Advice for order/install for Australia


I’m in Brisbane, Australia and I was after advice on what to order (and anything else related really).

We’re having a 6.66kW solar system installed on the 19th of January (Fronius Primo 5kW inverter with Fronius Smart Meter) and I’m keen to get a better understanding of our (excessive) power usage.

Here’s what our power box looks like:

I’m a fairly technical user but my knowledge regarding mains power is limited. I’ve made the assumption that I should order 1 x 100A CT and 13 x 50A CTs (with the cost of shipping being what it is I thought I might as well get some spares).

Does this make sense?

Also, which shipping method would you recommend if I wanted some confidence that the items would get here before the 19th? Of course I also have to source the power supplies locally.

I just want to get the ball rolling ASAP so that I don’t need to pay electricians to come out more than necessary (it costs a LOT here).

It just occurred to me that the inverter will be mounted inside the garage directly behind where the power box is mounted outside. Could the IoTaWatt also be mounted inside with all the CT cables routed in a conduit also? This might remove the need for weatherproofing for the unit and the two power bricks,

Thanks in advance for your advice.


Looks like a straightforward single phase system.

I don’t see 13 circuits, but your right, I often get follow on orders for one or two 50A CTs to Australia and elsewhere.

Right now, shipping is adversely effected by Covid. UPS was a faster option, but was removed after complaints of excessive hidden destination charges. Everything going out now is slow with unprecedented Holiday shipping. Maybe it will improve next week.

The cords on the CTs are 1.5m, so might work out.

Thanks for the response. Ordered.

The way I understand it the circuits are:

Main (mystery word) L + P: Lights and Power only?
NL2: Oven
NL3: Hotplate
NL4: Power points (upstairs or downstairs, will need to test which)
NL5: Power points (upstairs or downstairs, will need to test which)
NL6: Lights (light fittings) with RCD
Power Only: I assume this is an RCD for all power points (NL4 and NL5)
A/C Upstairs: Possibly two upstairs HVACs on the same circuit
A/C Unit Downstairs: HVAC downstairs (unsurprisingly)
N11 - AC UP 1/2: Two upstairs HVACs.

Once the solar is installed there will be a Fronius Smart Meter added to the power box.
My question is, where does it make sense to monitor?

  • Main
  • Oven
  • Hotplate
  • Upstairs Power
  • Downstairs Power
  • Lights
  • All HVAC circuits
  • Fronius Smart Meter?

Oh, and the electric hot water system doesn’t seem to be mentioned so I assume it ties directly into the constant load meter. I assume that will be put on a timer mounted in the power box so presumably I’d need to monitor that circuit too?

Just trying to wrap my head around it so that I can explain to the electrician what I want and be able to explain why.

Sorry if I’m being obtuse.


I’d need a line drawing of your service to indicate where the CTs should go. Your electrician should know where to put them for each circuit that you want to monitor.

That Main Switch should be isolating all circuits, not just the lights and power. If it isn’t, that needs to be rectified.

If the other side of the wall is the garage then your electrician should be able to drill through from behind the switchboard and run the CT cables through without too much trouble.

Just make sure it is directly behind it - 5 feet sounds like a lot for the length of the cables - but it runs out pretty fast !!

Also if you are getting the Fronius and you are on Electric Hot Water - you should investigate their power diversion option and make sure it is wired up - this essentially will allow you to divert excess PV to the HWS instead of exporting it to the grid - obviously makes sense depending on your rates for CL power and export.

There is no need to monitor the Fronius Consumption meter - then again unless you are going for the Fronius load diversion option you are wasting $300 or so getting this COnsumption meter as the IOTAWATT will already give you all that info.

Basically you will want to clamp the incoming live feed from the Fronius, the mains in from the street and the main CB cable to see what your total load is.

THen it is up to you where you want to use all of your other clamps - whichever circuits are important to you - for instance does it really matter to monitor the Oven individually ? Its not like you are going to turn it off 1/2 way through cooking a meal because power costs are high !

You might also want to get your incoming mains checked for size so you do not get too big a voltage rise when you are pushing power back to the grid - nothing worse than being export limited becuase of undersized mains cabling.


I’m sure it is, but the way it is labeled had me a little confused.

All the solar quotes I saw basically connected the Electric Hot Water via a timer so that it doesn’t draw power at night. None have mentioned anything like you describe. I’m not sure if those are alternatives or complementary.

I understand there would be duplication of functionality, but consumption information via the Fronius Solar Web portal is a required feature as I’m not the only one who will want access to an overview of power usage.

Main CB cable?

I’ve ordered 1 x 100A and 13 x 50A CT’s so I may as well use as many as I can. Besides that we have ungodly huge power bills so it will be helpful to track exactly where the power is going (I have power monitoring sockets all over the house because I care about granular data).

This is not something I’ve ever heard of. Thanks for bringing it up…
Will have to do some googling.

The Fronius power diversion system enables the inverter to divert power to a chosen load (usually hot water) so rather than a timer - the inverter manages the hot water heating - you could also have a two way switch installed by the sparky so in the event that you have multiple days of bad weather you could switch the HWS across to the Controlled load (if you have that) or normal mains (with or without a timer)

Main CB cable is the cable that goes to your main Circuit Breaker (CB) so this is all the load that the house is asking for - assuming your meters will be replaced with smart meters you would usually install the incoming solar line into a seperate CB on the switchboard - you would clamp this there so this would let you know total solar production, you would also clamp the mains cable after it comes out of the meter so you know how much you are taking (or giving) to the grid at any point, You would then also clamp after the main CB so you could see what your total house consumption was

You can never have too much information i guess. !


That’s very informative.

