Adding panels to a system

Ye, you're almost on the NC6 limits.

Are you planning on DIYing it or getting an installer to do it? If it's the latter do your sums as the payback period might be so long as to not make it worth it.

Yes, by going from 6.7kW to 9kW pv into the 5kW inverter you'll be getting a bit more on cloudy days and will be maxing out the inverter more but on the flip side that will lead to lots more inverter clipping which is just wasted energy not earning you any money.

How would you avoid clipping by heating water, charging the car or timing appliances?

Are you going to add optimisers for the 5 you are adding or you think they are ok. Orientation, angle the same as existing roof no shading?

i think you'll have to do a bit of homework on this!

You could use this site to get the power a panel on each roof will generate:

https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP

And figure out the difference between a panel on your roof and your shed And apply to your whole array on the better performing roof. Try get as accurate as you can with the orientation and the angle of the roof.

For example (I'm making up numbers):

• A panel on your house roof generates 1000kWh according to that site
• A panel on your shed generates 900kWh
• 900/1000 gives you 0.9. Your panels on your house would be generating 90% of what they were before.
• Use the tool again with your full array value on your roof, and multiply the number is brings back by 0.9
• Then figure out if the cost of optimisers on the worse performing roof is worth the loss.

To get your azimuth:

In this picture they are getting the azimuth of the roof facing the road at the bottom.

You will also need to take the figure it returns and take -180 from it. So in the picture example the figure you'd put into the above website would by -8 (172-180)

Hey,

I'm not an electrician, or a vaunted solar electrician ;-) So no advise, just my own experiences.

I have been messing about with adding various sets of panels to my setup.

Out of the box, 6KW ground mounted array to a 5KW dual mppt inverter, any sunshine, even in Feb and the inverter maxes out, I can change the GM panel slope up to 56 degrees, this is why the are so performant.

I have added two other 2nd hand arrays to my Inverter, using a Vevour PV joining box and the spare MPPT.

8 X 275W Gable wall mounted 90 Degrees ESE panels. 2KW

8 X 290W on a shed 5 @ 12degrees ESE, 3 @ 12 degrees WNW. 2.2KW

The two strings joined together run at about 250V, with the ESE morning string kicking in before the GM array and the shed mounted array ticks along nicely during the day & picks up a bit of extra electricity in the evening, I expect this to increase a little as the sun moves higher and sets more to the north.

From my limited knowledge, its mostly based on connecting the arrays & disconnecting the arrays in various sunshine states, all my mppt seems to care about is that the string voltages from the two arrays are the same, disconnecting the Gable Array in the late afternoon when the sun has moved off that wall, has no effect on the production of the shed mounted array, I have to conclude that either the tracking mppt in the inverter can just ignore that string, or the shaded array provides its required 250V with no backfeed and the amps generated just go to the inverter.

I tried temu blocking diodes, the just got hot and I did not see any difference anyway.

The current regs state that the fireman switch should be within 1.2M of the array, as technically you are going to wire the new array into the old array, I think you are meeting this requirement.

Not sure if this helps any!