Just going to paste these diagrams in here with the notes. Excuse the scraggy drawings, my OCD has allowed me to post them in the interests of speed, I need to order kit before the exchange rate kills me.
So youāve stated you have 3 ph at the house already. How are the flat , the garage and the pool fed? Surely you have an AC supply there already ( possibly fed from the meter box?). Is that supply 1 ph or 3 ph and from where to where.
The flat has itās own single phase municipal feed, separate meter, a single phase feed from before the main meter on my home to their meter. I am not considering the flat right now, but if my system works out I might give them an emergency feed just for a few lights and internet/tv. The garage comes from the flat municipal feed and DB. (I can see where you are going with this idea, but I think I would prefer to keep them separate - we have tenants in there who are responsible for their own municipal bill.
Pool from the main DB in the main house. The flat used to be fed from the main DB in the house as well - the cable is still there, but is under-rated badly - 4mm cabling, so how it ever got a COC i donāt know.
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4mm is fine for the size inverter you should get. how many cores does that cable have?
3 core cable which my electrician assures me is not going to pass COC. The electrician - someone I have worked with on big corporate projects for 12 years, so heās not trying to skin me - recommended 16 mm sq,for 3 phase will be a 4 core ECC cable.
The cable should be matched for its purpose.
What on earth does your electrician think youāll need 80 Amps/phase at the flat for?
If it is suitable for going underground, a 4mm cable is capable of 5kW with ampacity to spare.
The thing is, it must be sheathed like Surfix. If it isnāt it wonāt pass COC, if it is suitable and operating within its current carrying capacity it will.
He was basing his calculation on minimum 12kva from a 3-phase Sunsynch unit. I was planning on taking all three municipal phases to the garage in the flat building, then taking the three phases back to the main house.
It is an armoured ECC cable. I will just be putting in a 110mm sleeve under the driveway to make sure that cars donāt put pressure on that cable. I will also be pulling a separate 25mm conduit all the way to the garage to run 2 x Cat6 shield-twisted pair cables for comms (one for the Sunsynch CT coil, just in case). I will be putting a small switch/wireless repeated down there for comms to the inverter and the linux PC I will have for Home Assistant. Not going to rely on wireless links from there - been there and torn my last few strands of hair out about it.
Well, I think we have ruled out a 3ph solution. It is inflexible and limiting.
Your electrician will need a 4-core cable there and another one back unless he goes 1Ph.
Thatās expensive at 16mm2.
He intends to put your entire house load through the inverter, which is unnecessary as when you have load-shedding the inverter can only deliver its rating.
You are going to ditch most of the usual house load anyway, so it is only the load you intend to keep that needs to go through the inverter.
I would also recommend using optical fibre between buildings with a media converter back to CAT cable at either end.
I think what he is describing is extending the CT cables with CAT6 - so a media converter might not have the intended outcome. But I believe there is an alternative of using a (modbus?) power meter instead of the CT, which might be a better solutionā¦
A network connection is almost a must, but as you say, there are various alternatives to a CT, depending on what equipment is decided upon.
At about R190/m it is expensive. I have almost completely ruled out 3-phase, but still going to need 3 core, the 16mm ECC is R125/m, and even that might be overkill. Just thinking ahead though, if I ever want to tell Eskom and eThekwini Power to make a sexual departure completely, whether having 80amp in there is not a prudent idea. A few grand in cabling vs replacement later.
Fibre significantly more expensive, but also a thought. We donāt have Jozi lightning here but we had a pretty close strike on Thursday last week that made me twitch.
Actually, you want four cores, then you can take a phase and neutral to the inverter and come back with a phase and neutral on one cable. Iād say 10mm was plenty.
If you HAVE to run a light cable between the buildings for data or a CT, also run a nice thick piece of bloudraad nicely joined to each buildingās main earth at either end in the same trench. (Iād do that anyway).
I want you to consider another option which is a very low-lying fruit. It is not a full solution and only addresses reducing your bill.
