Unbalanced amperage

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nealtw

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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.
 

BAD

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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?
 

BAD

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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?
 

hornetd

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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
 

hornetd

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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

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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?
 

nealtw

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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?
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.
 

WyrTwister

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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
 

nealtw

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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
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.
 

Eddie_T

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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.
 

WyrTwister

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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
 

WyrTwister

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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
 

hornetd

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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
 

hornetd

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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
 

sadavis80

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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
 

hornetd

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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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