Author Topic: Single Pole or 1P + N circuit breakers  (Read 14052 times)

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Offline made2hackTopic starter

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Single Pole or 1P + N circuit breakers
« on: March 26, 2019, 01:28:22 pm »
Hi all,
I'm currently installing a new electrical panel in my workshop and would like to know whether to use just 1P (1 pole or Live only) circuit breakers? Or 1P + N (Live + Neutral) circuit breakers?
This is for EU, 220-240VAC single phase.

I keep finding conflicting information as most search results seem to come up as 2 Pole variants (used in North America).

Are 1P + N "safer" if you will than just 1P that disconnects just the live? Any advantages?

Thanks,

P.S: The panel will also have a 1P+N 30mA differential before the individual circuits.

Offline Zero999

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Re: Single Pole or 1P + N circuit breakers
« Reply #1 on: March 26, 2019, 01:58:26 pm »
Disconnecting the neutral is safer, because it might be live, if it's broken somewhere upstream of the breaker.
 

Offline made2hackTopic starter

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Re: Single Pole or 1P + N circuit breakers
« Reply #2 on: March 26, 2019, 02:43:14 pm »
So it's just for upstream concerns? But would you also wire a house using the same consideration?

Offline made2hackTopic starter

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Re: Single Pole or 1P + N circuit breakers
« Reply #3 on: March 26, 2019, 04:01:22 pm »
Of course I am assuming that this type 1P + N blows at the same time, I mean the breaker breaks both connections and is not like a 2P where one pole might still be active.

Offline Zero999

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Re: Single Pole or 1P + N circuit breakers
« Reply #4 on: March 26, 2019, 04:08:52 pm »
Of course I am assuming that this type 1P + N blows at the same time, I mean the breaker breaks both connections and is not like a 2P where one pole might still be active.
A two pole breaker always blows both at the same time.

Whether it's necessary or not depends on how it's wired and your local regulations. In the UK, the neutral and earth is normally combined in the same conductor up to where it enters most houses, so a single pole breaker is sufficient. I can't comment about other places.
 

Offline capt bullshot

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Re: Single Pole or 1P + N circuit breakers
« Reply #5 on: March 26, 2019, 04:16:04 pm »
Depends on your local regulations. Do it the same way your main breaker panel is made.
E.g. in Germany, 1P+N breakers are totally unknown and not used but I've seen such things in other European countries. Otherwise for a Ground Fault Interrupter, it's normal to break all phases and Neutral (1P+N or 3P+N).

In general I do consider disconnecting the Neutral rather dangerous, since a broken Neutral can cause strange and/or dangerous things to happen. So as you said, ensure the breaker breaks all phases together.
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Offline Benta

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Re: Single Pole or 1P + N circuit breakers
« Reply #6 on: March 26, 2019, 05:05:05 pm »
^^^ This.
 

Online ejeffrey

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Re: Single Pole or 1P + N circuit breakers
« Reply #7 on: March 26, 2019, 05:07:49 pm »
Certainly in north america standard circuit breakers only interrupt the live conductor.  Neutral is bonded to ground in the panel, so there is no need or desire to break it.

NA has two-pole 240 V breakers because we use split phase systems where both legs are live.  In a 120/240 4 wire circuit the breaker would interrupt the two live wires but not neutral or (of course) ground.  Similarly for a three phase circuit you would break all three live wires but not normally neutral.

However: there are differences from country to country about where and how the safety earth is connected to neutral so it is important to check your local regulations and wiring standards.
 

Offline Zero999

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Re: Single Pole or 1P + N circuit breakers
« Reply #8 on: March 26, 2019, 08:14:30 pm »
Certainly in north america standard circuit breakers only interrupt the live conductor.  Neutral is bonded to ground in the panel, so there is no need or desire to break it.
Yes, that's mostly the case here too. I say mostly, because I can think of instances where that may not be the case. For example, if there's an outbuilding with a thick cable running to it from the main property, it will have its own distribution panel and will not bond the neutral to earth again there. In that case, to mitigate the danger posed by a poor neutral connection, which would make the neutral float at a dangerous voltage, the breaker should disconnect both the neutral and phase conductors.
 

Offline made2hackTopic starter

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Re: Single Pole or 1P + N circuit breakers
« Reply #9 on: March 26, 2019, 09:02:05 pm »
Certainly in north america standard circuit breakers only interrupt the live conductor.  Neutral is bonded to ground in the panel, so there is no need or desire to break it.
Yes, that's mostly the case here too. I say mostly, because I can think of instances where that may not be the case. For example, if there's an outbuilding with a thick cable running to it from the main property, it will have its own distribution panel and will not bond the neutral to earth again there. In that case, to mitigate the danger posed by a poor neutral connection, which would make the neutral float at a dangerous voltage, the breaker should disconnect both the neutral and phase conductors.

Is there any reason why I wouldn't be able to bond the neutral and earth in this sub panel?