That is putting a PV inverter in the garage and using that existing 3-core cable.
It is as simple as that.
This will every inexpensive, but it doesnāt tick all your boxes, but it might be a halfway house to a future expansion.
I think actually a Sunsynk hybrid can be used without a battery like this. ā Check
Perhaps then the battery and heavy cable can be a future expansion.
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Thanks for the tip on the bloudraad, Iāve never thought about something like that, not even in a professional environment and it sounds like a very good idea.
Iām not looking for the cheap or interim solution for my solar. Iāve budgeted, (and Iām Scottish, so not going to throw money away) and Iām putting in the system I need to be independent of Eskom as much as possible. If it rains for days, then sure, Iāll pay the bar stewards some money, but for the rest, I need a safety blanket for our home.
My wife has some serious medical admin coming up in mid-July and I cannot be in a crippled house. So certain things are non-negotiable, hot water, fridges, lights and internet/TV.
If you havenāt done it yet, consider a heat pump. They run very nicely from even smaller inverters. For example, the 3.5kW (output) ITS unit Iāve got runs at 900W. For a large house you will probably have to go one size up.
In my house, there are three things that I cannot run reliably (because right now I only have a 3kVA inverter). I cannot run the pool pump. I cannot run the tumble dryer, and I cannot run the dish washer. Not without disconnecting a heap of other things. And of course, we have to be careful not to boil a kettle at the same time as another large load is running. So, not completely crippled, but getting somewhat irritating during those extended 4-hour slots.
I bring this up merely to illustrate how much even a 3kVA means. You go from completely crippled to merely hobbling on one leg. With a 5kVA and a larger battery, I could probably run everything.
Yeah, I have been watching my energy meter like a hawk and making notes. I will enforce new rules in the house, but will also have 2 x 5kva inverters, so have a bit of leeway. The pool will run only on non-essentials during the day, from solar only. The geyser will run during the afternoon, with a 5am top up for 30 minutes from battery. Tumble drier, only very rarely. Washing machine uses geyser water for hot, so not a big draw, and will never run at the same time as the dishwasher. We cook on gas.
I have budgeted for a 3rd 5kva inverter, and if pushed into a corner will add a 3rd 5kwh battery. Iāll hold on those - unless I am told that I need to match inverters (chipset etc) to run them in parallel - in which case I might need to bite the bullet now.
How big is your geyser and how long does the heat pump run per day at 900W?
Just wondering vs a good old 2 kW geyser element.
This is a nice little device. In combination with a 10 AM to 2 PM timer, you could feed your geyser and your pool pump through it.
The pool pump will kick in as soon as the geyser is up to temp. No wasted sunshine.
I have an old 200 liter tank on there, which is actually a little too big for the size of the heat pump. But weāre a 4-person family and you size the pump for the amount of hot water to use, not necessarily for the tank size (tank came with the house 
). The amount of time the pump runs, again, depends on the amount of water used, but on a cold tank it will be somewhere between 2 and 3 hours. Longer in winter when the COP is less and the ambient water is colder.
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I also have a 3.5kW heatpump that draw 900W. We have a 150L tank for 4 people.
In summer it takes about 45min.
In winter it takes about 60min. (starting water is colder and outside temp is also colder although last one does not seem to impact it that much)
PS. @plonkster my 3kVA Multi II does run the dishwasher without issues. But itās an 20 year old AEG model and I know the new stuff runs for much longer to wash the same cycle.
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Mine can, but there are some caveats. The dishwasher only needs a 2kW peak for a couple of minutes.
- Other loads must be low. If I have more than about 800W of other loads, it becomes a problem.
- Ambient temperature plays a role. At night, when loads are low and it is cooler, it is usually not a problem.
- I think the network case my system is built into, with the glass door in frontā¦ probably interferes with cooling.
The reason I cannot reliably use my dishwasher, is not because the inverter overloads. It is because it overheats when running at 2.8kW for long periods of time. And although I can probably do something about itā¦ Iām upgrading anyway, so Iām ignoring it for now.