That’s the solar up and running, I don’t think it’s the most attractive addition to my property but very practical.  It’s all bolted down and the tubs also filled with broken up pavers so I hope they don’t go flying in a storm.  At the minute the 6 on my house at 2.4 max and the 5x510 panels are producing 4kwh. A bit overcast today but I’m pleased at that. 

a big thank you to you all, especially transparent who is a star

I have just installed another string and now doubled my solar to 4.9 from the registered original 2.6.  Currently output is around 4kwh, do I need to inform the DNO, will they know and will I be in trouble for not informing them. 

If you have added or changed the inverter then definitely yes. Otherwise possibly not because they care only about the inverter which is what determines the max output to grid.

@jamespa same inverter, just added another string to the spare input.  I read somewhere that a max of 3.6 output was the max allowed in a domestic and I am sending out 4 on a good day. It’s hardly likely to cause an overload though and it’s only producing that on a good day.  Oversized to provide a decent output, most of the time it never got near the 2.6 of the previous panels.

Your inverter should limit power to the grid to 16A/3.68 kW unless you received permission for greater.  If it's not doing that then it has potentially not been correctly configured.

Posted by: @david999

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I have just installed another string and now doubled my solar to 4.9 from the registered original 2.6.  Currently output is around 4kwh, do I need to inform the DNO, will they know and will I be in trouble for not informing them. 

There's a threshold at 3.6kW / 16A, below this follows one process G98 which is typically connect and then notify with this being permitted, above this is G99 and you typically need to apply and get permission for these larger capacity installations.

More details on the ENA website - these are the standard processes most of the industry follows to give you some guidance. You should also look at the website for your local distribution network operator to see exactly what their processes require.

https://www.energynetworks.org/industry/connecting-to-the-networks/connecting-generation-to-the-electricity-networks

@jamespa my total dc voltage is 490 and the inverter max is 550.  I’m getting confused regarding outputs but it looks like I’m within the working loads. As you say my inverter won’t go beyond that 3680 kw.  Bit confusing the dc max and kw max of panels, but I think I understand now.

Mentally you have to separate the ac side and the DC side.  The ac side will cap the output if it is set up to do so. 

Posted by: @david999

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I have just installed another string and now doubled my solar to 4.9 from the registered original 2.6.  Currently output is around 4kwh, do I need to inform the DNO, will they know and will I be in trouble for not informing them. 

Yes, you will need to notify them even if the inverter remains the same. You originally had 2.55kW of generating capacity installed so would not have reached your inverter's rated 3.6kW output limit, but with the extra panels you will now be able to achieve the full 3.6kW and the DNO will want to know about that change as it affects the amount of export you will be able to achieve, although still within G98 limits.