# Unbalanced amperage



## Quatrix (Dec 19, 2018)

Hello experts!

I have a question about my circuit breaker panel. Could someone tell me why exactly the smarter than me individual(s) decided to put 180A on the left leg (sum of all circuit breakers) and 170A on the right leg? Would this be an unbalanced situation and overload the neutral? 

P.S. Circuit Breaker panel attached to this post.


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## Snoonyb (Dec 19, 2018)

NO.


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## Quatrix (Dec 19, 2018)

Why NO?


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## Snoonyb (Dec 19, 2018)

What you need to understand is that the breakers protect the circuit conductors, so you are not asking the right question, and even though because the value of the breakers appears to be unbalanced, you'll need to run a load test to ascertain the load on the two primaries which will undoubtedly be less then the ampasity of the primary service feed conductors.


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## afjes_2016 (Dec 20, 2018)

And from a bit of memory on balancing the load don't the two pole breakers cancel out each other?


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## hornetd (Dec 20, 2018)

The reason that the grounded current carrying conductor is sometimes a neutral is that the current on one half of the transformer's secondary winding balances out the current on the other half of the transformer's secondary winding.  In a residential neighborhood that transformer is likely to be single phase.  That means it takes it's supply for the primary winding, which is the one through which the utility's current flows, from only one of the three distribution wires.  In most utility arrangements each phase has the same voltage relative to each other and to the neutral.  Since the primary is a single phase conductor the secondary side is also single phase.  There is only one winding on the each side of the transformer.  On the primary side one end of the winding is connected to the distribution multi grounded neutral.  On the secondary side the neutral's grounding connection is made to the center of the winding and not the end.  The ratio of the turns in each winding results in a secondary voltage which is a total of ~230 volts.  Since there is only half of that winding on each side of the neutral connection point there is only half of that voltage, ~115 volts, between the neutral connection point and each end of the winding.  Since you have the same voltage between the neutral of the secondary and the grounded neutral the loads on either side of the neutral balance each other and behave as if they are a 230 volt load.  It is only the difference and not the sum of the two total loads that travel on the neutral conductor.  If the actual load on one energized conductor is 150 Amperes with 170 amperes on the other energized conductor then only 20 ampere difference in the two current flows will travel on the neutral.  

Warning:  The connection arrangement I have described is only, by far, the most common for residential service to individual detached homes.  It is not the only arrangement.  There are several others which are much less often used.  

As others have indicated the circuit breakers in your panel are sized to protect the conductors used in the circuit they protect.  The breaker can only respond to the current which is flowing through it on the energized conductor which is attached to that breaker.  It cannot protect the neutral except when the neutral is one of only two conductors in the circuit.  Even then it only protects the neutral from overload because all of the current flowing in that neutral has to come from that one breaker.  If there are 2 energized conductors in the circuit then, like the neutral in the supply wiring from the utilities transformer, the neutral of that feeder or multi wire branch circuit will only carry the difference of current flow on each of the energized conductors.  The present code requirements for the installation of Combination Arc Fault Circuit Interrupters prevents the use of Multi Wire Branch Circuits in new construction or major remodels because the presently available CAFCIs can only protect a single energized conductor.  That is why four wire cable with 2 separate neutral conductors is now commonly available.  It maintains most of the labor savings of a multi wire branch circuits without using the same neutral for two energized conductors.  

-- 
Tom Horne


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## Quatrix (Dec 20, 2018)

hornetd,

I appreciate your detailed reply. Essentially, the safety ‘buffer’ we have is that loads must be running on both phases simultaneously in order to have the current through the neutral be minimal. In situations when loads on one leg consume more current than on the other would result in an unbalance. If current on that hot service entrance conductor exceeds the Main breaker capacity, it may trip, causing every circuit to lose power. Please correct me if I’m wrong.


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## hornetd (Dec 20, 2018)

Yes the Main Breaker; which the code calls the Service Disconnecting Means (SDM); will trip if the current exceeds the rating of the breaker.  The closer the overload is to the breaker's set point the slower it will open.  In general breakers open much more quickly on a fault or short circuit than they do on an overload.  Most breakers contain both a thermal and a magnetic trip.  The thermal trip will open on an overload but in the case of a small overload it will take some time to do so.  In the event of a fault or short circuit the sudden spike in current flow trips the magnetic element of the breaker very quickly. 

