of the primary bushing.  You don't have to backfeed the entire grid if a wire is broken, or a fuse is blown.    Maybe you know what you're doing...maybe you don't.  Maybe you just think you do.


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## nate379

Sure.  I know to turn OFF the main and it's fine.  It's just like wiping my ass after I chit, not something I forget.


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## velvetfoot

Isn't bonding of neutral and ground only supposed to occur in one place, like the main panel?


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## BrotherBart

Personally I don't post my illegal activities on public Internet sites until a long time after the statute of limitations has run out.

Prosecutors use Google too.


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## bubba3228

When I took my apprenticeship the State of Wisconsin head inspector visited our class, he explained to us, the statute of limitations for murder is 7 years. There is NO statute of limitations for anything I am responsible for installing. I take my profession very seriously.


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## nate379

I torn the tag off my pillow and went 3mpg over the speed limit today... please come arrest me. ahahahahaahaha!


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## oldspark

This thread is out there orbiting the earth now, and it aint comeing back soon.


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## jharkin

A lot of arrogance on this thread. I'm no master electrician but I know enough from reading that I can tell folks are doing things over their head here.

Somebody IS going to get hurt. When that happens and you go to JAIL don't say we didn't try to warn you.

g1mp  - It seems like you are still not grasping a critical concept. Ground  x= Neutral. A neutral IS a current carrying conductor, its just biased to zero volts. a loose connection in the wrong place can put that at full line voltage. Thats why the old 3 wire dryer outlets are no longer legal for new installs -they were using the bare wire as the neutral current carrying conductor. It was an old exception that is no longer allowed for good reason. 

NATE379 - I checked you are right that you can still buy 3 prong 240v outlets - misstatement on my part. I'm still fairly sure that current code does not allow piggybacking of ground on the neutral for any new installs (our resident electricians should confirm).

velvet - Yes you are correct the neutral should only ever be bonded in one spot. Bonding in multiple places creates multiple paths and the potential for neutral current to follow the bare ground - again leading to the risk highlighted above. It is for this reason that when you use a generator feeding a main or transfer switch via a 4 wire (hot/hot/neutral/ground) you are supposed to break the bond of ground and neutral at the generator end.

Finally... For anyone who thinks they are so perfect they will never forget to kill the main. What happens when the power goes out in the middle of the night in pouring rain and your basement floods and you are frantically rushing, half asleep, to get that generator up and running to restart your sump pump. Ive been in that exact situation. Walking through an inch of water to hookup extension cords. Not fun or safe. I can tell you I would forget in spite of my best intentions. Maybe you are much more careful than me but I just cant stomach the risk.   You don't even need an expensive transfer switch.  A simple $50 interlock breaker will do it. You have a lot more than $50 into the generator.


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## gpcollen1

I think those of us responsible DIYers back feeding our panels are very careful and always open the Main Breaker.  The problem with discussions like these is that someone who knows nothing, like half the people buying generators out there in the past 2 months in CT for sure, could very well forget the open the Main Breaker.  I would not forget even with a foot of water int eh basement, which is impossible at my house anyway.


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## hemlock

CTwoodburner said:
			
		

> I think those of us responsible DIYers back feeding our panels are very careful and always open the Main Breaker.  The problem with discussions like these is that someone who knows nothing, like half the people buying generators out there in the past 2 months in CT for sure, could very well forget the open the Main Breaker.  I would not forget even with a foot of water int eh basement, which is impossible at my house anyway.



Suppose someone else (friends/visiting family, etc..) closes the main trying to "help"?  I've learned from years in industrial repair that some people just like flicking switches.  I'm not suggesting my little set-up is perfect, but I'm not back-feeding to the grid - which is precisely why I built my panel.  I'm not trying to come across as critical - but there's mistakes, and then there's *mistakes *, and one like this could be life-changing.  I'm no electrician, but I've worked around it enough to have a huge respect for it.


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## oldspark

Well I am (was) an electrician, industrial type and when ever some of these posts come up I do some research and usually learn a few things, one of the best things I have learned is NOT to give advice about wiring on a forum, you never know how much the other guy knows so its hard to cover all the things that can go wrong. There are so many varibles that change what you need to do, hooking up a gen in one of them, I would never cut the neutral off and not use it (think some one did that) electrical is easy to learn but not over night. So much good information on the net these days no need to ask joe blow for info, do your own research and if you dont understand some thing hire it done. Rambling now :sick:


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## gpcollen1

hemlock said:
			
		

> CTwoodburner said:
> 
> 
> 
> 
> I think those of us responsible DIYers back feeding our panels are very careful and always open the Main Breaker.  The problem with discussions like these is that someone who knows nothing, like half the people buying generators out there in the past 2 months in CT for sure, could very well forget the open the Main Breaker.  I would not forget even with a foot of water int eh basement, which is impossible at my house anyway.
> 
> 
> 
> 
> Suppose someone else (friends/visiting family, etc..) closes the main trying to "help"?  I've learned from years in industrial repair that some people just like flicking switches.  I'm not suggesting my little set-up is perfect, but I'm not back-feeding to the grid - which is precisely why I built my panel.  I'm not trying to come across as critical - but there's mistakes, and then there's *mistakes *, and one like this could be life-changing.  I'm no electrician, but I've worked around it enough to have a huge respect for it.
Click to expand...


I agree to an extent BUT there are very simple devices out there that can keep people from closing the main.  I am still working on what my final system will be.  for now, it is manual.

http://www.seton.com/no-hole-circuit-breaker-lockout-js171.html

http://www.grainger.com/Grainger/BRADY-Blocking-Bar-Lockout-Kit-3LY22?Pid=search


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## g1mb

jharkin said:
			
		

> g1mp  - It seems like you are still not grasping a critical concept. Ground  x= Neutral. A neutral IS a current carrying conductor, its just biased to zero volts. a loose connection in the wrong place can put that at full line voltage. Thats why the old 3 wire dryer outlets are no longer legal for new installs -they were using the bare wire as the neutral current carrying conductor. It was an old exception that is no longer allowed for good reason.



For the record:  I understand the difference between the ground and neutral circuits.  I never had any intention of using the ground (bare wire) to carry current.  I referred to the neutral wire on my 3 prong dryer outlet as ground because in an older 240 system I wouldn't have referred to it as a neutral per se.

I'm not going to get into a shouting match over back feeding an outlet as I am actually on your side of the issue.  But If I were to backfeed this 3 prong dryer outlet from my generator I would be backfeeding 2 hots legs and 1 neutral through a 10/3 cable to the main panel.  No bare wire involved.  As far as the bonding issue, even though the neutral and ground are bonded in my generator, I would not be bonding them in the house because I would be feeding a 3 prong receptacle, and not a 4.  If I were to backfeed a 4 prong (newer) receptacle with this generator as is, I would most certainly be creating a bond between the neutral and ground circuits in the house.


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## Vermonter2011

Six Dangers of Backfeeding Through The Dryer Outlet:  http://www.qsl.net/kc5qhh/backfeeddangers.pdf

One thing that people haven't mentioned here (maybe I missed it) is that if you are backfeeding through your dryer outlet and you leave the main open, the power company can fry your generator, your wiring and/or all kinds of stuff throughout your house.  They also will intentionally fry any generator that is live on the line, to protect their personnel.

So not only is there a risk of injuring a lineman, but there is also a risk that your property can be damaged if you leave the main open.


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