Ground Mount cable run questions!

[Fintray]

Why not fit the inverter in the outbuilding followed by an isolator then say a Henley block and spur off to a small consumer unit to give power and lights, also from the Henley block back to your main consumer unit in the 10mm SWA?

[Mr Gus]

For those who may read this years down the road..

https://learntechnique.com/technical-gu ... isolation/

(Explaining Henley blocks to the layman ..& beyond, a screwfix type staple stock item)
Hope it helps someone.

[nowty]

The other thing to be careful of (nothing to do with the cable run, although a long DC cable run may help with this) is the max string voltage at start up as its the Voc which kills inverters and not the max power Vmp. My reckoning is your panels would be normally 548V Open Circuit Voltage which is within the 600V of your inverter spec. But on a really cold sunny winter morning that voltage will be higher and may go close or even over the limit as panels have a negative temperature coefficient of Voc.

Datasheet for you panels (I think),
https://www.pluginsolar.co.uk/wp-conten ... 00603A.pdf
11 x 49.85 Voc = 548V

My rule of thumb is add 10% to the open circuit voltage for cold conditions which takes you right up to the 600V limit. I'd be thinking of limiting the string size to 10 panels.

Using the technical SMA method of re-calculating the cold Voc at -10 degrees.
https://www.sma-sunny.com/us/calculatin ... not-scary/

Your panels temperature coefficient of Voc = -0.272 % per degree

So for -10 degrees, thats 35 degrees colder than the the 25 degrees on the datasheet for Voc.
35 x 0.272 = 9.52%

109.52% of 49.85 = 54.59V

Multiplied by 11 panels = 600V, funny enough similar to my rule of thumb.

[marshman]

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[billi]

I have a choice of mounting the inverter in the new "shed" or 22m away in another outbuilding that has the battery storage and electricity meter.

Hmm maybe i am out of date , but first of all an "Inverter" from a PV array cannot be connected to a battery ! (as you know)

If you are talking about the location of a Grid tie inverter connected to an Hybrid-Inverter or off-grid inverter , that then is connected to a battery bank than this is a different scenario then as an Hybrid Inverter with a 22 m cable run to a 48 V battery would clearly be

If its just a question of a Grid tie Inverter , i would try to locate all close to the battery bank at one location , and run the PV high voltage DC cable along those 22 meters , for sure in a Ducting pipe to that one location

[nowty]

I have a choice of mounting the inverter in the new "shed" or 22m away in another outbuilding that has the battery storage and electricity meter.

Hmm maybe i am out of date , but first of all an "Inverter" from a PV array cannot be connected to a battery ! (as you know)

If you are talking about the location of a Grid tie inverter connected to an Hybrid-Inverter or off-grid inverter , that then is connected to a battery bank than this is a different scenario then as an Hybrid Inverter with a 22 m cable run to a 48 V battery would clearly be

If its just a question of a Grid tie Inverter , i would try to locate all close to the battery bank at one location , and run the PV high voltage DC cable along those 22 meters , for sure in a Ducting pipe to that one location

I'm fairly certain in an earlier post from the OP that his model of inverter is not a hybrid so they must have another battery inverter for the batteries in the outbuilding, that's what I have assumed.

[nowty]

It's a good point Nowty. Something that I encountered when I had the first system installed way back in 2010. I have 15 Sharp panels with a O/C voltage of 36.4V each on a single string. That gives 546V. The SB3000 I have only has a single MPPT. I had a discussion with the installers at the time who were slightly concerned that on a cold sunny day the 600V max input of the inverter could theoretically be exceeded. I took the risk as my panels are at a very shallow 11 deg angle. After 12 years it is still all OK - cue more freak weather later in the year to prove me wrong

TBH, I was just making a point that most folk are not aware of. In most situations a 5% increase is probably more realistic as once its light enough, its past the coldest part of the night, first light is going to pretty weak, and the 600V limit probably has at least a 10V or 20V real limit of comfort zone above the 600V spec.

[NikoV6]

Thanks everybody for the replies, very helpful!

I should clarify, the AC from the inverter will be going to Tesla gateway.

Interesting about the voltage Nowty, my inverter has three inputs, I think I should reconfigure my panels for three string

https://www.segen.co.uk/product/solis-8 ... e-with-dc/

This is my wiring diagram, thoughts please

[billi]

.... For me, then it makes sense to me to run those two strings in DC cabeling to the GTI next to the Powerwall etc , at the same location- so combined

Am pretty sure there are armored solutions for DC cables in the ground ( or just make one)

[nowty]

Thanks everybody for the replies, very helpful!

I should clarify, the AC from the inverter will be going to Tesla gateway.

Interesting about the voltage Nowty, my inverter has three inputs, I think I should reconfigure my panels for three string

https://www.segen.co.uk/product/solis-8 ... e-with-dc/

This is my wiring diagram, thoughts please

Nice picture.

Regarding the input for 3 strings, there are only two MPPTs, so if doing 3 strings, the two going into the larger MPPT should be identically sized. I note the installation manual does not specifically say this.

So the panel configuration would need to be something like 8 + 8 / 6 or 7 + 7 / 8 configuration.