Charl_CCU

2 hours ago, plonkster said:

But the original post here talking about putting an infini downstream from an Axpert,

Ah yea, I was assuming @sulyc was referring to inverter 2 being the only load connected to inverter 1. Is this not the  case?

@buffy Awesome app. I'd love to test it out but unfortunately my inverter isn't supported by either of the communications modules. If you ever need any help, I've got experience with full-stack web, API and mobile development.

Asking out of curiosity: Is there any business plan for the app or are you doing it as a hobby?

If I can give a bit of input if you are planning for this to be more than a hobby: Is power-datacenter.com a third-party data hosting platform or have you created it yourself? If it is the latter and you plan on having revenue coming in, I personally think that you should make use of a socket connection instead of regularly polling the backend to "reload" the data. From a UX POV, it would also be a big plus. I'm not sure how often you are polling the backend but having realtime data isn't something users want to have to worry about.

I am personally a fan of "dark mode" apps but I feel that it is easier to attract users from screenshots using "light and vibrant" colours/layouts. Think Google Material Design.

I'm sure someone will know for sure but here is my speculation so long - anyone please correct me if anything is incorrect:
 

I don't know much about the specifics of either brands or your setup. I'm going to make the assumption that your Axpert inverter is connected directly to your Eskom AC with all of your loads connected to AC-out and then a similar setup of your InfiniSolar inverter connected to your Axpert inverter: i.e no external power meters. Your Axpert inverter will measure how much AC is coming in from the grid and from that, adjust its production and battery charging. It's a constant game of catch-up where it's reacting to what's already happened: it's not precise. The reason some grid-tie inverters still trip the Eskom meter even when grid feed-in is set to 0 is because a small amount gets fed back into the grid in the time it takes to react to a big load being switched off.

Now when there is another inverter added on the end, you can imagine what would happen then. Both inverters are going to try produce just enough that nothing is being imported. Best case: the first inverter only charges its batteries and never outputs anything unless inverter 2's batteries are empty. Worst/likely case: inverter 2 disconnects itself because of something on the long list of grid-safety standards it has to adhere to where it feels the grid isn't being stable.

I don't know if this is possible with your setup but a similar setup would be possible with a Victron inverter running as the "master" where it will connect to and communicate with the "slave" inverter to run in AC coupled mode. It will instruct the slave inverter how much power it should be outputting. I don't know if these are Victron-specific terms/features but I'm sure @plonkster will know about that.

Again, I don't know if this a popular feature but when running in off-grid or (I'm not 100% certain about this one) UPS mode, the Victron inverter is able to create its own micro-grid which it will vary the frequency of by a fraction of a Hz to signal to other inverters (in on-grid mode) that they should increase or decrease their production. I'm sure that this approach would be quite inefficient if you are importing most of your power.

On 2019/10/18 at 9:06 AM, plonkster said:

Energy losses over the loop is untenable IMHO.

Yea, now that I think about how quickly the hot water in the taps cools down, you're right. The more it runs, the closer it is to just being an inefficient house heating solution.

On 2019/10/18 at 12:56 PM, plonkster said:

timer-setup, or a button that "summons" the hot water.

Even if I had to wait a similar amount of time after pushing an activation button, that would still be a really attractive option for me. It just feels so wasteful if I need to run the hot water taps for so long just to get hot water. And this would apply to another hot water point if I consolidated the geysers. I've been meaning to sit down with a plumber and have a look at the hot-water line because at one or two of the points it doesn't make any sense how long it takes the hot water to get there especially considering how close they are. I can't expect this is the norm. It always feels like such a waste of water to run the kitchen tap for so long just to wash a few things.

But in any case, it seems like these systems don't exist much in SA. Or at least in the home-plumbing market. I wouldn't want to get a system installed where I need to worry about whether or not a given plumber will immediately understand what it is and how it works in the future.

On 2019/10/18 at 12:56 PM, plonkster said:

Alexa... ready the shower!

Haha yeah, that would be amusing to see  . I'd feel like Iron Man.

On 2019/10/18 at 9:23 AM, DeepBass9 said:

If the pipes are either lagged or plastered into a wall they shouldn't lose heat too quickly?

I would think they'd be a good insulator but I'm speculating that bricks probably act as a giant thermal mass which absorbs all heat from the water as soon as the water isn't flowing.

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I think that I'll revisit the idea after the installation if the geyser temps are ever unnecessarily high. I'll also see what the solar-geyser installer says about the idea when he comes to quote.