Offline notsob

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Re: Single Pole or 1P + N circuit breakers
« Reply #10 on: March 26, 2019, 09:15:34 pm »
We had a case where a repair technician was hung up [ie. live power on his arm] on a card reader [ the size of 2 washing machines], an operator nearby had to run and drop the main breaker for the building. the breaker on the card reader was phase only - not neutral. However the person that wired the plug under the false floor had wired it incorrectly. So the card reader breaker was actually switching neutral. Very close call, we almost lost that person.


So be safe - switch both.
 

Offline Monkeh

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Re: Single Pole or 1P + N circuit breakers
« Reply #11 on: March 26, 2019, 09:38:27 pm »
Disconnecting the neutral is safer, because it might be live, if it's broken somewhere upstream of the breaker.

This is irrelevant for the purpose of a circuit breaker. It is not isolation, nor is it functional switching - it is overcurrent protection.
 

Offline Zero999

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Re: Single Pole or 1P + N circuit breakers
« Reply #12 on: March 26, 2019, 10:59:53 pm »
Disconnecting the neutral is safer, because it might be live, if it's broken somewhere upstream of the breaker.

This is irrelevant for the purpose of a circuit breaker. It is not isolation, nor is it functional switching - it is overcurrent protection.
No it's not irrelevant. It still has to make the circuit safe, i.e. dead, which won't happen with a single pole device, if there's a break in the neutral conductor.
 
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Offline Monkeh

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Re: Single Pole or 1P + N circuit breakers
« Reply #13 on: March 26, 2019, 11:11:34 pm »
Disconnecting the neutral is safer, because it might be live, if it's broken somewhere upstream of the breaker.

This is irrelevant for the purpose of a circuit breaker. It is not isolation, nor is it functional switching - it is overcurrent protection.
No it's not irrelevant. It still has to make the circuit safe, i.e. dead, which won't happen with a single pole device, if there's a break in the neutral conductor.

It has to end the condition of overcurrent. Again, it is an overcurrent protective device, not an isolator.
 

Online ejeffrey

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Re: Single Pole or 1P + N circuit breakers
« Reply #14 on: March 27, 2019, 04:05:36 am »
We had a case where a repair technician was hung up [ie. live power on his arm] on a card reader [ the size of 2 washing machines], an operator nearby had to run and drop the main breaker for the building. the breaker on the card reader was phase only - not neutral. However the person that wired the plug under the false floor had wired it incorrectly. So the card reader breaker was actually switching neutral. Very close call, we almost lost that person.


So be safe - switch both.

No.  If you are talking about building wiring (i.e., distribution panels), rather than equipment wiring, do it the way your local code and standards specify.  Do not install some unapproved non-standard device because some guy on the internet said so.

Edit: For instance, in the US it is allowed to have two branch circuits that are fed from opposite phases of the split phase input share a common neutral as long as the wires are run together (same Romex or same conduit).  In industrial/commercial settings it is allowed have three branch circuits on three phases share a neutral.  These do not use multi-pole circuit breakers but have independent circuit breakers for each branch circuit.  If someone listened to this "advice" and went and replaced one of the branch circuits with a breaker that switched both live and neutral, then you would have created a potentially dangerous situation where the other circuit(s) could have live but a broken neutral.  In the three phase case, the two remaining phases will try to force current balance causing one circuit to take a potentially severe overvoltage.

Even if you think this practice is dumb and that those circuits should be on a single multi-pole breaker, that is not the way it is done or the way anyone would expect it, and unilaterally changing part of the system because of your opinion can cause hazardous conditions.  Don't do it.
« Last Edit: March 27, 2019, 04:21:35 am by ejeffrey »
 

Offline Zero999

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Re: Single Pole or 1P + N circuit breakers
« Reply #15 on: March 27, 2019, 01:25:57 pm »
Disconnecting the neutral is safer, because it might be live, if it's broken somewhere upstream of the breaker.

This is irrelevant for the purpose of a circuit breaker. It is not isolation, nor is it functional switching - it is overcurrent protection.
No it's not irrelevant. It still has to make the circuit safe, i.e. dead, which won't happen with a single pole device, if there's a break in the neutral conductor.

It has to end the condition of overcurrent. Again, it is an overcurrent protective device, not an isolator.
It still has to make the circuit safe, i.e. isolate it. Over-current can cause electric shock, as the voltage on exposed metal parts can reach dangerous levels. Whether or not the circuit breaker is supposed to be used for isolation or not. It must safely disconnect the circuit from the supply.
 

Offline soldar

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Re: Single Pole or 1P + N circuit breakers
« Reply #16 on: March 27, 2019, 07:30:28 pm »
In Spain regulations require the circuit breaker to break both conductors and I understand there are several good reasons to do so but in my apartment I have a very simple panel which only cuts the phase side and not the neutral wire.

