Tripping Behavior of Circuit Breakers

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dtlZmq.jpg


For US residents. If you have the above circuit breaker put in your panel phase to phase (2 pole).. and one of the phase touches neutral.. would the circuit breaker trip or not? It's rated 240 volts.. yet one pole only has 120 volts.. would that 120 volts shorting the neutral trips it?

This was written in the label above reproduced here:

Current Interrupting Rating
Max RMS/Sym Voltage
10 KA 240VAC
5KA 415VAC
CU-AL 50/60Hz
Type TOC 2430WLX


And what does the 10kA at 240VAC, 5kA at 415VAC mean? at 120VAC.. it could become 20kA... would this make it trip if shorting to neutral (let's say the wire inside metal enclosure accidentally touch the enclosure connected to neutral)?

I mentioned specifically neutral and not ground because in our location. We only use phase to phase to create 240 volts. All our equipments are 240 volts. We never use phase to neutral of 120 volts. Hence our neutral is made our ground. We don't have separate ground because since we don't the neutral then they make it our ground.
 

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  • #2
jim hardy
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For US residents. If you have the above circuit breaker put in your panel phase to phase (2 pole).. and one of the phase touches neutral.. would the circuit breaker trip or not?
One pole on its output side touch neutral ? Of course it would trip .
Kirchoff tells us that current goes only back to wherever it came from, be that a transformer winding or a flashlight battery.
Neutral is centertap of our 240 volt transformer winding
and each pole is connected to an end of that winding.
Current will be perfectly happy to return to the centertap .
120 volts will push plenty of amps around that current loop: > out one end of the winding > breaker > neutral wire > back to centertap.of the winding ..............

And what does the 10kA at 240VAC, 5kA at 415VAC mean?
It means if your source of power is capable of delivering more than 10KA into a short circuit,
"We're gonna need a bigger breaker" .
upload_2018-10-5_19-52-36.png


it's called "Interrupting rating" and is the maximum current you can ask it to interrupt.

in our location. We only use phase to phase to create 240 volts. All our equipments are 240 volts. We never use phase to neutral of 120 volts. Hence our neutral is made our ground. We don't have separate ground because since we don't the neutral then they make it our ground.
So i take it you "ground" (i prefer to use the word 'earth' ) the centertap and connect an earthing wire ? Our earth wire is green but in some Euro cords i see blue and brown...
Many 240 volt appliances in US don't use a Neutral wire and are connected as you describe. My water heater is so connected.

You ought to read up on circuit breaker terminology. There's a section here
http://apps.geindustrial.com/publibrary/checkout/GET-2779?TNR=Application and Technical|GET-2779|PDF&filename=GET-2779K v6.pdf
 

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  • #3
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One pole on its output side touch neutral ? Of course it would trip .
Kirchoff tells us that current goes only back to wherever it came from, be that a transformer winding or a flashlight battery.
Neutral is centertap of our 240 volt transformer winding
and each pole is connected to an end of that winding.
Current will be perfectly happy to return to the centertap .
120 volts will push plenty of amps around that current loop: > out one end of the winding > breaker > neutral wire > back to centertap.of the winding ..............
But notice the rating of the breaker above.. it's written 240VAC.. shouldn't it be 120VAC since one pole to neutral is really 120VAC?

Or supposed in the US, if you used a 480VAC breaker.. what would happen.. would it take bigger current to trip it or couldn't it trip easily or is it invariant to any breaker voltage rating so even a 1000 VAC breaker would trip when shorted to neutral as easily as a pure 120Vac breaker?

It means if your source of power is capable of delivering more than 10KA into a short circuit,
"We're gonna need a bigger breaker" .
View attachment 231741

it's called "Interrupting rating" and is the maximum current you can ask it to interrupt.



So i take it you "ground" (i prefer to use the word 'earth' ) the centertap and connect an earthing wire ? Our earth wire is green but in some Euro cords i see blue and brown...
Many 240 volt appliances in US don't use a Neutral wire and are connected as you describe. My water heater is so connected.

