HennieL

Check the maximum open circuit voltage in the solar panel specification. I suspect that you would not be able to install more than 8 panels in series on one string without exceeding the maximum MPPT voltage. I would suggest that you buy another two (or four...) panels and install two strings of 6 or 7 panels per string. Although five panels per string would work OK, the higher voltage of 6 or 7 (or 8...) panels per string would make the system more efficient, and would reach the MPPT start-up voltage earlier in the mornings as well.

Not sure of your model, but my 12kW Sunsynk inverter has a 12V connection (Pins 11 and 12) that should be just what you need - just confirm in your user/installation manual... See screenshot from my manual below. Hope this helps 🙂

Here's my take... If the MPPT does not start up due to low voltage as a result of clouds, then you have zero PV input until the light intensity increases to above the threshold. Even just a bit of shading on one or two panels can reduce the power of the string by 50%, or even worse, even on good sunshine days. Solar panels are relatively cheap. I would add (say) two panels of the same make & output to the existing four to take you safely above the startup voltage of the MPPT. This will also result in earlier startup, and give you more "legroom" when it's cloudy. I would then add a second string (of higher power rating if you like) of 5 panels to the second MPPT if you have roof space to accommodate them. For the price of two or three additional panels (R2500 - R4500...) you will then have addressed both the voltage "sweet spot" and (to some extent) your early morning & late afternoon shading. If this is not an option, then I would just add all eight panels on the same MPPT.

Browsing through some old posts and found this one, that deserves a bump, as I also would like to know the answer 😊 BUMP

Agreed with @TaliaB . The secret to a long RO membrane life is to: Regularly replace the sediment pre-filters Most importantly, regularly replace the activated carbon pre-filter. This removes the chlorine in the water (chlorine actively damages the membrane and can ruin a membrane in a very short time - days, not months, if present in the water in measurable quantities). Ideally the membrane holder should also be flushed with "bypass" flow to actively flush away any mud/sediment that accumulates in this housing and around the membrane. It's normally a good idea to flush the membrane at least twice during the interval between replacement of the pre-filters. I would not fret about the "good elements" stripped from the water by the RO - I have been using RO water for many years, with no detrimental effect, but the post filtration mineralization cartridge does improve the taste of the water.

I have quite successfully "stored" 1200 litres of water in a plastic Eco tank over a period of nearly three years, by continuously using a small amount of water from the tank and replenishing the used water with fresh water from the municipal supply. I connected the tank through a pressure pump to our kitchen tap, an RO filter, and to the washing machine, in total using approximately 20-40l of water per day. This small amount of municipal chlorinated replacement water has managed to keep the total 1200 litres in the tank clean/fresh enough to use for washing dishes and clothes, and after filtration through the RO filter for all our drinking and cooking water. The rest of the house is still fed directly from the municipal supply. Over this period we have had a number of "water sheddings" lasting from hours to 3-4 days, and during those periods the stored water in this tank was used to also supply water to the bathrooms and geyser, and to flush the toilets. I'm happy to state that we survived even the longest of these shutdowns with water to spare. Although the stored water is still quite clear, and odor free, the bottom of the tank has accumulated a thin layer of sediment deposited by our rather muddy municipal water, and I would not classify it as fit for drinking without filtration The RO filter really does an excellent job of filtering this water and not only making it fit for human consumption, but also for making exceptionally tasty coffee and tea - the only down side being that one wastes about 75% of the water that's filtered. Hope this is of some use 😊

Yes, that would be the simplest, and best (IMHO) solution. One can choose to boost a car's engine to deliver nearly double the horsepower it was designed for, but then the engine just won't last. Even without modifying the engine, it would still not last very long if you continuously kept the revs on the red line - I know... did just that in my younger days with an old motorbike after drinking too much rum 🫠☠️ So, throttle back on your power export when conditions require, and your inverters will last much longer.

@bobah1248 I hear you... but look at it from another angle - you just want to keep the inverters from throttling down, thus keep their power elements below about 60-65 degrees C. If they are currently heating up to 70-75 degrees C during the day, then you just need to cool them down by 10-15 degrees, and the current cooling down systems (heat sinks, built-in fans, additional fans, etc. etc. should take care of the rest. Have a look at this thread: https://powerforum.co.za/topic/29611-cooling-sunsynk-5kw/

You could turn the two inside fans around so that they suck the cooler air from the bottom as well. If possible, you could also install another set of small computer fans in the top of the inverter housing (if there's space) or just make some vent holes in the housing and install these fans on top of the housing, and point them to suck air out of the housing and blow it up towards the ceiling. If you then install a large extractor fan in the ceiling (or in a chimney of sorts...) you could vent the hot air away from the inverters. Have you considered installing a largish Peltier pump on to the heatsink as an active cooling element. Given that you've already imported the inverters from Chine it should not be too difficult to source some Peltiers either. Here's a link to a data sheet from RS Electronics to give you some idea: https://docs.rs-online.com/b696/0900766b8001b623.pdf

Yes, but... a wall is not a house if they choose to identify as a wall😉

Sounds like the wiring of your property is not up to standard - how can the second tenant get his power through your meter without you also paying for his/her power... I think your landlord might be doing you in - deliberately or due to wrong wiring...

Perhaps you should start the ball rolling by explaining what a transwall is, and the principles that would make it work - the old Transvaal worked very well, but I'm sure that's not what you have in mind 😄

Sounds like South Africa 😁 For the curious, just where do you live?

Thanks for your detailed, and well thought-out and articulated response - and I agree that there are some very good (ethics and value wise...) installers, but the problem arise when an inexperienced new PV owner-to-be decides to bite the bullet and install "some solar". When I installed my first inverter (for myself) way before Loadshedding was even a word (around 2007 if I remember correctly...) there was very little information available on designing a system, and on available components. I basically had to bite the bullet and chose my inverter just based on country of manufacture (a Swiss made Studer XPC 2200-24...). Even in those days the batteries were ridiculously expensive, and I had to settle for 4x 12V telecoms type deep cycle VRLA sealed units that were made in China (and that lasted a good 16 years, I'm happy to say...). Although I did do my homework as best I could, given the scarcity of any decent reviews and data, it was still a gamble. Solar panels in South Africa were as scarce as chicken teeth, and I thus just used my system as a backup for some critical equipment that I wanted to always have power, fed from a rather reliable grid... I designed my current system myself, based on what I learned through my trial and error first system, and after having done a lot of online research over a period of a few years, and only once prices dropped to more reasonable levels after Escom managed to eliminate most load shedding (mid 2024...). I thus specified the equipment to be quoted on, and the installation was done by a licensed electrician that came highly recommended by some happy clients that I know very well. Even so, to this day I don't know if my choice of equipment was the best "bang for the buck", or if the installation could perhaps have been done better - after some 10 months everything is still working as expected, but 10 months is a very short time in the life of a PV system... So, from personal experience, I would have been much happier if I had access to unbiased feedback from experienced people on a Forum such as this, and I am still of the opinion that a "quality vs price" matrix of equipment would be of value to the majority of people just starting on their journey into solar.

Agreed, and that's why "we" would probably be more accurate and unbiased than "they" who do this for a living... It would be great if more Forumites would chip in with opinions.