I have 6x 550w Longi panels that have been doing duty since 2023 in 2 MPPT strings of 3 panels. They are combined at a single DC surge protector before being fed into the inverter. This works nicely since the Luxpowertek SNA5000 specs state PV Array MPPT Voltage Range 120Vdc~385Vdc with a start voltage of 110Vdc.

Now I am thinking of upgrading to the LXP 6000, but it has an MPPT start voltage of 140Vdc. The panels being around 40Vdc typically output 120Vdc~139Vdc.

Thus, they will have to go in series, but where is the best place to do this? Before the fuse or after the fuse?

Current combiner setup below, solar coming in from the top, passing through the fuse, then to the breaker and in parallel to the DC surge protector:

@Rouxenator ,

On the roof, if both strings have the same orientation.

OK, before the combiner then - thanks.

Assuming both strings are the same orientation, it would be best to run all 6 in series.
The inverter will also perform better with the higher voltage

Unfortunately not the same orientation - 3 horizontal, 3 vertical.

What is the downside of just putting them in series right as they enter the combiner box?

I think @Bl4d3 meant direction not orientation.

Yeah I was also thinking the same. Looks like I'm forking out for a LXP 6K and joining those two strings of 3 into a single string of 6 as it enters the combiner box.

3 hours ago, Virwat said:

I think @Bl4d3 meant direction not orientation.

Yeah, sorry, I meant direction. Brain isnt working that lekker today

3 hours ago, Rouxenator said:

Unfortunately not the same orientation - 3 horizontal, 3 vertical.

What is the downside of just putting them in series right as they enter the combiner box?

My apologies, I meant direction.

Those should be perfectly fine to connect in series on the roof

9 hours ago, Rouxenator said:

What is the downside of just putting them in series right as they enter the combiner box?

The 2 arrays of 3 panels are already in series and enters the combiner as 2 series strings so not a problem to connect the 2 strings in series inside the combiner. Connect the pos of string 1 to neg of string 2 then connect the pos and neg to the left fuses at the bottom and the bottom of the Noark breaker to mppt 1 on the new Luxpower LXP-6K. You can remove the 2 fuses and breaker on the right side or leave them and just add a 2nd Spd when you upgrade your array to use mppt 2 on the inverter.

Edited July 31, 2025Jul 31 by TaliaB

11 hours ago, TaliaB said:

The 2 arrays of 3 panels are already in series and enters the combiner as 2 series strings so not a problem to connect the 2 strings in series inside the combiner. Connect the pos of string 1 to neg of string 2 then connect the pos and neg to the left fuses at the bottom and the bottom of the Noark breaker to mppt 1 on the new Luxpower LXP-6K. You can remove the 2 fuses and breaker on the right side or leave them and just add a 2nd Spd when you upgrade your array to use mppt 2 on the inverter.

Thanks, that is exactly what I plan to do.

I am leaving the unused fuses and breaker since we plan to add 6 more panels on the garage roof at some stage. Then I can just add another DC surge protector for it and have two independent strings of 6 panels.