Well guys its finally up and running and I will never allow a contractor near one of my houses again after all the stuff up I had to fix.
Its only been 1 week and two days and haven't I learnt a lot about this Solar PV stuff.
Single String
Like I have said before I have 12 X 170 Watt PV Panels connected to an Sunny Boy SB 2500 inverter in conjunction with a sunny beam monitor and the SDC computer program.
So let me see if I am right here I have 12 X 170 Watt= 2040 Watts in total.
Off load the 12 panels deliver 460Volts, On load they deliver (depending how hot and cold the days are) 400 Volts so here are my calculations for expansion.
If I add another three panels in series (total 15 panels) I will have in total 2550 Watts (SB 2500 is rated at 2500W) but the biggest concern is the open circuit voltages and they would be with 15 panels 575 Volts and that could increase on a very cold morning and on load voltages would be 500 Volts and the both are too close to the magic number of 600 Volts for over voltage on one string.
Now 2 strings set Up.
If I connected the 12 panels using two strings I would have 6 X 170Watts = 1020W X two strings of the same equaling 2040Watts but the differences would be in the open/closed circuit Voltages.
string one and two would have 6 X 38.3V Open Circuit Voltage= 230Volts, and in closed it would be 6 X 33.8 Volts= 202.8 Volts with is too low to fire up the inverter so I cannot use two strings.
Now If I buy 4 more panels I cannot put them in series as the voltages would go through the roof (Above 600VDC) so I would go back to the two string system that I could not use before because of under Voltage.
So now I would have 8 Panels x 170 Watts x 2 strings = 2720 Watts in total that's 220 watts over the limit, The open circuit voltages would be now 306 Volts, On load closed circuit voltages would now be 270 volts and this would be sweet.
The thing that gets to me is that all inverters have a sweet spot where they like to keep the voltages at a certain point and for mine its 320-340 volts.
To achieve this I would have to increase more panels in series in both strings and by doing this I would dramatically increase the wattage outside the operating window so I have come to the conclusion in one week as a week ago I knew nothing about this stuff that I was supplied the wrong panels for this inverter.
Now If I had a Sunny Boy SB 3000 this is what I would have and I would ask for.
2 Strings of 9 panels.
string one 9 x 170 Watts= 1530Watts x 2 strings = 3060 watts and that's only 60 watts over the rating of the SB 3000 Inverter.
Open Circuit 9 x 38.3 Volts = 344.7 Volts and closed volts would be 9 x 33.8 Volts = 304 Volts which is as close as you are going to get to the Magic 320- 340 volts as if you increase the system by another 2 panels you will be spot on with the close circuit on load voltages but over with the wattage's allowed to the inverter.
Now are you all confused?
By the way as my system stands today I have no trouble in the middle of winter generating over 10Kw a day.
Its only been 1 week and two days and haven't I learnt a lot about this Solar PV stuff.
Single String
Like I have said before I have 12 X 170 Watt PV Panels connected to an Sunny Boy SB 2500 inverter in conjunction with a sunny beam monitor and the SDC computer program.
So let me see if I am right here I have 12 X 170 Watt= 2040 Watts in total.
Off load the 12 panels deliver 460Volts, On load they deliver (depending how hot and cold the days are) 400 Volts so here are my calculations for expansion.
If I add another three panels in series (total 15 panels) I will have in total 2550 Watts (SB 2500 is rated at 2500W) but the biggest concern is the open circuit voltages and they would be with 15 panels 575 Volts and that could increase on a very cold morning and on load voltages would be 500 Volts and the both are too close to the magic number of 600 Volts for over voltage on one string.
Now 2 strings set Up.
If I connected the 12 panels using two strings I would have 6 X 170Watts = 1020W X two strings of the same equaling 2040Watts but the differences would be in the open/closed circuit Voltages.
string one and two would have 6 X 38.3V Open Circuit Voltage= 230Volts, and in closed it would be 6 X 33.8 Volts= 202.8 Volts with is too low to fire up the inverter so I cannot use two strings.
Now If I buy 4 more panels I cannot put them in series as the voltages would go through the roof (Above 600VDC) so I would go back to the two string system that I could not use before because of under Voltage.
So now I would have 8 Panels x 170 Watts x 2 strings = 2720 Watts in total that's 220 watts over the limit, The open circuit voltages would be now 306 Volts, On load closed circuit voltages would now be 270 volts and this would be sweet.
The thing that gets to me is that all inverters have a sweet spot where they like to keep the voltages at a certain point and for mine its 320-340 volts.
To achieve this I would have to increase more panels in series in both strings and by doing this I would dramatically increase the wattage outside the operating window so I have come to the conclusion in one week as a week ago I knew nothing about this stuff that I was supplied the wrong panels for this inverter.
Now If I had a Sunny Boy SB 3000 this is what I would have and I would ask for.
2 Strings of 9 panels.
string one 9 x 170 Watts= 1530Watts x 2 strings = 3060 watts and that's only 60 watts over the rating of the SB 3000 Inverter.
Open Circuit 9 x 38.3 Volts = 344.7 Volts and closed volts would be 9 x 33.8 Volts = 304 Volts which is as close as you are going to get to the Magic 320- 340 volts as if you increase the system by another 2 panels you will be spot on with the close circuit on load voltages but over with the wattage's allowed to the inverter.
Now are you all confused?
By the way as my system stands today I have no trouble in the middle of winter generating over 10Kw a day.
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