I've just discovered these "integrated loop" hot water recirculators. Do they exist in SA? I can't seem to find any mention of them. Are they considered a bad idea? Would they be against the local plumbing standards?

20 hours ago, Sidewinder said:

My feeling is that if you go offgrid, then you must stay with regular electric geysers. The more the merrier. Rather invest in more capacity pv and inv. 

Off grid means you can do absolutely nothing with the eccess power you generate, except use it. Now it is actually quite difficult thing to do that. A few 200 litre geysers will help. Just 'rev' then up to max temp (that's about 64 °C), then family of 4 can have a shower in the evening and another the next morning. I put mine in series, not parallel. 

Oh, and downgrade the element to 2kW, so if needed, you can run a few more things whilst one of the geysers is on. Like hairdriers, microwaves etc. 1 or 1.5 kW elements are not easy to come by. 

With the current prices of batteries, I'm hoping to get enough batteries to be self-sufficient which I believe is possible if I take the geysers out of the equation. At the moment I'm running purely grid tied with no batteries. I'm running the geysers as a "battery" but there is still a lot of wasted potential output as this solution isn't perfect and relies on timers.

Without the 3 geysers, the only high-current appliances will be heating of the dishwasher and stove/oven which I plan on eventually replacing either with gas/induction.

19 hours ago, DeepBass9 said:

Solar geyser definitely. And a generator. You can get a week of cloudy weather sometimes. But grid tie is much cheaper and easier. 

Yeah, I definitely agree with the fact that I'd need a generator and that grid-tie is cheaper. I plan on having an automatic controller retrofitted to my 9kVA generator. I feel that adding a battery and solar geyser system would actually improve my overall ROI.

Because of technical limitations, I plan on being disconnected from the grid unless the battery starts to get low or there is an extremely high demand for power for whatever reason. This will also allow me to do a dry-run of going off-grid to see what needs to be adjusted/added/removed.

15 hours ago, DaveSA said:

Ring feed and properly insulate the other 2 units.

Thanks a lot for the info! What are you referring to with the above statement? I'm assuming you might be referring to creating a hot water "circuit" (kinda like a bus-bar or perhaps an actual loop with continuity) and having both of the geysers feed into it? How would this work with regards to how much hot water each geyser will output?

15 hours ago, DaveSA said:

it is user specific so pointless speculating without all the (usage pattern) info.

The information is greatly appreciated nonetheless. I never took a second to consider if heat loss to temperature isn't linear. In an ideal world, I shouldn't have to rely on the electrical element too often but as per your suggestions, I'll get a smaller element and also set the minimum temperature 55c..

14 hours ago, KLEVA said:

Without looking at your exact scenario, I would go with the 300l geyser and 24 evacuated tubes, with a Geyserwise Max and a small 12VDC pump. And if have a few bucks to spare after, add a 30-50W solar panel, a 14-30Ah battery supply, and a cheap PWM charge controller and it will be totally self sufficient.

Hi, thanks a lot for all the information. That addresses a lot of my uncertainty.

14 hours ago, KLEVA said:

Wall mounting a solar geyser needs a proper company to sort

Thanks a lot. I will definitely get a professional to sort this out. Is this purely from a pressure POV for pump requirements or are you also referring to structural concerns?

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Is it possible to oversize the panels or does pressure really become an issue? I also wouldn't want it to constantly be pushing out hot water when the pressure becomes an issue. What is the max "happy" temperature for a geyser so that it doesn't wear and tear too quickly?

If I had extra heating capacity, I love the idea of setting up a closed loop hot water return system which will circulate during the day and only when the temperature is above X to try save water at the taps. Would this have a significant impact on standing losses (even with insulation) when the circulation pump isn't running?

How will the geyser manage during the summer when I'm away and there is no hot water usage? Is it not going to dump a lot of water?

Hi everyone,

I've had a grid-tie solar PV system for almost 30 months now. Recently, I've revisited the idea of going "off-grid" and only using Eskom when absolutely necessary and then disconnecting once Eskom/Tshwane starts implementing kWp limits or capacity charges.

To accompany this, I feel a solar geyser is a no-brainer. Any input would be greatly appreciated. From what I've read on the forum, it seems like there isn't a "best" solution and that there are a lot of "it depends..." My experience is that I feel that there are just so many different approaches and everyone has a different opinion on what is best.

