Newbie help questions - Australia 3 phase

New to this stuff and I’m wondering what to buy.

I have an Australian 3 phase house with the meter box as shown:

I’m wanting to pull a fairly complete view of whole house power usage into Home Assistant.

I also have a fairly new solar system with Enphase inverters. This is currently working well and I can see the total solar produced vs total used and work out net consumption and export etc in Home Assistant, but I read that the latest firmware update breaks this. (Currently blocking their cloud service) so I was thinking that maybe I should just put my own CT clams on those cables and be done with it.

I’m assuming I’ll need:

  1. Three clamps to monitor power to the grid from the main breaker
  2. One to monitor solar generation
  3. One I can run all four light circuits through (or can I just clamp the cable to the RCD?)
  4. *Not sure what the “Spa” one does. Maybe the blower on the bath upstairs
  5. One for the Pool circuit (runs the filter pump and chlorinator and some lights etc)
  6. One for the combined Power circuits (or via the RCD) - ideally I’d like to split these up though
  7. Three for the 3-phase air conditioner (or can I run all three phases through one clamp?)
  8. One (?) for the Fridge? I’m not sure why the fridge is on a RCD and looks like two phases?
  9. One for the Oven
  10. Three for the spa pool. Or can I run all three phases through a single clamp here?

I think that’s 15 in total. I had some GPOs put in for the reference and power.


  1. Am I on the right track with my thinking?
  2. Would one base unit be enough for this?
  3. Can I use a single clamp for the 3 phase devices like the spa and air conditioner?
  4. I understand I’d need to source a reference transformer locally, but for 3 phase you technically need three. How accurate is it likely to be with just one?
  5. Base units look like they are out of stock. How often do they come back in?
  6. Would I have enough space in this box, or need to install externally? (There is another box they added for the solar)


I can answer some of these questions with the information provided:

Yes, three 100A.

I don’t see the solar feed breaker. If it’s three-phase would need three CTs.

I think you can just monitor the RCD with a single 50A CT

You have a single phase labelled spa, and a three-phase breaker below labelled spa. The single phase would be included in the above RCD.

That is also on the above RCD. You can put a 50A CT on it and then create an output that subtracts it from the RCD total.

Id say do the RCD and then if you have extra inputs, monitor those of most interest. As above, you can subtract the monitored from the RCD total.

You need three 50A CTs.

I don’t know either. You should look into that.

You need three 50A CTs

That adds up to 14CTs minimum if the solar is single-phase. The Mains, A/C and pool spa will use 9 inputs. The remaining 5 would be solar (if single-phase), RCD1, RCD2 and whatever 3 additional circuits are of most interest.

It is likely to be in the 1% range.

Next week.

There is a lot to consider, check with a sparky if in doubt.

Thanks overeasy! Very helpful

I don’t see the solar feed breaker. If it’s three-phase would need three CTs.

Sorry my bad. On another panel as per below. Looks like 3 phase. Would these need to be 3x100A again? Or reckon I could get away with 50A?

I see stock is back so I’ll order as soon as I figure that out! Thanks again.

3x50A for that. Why are there 2 breakers, is there something else in that panel?

1 Like

Thanks! No, just the Enphase solar. I’ll check with the sparkie, but I think it is just a regulation so you can disconnect the panels from the rest of the system or something.

If I add another power monitor such as a Shelly plug etc, can I get that into the IoTaWatt software to subtract etc? Or I’d need to do that in Home Assistant?

Ok so I think I need this as below. Is there any reason I can’t add 13 50A CTs though? It maxes out at 12. Is that just a stock issue?

Also I’m hoping the ESP8266 will work OK in a metal box. These units don’t come with any for of external antenna connection do they?


Don’t know. Would recommend you keep the solar on the IoTaWatt.

You just need to add the 13th from the CT drop down. The discount only applies to the first 12.

Not a good idea. Source a composite box.

Hmm…looks like I miscalculated and ordered more CTs than I can use.

What’s the deal with running multiple units? Supported from a software point of view? Can you just split the power from the VT(s)?

You can split the VT to multiple units, but each unit MUST use its own independent USB power supply.