Moved home. Using two IotaWatts across 3 Phases? also no more solid core CTs?

Hey guys and gals,

firstly, I cant find solid core CTs available on the store anymore?? I need some more.

I bought an IotaWatt a while ago for my old home. Worked great for our small duplex.

We since moved to Brisbane (Australia), and have a larger home now on acreage.

I’m an electrician by trade so am about to upgrade my old switchboard, and want to install my IotaWatt while i’m in there. However my new home has over 20 circuits and is 3Ph. I also have 3x solar systems (One on each phase. Ranging from 5kw to 6kw) One of which is located off a subboard in my shed.

Ideally id like to monitor all circuits individually however the shed I’m happy to just leave all together, as almost no power is ever used out there.

I already have a v5 Base unit, a single 100A Snap on Ct, and 7x 50A Solid Core CTs.

I’m assuming I’m going to have to buy another Base unit and multiple CTs. But what’s the best way to monitor the 3 phases? ( I have no 3 phase devices, but just circuits split across the 3 phases).

Do I need reference Trans for all 3 phases for both units? (Using up Ports 13 and 14 on both).

I’m pretty new to this side of things so am planning on learning a bit of RPi to consolidate the two units, but for now I’m just wanting to know the best way to setup the hardware.

The setup is as follows!

Single Line Diag Home|502x500

Sorry I couldnt get the image to preview

You could do this with 1 unit and use reference phases that leaves you with 14 ch
3 on Mains in
3 on Solar panels + 1 on Shed A (solar)
7 divided over the the consumption channels.
Have 3 calculated outputs for channels not measured

Hi @Samson_1,

@Bali is offering sound advice. Let me add a little to it.

He is referring to using “derived reference” for voltage reference. Essentially using one phase as a reference for all three by numerically phase shifting it within IoTaWatt. It does not account for voltage differences between the three phases, but that is relatively minor. The overwhelming majority of IoTaWatt users use derived reference. As you mention, you can use “direct reference” with three VTs using channels 13 and 14 for the additional VTs. My recommendation is to try derived first. You can always switch if it’s not satisfactory.

As @Bali says, with derived you will have 14 inputs available. Three will be used for the mains, leaving 11 for individual loads and solar. Plan on dedicating three for the solar arrays, leaving 8 for other loads. There are two ways those 8 inputs can be leveraged to do the whole job:

  1. Circuits on the same phase can be combined by passing multiple conductors through one CT, or, since you are an electrician, combining the neutrals from those circuit and monitoring that with one CT.

  2. Whatever circuits are not directly monitored on each of the three phases can be indirectly measured by creating an output that subtracts the monitored circuits of each phase from the main for that phase. This essentially adds three more inputs to the IoTaWatt allowing measurement of 17 circuits rather than 14.

Sorry about the solid core CTs. I really liked them as well, but my current CT supplier doesn’t have a small solid core. I sold so few of those that it would not be worth ordering a quantity from China with the cost and challenges of shipping these days and the oppressive tariff (25%) currently imposed. The 50A split core are really good CTs (0.5%). If you really want the 50A solid, get back to me and I can give you contact information for Echun in China.

I never thought about the idea of working out missing current. I did that with my previous setup (although I found it a little unreliable.).

I mainly liked those as their size is fantastic. Especially when using ALOT of them in a relatively small space.

I’ve planned it all out, and I’m thinking of just going a second unit.

In total I need to monitor 23 circuits (I’m missing one off that Single Line Diagram).

Even with derived refference and calculating 3x circuits, Im either forced to combine 6 of them in total or just not monitor them.

Being a fussy kinda guy I like accuracy, So i know it’ll annoy me to no end.

If I get a second unit, I can give each circuit its own CT as well as a proper reference voltage for each phase for each unit (We’re Semi-Rural so our phases can have a fair amount of Lead/Lag at certain times of day), and still end up with 1x spare CT for future (We want to install a pool in a couple of years).

I figure i’ll just setup one to monitor the main stuff like power/lights circuits, mains and solar while the second unit can do our shed, granny flat, Solar HWS, etc.

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