You ought to read up on circuit breaker terminology. There's a section here
http://apps.geindustrial.com/publibrary/checkout/GET-2779?TNR=Application and Technical|GET-2779|PDF&filename=GET-2779K v6.pdf
In our location. Our ground is just neutral connected to the centertap of the transformers without any earthing. So if the neutral is accidentally touched to the metal enclosure.. it would trip the breaker even before a person touch it.. so this is better than metal enclosure not engaged.
 
  • #4
jim hardy
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Our ground is just neutral connected to the centertap of the transformers without any earthing.
i don't understand - is there no connection to earth, right at the transformer supplying your building ?
Why then do you call it "Ground" ?
In US,
That little bare copper wire along the side of the pole earths the centertap.

polepigground.jpg


But notice the rating of the breaker above.. it's written 240VAC.. shouldn't it be 120VAC since one pole to neutral is really 120VAC?
No, why would it ? Either pole of the breaker might be asked to interrupt the full 240 volts between phases.

Or supposed in the US, if you used a 480VAC breaker.. what would happen.. would it take bigger current to trip it or couldn't it trip easily or is it invariant to any breaker voltage rating so even a 1000 VAC breaker would trip when shorted to neutral as easily as a pure 120Vac breaker?
Why would it ? Breakers sense current . Their purpose is to protect wire from overheating, not from overvoltage.
 

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  • #5
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i don't understand - is there no connection to earth, right at the transformer supplying your building ?
Why then do you call it "Ground" ?
In US,
That little bare copper wire along the side of the pole earths the centertap.
What would happen if the pole centertap is not grounded? I'd use my high power binocular to check the pole from 10 meters away if it's grounded.

View attachment 231752


No, why would it ? Either pole of the breaker might be asked to interrupt the full 240 volts between phases.


Why would it ? Breakers sense current . Their purpose is to protect wire from overheating, not from overvoltage.
So even if the circuit breaker is rated at 1000 volts.. if it is only 20 Ampere.. it would trip at 20 Ampere irregardless of the voltage? Good to know I don't have to replace any of my circuit breakers. I'd tell electrician to connect neutral to every enclosure because we have habits of not connecting the ground wire of say aircon metal frame. When I pass by the third floor.. I always touch this metal frame of aircon and knowing it's not grounded gives me chills now.
 
  • #6
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In countries where neutral is not used for equipment power where you only use phase to phase, you can use the neutral as grounding.

But here is a question:

D4niFd.jpg


If you use the neutral of one subpanel as ground for the aircon metal casing (top subpanel).. while for another panel (bottom subpanel).. you use the neutral as line 1 to neutral to get 120 volts service.. would the neutral in the top subpanel you are using as ground gets electrified?
 

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  • #7
jim hardy
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What would happen if the pole centertap is not grounded?
If there's no ground connection you have an unsafe installation. See below.

So even if the circuit breaker is rated at 1000 volts.. if it is only 20 Ampere.. it would trip at 20 Ampere irregardless of the voltage?
Yes, irrespective of the voltage.

I'd tell electrician to connect neutral to every enclosure because we have habits of not connecting the ground wire of say aircon metal frame.
Make sure it's grounded someplace.

ungrounded neutral.jpg
 

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  • #8
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Those kVA and kV ratings are for near instantaneous current/power conditions.

This circuit breaker is two-pole common-trip, meaning that if either breaker is to trip, both poles are disconnected. I'm not going to get into multi-wire branch circuits on this thread, but you can look more into NEC requirements for multi-wire branch circuit overcurrent and short circuit protection.

I'm afraid that you *may* be wrong with your idea that your country only uses "Phase to phase" 240 for your appliances. EDIT(Again): Correct me if I'm wrong, but I believe that most EU countries use 220V Line-to-Neutral voltage. Sorry about that, made the wording more specific.

