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Posted By Topic: Solar array earthing

Nov 14 2019 22:10

If I have 4 strings of solar at say, 9A 700V each using 6mm solar cable, for earthing the whole array, can I use one cable, and if so how would I work out the size?

Nov 14 2019 23:19

And should they be earthed back to the board in a 'star' fashion or daisy-chained?

Nov 15 2019 09:03

Thanks for adding. I feel a bit silly asking, but 5033 says to refer to 3000 for the answer, and it seems a bit vague to me, so I would appreciate some clarity around the matter.

Nov 15 2019 18:54

Doesn't 5033 say refer to table 5.1 in 3000

So if your largest active conductor is 6mm then a 2.5mm2 earth would be sufficient but 5033 also says a minimum of 4mm2 must be used so basically until your DC cable gets bigger than 10mm2 a 4mm2 earth will be sufficient

Nov 16 2019 14:43

Thanks Octane. I understand that, but my question is, would I need to run the equivalent of a 4mm earth per string of 6mm, or can I run one 4mm for 4 strings if all of the panels are bondded to the same frame?

Nov 16 2019 16:18

Oh apologies, yeah I'm not sure, I've tried to have a look through as well and can't find the relevant information

Can't see why you couldn't run one 4mm earth up and loop to the other parts, I suppose you'd just have to make sure that if the connection was removed at any part the continuity to the rest remained

I don't know if it's the right way or not but when I was working in solar my supervisor always used to run one up and loop to the various rails then use earth tags under each panel

Nov 18 2019 11:09

"5033" sets requirements for earthing of the array. None of the requirements are for strings.
as long as it's all on one frame, you only need one earth conductor.

Nov 18 2019 12:25

What about PCEs with MPPT inputs like mentioned in where it says "Each PV section connected to an input (refer to Figure 2.5) may be treated for the purposes
of this Standard as a separate PV array."

Would this mean that if each string is connected to a different MPPT that it is a separate array and would each require an earth run?

Nov 18 2019 16:48

good point; and fair question.
Pedantically may require a PEC for each "deemed array"; but practically I believe one PEC will do all that's needed.
I'll have another look when I get time.