petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
not an example of what the code is talking about in that provision though.
Panel ratings for overseas work
- Thread starter masonc
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not an example of what the code is talking about in that provision though.
- Location
- Illinois
- Occupation
- retired electrician
No...the code section you cited is one that tells you what systems are required to be grounded. It says nothing about systems that are permitted to be grounded or systems that are prohibited from being grounded.
The electrical distribution is of British origin, is 415v 3 phase star 60hz, with one phase and a grounded neutral ran to each residence. That's like everywhere in the world except America. However, because it is close to the US, many developments and commercial buildings opt for a US type service. They install 208/120v or 240/120v split so a lot of our work is US systems
Additionally, all houses install a 240/120 transformer and have US style electrical outlets, and some houses transform everything and use all US fittings. Almost all outlets are US, and almost all appliances sold locally come from the US. As the frequency is 60h, there is no choice.
I bring European inverters for our solar work because they are frequency agile.
We can get British electrical products but it takes longer and I don't have as good suppliers. All my conduit, fittings, disconnects and appliances come the the US.
I would prefer to get everything from the US but I can't find suitable panels, which surprises me.
I have sent a message to GE on the issue.
Just to bring you up to speed a little on the British system...
With few exceptions LV distribution is 400V, 3ph, 50Hz. Or 230V phase to neutral.
Neutral is earthed (grounded) and most dwellings are served with L-N 230V. All appliances, lighting, and power supplies use 230V.
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
Most GE and square D residential load centers are rated for 240 volt 3 phase corner grounded delta and ungrounded delta. I know some GE load centers mention single phase straight 240 as well. When ever a panel is rated for 240 volt corner or ungrounded delta it can handle 240 volts phase to ground.
The breaker in this case however must be straight 240 volt rated instead of the slash 120/240 rated breakers. As long as they are straight rated they will clear a 230 volt fault at the rated AIC without issue.
I know straight rated 2 and 3 pole breakers are readily available in the US. A bit more expensive yes, but defiantly worth it. Im not to sure is about the availability of single pole 240 volt breakers in the US. Any one know if they are even made?
The best option would be using straight rated 2 pole breakers having on buss the hot the other the neutral.
If you do obtain straight 240 volt single pole breakers use only one buss and every other space. In theory you could jump to the other buss bar, however Im not sure if the neutral buss in American load centers are big enough to handle twice the power. Or is its a good idea to double tap one of the lugs to jumper across.
Here are some ratings from American residential load center and service disconnects:
http://www.farnell.com/datasheets/1626663.pdf
The breaker in this case however must be straight 240 volt rated instead of the slash 120/240 rated breakers. As long as they are straight rated they will clear a 230 volt fault at the rated AIC without issue.
I know straight rated 2 and 3 pole breakers are readily available in the US. A bit more expensive yes, but defiantly worth it. Im not to sure is about the availability of single pole 240 volt breakers in the US. Any one know if they are even made?
The best option would be using straight rated 2 pole breakers having on buss the hot the other the neutral.
If you do obtain straight 240 volt single pole breakers use only one buss and every other space. In theory you could jump to the other buss bar, however Im not sure if the neutral buss in American load centers are big enough to handle twice the power. Or is its a good idea to double tap one of the lugs to jumper across.
Here are some ratings from American residential load center and service disconnects:
http://www.farnell.com/datasheets/1626663.pdf
Here's a related question. In the US, Ground and Neutral are bonded in the first panel of a building. In Europe, I am told that is not the case, that the utility bonds at the transformer and never in the building, the ground and Neutral wiring are always independent. Can you comment?
As I said earlier., the breakers are defginately available, GE lists them as GE THQL-1-2-NN which are single pole 240V as opposed to GE THQL-1-1-NN which are single pole 120V. When we order 415V 3P 4W panels, these are the single pole breakers, so I have loads of those.
The issue with the neutral is a big issue and one I had not thought about.
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
I dont know much about earthing in the UK, but just to add my 2 cents I do know that in most of Europe the TN-S system is used. In this system ground and neutral only meet up at the utility supply transformer and after that point do not connect anywhere else.
Older installations tended to be TT. In this install a hot and a neutral is given only and the customer grounds via ground rod. An RCD is used to clear faults since rarely do ground rods give a low enough impedance to clear a standard breaker.
Less common but found in some parts is the TN-C-S system, which is a hot along with combined neutral ground like in the US. It latter splits after the main disconnect just like the US.
Norway is IT, which either resembles the TN or TT system but none of the phases are grounded down. The neutral tends not to be brought along with the phases and the voltage is 230 volts, all loads connected phase to phase.
OK thats good to know. Around here the supply houses dont stock single pole breakers rated 240, hence my doubt.
I dont know how neutral buss bars are rated in all panels but I do know most of the time they are 100% listed so a 100amp breaker panel would have a 100 amp rated neutral. The issue could come if both buss bars are fed from the same phase, which could result in 200amps on the neutral since the current could be adding.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Just for completeness, the same argument also applies (only 50% worse) for a three phase panel used this way.
For a slash rated panel, the neutral bus is sufficient for the full panel rating (i.e. equivalent rating as an ungrounded bus). Some 3? panels are available with an oversized/double-sized neutral bus, intended for systems with excessive and additive (aka triplen) harmonic currents.
If the feeder (L-N) is protected not greater than panel rating, it doesn't matter how the ungrounded buses are connected. If the feeder is rated greater than panel rating, the best method to connect 1? slash- or 3? corner-ground-rated panel is to use just one pole of the panel's main breaker and use feed-through lugs to jumper the buses.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
So if you could find one with a double size neutral, you could at least use two of the three ungrounded buses, right? (Assuming that the feeder size is greater than the bus rating and you are using a multipole main breaker to protect the ungrounded buses.)
I believe so... but every third space would be unused.
I'd probably go for a 240V 3? 3W corner grounded delta (aka grounded "B phase") MLO w/FTL panelboard at whatever rating I needed.
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