Another misconception you have this this "phase-to-phase" idea when dealing with single phase systems. For the transformer systems described above, it is called single phase. It is actually two phases that are 180 degrees out of phase (so that they are *IN* phase) but have opposing polarities. This is not to be confused with a two-phase system, which is a real type of utility service. The proper terminology for this type of residential/light commercial equipment is line-to-line so as to avoid any ambiguity in that regard.

What country are you from, exactly? A neutral and a ground are NOT the same thing. One serves as a circuit completion at the 0V tap on a transformer, while the ground serves as a low resistance path for fault current so that your body does not become a grounded conductor.
 
  • #9
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Ok. I live in the Phillippines. 99% of our appliances or metal enclosure are not grounded. Most (including me) didn't even know the purpose of grounding. Therefore I reveal my country as I think it is very important to initiate grounding awareness drive...

Only US citizen who came to Philippines are aware of grounding.. the following is a construction blog by a American who married a local.. He wrote: http://myphilippinelife.com/philippine-electrical-wiring/

"Most Philippine houses are not wired with three-prong, grounded outlets. Most outlets have only a load wire and a neutral wire. The quality of grounding of the neutral wire can be uncertain due to improper earthing at the pole or in the residence. If you’ve spent any time in the Philippines, you’ve probably been repeatedly shocked by your computer, refrigerator and so forth. The metal parts of these appliances either have no ground (earth) connection and/or the neutral is not properly grounded. When you touch them with bare feet on a tile, you become the ground. Since bare feet on tile are a pleasure of Philippine retirement, this is best avoided."

He described our power system:

"MANILA AND CITIES: Three wire 120/240V Systems. In Manila, Iloilo City and other large Philippine cities, residences are supplied with 240 volt, alternating current, 60 cycle power. Power from the utility transformer to the residence arrives through three wires, two 120 VAC load (“hot”) wires and a single neutral. Circuits in the residence are generally wired to supply 240 VAC to outlets using the two 120 VAC load wires, much the same as a heavy appliance (dryer, hot water heater etc.) would be supplied in the U.S. All small and large appliances sold in the Philippines are designed to use 240 VAC, 60C."

"OUTSIDE OF BIG CITIES: Two wire 230V Systems Areas outside of the old established cities were electrified later and use a different and more economical system using a two wire service drop to the residence. This consists of one 230 VAC load wire and one neutral wire."

In the grounding description above.. he was describing this two wire 230V system. In our capital where we mostly use split phase 120/240V systems. It's not grounded either. In all the buildings I see. We only have 2 wire outlets (from the two live wires).. which came from the 2 lines of the 120/240V. The neutral was often not used and we don't have any grounding wires. In my home and my relatives.. we don't even have neutral or ground in our main panel (I just checked mine... the other building mentioned in another thread is an office building with co-partners).

So I guess the government must initiate grounding awareness drive.. but problem is.. they may not realize the problem. If I didn't go into trying to install surge protectors. I couldn't have understood the purpose of grounding either.
 
  • #10
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Fun fact, remember that two phase system I said that is a rare thing? The Philippines is one of the few places I believe still has it, somewhere at least. I can't remember exactly where I was reading about it you may actually be the exception to my comments about it being line to line, rather than phase to phase if that is the case.

That's pretty cool. And yes, having a service improperly grounded is a nightmare. Hopefully you guys start enforcing the NEC soon, as I believe your country already uses it as the standard.

Found it on wikipedia, it was Pennsylvania and Philadelphia.
 
  • #11
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Fun fact, remember that two phase system I said that is a rare thing? The Philippines is one of the few places I believe still has it, somewhere at least. I can't remember exactly where I was reading about it you may actually be the exception to my comments about it being line to line, rather than phase to phase if that is the case.

That's pretty cool. And yes, having a service improperly grounded is a nightmare. Hopefully you guys start enforcing the NEC soon, as I believe your country already uses it as the standard.

