New member from Durban

Howzit all.

Name is Trevor, hail from Durban. Just about to start the solar journey, torn between the various options but need to pull the trigger as the municipal wossops have just told us we join the full load shedding schedule as at 25th May. We have been partially exempt due to the widespread damage from the June 2022 floods. They have fixed absolutely nothing, the distribution network is on it’s last legs, hence the urgency to now get as much independence as possible.

3-phase home, although I use no 3-phase equipment, but planning around the 3-phase supply which is too expensive to replace (municipal compliance with new meter on the boundary etc).

Planning a 3-phase install of sorts (probably 3 inverters in parallel for redundancy), 2 x 5kwh batteries, 6kwh of panels. Leaning towards Victron at this stage.

Wish me luck, thanks in advance for the advice offered here.


Welcome Gungets
You pay alot for 3-phase availability, so would suggest you get it changed to single. You solar will be much cheaper and your backup connection as well.


Regarding your 3-phase supply, keep it, but adopt a 1ph solar installation around it.
If you have no 3-phase equipment, there is no need for the complexity, expense and limitations of a 3-phase solar installation.

Nevertheless, you will be faced with rewiring your DB regardless, so it is best to have a semblance of a strategy. So in broad strokes:

Use the first phase for all your essentials. These are the lighter loads that are deemed essential.
Certain Lights, routers, security alarms, fridges etc. Think about attaining maximum convenience from minimal power.
This is the phase that your solar will supply constantly.

That is where most installations would stop, and all other circuits would be spread across the remaining two phases.
I propose going a bit further whilst you are at it.

Use the second phase for all your heavy loads that are not time critical. There will be a time when you have a surplus of solar ( midday). This is when you want to use this surplus power. Pool pump, washing machine, geyser etc. These are the power-hungry essentials.
This is the phase that your solar can also supply, but optionally, when you allow it.

The third phase for everything else that you are prepared to do without.
The Solar never supplies these loads.

The strategy is always to supply the essentials phase, and when batteries are charged, and there is a surplus to put it into the phase with the essential power guzzlers.
The third phase is the nice-to-have when there is ESKOM.
Try and keep some semblance of a phase balance, but it isn’t essential.

Of course, you can decide which phase does what. (The first phase might actually be L3 as opposed to L1).
Check which phases are already weighted in favour of a certain application by virtue of what circuits pre-exist on them.

This strategy will allow you flexibility in the future. You may as well do it now whilst the circuits are going to be redirected. It won’t cost that much extra now, but it will be expensive to implement later.


Welcome to the dark side Trevor.

There are many options when it comes to 3 phase and even more if you don’t actually use / need 3 phase.

What 3 phase Eskom meter have you got, does it only show one reading, basically the sum of the 3 phases, or do you still have the old style meter which shows 3 separate readings for the phases?

If you have a new meter which only shows one reading and you only get billed for the sum, then as far as I know balancing phases is no longer important at all.
Maybe @Phil.g00 can confirm, I know you are on a 3 phase supply, is there any reason why he can’t just dump his entire house on to one of the phases and ignore the rest, then install a “normal” single phase inverter system?

1 Like

That’s what I did (my 3 phase breaker has 3 lives going in, and only 1 coming out)

This needs to be a consideration. Costs are the NB factor and then redo the DB to suite the loads.

My previous 3P installation on the farm was darn expensive and more complicated.

Yes, he can bridge all 3 phases at the supply point and connect to 1 phase if his total load does not exceed his MCB.
But what does this achieve?
1Ph solar can co-exist with a 3ph grid.

On the farm my 3 phase connection fee is R3500 pm now, that’s before using a single kWh.

I actually only need 3 phase for the borehole pump, but switching to a single phase pump and then switching over to a single phase supply will be kark expensive, around R40, R50k last I did a quick guesstimate

Thinking Victron, he will only have to install one Multi if everything is on a single phase and then further split things out to essential and non essential, but still keep it on the one phase. KISS principle.

True, but the OP did mention he does not need 3 phase. So then I would reduce the cost. Last I heard it was about R2k less just by switching to 1 phase.
You don’t need a lot of rewiring. Just join all the phases to the one new phase on the input box.