1. Evacuated tubes or flat-plate collectors?
From what I've seen in person in my area, it seems like flat-plate collectors are a lot more popular. Is durability/quality an issue with EV tubes? If not, it seems like there is no disadvantage to using them besides upfront cost. Will there be a performance difference in my scenario? Is there a big difference between high-pressure and direct flow EV tubes? I believe that is the correct terminology?

2. Indirect or direct?
KwikSol/Sustainable claims that their indirect systems should be used "where the ambient temperature falls below 5°C and where the water quality is poor (more than 600ppm Total Dissolved Solids / Minerals)". Tshwane claims their water is soft at 80-100ppm.  Suntank states that in Pretoria Indirect systems should definitely be used.
What sort of maintenance and reliability can I realistically expect with either setup? For indirect systems, I've seen the mention of having to replace the glycol every 3-5 years. If it means the solar system isn't getting fouled up, indirect seems like a big benefit and especially with direct flow collectors.

3. How many geysers, which size and in which arrangement?
At the moment I have 3 x 150L geysers which have been kept in the same setup since I moved in. They've been replaced as they burst. Geyser 1 (G1) is located centrally to the house mounted outdoor in a ground-level enclosure against the exterior wall of the kitchen. All hot-water consumption points are within 15m at the most. G2 is located at the edge of the house and provides water for one bathroom. G3 is used for the domestic worker's shower which I plan on replacing with a gas geyser.
Is there any reason (barring piping issues) a single 300L geyser shouldn't be used to replace G1 and G2 and installed at the location of G1? I understand that it means a lot more energy is necessary to heat the water up when using an electrical element but it also means I shouldn't have any capacity issues? With the current setup of running the geysers on a timer with the PV system, supply is no regularly an issue except for when guests stay over. In that case G2 has plenty of hot water but G1 must be run on non-solar time to keep up with the demand.
It seems like putting 2 geysers in series is a popular option? I don't quite understand (and I would appreciate it if someone could help with that) it unless rarely need more than 1 geyser full of hot water. Why not just one big geyser with twice the collectors?
It seems like having one big geyser would be a benefit from a heat loss point of view as per @plonkster's post but it also seems like all the manufacturers I've looked at keep their diameter the same across all models and just extend the length.

4. Thermosyphon or pumped?
I think it is unlikely that my corrugated-iron roof will be able to support a large solar geyser with its collectors but in the scenario where a professional is able to determine that it is a safe option, is it specifically advised that I should or shouldn't make use of a thermosyphon setup? How reliable are the 12v Geyserwise pumps when used in a pumped system? I've seen a lot of complaints about it online, especially with direct systems.
What sort of maintenance and reliability can I realistically expect with either setup?

5. For EV tubes and direct/indirect geysers, which brands are known for their quality and performance?
Solar Ray seems like a good option for an EV tube setup. They only manufacture geysers up to 200lt for both integrated and non-integrated EV tubes so (unless you guys suggest a series setup) I would only be able to make use of their manifold collector. They provide a 10 year warranty. I'm not sure if that's only on the collectors or if it also includes their geysers. Solar Ray sells their 200lt 25-tube unit for R12.3k excl.
Suntank seems like a good option for the geyser and flat-plate collector as they also provide a 10-year warranty. Again, I'm not sure of the specifics.

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Unless you guys suggest there is a better approach (such as purchasing the parts myself and getting a plumber to install it), I plan on getting a professional to quote and install the system. The reason I'm asking for everyone's input is that, from my research, I've gotten the impression that a lot of installers have their preferred setup/brand which isn't necessarily what I would have wanted to go with if I didn't know any better. I made that mistake with my PV system.

19 hours ago, wjb2103 said:

Hi @Charl_CCU do you have a 3 Phase or single phase SolarEdge inverter? I am now at the point of removing the SMA 10kW Tripower and replace it with a SolarEdge inverter but the technical support at SolarEdge informed me that I will still experience the same problem with the Conlog tripping. Don't really want to spend another R50k to end up with the same problem. 

Must admit after weeks of reading manuals of different inverters it seems that the only real solution is to go off-grid. This of course poses another challange / cost implication since I don't have any batteries with my current frid tied solution (non-working).

Is there any member that have a working 3 phase grid tied system working with a Conlog meter installed? Will be great to hear what inverter you are using.

I have a single phase inverter. I can't speak about the 3-phase or industrial products products but I wound't recommend the SolarEdge setup I have for a few reasons. I would much rather have gotten a Victron inverter if I knew then how much  I now know about solar tech. I'm actually planning on getting a Victron Multiplus to add to the SolarEdge inverter.

