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You can probably link 3 Arduinos using the serial port, how to do it is described (for emonTx V2's) in the post "Full fat 3-phase monitor" by MartinR. You'll need only one Shield with the radio.

Those CTs look to be suitable (but you'll need to disconnect each circuit to install, and of course use both legs if you have a ring final subcircuit - but you should know all that. I have to put bits like that in for others reading who think they know it and don't). All the data you need for calibration is in Building Blocks. You'll most likely need to change the burden resistors to suit each circuit - remove the SMT resistor and replace with a wire-ended one, holes are provided.

The Arduino can drive an SSR, see http://openenergymonitor.org/emon/node/12184#comment-39566

"Can the Arduino be used to take the pulsed output from the generation meters to show the solar PV generation? I have heard that the CT method for gid tied inverters are not accurate."
Yes, but that point is contentious. If yours is the generation meter, then counting pulses should give the same numbers that the meter does. But it will not give you instantaneous current or power as a CT can, it can only tell you the average between pulses, and that only after the next pulse. If you're talking about the Grid meter, then most don't emit pulses on export, so counting pulses there is largely meaningless in terms of nett energy.

You can put together your own dashboard, and there's the Official app too.

Hi Robert

I hadn't seen that post on Martins design, but hats off its a well designed PCB and Martin is a clever guy! I think I will replicate that design as its very compact!

Ahh, I'd prefer to have donut type CTs as its so easy to put pressure on split CTs and introduce air gaps in the core, plus the donut CTs are smaller. I am a qualified supervisor for my own NICEIC company so electrical wise Im sorted for safety and best practice.

The holes for the end user to put their own burden resistor is very clever PCB design and very handy!

I think what I might do for the PV generation is use CTs for instantaneous indication of generation but use the pulsed output for the days/week/month total generation, do you know what pins do you have to use for pulsed meters? Also you can give accurate totals of moneys earnt through the FIT scheme.

Regards

Dave

I don't know the Arduino range, so I can't tell you pin numbers. But it should be easy: look at the processor pins used on the emonTx or emonTH (diagrams in Hardware Wiki/Github, code on Software GitHub), get the circuit diagram for your particular Arduino, and follow the same processor pin to a terminal/header... 

Looking again at the CT data, the transfer curve appears to bend just above 2 V. You only want 1.6 V max for a 5 V Arduino, so if you keep below the equivalent VA loading (~0.12 VA), those CTs should be fine. We have to recommend the split-core type because too many users aren't competent to work inside distribution boards, and the whole system was originally intended for whole-house monitoring anyway, which means a CT on the meter tails.

I presume that you can design a dashboard on emonCMS and display this on a tablet to show detailed information of the circuits?

Here's a dashboard I came up with to display my per-circuit consumption monitoring.  PV production and net imports/exports are on a different page.  Feel free to pinch any ideas you like and if you come up with anything better and you're happy to share, please do.  At the moment I display instantaneous and long-term energy percentage usage for each circuit as a simple numeric feed value.  Turning that into some sort of pie chart would be nice, but I'm not familiar enough with emoncms to know if that's feasible.

My energy monitor is not OEM-based, but thanks to the openess of emoncms that doesn't matter.