FoxESS Community - Owners & Installers Forum

I'm planning a new system based on:
18 x 455w 54/108 cell panels (Vmp=33.8v, Imp=13.47A, Wp = 455*18 = 8,190 W)
KH10 inverter
ECS4300H-H3 (172.8v nominal 35A recomended, 50A max charge/discharge) or maybe H4 at 230.4v.

Firstly, I am looking at the KH10 inverter, as I cannot see any advantage to using a smaller KH7 or KH8, other than a small reduction in price.
All of the start up voltages (75v) and MPPT ranges (80-500v) are the same for all KH series inverters.
The advantage being the KH10 will allow higher charge / discharge from grid <> battery (subject to DNO)


What has confused me is the smallprint in the datasheet / user manual:
"The maxium generating power of each pv string is limited to 3300 watts"

Does this relate to AC power? and also Battery Charging?
It doesn't fit with the maximum PV input ratings:
KH7: 12,000 / 3 strings = 4,000 W
KH10: 15,000 / 4 strings = 3,750 W

It doesn't fit with the recomended PV voltage, given that a typical >450w 54/108 cell panel Imp = 13.5 A):
KH10 Norminal DC Operating Voltage: 360 v * 13.5 A = 4,860 W

For my 18 panel array, it would appear best to arrange it as 3x strings of 6 panels,
But this limits the string voltage to ~203v, which is well within MPPT range, but nearly half their ideal. And that string voltage will fall if panels are shaded.

Arranging the strings as 2x8 would exceed the 3,300 W rating (455 x 8 = 3,640 W)


Is there any chance they may up this limit via a firmware update?

Any advice would be welcome.

Regards

You're quite correct, and the inconsistency has been raised with Fox ESS.

As it stands the inverter will clip the PV inputs should they exceed the per string 3.3kW (dc) limitation, however Fox ESS have confirmed they will release a firmware update that will raise this limit to 5kW per string. As always they won't say when that release will be made but my guess is it won't be long as it's a big selling feature of the KH series.

Fox said on the Q&A that the limit would be increased to 5500watts per string in a future software update.
Timestamped here