Found it on wikipedia, it was Pennsylvania and Philadelphia.
Why what is the difference between phase to phase, and line to line.. if our country power system uses 120v in each phase that is 180 degree out of phase to produce 240v. Then what power is in each line to line in other countries for example?
 
  • #12
jim hardy
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If you use the neutral of one subpanel as ground for the aircon metal casing (top subpanel).. while for another panel (bottom subpanel).. you use the neutral as line 1 to neutral to get 120 volts service.. would the neutral in the top subpanel you are using as ground gets electrified?
See my post above.

ungrounded neutral1.jpg


In US we are allowed to use a metal conduit or raceway for the safety earth ground conductor between receptacle and breaker panel so long as it is of "approved" design.. In non conductive or discontinuous conduit we must run a green wire with the hot and neutral wires.

It is not clear what you mean by
use the neutral as line 1 to neutral to get 120 volts service.
Any wire connected from tall slot to transformer centertap would serve as a neutral line but you might be violating your electrical code - i wouldn't know.
In US you CANNOT use the same conductor for both Neutral and safety earthing functions.
Neutral carries normal load current back to transformer centertap
Safety Earthing Conductor (often called Protective Ground) carries current ONLY when there's been an insulation breakdown.


Draw yourself a centertapped winding schematic like i did in post 47,
draw in your circuit breakers
and an outlet receptacle

then trace out load & fault currents
you'll see why we use three conductors unless it's a double insulated appliance.
 

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  • #14
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Fun fact, remember that two phase system I said that is a rare thing? The Philippines is one of the few places I believe still has it, somewhere at least. I can't remember exactly where I was reading about it you may actually be the exception to my comments about it being line to line, rather than phase to phase if that is the case.

That's pretty cool. And yes, having a service improperly grounded is a nightmare. Hopefully you guys start enforcing the NEC soon, as I believe your country already uses it as the standard.

Found it on wikipedia, it was Pennsylvania and Philadelphia.
Well. It took me a week to understand the principle of grounding after trying to understand the electrical principle of surge protectors. For other citizens here including government.. they won't ever understand the purpose of grounding. Two weeks ago. I thought grounding can make the equipment behave better.. but since we don't get broken appliances every so often, we ignore grounding.

See my post above.

View attachment 231769

In US we are allowed to use a metal conduit or raceway for the safety earth ground conductor between receptacle and breaker panel so long as it is of "approved" design.. In non conductive or discontinuous conduit we must run a green wire with the hot and neutral wires.

It is not clear what you mean by


Any wire connected from tall slot to transformer centertap would serve as a neutral line but you might be violating your electrical code - i wouldn't know.
In US you CANNOT use the same conductor for both Neutral and safety earthing functions.
Neutral carries normal load current back to transformer centertap
Safety Earthing Conductor (often called Protective Ground) carries current ONLY when there's been an insulation breakdown.
In my country. Since the neutral was not used for 120volts. Then it's only purpose may be for grounding metal enclosure. This would work as when the line touches the enclosure connected to neutral. It can n trip the breaker. This is better than 99% not using any grounding in the metal enclosure.

So what I mean to say was. One subpanel uses neutral for safety grounding of the appliances connected to it. While for another subpanel, the neutral would be used as return conduit for Line 1 to get 120 volts. Note 99.9% in my country don't use this because government prohibited use of 120 volts for our appliance to avoid us buying products from the US instead of locally. But in my case. I'd need to use surge protectors and get 120V volts model for better clamping voltage.. therefore is there any problem if one subpanel would use the neutral as ground, and the second subpanel would use the neutral as return conduit for 120 volts.. ?


Draw yourself a centertapped winding schematic like i did in post 47,
draw in your circuit breakers
and an outlet receptacle

then trace out load & fault currents
you'll see why we use three conductors unless it's a double insulated appliance.[/QUOTE]
 
  • #15
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We can't give you specific advice on how to accomplish what you want. There are too many variables an untrained eye can miss, and there is a lot of potential for things to go wrong. You could potentially electrify all bonded metal in your home, or burn up your entire electrical system, likely both.