The main CB cable wouldn’t include the aircon circuits would it?
Would it be were I would want to utilise the 100A CT?

50A for the others?

Absolutely everything MUST go via that Main Switch. Even your solar export will be going out via it back to the grid.
Yep, put the 100A on the Main supply cable, just remember that it will be a total of all sub-circuit loads minus the solar output.

I’ve just been mulling over the details of what I will want to convey to the electrician and I realised I don’t fully understand how the AC frequency is measured… Is this universal across all circuits or does it differ among circuits?

Also, is it within code to have one power socket with a power board if installed in the garage as I’ve suggested? Or should I still request multiple sockets? And does it need an enclosure in such circumstances?

I wish the AS standards weren’t behind a paywall so I could easily discover the requirements myself.

EDIT: And I almost forgot. A Happy New Year to you!

If you have a normal enclosed garage then it it fine to get a standard power outlet installed - this could be a dual outlet with one of the stand off wall mount boxes (assuming your garage is brick) or you coulod just get a single outlet and then run a power board from it. (There is minimal cost difference between a single and dual outlet so just get the dual)

You will need at least two powerpoints (or a power board) as you will have the VT (the one from Jaycar is fine and easily sourced) and a USB power source to actually power the IOTAWATT.

The AC frequency is the same (theoretically) across the whole of the interconnected power grid - so within your single phase within the house - all the circuits will see the same frequency - the voltage can vary dependent on the load you are pulling on a circuit, how long the cable is and the thickness of the wires ( my mains incoming from the street if 248v at idle) - but all the way down at my pool pump in the back yard is down to 239v.


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Thank you. That was helpful.

At this stage I’m just hoping the IoTaWatt arrives in time for the installation. I’ve already gotten the AC power pack and USB power supply from Radio Parts as I thought they were visually simpler, slimmer and looked easier to work with.

It just occurred to me that I need to check if the two plugs will fit side by side in a standard double GPO… Argh… Tight fit on the Clipsal ones we have. They push against each other when forced in. Are all double GPO’s sockets spaced the same or is there variation?

If they aren’t identical I may take the plugs to Bunnings and see if there’s anything a little wider apart.

Nope the spacing is pretty much the same for all of them - just get the double installed by the sparky and then run a 4 port power board for the USB and the VT. (Thats how i have one of mine)

Alternatively you can get one of the short piggyback extension leads from Bunnings - they plug into a power point and have a socket on the back of the plug - so you can plug the VT into one end of the Extension lead and the other onto the piggyback portion


How about this one?

Yep looks pretty good if it is a standard bunnings item they carry all the time - take your gear down there and check for fit.

As it is going on a brick wall make sure you get a mounting block for it as well as the screw holes might be strange and the sparky may not have a matching one in his arsenal


In trying to formulate an email to the installer I ran into the problem of realising that I do not fully understand the pros/cons of this solution… I Googled and found this:

I remain deeply confused. It seems like a timer is BETTER than the Fronius controlled relay?

Nope - there are almost no situations where a timer is better than the Fronius controlled relay.

Note that the article is from 2018 - Solar Feed In tarriffs are falling and will continue to fall - there is an ongoing costs to have a Controlled Load meter (even if you are not using it) and you need to find out what the CL rate is - simple maths if you Solar FIT is lower than your CL tarriff you are better off using your Solar to heat you hot water and vice versa (obviously if you are export limited the equation becomes more dificult.

Think of the Hot Water tank as a big battery - you are either going to fill it pretty much for free from your solar (less the forgone Solar FIT) or pay to feed it from the CL

WHat you want to ask the sparky for is a two poisition relay/contactor - one side of the relay will connect (by default) to your controlled load (or normal mains through a timer) and the other will connect to the “live mains”

The Fronius will initiate the contactor when you have enough solar and the timer will take over the rest of the time


The way it was explained to me was that during the night the dumb timer relay is off and water cannot be heated. During the day if hot water needs heating it will use available solar power or if there is none then the CL.

Did I misunderstand?

As of our last bill (with AGL at postcode 4037) our rates were as follows:

General Usage at $0.255 with a Supply Charge of $0.99/day
Tariff 33 Controlled Load at $0.218 with a Supply Charge of $0.03/day.

It appears that the FIT is $0.15 according to the plans page but $0.08 according to elsewhere on their website. It was implied during the solar quotes that the rate drops after a certain export but I cannot find any details. This may have been a total misunderstanding based on theoretical discussion of systems with more than 10kW of panels.

EDIT: For what it’s worth, and if I’m reading the bill correctly, we use around 1kWh to heat water on the last quarterly bill.

EDIT2: It seems only the AGL Solar Savers plan has a FIT of $0.15 and all their other plans $0.08.

It depends on your water useage and how you set it up.

If you tend to have early morning showers (as an example) - then you would want the timer to come on overnight - this would mean that you would have a full tank of hot water to start the day - so during the day you would heat the hot water with solar, then use anything in the evening for washing up in the sink etc - the timer then kicks in overnight to top up whatever is needed.

On the other hand if you have showers in the evening - then you would put the timer on for the end of the (solar day) - say around 5PM - anything that was not heated up by solar would then be topped up - but if someone had a long shower and drained the tank - there would be no hot water in the morning.

Check your tank - depending on how old they are so of them have two elements - so a solar element at the bottom and a CL load at the top.

THat CL tarriff is very high - usually they are around 10 to 11c

A FIT of 15c is not unheard of but is getting less and less available - usually for 12 months only and capped to a certain # of KWh

I assume you mean per day you use 1Kwh - sounds pretty unlikely unless you have a heat pump - or you take REALLY short showers.