New build: Choosing an inverter and Water heating

Inverters
50

What I can tell you is that based on the super-secret profit/cost ratio… if you sell an inverter at half the price, you are either making no profit at all, or it must by necessity cut corners somewhere or make up the shortfall somewhere else.

I always use the example of Sinotec televisions. They are imported from China in kit form and assembled in Pretoria. They come with a 5-year warranty. The recipe is this: They are so cheap, that you can supply a replacement and still break even. Your profit is in the units that don’t fail, or end up in guest houses where they are rarely used. Warranties are marketing tools, they only vaguely correspond with the actual quality of the item :slight_smile:

Nevertheless, the sunsynk is a compelling machine. It just doesn’t have the support…

And… of course you are absolutely allowed to take whatever I say with oodles of salt, because that’s how I butter my bread :slight_smile:

51

And when we start talking about initial value for money then the Growatt must also come into play…
R12k for a 5kw and can be paralleled.

52

There is a lot of waste of PV capacity now that exporting to the grid is such a mission. However if your inverter has a non essential load output you can connect this to your geyser. This will allow you to use the full PV capacity for your pool pump etc.

53

Growatt. No. I had one, it was the most horrible experience of my life. Maybe it is better now. Maybe they fixed their firmware. But I shall fight anyone, even my worst enemy, tooth and nail if they plan to go that route.

@plonkster I think with Sunsynk and the profit/cost ratio there might be an argument for the “trying to get a good market share by undercutting competition then slowly upping the price” method. In my mind, that can go one of two ways: 1. They go bankrupt and there’s no support ever again. 2. They retain enough market share and become a brand you see for years to come. Only time will tell.

I hear about many people going the Sunsynk route now. Personally I highly value the support and knowledge available out there for the Victron products, even the modularity I find to be much more of a selling point than a detractor. In a price vs performance vs reliability comparison I place much less weight on the “price” advantages, just because I have had bad experiences before. However, in SA I find that most people place the “price” advantages right at the top, and then all my arguments are moot…

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54

Agree… but when price is the key criteria then… I’m throwing oil on the “price fire” … :wink:

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55

But the Growatt can’t blend grid and PV, so you have to be more careful about loads. It’s just not as seamless.

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56

Definitely. If you are going to grid-tie getting something that can’t blend will be very restrictive. As would something that do not have enough transfer capacity.

57

I’m running mine the same way like this. Solar geyser with Geyser wise controller, that controls that part. So the sun heats the unit, then on the other side i’m running the inverter to the geyser controlled with the sonoff th16, but I’m running 2 contactors that is interlock. The contactor is controlled via the Geyser wise, so of if you press the red button, then switch the element on but locks out the 2nd contactor that is controlled with the sonoff, and it’s works the other way around to. So it protects that no power from the inverter gets inject back in to the grid.

Grid is still there if we want to head the geyser or I can run hybrid mode mixing the grid and pv to heat the geyser.

This helps allot in winter time to when the sun don’t heat the solar geyser to much, then I boost it with my PV side.

@karischoonbee Ek is in die selfde boot as jy. We moving to a bigger house and I need to setup my stuff there to. Still in 2 minds going Heat pump but I founded that solar geyser is working really good with the connect PV side on the element.

58

@karischoonbee i see it’s a new place you building. Check if you can add under floor heating, but the water version, then you add a combustion wood heater but with twist in it.

https://i.pinimg.com/originals/a9/35/8c/a9358ca5362b75b0ab43098e779a6237.png

1400×1400 362 KB

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcS7aFJn6ssbZAib1LyZh1gXNquTj2UG3vAU0AoXPcW5n1darJVplQfkLFKx0E86SqVrpBw&usqp=CAU

You will find loads of photos on Instagram of this setups. There is a guy in Noord Hoek that is running a setup like this. The wood oven heats the geyser setup and the under floor heating and the heater supply heat in to the house to. This one of the stuff i want to do to.

59

Still full of problems, spotted a post over the weekend again and one guy said the remove a few of them, like 20 plus of them and went over to Sunsynk.

60

indeed there is - however I don’t see any point in feeding into the grid unless it’s on a 1/1 bases. I hate corruption and incompetence and especially eskom with a passion, so I will do whatever to limit my hard earned cash going to waste.

my SWH is an Israeli product - expensive, but very efficient. I paid cash so ROI doesn’t bother me.

summer time I see temps in excess of 100 degrees. the gas geyser only kicks in if the SWH temp drops below 40 degrees which only happens sometime during winter. so gas is not used continuously for heating water, only cooking.

SWH repair costs to date - zero. Maintenance is easy I just check for leaks & test all safety valves. the combination of the 2 natural resources - gas & solar just works for me. my eskom bill this month besides the R1252.00 credit - was only R388! and that’s mainly my pool pump running for 4hrs a day.

some PV panels will be used to charge batteries during the day which will power light loads like LED lights / TV / media player / PC at night. during the day other PV panels will power the pool pump any excess from that I will use it to run an aircon for either heating or cooling.

61

The Old Axpert type, Yes. But its a very cheap loadshedding option.

Personally - no thanks :wink:

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62

I started in 2008 looking at MPPT’s, there where none, and panels, R35 per watt.

By 2011/12 I bought my first MPPT and 2 x 200w panels.

