Hi guys,

 

I have another n00b question please. I have an 8kW RCT Axpert Max inverter connected to 10x 540W solar panels. It is my understanding that the inverter supports a maximum of 4000W per input, yet my installer insists on wiring them all into one input. With a theoretical maximum of 5400W output, won't I be 'wasting' a potential 1400W by connecting them all into one input? Does it not make sense to split the panels into two arrays of 5 panels (PV1 and PV2), each into their own input, thereby also allowing for future expansion up to the 8KW maximum PV input supported by the inverter? What am I missing? Please see pics attached. 

My question is what is the VOC of your panels?
540W panels typically have around 49 -50V, which means, with 10 panels that would be around 490-500V in a series string potentially, unless they are wired 5 each in parallel?
450V is the max per MPPT as far as I can see. So if these 10 are in series the MPPT may get damaged. Can you check the panels specs and see what the VOC is.
I would have put 5 on each MPPT. The real advantage of 2 MPPTs is that you can have two sets of panels facing different directions to maximise the solar irradiation from morning till noon.
 

Assuming that these are the specs for your inverter:

Solar Charger & AC Charger
•Solar Charger Type: MPPT.
•Maximum PV Array Power: 8000W (4000W x 2).
•MPP Range @ Operating Voltage: 90 ~ 450 VDC.
•Maximum PV Array Open Circuit Voltage: 500 VDC.
•Number of MPP Trackers: 2.
•Maximum Solar Charge Current: 120 A.
•Maximum AC Charge Current: 120 A.
•Maximum Charge Current: 120 A.

 

And assuming that the Voc of your panels is just short of 50V, then 10 panels on one string is already hitting the maximum, and one should aim for at most 9 panels (Voc 450V). 

Using two strings - 2x 5S split - you'll be well above the minimum (90V) and safely below the maximum (450/500), and that allows further expansion on both strings. Not quite sure whether the V in the early 200's (in a split scenario) will impact performance much, though, others can answer that better. Also bear in mind on your stats that the panels deliver according to the load attached, so if you're only using 3kw at that point, the panels will produce accordingly. 

Your actual "real-world" PV voltage there is short of 400V, which is fine, but one should specs for Voc for when there's an issue or for those sunny/cloudy days where you may see spikes. Had it been only 9 panels the installer's recommendation would have probably been the correct one, although that doesn't address the panel "over-speccing" aspect.  

Edited March 2, 20233 yr by Kalahari Cruiser

Two strings costs more, and takes longer to install. That's likely the reason.

You will likely do better with two strings of 5 panels, as others have said.  We can help you more with specifications for your panels.