Here is my question: I am in Italy where the electrical system is 220v 50hertz. In the United States, we get 220v out of two ungrounded conductors. In italy, we get 220v out of one ungrounded conductors and one grounded conductor (neutral). What happens when you take an American type, two pole breaker and wire it to a European System? Where you would normally have two "hot" (ungrounded) conductors on both the line side and load side of the American type two-pole breaker; now you have one hot conductor and one neutral conductor wired to both the line side and load side of the American type breaker. Will the breaker still operate properly in case of a ground fault?

I hope this is a clear explanation. I also have picture but I don't know how to insert them into this e-mail.

Are you talking about GFI or simple breaker? A double pole breaker won't detect ground faults if the current doesn't exceed the breaker's rating. However, the breaker should detect overloads and shorts just like on a US 240V system. A GFI breaker should work as well. In Vienna many old installations have individual fuses for both line and neutral, so I can't see any technical reason why a DP breaker shouldn't work. I don't know whether the Italian codes prohibit the fusing of the neutral though.
But why don't you take a European 1+N breaker (fuses only the phase but always breaks the neutral on tripping, basically a breaker and a switch tied together) or a European double pole breaker or a simple Italian sigle pole breaker? Then you're definitely on the safe side.

Welcome to ECN!

A U.S. breaker will still function properly on a 220V supply which has one side grounded. The only thing I can think of that might be of concern is whether the breaker is rated for such use. I believe that residential type 2-pole breakers are generally rated 120/240V and that to operate the breaker within its UL specifications you might need one rated for a straight 240V. I'm sure one of our U.S. members will step in here.

With regard to clearing a ground-fault, remember that in many parts of Europe the TT system is used, meaning that there is no direct bond between the building grounding system and the neutral. The regular breaker just acts as an overcurrent device, and a main GFI is fitted to protect against ground faults.

Hi Sparky
I would be inclined to reiterate what Paul has said, but also:
Is US breaker rated for use on 50Hz 220V to ground?
Do US breakers have tripping characteristics in accordance with EN 60898 (IEC 60898), EN 60947-2 or other standard that may be required for Italy?
I would be inclined to fit a European breaker to ensure compliance. I would also seek local advice regarding RCD (GFI) requirements. As Paul stated the supply may be TT, requiring such a device for ground fault protection.
These questions can only be correctly answered by someone with local knowledge.
Good luck with your installation.

I take it that our new friend is Italian?

Well, the good news first:

The difference in frequency is to small to cause a problem. You have to get into special system like 16 2/3Hz or 400 Hz before it seriously affects the breaker. I checked the specs for the Cutler Hammer IEC breakers. They have constant performance from 16 2/3 Hz to 60Hz.

The breaker doesn't know of the respective potential to earth of the wires, so it won't have any problems with a normal fault.

As you knwo, a ground fault on a system where ground an neutral are bonded somewhere (so called TN-C-S or TN-S systems) the fault is sensed by the breaker as a very high over-current. Detecting the fault should work just as fine in Europe as in the US.

The problem comes when it acts on the fault. If the breaker is only rated for 120V, the voltage between the "contacts" in the breaker is twice the usual. This mean that the spark is longer. The effect of this can be seen if you look in the documentation from a manufacturer. Back to Cutler Hammer: Used in a 127/220V system the breaker I picked (a model called WMF) breaks 15 kA, whereas it in a 220V system breaks 10 kA.

I didn't find a 120 to 240 comparison, but from memory I think doubling the voltage reduces the breaking capacity by half.

If you look in the technical documentation from the manufacturer, you will often find that the breaker is tested with a number of systems, including 230/400V 50Hz. I would expect an American 277/480V breaker to work just fine electrically.

If the breaker isn't listed for 230/400V, it is unlikely that it is tested or designed for this system. I don't dare to predict the electrical nor the legal consequences of using it.

[This message has been edited by C-H (edited 05-09-2003).]

Came to think of something. The loophole is that a breaker listed for the American 240V corner grounded delta should be fine as well, as the voltage to ground is 240V in that case. I have no idea how common this is. Help from our American friends appreciated!