In the absolute worst case scenario of an unbalanced load, were the load on one energized conductor is nothing and the load on the other energized conductor is is near it's maximum ampacity, the neutral will only carry the same current as the energized conductor which is carrying all of the current that is coming in to the home.  There is very little danger of exceeding the capacity of the neutral as long as it is only getting current from an identically loaded conductor.  If however the neutral has to carry the current from 2 circuits which are not on different halves of the transformer secondary winding it can end up carrying a load that is the sum of the two energized conductors loads.  That will overload the neutral and since the neutral does not have over current protection, except that which is installed in the energized conductors it is properly paired with, it will overheat, fault, and possibly develop an arc which would kindle a fire almost immediately. 

--
Tom Horne


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## Eddie_T (Dec 21, 2018)

Great explanations Tom, balance would be fleeting at best since a home has many intermittent loads. When I wired my house I didn't give it any thought but the heaviest loads are 240v anyway. My heaviest 120v loads would be microwave, electric iron, vacuum cleaner, space heater and shop tools. At a NASA tracking station I worked at they balanced loads at least once annually to minimize neutral current (most loads were constant from electronic equipment). I have thought it might be nice to have a current loop on my home neutral as a curiosity item but I am not sure if it might be a code violation to do it the way I was considering.


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## hornetd (Dec 21, 2018)

If by a current loop you mean a current measuring transformer I do not know of any reason you could not have one.  They do not actually connect to the conductor which they are measuring the current in so I cannot see anyone having an objection to it.  Some of them are quite bulky so you would need to be careful not to overfill the wiring trough of the panel's cabinet. 

It is quite common for utilities to use current transformers to measure usage in properties with large loads or multiple buildings.  In farm properties it used to be common practice to have current transformers on the service drop from the last utility owned pole to the premises owned Yard Pole.  The Service Disconnecting Means would be located at the Yard Pole and from there separate feeders would run to the individual buildings.  Sometimes the Current Transformers and the meter that read the flow through them would be mounted at the last utility owned pole to assure reading access to the meter. 

--
Tom Horne


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## bud16415 (Dec 21, 2018)

Where I worked for 43 years was a huge industrial plant we had our own coal fired power plant and could co generate power on and off the grid to fully power the facility. We had in the hay day 16,000 employees and huge inductive loads throughout the plant and power factor correction was a major concern. It is somewhat similar to what we are talking about here but instead balancing the power factor.


We had a compressor house as part of one building that supplied compressed air underground for the whole plant. The compressors were gigantic and they were powered with special motors that introduced a capacitive power factor that would correct the inductive factor and losses.


The end result was that 100% of the compressed air needs was done at zero cost in electricity as the installation saved more money than it cost.


The really remarkable part of this it was all done around 100 years ago and has ran 24-7 for all that time with hardly anything except some preventive maintenance once a year during the two week plant shutdown.


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## nealtw (Dec 21, 2018)

Okay maybe I am dense, I understand that you want to lower the current in the neutral by matching likely users like fridge and freezer.
But I don't understand overloading the neutral to melt wires, the ground will take half the load so the load going back to the meter will never be more than the main breaker.  Correct me? Is that not what the ground is for, or at least one reason.


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## JoeD (Dec 21, 2018)

The ground does not ever carry current except in a fault. At least it is not supposed to.
Current on the neutral in a standard home installation is always going to be less than the current on the hot unless all your loads are on the same leg of the service. This is next to impossible to accomplish. The current on the two hots cancel each other out on the neutral. The neutral only sees the difference in current.


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## nealtw (Dec 22, 2018)

JoeD said:


> The ground does not ever carry current except in a fault. At least it is not supposed to.
> Current on the neutral in a standard home installation is always going to be less than the current on the hot unless all your loads are on the same leg of the service. This is next to impossible to accomplish. The current on the two hots cancel each other out on the neutral. The neutral only sees the difference in current.


