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I have had 16 (1 string of 10 facing west, and 1 string of 6 facing south) solar panels on my roof for 5 years and they have been fabulous. In the UK, we are paid for making solar electricity and it has been a good investment. Since January, the output has dropped. At 1pm today, I looked at the inverter. It reads "P in 1, 1170W; P in 2, 0W". I'm thinking that this means that P=Power and there is a fault and one of the strings (string 2) is not generating electricity; probably the South facing string of 6. It also says Riso 20 M ohms; V in 2 39V; I in 2 0.00A. Again, I'm thinking that this is voltage and current in string 2. Can anyone explain this any further for me and offer any advice as to what I should do? Thank you
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Not familiar with your (apparently dual input) inverter, but it sounds like a bad string. I'd take my clamp on ammeter on
a sunny day and see what each string is conducting. Zero current string, I start checking voltages. The working string
probably is delivering something like 30V per panel to the inverter. If the no current string is delivering even more
voltage to the inverter, the inverter section probably has failed. If that voltage is absent, use your voltmeter to find
a break. Not so easy to measure V on waterproof MC4 wiring; I insert an MC4 3 way half way up the string when its
dark. Plug the V meter into the 3rd terminal and measure to each end; when things don't add up, close in on the
problem by moving the tap. good luck, Bruce Roe -
Thank you Bruce, that's really helpful. I'm a psychologist rather than an electrician (I did A level physics though, so I know a bit about P,I,V,R)! However, I have now rung the company who fitted the panels and they are coming out in 2 weeks. They charge quite a lot to come out (which is refunded if it's a fault), so I really need to be sure that it is a fault before I ring up, and I wasn't sure. It just didn't seem right to have a zero current on one of the strings, when it's bright and sunny. When they come out, it also gives me something to ask and check, so I feel much more informed now. Thanks again.Comment
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You have 2 inputs with 2 strings . Each string should have its own DC disconnect . Swich one at the time to find and confirm the bad string. Once you sure about the wich string is at fault you will need to test each panel for fault . My bet is the first 2 mc4 from the cable fitted to the panels. I found many badly crimped connectors and panels are usually 99.9% ok.Comment
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I'd also suspect the on location crimps above those from the factory. Failing that you can test every panel and
possibly that is most expedient. HOWEVER, I prefer to do a test to divide things in half, then I don't need to even
consider half the panels. A couple more divisions brings you to the problem. There is some danger that if
everything is disturbed, the fault will temporarily start working again and you have wasted your time. Sneak up
on it instead.
MC4s aren't that easy to work with; and there are a lot of variations. I broke a few MC4
tools, finally made a couple versions of my own out of substantial metal. Probably more
dangerous? The handles are well taped up. Bruce RoeLast edited by bcroe; 04-05-2017, 11:08 AM.Comment
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Thank you Raul & Bruce. I'll print these out and discuss them with the people who come to look at the panels; it's been really helpful. However, wasn't quite sure what you meant by "There is some danger that if everything is disturbed, the fault will temporarily start working again". Does this mean that there are crimps in the wiring or crimps in the connectors and this consequently stops the current flow, so that when you move things and they 'uncrimp', the current flows again, but later, they may crimp back up again and stop the current once more?
Does anyone provide circuit wiring diagrams on this site btw? Thanks againComment
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