On 2019/09/19 at 9:30 PM, wjb2103 said:

Hi Charl

Did your installer manage to sort out the tripping problem with the settings he changed on your SolarEdge inverter?

Yes, SolarEdge SA set it that there is a minimum draw of 200W from the grid at all times.

7 minutes ago, plonkster said:

Aaah , but you see I am capped at 3.6kw. I'm not there yet, but I will have to combine this with a reduction in consumption. The easiest way to do that would be to reduce the amount of air conditioner energy required in summer... which I could do for not very much money. Roughly the cost of painting the roof with the right stuff...

That's the CoCT's 60A-supply solar limit, correct? Does that limit apply for how much you can export or is it the limit on the size of your solar system regardless of how much, or even if you are, exporting?

1 minute ago, plonkster said:

Oh yes, you're absolutely right. That is why I estimate how much top-tier will be needed in the coming months, and I try to buy that amount in June (of course it also depends on your budget, if you're down to ProVita at this point then of course you can't do it). In other words, I'm not offsetting block2 before June against block1 after June... I'm offsetting block2 against block2. It is an estimate though, but in general an extra R2000 worth of electricity bought in June will work out cheaper than buying it in the last week of July and August. At least for me

Ah yeah, I understand now. I only go into the top tier in winter months and when my solar system has been out of commission for almost 2 weeks

1 minute ago, plonkster said:

Another tip: If it is the last day of the month and you are about to run out... buy just enough to make it until the next day. Never buy your monthly electricity on the last day of the month (unless you know you are under the limit). There is one exception to this, something I have also done.

That exception is in July. The tariffs increase in July. Usually I can make a fairly good estimate of how much electricity I will be using in block 2 in July, August and the first half or so of September (which in my particular case is when I finally go under 600kWh again), so any electricity I buy in June of the previous year, even in block2, represents a saving over the next three months.

Surely buying top-tier electricity at the rate is more expensive than what the second-from-top tier will cost after the increase.

For Tshwane electricity users who want to do this and get 650kWh each month, it's R1251.19 : ((141.78*100)+(165.92*299)+(180.77*249))*1.15/100.

Just now, plonkster said:

It happens transparently, they automatically switch you to the higher tariff, even in the same transaction.

Eg, if I buy R2000 of electricity in one transaction. I'll get 600kWh for R1111.92, and then the remaining R888.08 will buy another 347 units, for a total of 947 units.

If I buy in smaller blocks, same thing happens, the transaction that sends me over 600kWh ends up having two parts at different tariffs.

The banking app I use refuses to sell me R1111.92, so I buy R1112. It's close enough

Ah yeah, so it's how I assumed - just like Tax. I'm going to start doing that from now on. Probably won't help now but it means I can save up for the winter months and ultimately save some cash. Thanks for the awesome idea!

1 hour ago, plonkster said:

Also... every month I buy at least R1112 of electricity. On the last day of the month, if I've spent less than R1112, I go and buy the remainder before the new month. I buy as much of the cheap electricity as I can, because in winter I use more than 600kWh a month, and then the amount that I "banked" on the meter comes in handy. Unfortunately I usually run out of cheap electricity around the middle of May. We'll see how it goes with the new Pv modules I installed only in March (so they did not yet have a whole year's impact).

That's really clever. I need to try that. So is my assumption that you can buy multiple tiers at once, incorrect? I draw about 570kWh/month in summer.

2 hours ago, IdlePhaedrus said:

A neighbour of mine was complaining about being overcharged by Standard Bank earlier this week (Cape Town).  I topped up with FNB yesterday and the charge was the same as usual.

I don't believe it would be legal for SB to take a commission on electricity sales, it is more likely to be some sort of billing system snafu.

Check my previous reply. Was a misunderstanding on my part.

1 hour ago, plonkster said:

nd no matter how many times you explain it, some idiot will still sell that nonsense as gospel truth

Yeah, haha I think I get it. It's like the people who claim you can have more money in your pocket if you earn less and fall into the tax bracket below. If my assumptions are correct, if you buy enough you could be buying multiple tiers of electricity at once.

So, actually, if you buy more than enough electricity to last you until the end of the month you are doing yourself in.