The question was at the top of the page was about over loading the neutral when out of balance. That would only be the neutral to the road. The ground and neutral are tied together at the main. ???


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## Eddie_T (Dec 22, 2018)

It is correct that the neutral and the earth provide parallel current paths to the center tap of the pole transformer.  However the current through the earth requires a voltage to push it. The available voltage at the panel would the voltage drop of the neutral to the pole, 3/0 SE cable would have a negligible resistance compared to the resistance of the ground connection  and its earth path to the pole ground connection. Most ground connections are not tested so probably don't meet stated code resistance value. I saw a ground test by Mike Holt on youtube where a 50' ground rod had 68 Ω resistance. My ground rod is 10' about the same as the pole ground so any earth path current would be negligible compared to the neutral.


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## nealtw (Dec 22, 2018)

Eddie_T said:


> It is correct that the neutral and the earth provide parallel current paths to the center tap of the pole transformer.  However the current through the earth requires a voltage to push it. The available voltage at the panel would the voltage drop of the neutral to the pole, 3/0 SE cable would have a negligible resistance compared to the resistance of the ground connection  and its earth path to the pole ground connection. Most ground connections are not tested so probably don't meet stated code resistance value. I saw a ground test by Mike Holt on youtube where a 50' ground rod had 68 Ω resistance. My ground rod is 10' about the same as the pole ground so any earth path current would be negligible compared to the neutral.


Okay, that is a little deep but I will buy but could not explain it to anyone.
Why are ground and neutral connected?


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## hornetd (Dec 23, 2018)

nealtw said:


> Okay, that is a little deep but I will buy but could not explain it to anyone.
> Why are ground and neutral connected?


To give the current flowing to ground from a lightning strike to the overhead power lines a less destructive path to get there is one reason.  The National Electric Code puts it this way: 250.6 
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.  

-- 
Tom Horne


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## hornetd (Dec 23, 2018)

nealtw said:


> Okay, that is a little deep but I will buy but could not explain it to anyone.
> Why are ground and neutral connected?


Nealtw 

Just apply Ohm's law to the normal situation and you will see what is going on.  The National Electric Code (NEC) requires that a driven electrode have a resistance to ground of 25 Ohms or less OR that a second ground rod be installed at least 6 feet away from the first.  Once I acquired the tester to do it easily I got in the habit of measuring the resistance to ground on all the ground rods I installed and all the ones at the existing installations I worked on.  It takes about 5 minutes.  I learned that just about every electrician didn't bother measuring because the resistance to ground of the single rod was never, in my experience of measuring them, lower than 25 Ohms.  Even with the second rod the resistance still did not go below 25 Ohms.  In nearly all installations, that I measured, the resistance to ground at the house was over 50 Ohms.  The other end of that return path would be the Grounding Electrode at the transformer with the earth as the conductor in between. 

Power Utilities are not regulated using the NEC rules.  The code that the state regulators apply is the National Electrical Safety Code (NESC).  Thus the Grounding Electrodes that they use are sometimes similar to those in the NEC but often very different.  One common power utility transformer grounding electrode is a spiral of bare copper wire which is stapled to the but of the pole before it is set.  Another is to cover the first foot of the but of the pole with copper sheathing.  Whenever I could measure the utility's electrode without tampering with the installation I did so.  That wasn't very often because the Utility's Grounding Electrode Conductor is often covered by a wood or plastic molding for the first 10 feet from the ground and the Linemen staple the GEC to the pole very tightly.  If you cannot get the transformer jaw of the Ground Loop Impedance Tester around the GEC you cannot take the measurement. 

