Fronius IG4000 Sting Inverter - question regarding string configuration

[JanS48]

Thanks so much for the reply, I'm in North Smithfield RI at 41.9 lat. Very interesting how you set your orientation. For me the panels will be mounted on the roof of a ranch style house, One side gets sun much of the day where the other side gets a lot of early sun. I'll have to measure the exact orientation of each and get back to you. That may well work using two strings of 8 panels each in parallel. Thanks so much for the input - I'll get the exact roof orientation and a couple of pics.
Jan

[bcroe]

The 500V maximum is the critical thing. The string OC voltage must NOT
exceed this. Remember that panel OC voltage will rise with colder temps.
I would stay away from the 500V number a bit, remembering that things
like lightning might induce a bit more than the system.

With Fronius here at 42 deg latitude, it would be possible to utilize 2 strings
of 8 panels, in parallel. Operation here has half the panels favoring the
rising sun, the other half favoring the setting sun. With each string capable
of 3200W, this orientation will limit peak power to something like the peak
input of the inverter, which is 4000W divided by the efficiency decimal. My
Fronius are about 95% or decimal 0.95, so peak usable input is 4000/0.95
or 4210W. Exceeding this a bit is not critical, the inverter will just clip down
to its rating. Orienting the 2 strings so the peak stays within 115% of the
peak inverter rating should be sufficient, check the inverter rating. Here at
42 lat I actually point them straight E or W with an elevation of around 60deg,
a good center compromise for sun rising and setting variations over the year.
Has been operational 10 yearrs.

2 reasons for the above orientation. First is to keep the inverter operating
at near peak for much longer than several hours near solar noon. Mine
are at peak 8 hours straight under good sun, for most of the year. The
other reason is to boost output under clouds, when light is dispersed and
orientation is not very critical. My day output under our frequent clouds is
around double a straight south facing array. This is achieved by operating
more panels, at less than optimum panel efficiency. But you already have
the panels, the racking and space for the panels might be an over riding
consideration. Mine are ground mounted in a snow rejecting arrangement,
again not practical on existing structure. Your latitude impacts the best
configuration for this approach. good luck, Bruce Roe

NScurve.jpg

[JanS48]

Greetings everyone - newbie here - I have acquired the following equipment for very little $$$
17 Canadian Solar panels : CS6x-320P and a Fronius IG4000 NEG String inverter.

Specs of the panels:
Operating volts: (vmp) 36.8 Open circuit volts: (voc) 45.3
Operating current: (imp) 8.69 amps Short circuit current: (isc) 9.26 amps

Fronius IG4000 NEG:
AC max cont. output: 4000w
AC max cont. current 16.7 A
DC operating voltage range 150 - 450v
DC max system voltage 500v
DC max continuous current: 26.1 A

Doing the math I should be able to string 12 of these together to get close to the 4000 watt output, however is it safe to use the optimum voltage of 36.8 which would be close (441.6) to the 450 v max DC of the Fronius? If I calculate using the voc of 45.3 each I'm over the max of 500 at 543.6
-or-
My other option is to configure an array using pairs in series/parallel. This way the amperage doubles but the voltage drops to max voc: 271 and vmp: 220.8 with the amps going to 17,3 which is still under the max amps of the Fronius.

I have read that the higher the voltage in the string inverters the more efficient they work, however I'm leaning towards the series/parallel array since the voltage is lower.

About Me: I'm a pretty good electrician but I have zero experience installing solar panels.

Racking: I was leaning towards unirac

Any comments are much appreciated.