rev_polarity
Member
- Location
- Sydney, Oztralia
- Occupation
- Electronic systems design
At a new house I have two 5kW, dual MPPT inverters which state a maximum working load of 11A for each MPPT. One of them is hooked up to two strings of 7 modules in parallel, and reaches 13.4A in full summer sun. The other (serial) string maxes out at 9.4A to the other MPPT (22.8A total).
The installer swears that the inverter vendor approved the configuration, and that 'these inverters can handle more current on one MPPT than the specs state, so long as the overall current isn't exceeded'. The specs state: Max input per MPPT: 11A, and Maximum short current: 13.8A.
However given the lowest temp for the location will generate a lot more current than this, it seems an 'enthusiastic design'. How it has survived a year was beyond me, until I found the Zeners he used had quite literally vaporised. After replacing them, I checked the current and decided I'd better fix it properly.
Best option is to replace the parallel strings with a single, serial string of 12 panels. However I'd be switching to newer panels which are a different size. I don't mind as I can use the 14 freed up from the parallel strings at the farm. However, the new modules will produce a lot more current than the present ones.
What do you people think? Will I not solve problem of 'smoking' the inverter one cold, sunny morning if I use these modules?
At one degree below freezing, the new modules on this MPPT produce a max current (Impp) of 11.81+1.48=13.29A. The existing string on the sister MPPT will produce a max current (Impp) of 9.38+1.30=10.68A. The maximum voltage through any of the strings will not exceed 400V (max allowable is 550V), and the inverters are both single phase Goodwe 5000DN-Ss.
Hopefully not too ling a first post... and many thanks in advance for any comments!
The installer swears that the inverter vendor approved the configuration, and that 'these inverters can handle more current on one MPPT than the specs state, so long as the overall current isn't exceeded'. The specs state: Max input per MPPT: 11A, and Maximum short current: 13.8A.
However given the lowest temp for the location will generate a lot more current than this, it seems an 'enthusiastic design'. How it has survived a year was beyond me, until I found the Zeners he used had quite literally vaporised. After replacing them, I checked the current and decided I'd better fix it properly.
Best option is to replace the parallel strings with a single, serial string of 12 panels. However I'd be switching to newer panels which are a different size. I don't mind as I can use the 14 freed up from the parallel strings at the farm. However, the new modules will produce a lot more current than the present ones.
What do you people think? Will I not solve problem of 'smoking' the inverter one cold, sunny morning if I use these modules?
At one degree below freezing, the new modules on this MPPT produce a max current (Impp) of 11.81+1.48=13.29A. The existing string on the sister MPPT will produce a max current (Impp) of 9.38+1.30=10.68A. The maximum voltage through any of the strings will not exceed 400V (max allowable is 550V), and the inverters are both single phase Goodwe 5000DN-Ss.
Hopefully not too ling a first post... and many thanks in advance for any comments!