Impedance is the complex resistance which at 60 Hz is always quite close to the resistance alone in value and is calculated in the same way.  So with 50 Ohms at the Service Disconnecting Means; read main panel; and 70 or more at the pole the total Impedance of the Ground Return Pathway is 120 Ohms.  The earth is so large that the Earth's effective resistance in this pathway is Zero.  If the Neutral conductor of the Service Entry Conductors is intact then the voltage over that entire pathway is very low.  Lets take the worse case.  An old service in which the Service Disconnecting Means consist of a fused pull out and one of the fuses has opened for whatever reason.  That way the surviving fuse, which is the only source of current flow, loads the neutral with all of that current.  Now all of that current is flowing on the neutral and the Ground Return Pathway, *in proportion to their resistance*, as well as on the energized conductor with the surviving fuse.  There is no opposing current from the other energized Service Entry Conductor to cancel out a portion of the current and reduce the load on the neutral. 

For example if the current through the intact fuse is 120 Amperes.  The resistance of say 100 feet of  #2 American Wire Gauge Aluminum Clad Steel Reinforced (ACSR) overhead conductor; because that is what the utility is likely to have used; is only .519 per 1000 feet.  So over my example of 100 feet would have a resistance of 0.0519.  Ohms law says the Current times the Resistance will equal the voltage.  Thus E = I X R.  E is the  Electro Motive Fore measured in Volts,  I is the current in Amperes.  R is the Resistance in Ohms.  So in our case the Voltage Drop; which is the voltage reduction caused by the resistance of the conductor; is 0.0519 Ohms of Resistance X 12o Amperes Of current = 6.228 volts over the utilities Service Conductors between the Main Bonding Jumper; in the panel cabinet that contains the SDM, and the center tap of the utility's transformer.  That is the only voltage that the Ground Loop Pathway is subjected to.  So with only 6.228 volts to "push it" and 120 Ohms of resistance the Ground Loop will carry about 50 Milliamperes of current.  _Yes I know that I took some shortcuts by not calculating the parallel resistance of both pathways first but any difference is outside the measuring accuracy of the available instrumentation._ 

So out of  all of the 120 Amperes of current the Ground Loop pathway carries only 50 Milliamperes of current.  No where near half. 

--
Tom Horne


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## JoeD (Dec 24, 2018)

nealtw said:


> Okay, that is a little deep but I will buy but could not explain it to anyone.
> Why are ground and neutral connected?



The ground and neutral are connected for one reason. That is to give the current a return path to trip the breaker if the hot should come in contact with any metal parts of the system or anything plugged into it with a grounded plug.


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## hornetd (Dec 24, 2018)

JoeD said:


> The ground and neutral are connected for one reason. That is to give the current a return path to trip the breaker if the hot should come in contact with any metal parts of the system or anything plugged into it with a grounded plug.


JoeD

I suspect that he was asking about the Grounding Electrode  Conductor rather than the Equipment Grounding (Bonding) Conductor (EGC).  

I could be wrong of course.  

-- 
Tom Horne


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## nealtw (Dec 25, 2018)

JoeD said:


> The ground and neutral are connected for one reason. That is to give the current a return path to trip the breaker if the hot should come in contact with any metal parts of the system or anything plugged into it with a grounded plug.


The question which really was not important but was about over loading the neutral back to the transformer when the panel is out of balance.
Would some of that overload be shared with the ground.


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## BAD (Dec 25, 2018)

Quatrix said:


> Hello experts!
> 
> I have a questions about my circuit breaker panel. Could someone tell me why exactly the smarter than me individual(s) decided to put 180A on the left leg (sum of all circuit breakers) and 170A on the right leg? Would this be an unbalanced situation and overload the neutral?
> 
> P.S. Circuit Breaker panel attached to this post.



Perhaps an expert can explain why I'm wrong, but it seems to me that the breakers on each leg protect against a maximum current which is unlikely to ever be reached.

There can't (??) be unbalanced voltage since there is only one power source (the incoming cable from the street) so that's a non-issue.

It seems to me that the worst case would be if the total load on from all circuits on the right leg were to be 169 amps, while the total load from all circuits on the left leg were to be 179 amps (a situation extraordinarily unlikely to EVER occur).

Neither breaker would open, and the difference in load (10 amps) is the maximum the ground/neatral would ever see.

Current on the ground/neutral is NOT a good thing, but since the lightest wire used in residential construction is 14 guage, I don't see that it would present a fire hazard.

EXPERTS: Am I wrong? If so, how/why?