Regulations here also require a GFCI which protects all circuits and cuts both wires but I have it protecting only kitchen and bathroom but not the other rooms.
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Offline Monkeh

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Re: Single Pole or 1P + N circuit breakers
« Reply #17 on: March 27, 2019, 07:49:59 pm »
It still has to make the circuit safe, i.e. isolate it.

No, it has to clear the fault. Isolation is not the same thing.
 

Offline Benta

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Re: Single Pole or 1P + N circuit breakers
« Reply #18 on: March 27, 2019, 08:34:28 pm »
It still has to make the circuit safe, i.e. isolate it.

No, it has to clear the fault. Isolation is not the same thing.

Agreed.
Let's go back some years: circuit breakers were thermofuses/filaments that melted. They were only placed in the live conductor in the fuse panel.
The resettable breakers have the same function, which is to open the circuit in case of overload.
Fusing neutral is nonsense.
 

Offline soldar

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Re: Single Pole or 1P + N circuit breakers
« Reply #19 on: March 27, 2019, 09:06:30 pm »
Fusing neutral is nonsense.

In Spain it is required by the regulations and there are several good reasons. One is that some places are supplied 230 V with two phases from a 127/230 volt system and there you, obviously, need to cut both wires just like in America you need to cut both wires in a 220 V circuit.

And there are other reasons.

Also, there are different ways of implementing and connecting protective earth and a lot of people think there is only one correct way to do it and any other way is wrong.

Again, in my apartment I have single circuit breakers on the phase side but there are good reasons to cut both wires after an overload or GFCI.

In Spain, like most of central Europe, we use Schucko plugs which are an abomination to everything that is decent and holy. Non-polarized, requires great force to pull, earth tabs can bend out or shape or make bad contact, too big.
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Offline Monkeh

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Re: Single Pole or 1P + N circuit breakers
« Reply #20 on: March 27, 2019, 09:11:17 pm »
Fusing neutral is nonsense.

In Spain it is required by the regulations and there are several good reasons. One is that some places are supplied 230 V with two phases from a 127/230 volt system and there you, obviously, need to cut both wires just like in America you need to cut both wires in a 220 V circuit.

That's not fusing the neutral, because it isn't a neutral.
 

Offline soldar

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Re: Single Pole or 1P + N circuit breakers
« Reply #21 on: March 27, 2019, 09:45:21 pm »
In Spain the electric code requires cutting all conductors, always, including neutral, always. always.

I thought I had made that clear in my earlier post.

Relevant regulation is Reglamento de Baja Tensión ITC-BT-17. It mandates (1) General shutoff switch which must cut all wires, (2) General GFCI which must protect all circuits and cut all wires, (3) individual circuit breakers which must cut all wires.
« Last Edit: March 27, 2019, 10:00:07 pm by soldar »
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Offline Monkeh

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Re: Single Pole or 1P + N circuit breakers
« Reply #22 on: March 27, 2019, 10:26:41 pm »
In Spain the electric code requires cutting all conductors, always, including neutral, always. always.

I thought I had made that clear in my earlier post.

Relevant regulation is Reglamento de Baja Tensión ITC-BT-17. It mandates (1) General shutoff switch which must cut all wires, (2) General GFCI which must protect all circuits and cut all wires, (3) individual circuit breakers which must cut all wires.

I didn't claim otherwise. I simply made the point that if you have two active conductors you don't have a neutral.

I've yet to see any of the good reasons for requiring a breaker to interrupt neutral.
 

Offline soldar

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Re: Single Pole or 1P + N circuit breakers
« Reply #23 on: March 27, 2019, 11:09:57 pm »
Two scenarios I can think of.

(1) If the neutral wire breaks then the neutral wire can be brought to live voltage through devices plugged in.

(2) If a 220/380 distribution transformer fails and temporary emergency supply needs to be provided it can be done with a 127/230 transformer or 127/230 mobile generator using two live phases. 

I am sure there are others.

I am not saying it is a must do. Every technical decision has its pros and cons. Cutting both conductors is, obviously, safer. OTOH there is added cost and complexity.

As I said, In my apartment I only cut the live wires because I like it that way but it does not meet code regulations.

Note also that in Spain earth and neutral are not connected as they are in America. Another case of doing things differently.
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Offline Monkeh

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Re: Single Pole or 1P + N circuit breakers
« Reply #24 on: March 27, 2019, 11:22:48 pm »
Two scenarios I can think of.

(1) If the neutral wire breaks then the neutral wire can be brought to live voltage through devices plugged in.

If the neutral wire upstream breaks, how many additional faults are required for danger to be present?

Quote
(2) If a 220/380 distribution transformer fails and temporary emergency supply needs to be provided it can be done with a 127/230 transformer or 127/230 mobile generator using two live phases.

That is a very country specific situation involving attempting to connect two incompatible systems, and requiring the use of a two-pole breaker universally is a lazy fix at best.

Quote
Note also that in Spain earth and neutral are not connected as they are in America. Another case of doing things differently.

If earth and neutral are not connected then by definition there is no neutral. Note that I'm not American, also..
 


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