1 Like

I know exactly how to make the change, I have done it before to maintain supply for an incoming cable phase fault.
The monthly fee doesn’t change from ESKOM though, you still are charged for a 3ph supply.

I am interested to know how a 1 ph solar installation is cheaper on a 1ph box than an existing 3 ph box. Where are the savings?

We are talking about switching your connection from the utility.
3 phase is about R2000pm more expensive that 1 phase connection.

You can of course wire a manual transfer switch that bridges all three phases to one during an outage. Probably not necessary as Phil said, but it is an option.

The upside, any 3-wire 3-phase stuff (no neutral) are automatically disconnected (no potential difference between the phases, so they see no power). But 4-wire stuff (with neutral) might not like that, so if you have anything like that, then I would not do it.

I realize there is that saving to be had, but the OP ruled out that option in his first post.
I agree with you that a 3ph solar installation is not the way to go, so I am suggesting within the confines of his 3ph grid supply, he uses a 1ph solar installation.
I am suggesting that as he has to segregate circuits anyway, he does it in a strategic manner.


Thanks. The costs are not high in Durbs - my average monthly bill is R1,500. The energy tariffs are the same for single and 3-phase in Durban residential.

To change to single phase is going to cost about R80,000. I would have to:

  1. Buy the new municipal meter
  2. Move the meter to the boundary from it’s current (sic) location. That’s about 40m of cabling and trenching to do, across a big paved parking area.

For that, and the same tariff, I can fund a new inverter and a 5kwh battery and have some change.

I am trying for daytime zero grid use, so going to cater properly for inverters, and will jack up panels if I need to, although I am limited by roof real estate.


Single reading across the phases, so you’re correct, balance not really necessary. However I will balance as far as I can, because if I go with my gut - 3 5kw inverters, one for each phase in parallel, then it makes sense. I’ll change the DB - I am moving it through 180 degrees to a wall in the scullery from the kitchen, will make some changes when I do that. Things like the pool will be on non-essentials, only ever run off solar. Then I’ll split the other kit across the three phases and use smart switches to make sure that things like dishwasher, washing machine etc have their time slot during the day. Same with aircons, although only two are really needed (office and main bedroom), and office only during the day. I’ve got some ideas, I’ll tabulate and share, already a ton of good advice in this thread.

I get where you are going, but please explain, what you said in post number 3 confused me a bit. :smiley:

You said essentials on the first phase, this also the phase where the inverter is connected, the always on phase.
Then you said heavy users call it non essentials on the second phase because sometimes there will be surplus solar during the day which you can then use to run these heavy users.

But how would you use the surplus solar on the second phase if the inverter is only connected on the first essential phase?

We of course not talking feeding back on one phase to balance the meter here, I know that is possible, but not legal unless registered to do so.

Yes if you go the route you initially planned, a 5 kVA inverter on each phase, then you’ll have to balance the best you possibly can, as far as I remember reading, Victron 3PH systems like to run balanced, plus I think things are over all more efficient that way.

Do you already have a energy meter on your DB to actually see what you are drawing?

Yes, have had an Efergy 3-phase meter running for 3 months now. I have plenty of data, plus have measured the use of each individual appliance that matters (not lights and arbitrary stuff). It’s a pity it does not measure use on each phase, it sums them up, but that’s also OK, it gives me a good view of the overall totals.

1 Like

I suggested segregating the existing loads across the 3 phases in strategic manner.
I suppose you are happy enough with the conventional inverter connections for phase 1.

How I get a second phase out of a 1ph inverter puzzles you. Well, I don’t. something will have to done, the point is now you are ready to do that something.
It could be:
An intervention necessary to parallel the phases with the first governed by SOC, manually, or many other ways.
It may even be that you have a role for a PV inverter+CT in the future on that second phase
Or a second 1ph hybrid inverter on the same battery on that second phase.
Or, or, or… this is just detail.
If you are to segregate the loads anyway, segregate them in a way that will lend itself to future plans. Build the foundation right, and you can have a second storey that suits if you don’t think ahead, you’ll replace the foundations in the future.