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## BAD (Dec 25, 2018)

Quatrix said:


> Hello experts!
> 
> I have a questions about my circuit breaker panel. Could someone tell me why exactly the smarter than me individual(s) decided to put 180A on the left leg (sum of all circuit breakers) and 170A on the right leg? Would this be an unbalanced situation and overload the neutral?
> 
> P.S. Circuit Breaker panel attached to this post.



Perhaps an expert can explain why I'm wrong, but it seems to me that the breakers on each leg protect against a maximum current which is unlikely to ever be reached.

There can't (??) be unbalanced voltage since there is only one power source (the incoming cable from the street) so that's a non-issue.

It seems to me that the worst case would be if the total load on from all circuits on the right leg were to be 169 amps, while the total load from all circuits on the left leg were to be 179 amps (a situation extraordinarily unlikely to EVER occur).

Neither breaker would open, and the difference in load (10 amps) is the maximum the ground/neatral would ever see. 

Current on the ground/neutral is NOT a good thing, but since the lightest wire used in residential construction is 14 guage, I don't see that it would present a fire hazard.

EXPERTS: Am I wrong? If so, how/why?


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## hornetd (Dec 25, 2018)

In the case of a Fused Pull Out, 
	

	
	
		
		

		
			





  which used to be very common as the Service Disconnecting Means (Main Disconnect) in residential service equipment, there are two fuses in the pull out, one for each of the energized (Hot) conductors in the Service Entry Conductors;  which are the wires between the Service Drop (overhead) or Service Lateral (underground)and the Main Disconnect; there are two fuse holders in the pull out.




If one of the energized conductors (hot) becomes overloaded only that one fuse will open leaving the other fuse intact to carry current to one of the hot buss bars.

The same thing is true of a Fused Switch Disconnect.  With only the one hot load conductor still connected the neutral would then carry the same amount  of current as the still energized hot conductor.  Even when the Neutral is reduced in size below the size of the two hot conductors only the 120 volt loads would be drawing current that load would not exceed the current that the Neutral was selected to carry.

That is the actual worst case and as you can see it will not overload the neutral.  *There is no way to accidentally overload the neutral in a 240/120 1Ø service!*  Any amount of current that is flowing on both of the hot conductors behaves like a single 240V load so that no current that is part of the two equal flows is carried by the neutral.  Only the current that is not balanced on the two hots will be carried by the neutral conductor.  So, in the example that everyone keeps using, with 175 amperes on one hot and 165 amperes flowing on the other 165 amperes of both hots load will behave as a single 240 volt load and no part of either of those equal currents will flow on the neutral.  The 10 amperes left over on the hot that is carrying the 175 ampere load will not have enough current on the other hot to cancel it out.  Only that remaining 10 amperes which is the *DIFFERENCE BETWEEN THE CURRENT ON THE 2 HOTS* will flow on the neutral.

--
Tom Horne


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## hornetd (Dec 25, 2018)

BAD said:


> Perhaps an expert can explain why I'm wrong, but it seems to me that the breakers on each leg protect against a maximum current which is unlikely to ever be reached.


What protects against a current which would overload the two hot service entry conductors is the main breaker or fuses.  If there were enough current available then the individual branch and feeder circuit breakers, that protect the conductors of the individual circuits to all carry their maximum ampacity, then that might be important but there almost never is that much current available because the total current available is limited by the main disconect's ampacity which has been selected by the electrician to carry the calculated load of that dwelling.  LET'S GET THIS STRAIGHT!  The size of the Service Entry Conductors is selected to carry the calculated maximum demand of the building.  There is no other code compliant way to select the minimum size of those conductors.  The Service Disconnecting Means and it's installed overcurrent protection is sized to protect the Service Entry Conductors from overload.

