[chbot] OT: Solar PV panel configuration for fault detection.

Robin Gilks robin at gilks.org
Thu Oct 31 01:31:07 GMT 2013

> I'm at the point of ordering a 14 panel Grid Tied Solar Photovoltaic
> system
> using LG panels and EnaSolar inverter. The array will be mounted on steep
> sloping high roof and so faulty panel detection could be an issue. The
> standard practice is to wire up to 14 panels in series with bridging
> diodes
> in the panels to bypass faulty or shaded panels. I don't want to run a
> season or two with faulty panels. Its been suggested that bringing two
> arrays of 7 panels back to the inverter would allow me to compare the
> output from each string with a reasonably standard wiring configuration.
> I'm beginning to see the benefit of the enphase microinverter solution.
> Innovative suggestions anyone?

My recommendations are based on my own system with a 5kw inverter which
has 2 power point trackers so can take 2 separate strings of panels.

I'll run a couple of numbers, adjust for the real figures and see if it
works for you.

My panels are rated at 30.4V for maximum power, 37.9V open circuit, 250W
nominal. Going to the spec sheet for the inverter shows that it can make
maximum power over the range 235V to 500V with a maximum open circuit of
600V per input. Maximum power input is 3.5kw per string

That gives 235/30.4 as the minimum number of panels = 8
600/37.9 as the maximum per string = 15
3500/250 as the maximum per string = 14

I have 12 panels per string so it sits comfortably in the 'golden' zone.

Take a look at the 4kw inverter from EnaSolar which also has 2 inputs so
that you can separate the strings, the panels should have built in diodes,
mine have 6 schottky by-pass diodes sealed in the junction box.

Robin Gilks

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