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Two Phase CU

Good morning,

Came across a strange one doing an EICR yesterday.

The fuse board is fed with two phases and one neutral...phases L2 and L3 are linked.

I'm looking for a coding or deviation.

As I see it, best way is it's unbalanced loadings with pressure on the neutral.

Worst way is two supply circuits with a shared neutral.

The spare phase is being used to supply a flat in the building.

Loading wise, it would be possible to link out all phases in the main CU, making it a single phase board...but that would only push the problem back to the intake.

Any suggestions please.

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0 Chris Pearson over 4 years ago

I don't really see a problem, but I'd like to know a bit more. You mention a "fuse board" and a "main CU". How are they connected please?

Provided that the neutral is the same size as the lines, and there are no substantial harmonics, it should handle the current. If a service head was connected to a 3-phase switch fuse and you took out one of the fuses, would it present a problem? (Other than de-energising anything downstream.) No.

It seems to be quite a creative solution. ?
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0 Chris Pearson over 4 years ago

I don't really see a problem, but I'd like to know a bit more. You mention a "fuse board" and a "main CU". How are they connected please?

Provided that the neutral is the same size as the lines, and there are no substantial harmonics, it should handle the current. If a service head was connected to a 3-phase switch fuse and you took out one of the fuses, would it present a problem? (Other than de-energising anything downstream.) No.

It seems to be quite a creative solution. ?
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Two Phase CU

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