_*THE SERVICE ENTRY CONDUCTORS HAVE NO PROTECTION AGAINST GROUND FAULT OR SHORT CIRCUIT.*  The main breaker or fuses are at the wrong end of the service entry conductors to provide fault or short protection.  That is important because it means that the entire ampacity of the utility's supplying transformer is available on the line side of the Service Disconnecting Means.  If you fault of short that portion of the Service Entry Conductors which is inside the cabinet that encloses the Service Disconnecting Means there will be an arc flash that will instantly burn all exposed skin of any  person closely exposed to it and it will set any combustible clothing on fire!  Do Not work inside that enclosure unless you are quite certain you know how to do so safely!_



> There can't (??) be unbalanced voltage since there is only one power source (the incoming cable from the street) so that's a non-issue.


That is true as long as the Incoming wires; Service Entry Conductors; are properly selected and installed.



> It seems to me that the worst case would be if the total load on from all circuits on the right leg were to be 169 amps, while the total load from all circuits on the left leg were to be 179 amps (a situation extraordinarily unlikely to EVER occur).


  Since those feeder and branch circuit breakers were selected to protect those feeder and branch circuit conductors, rather than to limit the total current through the Service Entry Conductors, they will never have the role of carrying their maximum ampacity all at the same time.  If the  calculation of the Service conductor size required was properly done it is so unlikely as to be safely ignored.



> Neither breaker would open, and the difference in load (10 amps) is the maximum the ground/neutral would ever see.


  If the Service Disconnecting Means is properly sized it may very well be a smaller ampacity than the total loads that the Feeder and Branch circuits could carry but that the Feeder and Branch circuits would ever have to carry their maximum ampacity is again totally unlikely.



> Current on the ground/neutral is NOT a good thing, but since the lightest wire used in residential construction is 14 guage, I don't see that it would present a fire hazard.


There is absolutely no problem with having current flowing on the neutral.  If it were not expected to carry current; such as when the entire service is installed to supply a 240 volt load, such as an irrigation pump; then the neutral would be downsized to the size of an Equipment Grounding Conductor and it's only role would be to carry any ground fault current back to the supply source long enough so that the overcurrent protective device protecting that load could open.  No current would ever flow on that Neutral conductor during the normal operation of such a load.



> EXPERTS: Am I wrong? If so, how/why?


I really do hope that explains the role of the neutral conductor of Service Entry Conductor.  Branch Circuit and Feeder Neutral conductors are an entirely different matter.  It is a relatively common mistake for poorly trained or untrained individuals to miss-arrange the Multi-wire versions of those circuits so as to dangerously overload the neutral of that particular Branch or Feeder circuit.  In 35 years of active service as a firefighter I attended several fires were that was the cause of ignition.

--
Tom Horne


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## BAD (Dec 25, 2018)

Quatrix said:


> Hello experts!
> 
> I have a questions about my circuit breaker panel. Could someone tell me why exactly the smarter than me individual(s) decided to put 180A on the left leg (sum of all circuit breakers) and 170A on the right leg? Would this be an unbalanced situation and overload the neutral?
> 
> P.S. Circuit Breaker panel attached to this post.



Perhaps an expert can explain why I'm wrong, but it seems to me that the breakers on each leg protect against a maximum current which is unlikely to ever be reached.

There can't (??) be unbalanced voltage since there is only one power source (the incoming cable from the street) so that's a non-issue.

It seems to me that the worst case would be if the total load on from all circuits on the right leg were to be 169 amps, while the total load from all circuits on the left leg were to be 179 amps (a situation extraordinarily unlikely to EVER occur).

Neither breaker would open, and the difference in load (10 amps) is the maximum the ground/neatral would ever see. 

Current on the ground/neutral is NOT a good thing, but since the lightest wire used in residential construction is 14 guage, I don't see that it would present a fire hazard.

EXPERTS: Am I wrong? If so, how/why?


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## nealtw (Dec 26, 2018)

BAD said:


> Perhaps an expert can explain why I'm wrong, but it seems to me that the breakers on each leg protect against a maximum current which is unlikely to ever be reached.
> 
> There can't (??) be unbalanced voltage since there is only one power source (the incoming cable from the street) so that's a non-issue.
> 
> ...