The short answer is that yes, you can use a spare conductor as the grounding conductor.

No, you can not just tie your neutral to the grounds for the reasons mentioned above. You should consult a local electrician, which can be done for cheap to find out exactly what you need to do.
 
  • #16
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We can't give you specific advice on how to accomplish what you want. There are too many variables an untrained eye can miss, and there is a lot of potential for things to go wrong. You could potentially electrify all bonded metal in your home, or burn up your entire electrical system, likely both.

The short answer is that yes, you can use a spare conductor as the grounding conductor.

No, you can not just tie your neutral to the grounds for the reasons mentioned above. You should consult a local electrician, which can be done for cheap to find out exactly what you need to do.
Of course I never do it myself. I hired licensed electricians.

Anyway. Besides the Philippines. What other countries have homes that are not grounded?
 
  • #17
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Here in America we have homes that are not grounded. I do work in them all the time. Grounding wasn't introduced until the 70s, so pretty much anything built before then doesn't have a ground.
 
  • #18
jim hardy
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So what I mean to say was. One subpanel uses neutral for safety grounding of the appliances connected to it. While for another subpanel, the neutral would be used as return conduit for Line 1 to get 120 volts. Note 99.9% in my country don't use this because government prohibited use of 120 volts for our appliance to avoid us buying products from the US instead of locally. But in my case. I'd need to use surge protectors and get 120V volts model for better clamping voltage.. therefore is there any problem if one subpanel would use the neutral as ground, and the second subpanel would use the neutral as return conduit for 120 volts.. ?

The problem i see is how will the next guy figure out what you did ?
There's been a problem in understanding "Ground": in US too and our code is still being clarified. Here's a primer.
https://electrical-engineering-portal.com/what-is-the-difference-between-bonding-grounding-and-earthing
The reason for NOT letting load current flow through safety earthing/protective grounding conductors is so there won't be any voltage on the case of an appliance.

You want consistency. That's why we ALWAYS use white wire for neutral and green for earth/protective ground.

Where you propose to change the function of your earth/protective conductor (which you call Neutral) and use it to return load current ,
what will you now use for an earth/protective conductor ? What colors will they be ? How will the ext guy know what you've done?

There IS a Phillipines electrical code - Learn and follow it !
https://filipinoengineer.com/wiki/Philippine_Electrical_Code_Part_1/Chapter_2._Wiring_and_Protection/Article_2.50_-_Grounding_And_Bonding
 
  • #19
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The problem i see is how will the next guy figure out what you did ?
There's been a problem in understanding "Ground": in US too and our code is still being clarified. Here's a primer.
https://electrical-engineering-portal.com/what-is-the-difference-between-bonding-grounding-and-earthing
The reason for NOT letting load current flow through safety earthing/protective grounding conductors is so there won't be any voltage on the case of an appliance.

You want consistency. That's why we ALWAYS use white wire for neutral and green for earth/protective ground.

Where you propose to change the function of your earth/protective conductor (which you call Neutral) and use it to return load current ,
what will you now use for an earth/protective conductor ? What colors will they be ? How will the ext guy know what you've done?

There IS a Phillipines electrical code - Learn and follow it !
https://filipinoengineer.com/wiki/Philippine_Electrical_Code_Part_1/Chapter_2._Wiring_and_Protection/Article_2.50_-_Grounding_And_Bonding
We mostly copied our codes from abroad. For example our Structural code was copied word for word from the American ACI structure code. But the problem is contractor and even designers never follow the code. So our structural design is very bad. Likewise for electrical. In my own home. I don't even have any grounding in my main breaker panel. I don't know how to add ground in my own home. The other building I mentioned is an office building and 3 phase was applied that was why we have neutral.
 
