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The wire colours are wrong for a three-phase supply with no neutral, and in any case I very much doubt that you have a 230 V supply with loads connected in delta - your single phase appliances (and light bulbs!) would all then have to be 400V. Your wire colours indicate to me that you have a neutral (blue) and two phases, brown and black. The third missing phase would be grey. You can check the voltages to make certain, but be careful. You should read zero or only a volt or two between the blue (neutral) and earth; you should read 230 V between brown and blue and between black and blue, and between brown and earth and between black and earth; and you should read 400 V between brown and black. If you've got a wire with grey insulation (not to be confused with a wire with a grey sheath) then you should read 400 V between grey and brown and between grey and black; and 230 V between grey and blue.

If I am correct, then to measure the whole house consumption you need two CTs, on brown and black, and you need to use one of the three-phase sketches, with the ac adapter on the brown phase to neutral.

The other possibility is that the installer has used the wiring colours for two phases when you have only one phase (for reasons best known to himself). If the voltage between brown and black is zero, then that is indeed the case. What does the utility meter tell you?

Hi Robert,

Thank you for the reply.

One thing I did not mention is that I have  day/night tariff. I have attached a few photos of the utility panel. The third picture is numbered as follows;

1. Supply from the street. Two Black, one Blue and one Brown.
2. Feed from the street terminates on this terminal strip and one of the black cables becomes red.
3. 3 x 32Amp breaker. Input from (2) and output goes to (4) Meter.
4. Meter (as in the image attached) 
5. Output from the utility panel to (7) with Brown, Red and Black cables.
6. This is an external pulse Watt meter. (I can see the pluses) Could it also be connected to the dual tariff?
7. This is a mystery box! Red, Brown and Black cables go into it from (5),  but there must be a junction box in there as by the time the cables get to the input of main breaker in the distribution board, they have changed to Blue, Brown and Black nd gained an earth.(as in my last post).

Looking at the diagram on the meter (and  bearing in mind that I have never had a dual tariff meter), could it be that L1 switches over to L3 depending on the time of day? If this is the case, then is L2 Neutral? So I would need 2 x CT's over Brown and Black (as you noted) but i may only see a draw across the night one during the correct tariff period?

I double checked the distribution panel again, and what I though was the 3 bus bars connected together is not. There is a plastic insulator over the bars concealing 3 rows of bus bars. I'm not competent enough to check past this.

I need to fix my DMM before I can check the two different phases as you suggested.

thank you again for taking the time to help me out.

Regards

Kevin

<Edit: Uploaded clearer image of the diagram on the meter>

That meter is intended to be used on 3-phase without a neutral, and I think you're right, they are using L2 as the meter neutral. It's still possible that you do have 2 phases, or it could be as you suggest single phase with the dual rate switching wired to look like a second phase. The meter would read correctly both if there are two phases 120° apart or if one was a switched feed of the same phase. The dual-rate switch is likely to be operated by a synchronous motor-driven clock, unless they've gone hi-tech and are using a GPS clock, and that's probably what the mystery box (7) is. The only way to tell for sure will be to measure the voltages. Until then, everything is pretty much guesswork.