There is a lot of theory here but not a lot of answers. So I will try one more time.
If the 2 legs and the neutral are the same size a complete out of balance close to 100 % of one leg cannot over load the neutral back to the road.
If for some reason that there was a defect in the neutral which added to the resistance, if that resistance matched the resistance of the ground the ground would share the load.
Worrying about an overload on the neutral is a non issue.
That is not to say balancing isn't important for other reasons.


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## WyrTwister (Dec 26, 2018)

Actually , there are a very few instances where a neutral can be theoretically overloaded .  They are in situations where harmonics are created by the loads .  Computer equipment ( a lot of computer equipment , like a server farm ) and florescent ( older , I think )  lighting .

     But it unlikely you will run into this in a residential environment .

     Now , if you loose your neutral , unlikely you will overload the neutral , but all sorts of crazy / bad things happen .

     As for as unbalanced voltage , on single phase 120/240 VAC , voltage phase to phase will be what ever it is .  Voltage to neutral can be different .

     And load affects voltage .

     The short answer of why the neutral & earth ground are bonded at the service entrance main disconnecting means , has been answered .  It involves having a safe / reliable / low impedance  path for the voltage / current to go , to facilitate tripping overload devices .

     All in all , balancing load on a home loadcenter is not normally a thing to loose sleep over .

Merry Cghristmas and Happy New Year   

God bless
Wyr


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## nealtw (Dec 27, 2018)

WyrTwister said:


> Actually , there are a very few instances where a neutral can be theoretically overloaded .  They are in situations where harmonics are created by the loads .  Computer equipment ( a lot of computer equipment , like a server farm ) and florescent ( older , I think )  lighting .
> 
> But it unlikely you will run into this in a residential environment .
> 
> ...


Sounds to me that trying to balance a house with intermittent use of things like washers, microwaves, toasters and vacuums would be a crap shoot at best.
Sounds like some one should make a meter to constantly read the balance and phone the homeowner when it get out of some predetermined value and they could have the electrician out to fix it.


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## Eddie_T (Dec 27, 2018)

nealtw said:


> Sounds to me that trying to balance a house with intermittent use of things like washers, microwaves, toasters and vacuums would be a crap shoot at best.
> Sounds like some one should make a meter to constantly read the balance and phone the homeowner when it get out of some predetermined value and they could have the electrician out to fix it.


It seems that the utility is designed such that unbalance doesn't present a problem and it ends in the secondary of the pole transformer. The only concern for customers might be if we feed circuits with a small 240v emergency generator. If we need the max out of a generator we might do well to maintain some sense of balance, though in my case I usually run minimum loads and only use 240v for the well pump and water heater.


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## WyrTwister (Dec 27, 2018)

Any unbalance on the secondary should reflect on the primary .  My guess is , across a large number of customers  , this should cancel out ( from the point of view of the power company ) .

     In a residential area with little three phase load , I an further guessing , the power company tries to alternate between 2 of the 3 phases , to attempt to even out the load across all 3 phases .  But this nothing the single phase customer can make better .

God bless
Wyr


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## Eddie_T (Dec 27, 2018)

What do you mean by "reflect on the primary"?


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## WyrTwister (Dec 27, 2018)

The power company's high voltage lines may be 7200 , 4160 or some other voltage , 3 phase .  This is the primary voltage system .

     If your area is served by overhead wiring , you will see transformers mounted on some of the poles .  The purpose of the transformer is to step the primary voltage down to the voltage needed to supply equipment , appliances & lites .  For homes , commonly 120/240 VAC single phase .  This is the secondary voltage system .

     Any load on the secondary , causes a load to be applied to the primary .  If the secondary load is unbalanced , the load applied to / reflected on the the primary , will be unbalanced .