  • #20
jim hardy
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We mostly copied our codes from abroad................. But the problem is contractor and even designers never follow the code. So our structural design is very bad. Likewise for electrical. In my own home. I don't even have any grounding in my main breaker panel. I don't know how to add ground in my own home. The other building I mentioned is an office building and 3 phase was applied that was why we have neutral.
That's reason enough for you to
1. develop rudimentary DC circuit analysis skills
2. understand basics of grounding , neutral, protective earth ground which will tell you why the code says what it does
3. learn how your house SHOULD be wired with what conductors if what colors
4. bring your house up to code
5. advise whoever owns that office building of his code shortfalls.

Good starting place is this old PF thread
https://www.physicsforums.com/threa...t-live-and-neutral-wires.892309/#post-5613568
and IEEE Green Book standard 142. https://www.mercury-group.com/wp-content/uploads/2017/02/groundingandbonding.pdf
 
  • #21
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Ugh. This is one of my least favorite topics on PF. There are hundreds of "standard" wiring schemes used around the world. Therefore, when we have participants from many countries in a thread, the discussion rapidly becomes too confusing to follow. Several PF members said that they would never again participate in any thread that uses the words "neutral" or "ground"

As far as what is best, in most cases you have no choice other than to follow local practices, because deviations from the local norm are themselves a hazard. The wisest advice is given above in @jim hardy 's post #20.
 
  • #22
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That's reason enough for you to
1. develop rudimentary DC circuit analysis skills
2. understand basics of grounding , neutral, protective earth ground which will tell you why the code says what it does
3. learn how your house SHOULD be wired with what conductors if what colors
4. bring your house up to code
5. advise whoever owns that office building of his code shortfalls.

Good starting place is this old PF thread
https://www.physicsforums.com/threa...t-live-and-neutral-wires.892309/#post-5613568
and IEEE Green Book standard 142. https://www.mercury-group.com/wp-content/uploads/2017/02/groundingandbonding.pdf
I will.
Note any electrical work in my building will always be supervised by licensed electrical engineer because I don't want to get electrocuted. I just talked to one. He said we don't have neutral in the country but only ground. I checked the utility pole.. good there is this rod stuck to the ground (picture below). It is just 3 meters away from my service entrance. The pole only service my building and another building beside it. So I guess we own the ground. If you have pole rod stuck to ground 3 meters in front of you. Does it make sense to stick another earth rod for the building. The electrical engineer is not so interested in doing that I don't know why.

6qSise.jpg
 

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  • #23
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According to your code, yes there should be a grounding electrode at your house and to your FIRST POINT OF DISCONNECT.
 
  • #24
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According to your code, yes there should be a grounding electrode at your house and to your FIRST POINT OF DISCONNECT.
In my country where corruption and cost cutting is the middle name (in all industries and community) . Most homes don't even have the centertap of the powerline connected to the house. For example. In my home now (built in 2001.. I bought it second hand). The following (pictures) is the main panel. No ground bar. Now supposed i'll let contractor dig ground to create grounding electrode and use it as ground.. would it trip the breaker when the ground is not connected to the centertap of the transformer? (I read about bonding requirement of neutral and ground at main panel in US so I'm wondering). I need to know because I need to write a letter to the power utility company to request center tap wire be added to my house because right now I only have phase to phase of 240 volts supplied to my house (note my house is not to be confused with the office building I was describing in the other thread).

oOpP32.jpg


EEy4UJ.jpg
 

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  • #25
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Now supposed i'll let contractor dig ground to create grounding electrode and use it as ground.. would it trip the breaker when the ground is not connected to the centertap of the transformer? I need to know because I need to write a letter to the power utility company to request center tap wires be added to my house because right now I only have phase to phase of 240 volts supplied to my house
That sounds contrary to the advice of following the local norm.

We are at the the limits of advice that PF can give. You are advised to ask local experts in person rather than strangers on the Internet.
 

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