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  1. Hi to all and thanks for all the input so far. In reply to Jaco - no, I cant handle all 40 panels at once. We are set up to use about 5Kw at a time. This we get from 20 panels on a bright sunny day, no problem. But when it is overcast, we can only get about 3.5Kw as an example. We then turn on the extra 10 panels, bringing 30 panels online and this brings us up to 5Kw again. But if I go out and forget to turn off the 10 extra panels and the sun pops out, I risk damaging my inverter as emails from Antony in earlier post show. So in a perfect world, 20 panels will be great if the sun shines every day. But this is not true so we want to put up extra panels safely. Bright sunshine - 20 panels = 5Kw Overcast - 30 panels = 5kw So we have to look at external MPPTs. In the old days you set the jets in your car for Jhb or Durban. So if you jetted your carb's for jhb, as you went down hill you could either lose or gain power as things changed, but your carburetor was dumb and was not variable. Modern fuel injectors sense the amount of air pressure to work out O2 levels and and adjust spray to optimize so no matter the altitude your car is efficient. This is the thrust of my argument - how can we put up excess panels to allow for variables like overcast cloudy days. Safely that is. Cheers.
  2. Hi to all. Please excuse any errors I make here, I am an amateur at this. We have installed a Goodwe hybrid grid tie inverter, 5Kw unit. It was supplied with 20 panels - 2 strings of 10 connected to the 2 MPPT inputs. Due to the construction of our house in a "H" shape, we throw shade over the north facing panels till about 09h00. To get around this we have added a 3rd string of 10 panels on our east facing roof. So now at night we turn off one of the north facing strings and turn on the east facing string. So still only 20 panels connected at any one time to the inverter. At about 09h00 when the full sun is on the 20 north facing panels, we turn off the east panels and turn on the north facing string that was off, so only 20 panels on at a time. All well and good, works like a bomb. BUT, BUT, BUT - we have now learned on an overcast day, we can turn on all 30 panels and make more power from less light. All well and good. But what will happen if the clouds suddenly disappear and all 30 panels are producing max power? The installer has explained to me that basically my system max spec is a day in October where because of roof angles etc, that is the day my 20 panels will make the most power ever if the sky is clear and that is the maximum input the inverter can handle. Lets call this the "perfect day". So, all other days we can make less power because of angles, cloud etc etc. This seems wrong. On a cloudy day, we could do with 40 panels, not 20. Why can we not just put more panels up than needed on the perfect day, but each other day we could make the "perfect day" if we could have 40 panels on line all the time, but the inverter must only take what it can handle max. Does this make sense or am I lost here? Why are we limited like this?? Or are we? Any advice appreciated here. Cheers.
  3. Plonkster you right, KISS. We are going to look at another MPPT solution.
  4. Thanks Plonkster and TTT. Agreed 100%, except for the design and actual layout of our house. There is a period from 10 to 2 that no sun is shining on the East or the West panels. Steep pitched roofs, layout of house is in a "H" configuration. Our panels are at right angles to each other. Looking at the house, the center faces exactly north, with East and West at 90 degrees to this. So with a high vertical sun in summer, it will only shine on the top edge of the East and West panels. Our spread sheet calcs show 80% of the power comes from the main panels. 20% will come from East and West. So the East panel will only help from sunrise to about 10h00. And, the West panel is still in shadow at this time. And the West panel will only generate from about 15h00 onwards. By doing it the suggested way, we only have one panel on line in the brightest part of the day. Seems to be that switching is going to have to be done. cheers.
  5. Hi Plonkster, thanks for the replies, well informative. The inverter has 2 MPPTs - the main panels are in 2 banks of 10, each bank uses up 1 MPPT on the inverter. These panels bring us to just shy of absolute max input if the sun is shining and we at midday, all is running well. We cannot now just flip on the West panels or the East panels as we will go over max input allowed into the inverter. Parameters: We have four sets of panels, only 2 can be online at a time. 2 equals the max the inverter can handle. Four incoming wires from the 4 banks of panels come into the garage. Our inverter has 2 MPPT inputs. Recommend the best way of being able to isolate the 4 panels and then be able to bring online only 2 of the 4 panels at a time. Our intention: At night, we will switch on East panel and 1 main roof panel - 2 online - West and 1 main roof panel off This allows us to catch the early morning sun as it rises and supply power to the laundry geysers and washing machines. By 10am, the sun will have moved past our East gable and the best power is now from the 2 main roof panels. So we will isolate East panel, leaving only 1 panel on line. Then we will turn on the 2nd main roof panel - 2 online, East and West offline By 15h00, sun will be more to the west, so will isolate 1 main roof pane,, leaving only 1 panel on line. Then we will turn on West panel - 2 online, East and 1 roof panel offline. It is the isolating and switching off of the incoming lines from the PV panels that we need advice on. Cheers.
  6. Hi to all. My first post, and I hope it is of the standard required on this forum. I have been lurking for a while to get a feel for the personality's on the forum. We are in Prince Albert in the Karoo. Our main house has gables on either side of the roof we are putting our solar panels on. This leads to shadows been thrown over the solar array in the morning till about 9 and starting in the arvie from about 4. This shortens our solar day by about 6 hours in the summer and 3 hours in the winter. A lot of generation time. Option 1 is of course to bash the house down and rebuild. Option 2 is to add more panels, lets call them East and West and the main panels we call Center. We can only have maximum 20 panels on line at a time in 2 banks of 10 panels each. Our Center panels are 2 x 10 - total 20 and this pushes in the max amount allowed of DC power to the inverter. But in the morning we want the 10 panels on the East roof to come into play, so we want to turn off one of the Center panels and turn on the East panels - total of 20 panels on line. This will be from 05h00 to 09h00. After 09h00, we want to turn off the 10 East panels and turn on the second bank of Center panels till about 15h00 when we want to turn off one bank of center panels and turn on the 10 West panels. So all day we have a max of 20 panels on line at any one time. So now we come the crux of the matter. High voltage DC 3 way switches or any other suggestion to be able to allow us to configure any combination of 2 of the 4 banks online at a time - BUT NEVER BE ABLE TO HAVE 3 OR 4 BANKS ON AT ONCE. Any legitimate advice and input will be welcomed. I am posting this post on other sites as well as someone out there has had this problem and solved it, I am loathe to pay school fees on this. Need to know what worked on other sites. Thank you in anticipation for assistance and advice. Cheers.
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