God bless
Wyr


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## hornetd (Dec 27, 2018)

A word of caution here.  When talking about the load on the secondary being balanced we are talking about it being apportioned so that the two halves of the secondary winding are carrying roughly the same load.  Just keep in mind that the entire secondary winding is opposite a single primary winding that is attached, in most places; between the single primary phase conductor and the Multi-Grounded Neutral.  Which, by the way, is the same neutral conductor that the secondary center tap is connected to.  That single phase (1Ø) primary sees all of the load on the secondary winding regardless of whether or not it is balanced over the secondary winding.  The balancing of the transformer's secondary winding is to avoid overloading the more heavily  loaded half of the secondary winding.  The Balancing of the load on the primary conductors is done by connecting each transformer to the next phase sequentially.  Transformer 1 on AØ, transformer 2 on BØ, transformer 3 on CØ, transformer 4 on AØ, transformer 5 on BØ,  and so on.  In a neighborhood that is composed entirely of single family detached homes applying that sequence of attachment of very similar transformers will balance the load on the distribution conductors quite well.  If something went wrong on the secondary wiring such as a tree limb falling or a fence post being driven right through one of the two energized conductors (Hot) so that that transformer became totally imbalanced, with the only load was on half off the secondary winding, the primary winding would see a reduction in load that would have a relatively light effect on the primary load balance but that would be insignificant in the overall balance of the primary circuit.  To say that the imbalance of the load on the secondary will be reflected on the primary is technically correct but of no consequence operationally. 

--
Tom Horne


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## Eddie_T (Dec 27, 2018)

Thanks Tom, that's what I was thinking.


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## hornetd (Dec 27, 2018)

nealtw said:


> Sounds to me that trying to balance a house with intermittent use of things like washers, microwaves, toasters and vacuums would be a crap shoot at best.
> Sounds like some one should make a meter to constantly read the balance and phone the homeowner when it get out of some predetermined value and they could have the electrician out to fix it.


The only place were the costs of an imbalance warning system would justified would be in an occupancy that has some likelihood of having a dangerous imbalance.  I can't think of any such occupancy off of the top of my head.  There are individual loads that should never be imbalanced but they are electric motors which are protected against that by the motor overload detectors  in the motor controller unless the load needs to run until it destroys itself rather than be deliberately shut off.  One example of such a load is a fire pump.  

Load balancing is essentially about efficiency rather than safety or loss prevention.  Balancing the load avoids the need to install more capacity than will actually be used so that electricians wouldn't have to do that part of their presently required work.  I never minded leaving a memory amperage tester and it's two current transformers at the premise overnight; which is, after all, when the family will be there and making the heaviest use of the electrical system of their home.  It is true that that those testers are expensive and I only bought a used one after waiting patiently for one to be available at a price I could afford.  I would look at the current curves on the recording ammeter and unless there was a period of more than say half an hour were the system was radically out of balance I would declare victory, make pleasant conversation with the electrical inspector, and go on to the next job. 

--
Tom Horne


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## nealtw (Dec 27, 2018)

*Thank you* to whoever moved this to a new thread.


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## sadavis80 (Jan 1, 2019)

Beyond all of the valid and very correct answers posted in this thread, it would seem that the OP was LOOKING at his power box and assuming that the LEFT and RIGHT *SIDES* of that box represented the two poles of the incoming power .. that is most likely incorrect.  In EVERY box I've seen the 2 poles alternate down each SIDE of the box.  That is what allows double pole breakers to be installed on one side or the other and pick up both poles for 220 service devices.
Just thought I'd mention that .
Steve


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## WyrTwister (Jan 1, 2019)

You are 100% correct .

Wyr
God bless

Happy New Year


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## hornetd (Jan 1, 2019)

sadavis80 said:


> Beyond all of the valid and very correct answers posted in this thread, it would seem that the OP was LOOKING at his power box and assuming that the LEFT and RIGHT *SIDES* of that box represented the two poles of the incoming power .. that is most likely incorrect.  In EVERY box I've seen the 2 poles alternate down each SIDE of the box.  That is what allows double pole breakers to be installed on one side or the other and pick up both poles for 220 service devices.
> Just thought I'd mention that .
> Steve


That is certainly true of all of the modern panels but there are several types of legacy panels were that is not true.  The most obvious being Federal Pacific Electric (FPE).  The FPE panels I'm thinking of used two pole breakers that mounted like a bridge between the two buss bars. 

I only point this out so that people will know that the use of alternating breaker connection points from each buss is a somewhat newer development and that there are a lot of these older panels still in service.  They are a lot more common in some parts of the country than in others. 

--
Tom Horne


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