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Old 01-28-18, 10:34 AM   #1
NeilTheCop
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Join Date: Mar 2011
Location: Roswell NM
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Default Solar A/C, again

Need a little bit of advice.
I have just ordered my 2nd split system to put in our 400 sq ft living room and would like to run it off solar. I know that itís normally a non starter due to the size and cost of the battery bank, but I want to use a different approach. Here in southern New Mexico we have the maximum 5.5 hours of direct sunlight a day in the summer, seems more but thatís what my calculations are based on. My roof faces due south, is at the perfect angle, about 1000 sq ft and is unobstructed, so I have the potential to fit plenty of panels.
So hereís the plan. The split system is a 17.5 SEER with a digital inverter. The manufacturer says itís a soft start and does not have the normal A/C start up current draw, has no problem with using a modified square wave inverter, and the absolute maximum running power draw will be 1430 watts. I want to run the system directly from the solar panels during the day which will not only cool the room but take heat out of the 1200 cubic feet of concrete the room is built on therefore using it as a thermal storage for the evening. There will also be a manual switch to use grid power if anything goes wrong with the solar set up.
Now the question. I know that I will need to use batteries as a buffer between the panels and inverter, but how much capacity? Every on line calculator assumes battery capacity will be needed at night or when cloudy, but none can calculate as a buffer for running direct from panels. Any input?

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