FF to 2021, now I have a 5kv and 4.2kw array and a lithium bank, after I horse trade my beloved Trojan bank after 5 years.

On the journey I had a 24v 1600va Phoenix, I had a 24v 3kva Multigrid and then a 48v 3kva MPII. All sold on to offset the next upgrade costs.

I had 75/15’s, 150/35, 150/100, all sold on, to where I got a 250/100 at a price I would have been stupid to ignore.

My point is, you don’t have to go big day one.
You can buy today and sell the equipment in the next while, and upgrade.
2nd hand Victron equipment is kinda scarce.

Walk the Talk is another approach.

What I saw over the years, which necessitated the upgrades, is that over a 1 year period one can define exact upgrades so much more accurately than going big and be done. Small well defined and thought-out upgrade bites. I got it down so tight that I knew I needed 500w more in winter to cover the geyser heating whilst powering the house.

Or one can go i.e. 3kva, 1-2 years later, add another one and parallel them.
Get a smaller MPPT maxed ito array then add 2nd one with more panels later.
The benefit of this route is IF there is a breakage, there is a “spare” to hop along on.

Go Rpi Venus and not Venus till funds arrive.

And, seeing as you are now doing it, winter production is a good base level to NOT go big … for in summer you will have too much power. First, install in winter, then sit back, relax, have a beer. Wait for peak summer, then you make the next move.

My 2 cents.

Ps. And then you also make the effort to find the right people to get the equipment at very VERY good prices, cause you have become a “believer”, a “team member”. :slight_smile:

Cause some people one sells to at a profit for you are going to have to earn that profit in after-sales services. With other people you drop the profit margins to a bare basic “case of beer profit” cause one won’t have to support anything afterwards as the person is technically minded, is deeply interested and will DIY all themselves cause they can. The questions you ask, the answers you give, all points to that you are such a person.

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63

For sure! These are exciting times to be involved in RE because it’s still fairly new. What I hope doesn’t happen is what typically happens to massive products such as mobile phones or motor cars where you aren’t able to get involved. I have seen how electronics has evolved to the point where you can’t work on the stuff. And the manufacturers don’t care at all. When last did you see a service manual that went into detail about your gizmo??

64

Just an update, got a great price on a 2 year old 4.6kW Solis Mini 4G so going with that to get my system signed off and my home certified for 10400-XA. All in so far under R40k for the 8 panels and the inverter with all accessories. Considering I’m saving about R25k on the gas/solar geyser installs in the process I think this was a good option.

Just thinking of upgrade paths, has anyone run a Solis AC coupled to a Multi?

65

Yes its been done, quite often. It reacts perfectly to frequency shifting. Reporting is a little tricky but if you install a Carlo Gavazzi between the Solis and the Multi you will be able to have a record of the PV production.

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66

I have, but on an off-grid system, as Jaco says the frequency shift throttling works well.
However, that won’t help you if you are grid-tied, because the frequency is fixed by the grid.
Only Fronius and ABB inverters can be directly throttled by the Multi.
All is not lost, Solis have their own CT sensor and can limit export power to the grid through an independent mechanism.
I haven’t used this part, but it is a relatively inexpensive solution.
How well it works, I don’t know.

Be aware that AC coupling on a Multi output has rules regarding the size Multi and the battery relative to the size of the PV inverter used.

67

Thanks, yeah I know about the 1.0 factor. It will have to be a 5kW Multi and about 10kWh of battery. So when the grid is connected, the Solis will push back into the Multi and charge the battery. When the battery is charged, will the Multi try sending the excess power back to the grid? In which case the CT clamp should limit the PV power produced by the Solis.

Now when the grid falls away, can the system automatically switch over to frequency shifting and run in offgrid mode?

68

Me, would have sold the Solis at upgrade time and buy a MPPT.

69

Yes, frequency shift throttling will be automatic if it is set up.
It should also still charge the batteries from excess AC before resorting to frequency shifting.
Note: that if the frequency is such that the PV inverter is told to shut down by the frequency shift, there are certain reset conditions that have to be met before it starts up again.
Otherwise, it would be on & off all day.

Your battery capacity is too small though for that size PV inverter:

From:

https://www.victronenergy.com/live/ac_coupling:start#minimum_battery_capacity

3.1 Lead batteries

1 kWp installed PV power requires approximately 5kWh of lead acid battery:

  • 100 Ah at 48 Vdc

  • 200 Ah at 24 Vdc

  • 400 Ah at 12 Vdc

Each additional 1 kWp of AC PV will require an additional proportional 5 kWh increase in lead acid battery storage.

3.2 Lithium batteries

1,5 kWp installed AC PV power requires 4.8 kWh of battery storage:

  • 100 Ah at 48 Vdc

  • 200 Ah at 24 Vdc

  • 400 Ah at 12 Vdc

Each additional 1.5 kWp of AC PV will require an additional proportional 4.8 kWh increase in battery storage.

Yes

No, not exactly. The Multi will be set up not to export. Once the battery is charged the Solis will want to push power back into the grid. The Multi can’t vary the frequency and has no way to prevent the Solis from doing this. This is where the Solis’ own independent no-export gear stops it from exporting.
Caveat:
I have used the Multi’s no export facility, but I have never used a Solis’, but this is my take on it.