Hi,
I am living in the South of France and the power supply to my house is 3 phase. The overall supply is 9kv giving a max of 3kv on each phase. I tried to fit a type AC 30ma breaker to each phase for safety reasons but have failed somewhere!
The supply is 3 lives (220v each) and 1 neutral. I connected each live to term 1 on the breaker and then out of term 2 and back to original position in the distribution unit. I took the neutral to a terminal strip and ran 3 wires from that strip though the ac breakers to a separate terminal strip and then a single wire back to the original neutral terminal in the distribution unit.
Each ac breaker will work until an ac breaker on the other phase is switched on. Switching on the second ac breaker seems to cause a dead short (I'm assuming because the neutral is a single wire common to all three ac breakers?). Each ac breaker will work fine on its own. Am I trying to do the impossible?
I really can't see where I've screwed up based on the wiring principles I work with normally - but this is the first time that I have tried anything like this with three phase.
As an aside, the main trip in the supply breaker didn't trip.
If you can give me an idea where I've gone wrong I would be very grateful! :p
Best regards,
Ed Coombs
St Antonin Noble Val, France.

While I am not familiar with the exact equipment you have, I suspect either Schneider or Telemecanique, I believe the issue is you are using one load neutral for each circuit. One GFI must only have the one load neutral for one circuit. Any other neutrals will cause an imbalance of current, which is detectable by a GFI, and will trip one of the GFI breakers.

I tried to review the Schneider French website, but I do not understand French, and my wife only understands Canadian French, and no electrical terms.

So no help there. If you can give me a link to the circuit breaker you have, I can probably confirm my advice. In any case, I am sure the common neutral for multiple circuits is the problem.

Thanks for your prompt reply.

I think you have hit the nail on the head with the combined neutrals throwing the trip. I had another look through my catalogue and there seems to be a three phase option that will cover all three phases... it was tucked away on the corner of the page! Only problem is that it is 10 times the price of the single phase options!

It just proves that sometimes a bit of advice before starting a job is a good idea!

Again, many thanks for taking the time to answer. I really am grateful.

Best regards,

Ed

Why not three individual GFI breakers, as I think you have, but only connect each circuit neutral to that Load Neutral on that breaker?

What brand breaker do you have?

The breakers are by Legrand. They are standard 40 amp type AC breakers with 30ma trip.
I'm not sure that I fully understand what you are suggesting... Do you mean spur off a neutral for each breaker an attach to load terminal only?
Sorry if I sound a bit thick but I am a reasonably competent (I thought!) diy electrician and am clearly out of my depth here! It's a shame I can't draw a diagram and post that!
Many thanks again for spending your free time helping me.
Best regards, Ed

You sure can provide a sketch or even photos, use the Advanced method to post, and click on the paperclip to attach various file formats.

Is this your breaker style? Exactly which one?

http://www.electrika.com/products/m/man-0550/pdfcat/leg07-130.pdf

It is cat no. 089 10 - 40a type AC 30ma.

OK, I am getting a bead on this, part of the issue is the 3 phase consumer unit.

What I think you need is a single pole breaker, for one hot to each circuit, and then the neutral connects to the neutral bar.

I am at work and need to get "working" so if I helped, great, otherwise I will not be anble to look further into this until later.

Have you made any progress with this problem?