this is very instering suject to disscussion here therefore right now i am in usa now and i see the northamerica system pretty clear and i will make it clear here if you use the north american breaker to use the europen system it can i say it can but cant say yes but you have to rember to derate some how with diffrent HZ in usa they do test it with 60 hz but try to test some breaker with 50 hz it dont really work with some type but can use the international type like iec or ec type to meet other coutries and they will listed on the spec sheet what breaker will approve for both 60 and 50 hz i will try to find some details asap and the other question about useing 277/480 volts breaker yeah you can use it but i cant hold it responity and it is not my risk to say ok to use it without see it myself or the spec say can use 215/400 system ( common voltage in europe) and you say about corner ground system in usa we use straght 240 breaker not the 120/240 breaker due the corner ground system it and the second moot point that you have to rember that corner ground system wild leg ( or whatever you call it i cant say too many word here he he smile ) from mid tap to c phase run 208 or 190 volts depending on set up and 120 volts breaker cant meet the code at all and safety too i will expain more later with wild leg later

merci marc
ps if need more question just ask us we will try our best to help you

I would like to thank everyone for sharing their electrical knowledge with me and the other members. Thanks to everyone for your comments and suggestions. Now, I have a new perspective on how to go about solving the issue at hand--thanks to your inputs. By the way, I am an American working in Italy. Thanks again, Sparky74

You would not be using the double breaker. You would only need a single breaker since your bus is 220 to neutral not 220 bus to bus.

If the breaker is fitted as part of the building's equipment though, it might be subject to the wiring rules applicable in that locality.

Some European countries (e.g. France) are now specifying that breakers must open the neutral as well. I don't know if that's the case in Italy.

Yep, that's called 1+N breakers. They only fuse the phase but also switch the neutral upon tripping (older types were actually obviously 2 devices in 1 case with only 1 handle). Autria (or at least Vienna) uses them extensively. We even have 2 fuses in older installations.

I've never seen a 1+N breaker. Two pole yes. Where do you find these?

At each and every hardware store in Austria. You'll find 2 racks side by side, 1 with single pole breakers, 1 with 1+N. About twice the price, but strongly recommended (if not even required). Saves the need for a neutral bus in the panel and makes split arrangements with more than 1 RCD much easier.

When we had DC mains, I've read that sparkies used to fuse both legs of the circuit (positive and negative). This makes sense.

However, this practice carried over to AC where sometimes the hot and neutral were fused instead of just the hot. What happens when your "neutral" fuse blows but your "hot" fuse stays closed?

That could be a bit of a problem....from a safety point of view, especially if an ignoramus DIYer pulls the "neutral" fuse to do a repair and leaves the hot in place

[This message has been edited by SvenNYC (edited 05-14-2003).]

Ragnar,
if it's twice the price I fail to see the point of not making them real breakers. Are you sure it isn't a double pole breaker? In case of a fault on the live it also switches the neutral.

Just because it says L and N on the terminals, it doesn't have to mean that it matters electrically.

(Sorry if it sounds like I'm attacking you. Not my intention)

We used to have double-pole fusing in Britain back in the 1930s. Nowadays, the regulations permit a circuit breaker to be inserted in the neutral, so long as it simultaneously breaks all phases. Double-pole isolation switches are quite common for ranges, fixed heating units, etc.

Even though the "regs" permit a C/B to open the neutral, it's not common in the U.K., except for RCDs (GFIs).

I would like to say that:

1, We always use double pole (or 3+N) breakers.

2, The breakers fuse the phase as well as the neutral.

3, It always breaks simultanously all poles.

4, When using 3+N breakers then the neutral opens a fraction of a second later and upon closing, a fraction of a second earlier.

5, The reason that we are required to use double pole breakers is because a lot of regions are still the old Y230/120 systems. In those regions only the two phase (or eventualy 3 phase) are delivered to the consumer, therefore getting 230V. Therfore all the phases have to be broken.

I keep thinking about that too, but there are definitely 1N and 2P breakers available. 127/220V was used here until about 1975, so the 2 fuses of the old wiring make sense. Probably this was just kept until today. It definitely makes tracing of neutreal-to-ground faults much easier since you can isolate each circuit by just turning off the breaker.

Ragnar could be right:

C-H, How come you call Ranger Ragnar? Is this his real name?
Anyway, Ranger is right but I am, too. Here are some pics.
The footnote 1 of the first pic describes that the Neutral is thermicaly and magneticly fused and that it shuts before and opens after the other phases.



[This message has been edited by Belgian (edited 05-16-2003).]

Yep, that's my real name, I explained that some time ago when a long since disappeared US-guy accused me of making things up.
It's interesting that in Flemish the word "nulleider" is still used. In Germany "Nulleiter" has almost become a "bad word", "neutralleiter" is the only acceptable term.
(Nulleiter means zero-conductor and refers to the fact that in a balanced 3ph system the neutral doesn't carry any current).

Ragnar,
the Swedish term is still "nolla" or "nolledare". The Danes call it "nul".

Interesting. Try writing "Nulleiter" in de.sci.ing.elektrotechnik and you started a perfect flame war.
The guys there say the name implies that the neutral isn't important. However, in an unbalanced 3ph system with lots of different 1ph loads (which is the most common service type here) losing the neutral will cause all sorts of trouble. That was their explanation why they don't want that term any more.