October 8, 20241 yr Hi Guys, Some advice from you Solar Gurus Please. Easy one. INVERTER 5KW OC ( AXPERT KING FAMILY ) Solar Charge - 80 Amps Min Input solar - 40 Vdc Max input solar - 145 Vdc PANELS CS-585w-N X 6 Operating voltage - 43.3 vdc open circuit voltage - 52.4 vdc operating current - 13.52 Amps Short Circuit current - 14 Amps SO HERE IS THE QUESTION My installer wants to use 2 strings of 3 in series then parallel into a 1 in 1 out combiner box . With OSV the input voltage is 157.2 vdc And 27 Amps. ( Operating voltage will be 129.9 vdc ) He says this is perfectly fine and the higher ocv is nothing. We initially asked him for 3 strings of 2 in series into a 3 string combiner box. With this OSV is 104.8 and 40 Amps. We assumed that this was safest for these problematic Axpert inverters. But the installer says that this is a waste and too expensive. Some advise will be much appreciated here as I want to address it before the connections begin.
October 8, 20241 yr 18 minutes ago, TERRENCE P said: Hi Guys, Some advice from you Solar Gurus Please. Easy one. INVERTER 5KW OC ( AXPERT KING FAMILY ) Solar Charge - 80 Amps Min Input solar - 40 Vdc Max input solar - 145 Vdc PANELS CS-585w-N X 6 Operating voltage - 43.3 vdc open circuit voltage - 52.4 vdc operating current - 13.52 Amps Short Circuit current - 14 Amps SO HERE IS THE QUESTION My installer wants to use 2 strings of 3 in series then parallel into a 1 in 1 out combiner box . With OSV the input voltage is 157.2 vdc And 27 Amps. ( Operating voltage will be 129.9 vdc ) He says this is perfectly fine and the higher ocv is nothing. We initially asked him for 3 strings of 2 in series into a 3 string combiner box. With this OSV is 104.8 and 40 Amps. We assumed that this was safest for these problematic Axpert inverters. But the installer says that this is a waste and too expensive. Some advise will be much appreciated here as I want to address it before the connections begin. Big mistake and MPPT should go up in smoke using 3 in series. No question about it. Even if it works when switching on it will just be a MB matter of time. Will he stand in for the cost when exceeding the specs?
October 8, 20241 yr Author Thank you so much for the response. Now I have a situation on my hands. With the components mentioned what would you advise. Unfortunately the inverter and batteries have already been installed and working.
October 8, 20241 yr 1 hour ago, TERRENCE P said: Thank you so much for the response. Now I have a situation on my hands. With the components mentioned what would you advise. Unfortunately the inverter and batteries have already been installed and working. Point the installer to the label on the side of the inverter which shows Voc of panels at 25 deg C and adjust the panel Voc upwards to say minus 5 deg at which point it will exceed the inverter Voc on the side sticker.
October 8, 20241 yr Author Unfortunately he can't understand you and neither can I. Adjust VOC Upwards to Minus 5 Deg ???. Sorry for being Dumb. He did see the inverter sticker etc . Now the installation is on hold ..... will cost me another call out but I can live with that to do the right thing here
October 8, 20241 yr Agree with @Scorp007 .The max PV Array Open Circuit Voltage is 145 V and above 145v will cause damage to the MPPT .The operating voltage range is 60v - 115v . So any voltage above 115v is a waste . The MPPT cuts back if 115v is reached. Stay with 2 in series..
October 8, 20241 yr Respectfully - really sorry - but for a professional installer this should not even be a topic of discussion, nevermind something he insists on. Two panels in series at most.
October 8, 20241 yr 1 hour ago, TERRENCE P said: Unfortunately he can't understand you and neither can I. Adjust VOC Upwards to Minus 5 Deg ???. Sorry for being Dumb. He did see the inverter sticker etc . Now the installation is on hold ..... will cost me another call out but I can live with that to do the right thing here Let's get the info from a Canadian solar panel as per picture. At 25°C the Voc is 52.4V. If the temp goes down to 0°C you will get 3.4V more.(0.0026x52.4Vx25) This gives you 55.8V. 3 panels in series will thus give 165V. Now refer to the inverter specs label which indicate the maximum Voc never to exceed 145V. Current can be throttled by equipment but not the voltage. At a higher voltage the components just break through their insulation and a short takes place. More I cannot explain why you should not have 3 in series. Perhaps another installer will know how to calculate it. Edited October 8, 20241 yr by Scorp007
October 8, 20241 yr Author Thank you Guys.... That's what I have been telling him. The Frightening part is that he is willing to issue a COC for this work. But if he does what i ask then he will get 104.8 VOC / 40.5 Amps. This should be safe Right ?? 3 Strings ( of 2 in series ) into a combiner box 3 in 1 out. maybe after this lesson he will not charge another call out and issue the COC ( for whatever it's worth ). Sadly I'm stuck with this company for this.
October 8, 20241 yr 1 hour ago, TERRENCE P said: Thank you Guys.... That's what I have been telling him. The Frightening part is that he is willing to issue a COC for this work. But if he does what i ask then he will get 104.8 VOC / 40.5 Amps. This should be safe Right ?? 3 Strings ( of 2 in series ) into a combiner box 3 in 1 out. maybe after this lesson he will not charge another call out and issue the COC ( for whatever it's worth ). Sadly I'm stuck with this company for this. Your inverter can charge batteries at 80A @ 48V and no problem to have 40A from the 3 strings in parallel.
October 8, 20241 yr Author Thank you Guys.... That's what I have been telling him. The Frightening part is that he is willing to issue a COC for this work. But if he does what i ask then he will get 104.8 VOC / 40.5 Amps. This should be safe Right ?? 3 Strings ( of 2 in series ) into a combiner box 3 in 1 out. maybe after this lesson he will not charge another call out and issue the COC ( for whatever it's worth ). Sadly I'm stuck with this company for this. ** Thanks guys for all the helpful info. I will insist on the 3 strings of 2 in series. And the 3 string combiner box is the best / safest option ??
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