Wow what is up your CoCT prices? Your top bracket is 256c/kWh. Perhaps this is outdated or perhaps there are more brackets than Tshwane shows but their top tier is 195c/kWh. Ah wait, I see where the confusion comes in. I assumed that Tshwane's rated are VAT inclusive but after seeing that CoCT mentions prices with/without VAT I double checked Tshwane's pricing and I see that right at the top of the 26 page document, it mentions that prices exclude VAT. I never actually checked how many units I got because with the non-Conlog smart metering project you loaded up money, not units.

That makes quite a difference to my battery feasibility calculations. Back to the drawing board.

Also, I topped up my new meter for the first time today with my Standard Bank online banking app. I tested it out with R100 and got almost R2.5/kWh. How does this make sense? Does SB put a big fixed/percentage based commission on the purchase?

I had the first trip since the "fix" today. I hope it wasn't the meter. I really don't want to have to increase the import minimum to 300w.

2 minutes ago, Coulomb said:

I think so. I'm not aware of any other country that is so scared of a few kilojoules of energy going into their grid. Energy as small as that will hardly make it to the end of the street (presuming an urban area), let alone to the local transformer, let alone a substation or the high voltage transmission system.

Ah yeah, it is still really annoying. Maybe people would abuse it somehow to cause chaos/damage - I'm not sure. Then again, our population is known for some not-so-safe/compliant electrical systems. Especially when it comes to load shedding. I've seen some really unsafe installations and also a lot of cheap DIY kits going around back then.

Just now, The Terrible Triplett said:

Ja, going off-grid is not that easy. But like I said, if I was pushed, I'll keep the kitchen on the grid, rest I take off.

BUT, one must be wise.

You can always take it all with you. Nothing says you must leave it behind.

Any case, just thought I share my thoughts on the matter. Be wise!

Thanks a lot for your input - I appreciate it. I really wished I could've gone off-grid.

I suppose you are right that I can take my battery with me. But again, there is the practical POV that it doesn't make sense to spend that amount of cash on a battery right now.

54 minutes ago, The Terrible Triplett said:

...

I skimmed over that study - which was really long. It is still really silly. It's like asking the oil industry doing a study to see if they will lose money if EVs become popular.

I wish I could have used this opportunity to go off-grid but unfortunately it just doesn't make sense ROI-wise with the current battery prices. Especially considering that I don't see myself living at my current address for longer than 5 years.

Has anyone on the forum managed to get an energy diversion system working - and in a way which will pass CoC? From a physical electrical/electronic POV, how does it work and if it's a straightforward process, why do inverters not come with the functionality? Are we a minority which needs it?

Quote:

Quote

For the mains section, the choices are:

    a home-built switch principally comprising a trigger IC, triac and heatsink, or
    a commercially produced solid-state relay.

How would the relay even work? Is a solid state relay and its controller able to react fast enough to divert when the current flow is reversed and then switch back to mains without any noticeable affect? And then there's the fact that it's another link in the possible-failure chain.

11 minutes ago, plonkster said:

That's the usual way to do it. Again, since it looks at the energy within a small time window (15 seconds on at least some conlog meters), if you run at 200W just prior to a large appliance turning off, you have 200*15 = 3000 joules in "savings", as opposed to the normal 600 joules if you were running at zero. That literally gives you 5 times more time to work with. But it means 4kwh from the grid per day. Which is fine if you're not covering your full load from PV... but many of us are.

Ah, yeah. I didn't realize that. If I'm using 30-50kWh a day - it's not the end of the world. I'm still going to push to get this sorted, though. It's adding even more to the already wasted 30-40% PV output during the day. It's still a lot better than how I was sitting for 10 days paying double what I normally would for electricity with my inverter off.

Update for anybody who comes across this thread: https://powerforum.co.za/topic/3713-infinisolar-inverters-disconnecting-from-grid-with-new-smart-meters/?do=findComment&comment=55166

Tshwane is not going to help: https://powerforum.co.za/topic/3713-infinisolar-inverters-disconnecting-from-grid-with-new-smart-meters/?do=findComment&comment=55166

Bad news guys: I'm sorry to report this Conlog has said that Tshwane would rather you disconnect your system than try figure out a solution (an easy token).

Thanks for nothing DA. Why do they have this stance whereas in CoCT they are embracing it and even offering feedback at reasonable rates. I wonder if they really are experiencing technical challenges or if that is another cover-up story.

I'm not sure what my installer did but they got my inverter (SolarEdge) to stop tripping the meter. I'm not sure exactly which settings they changed but I've notice that no matter the PV output, at least 200W will always come from the grid. Has been working perfectly for a few days now. Perhaps try doing this with your inverter?

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