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Cu change before pv install.

hertzal123
Customer wants to install pv panels after the new cu has been fitted and I just wondered what devices to fit for it.Think the PV is 4kw,so I thought maybe a B20 mcb and a DC sensitive rcd?Thanks for any advice.

                                                Regards, hz
  • 0
    Check the RCD requirement for the inverter.  Don't assume it will be 30mA.  Even if the inverter is suitable for a 30mA RCD, you may have problems with nuisance trips after storms, and this may only show itself as the installation ages.  So giving the inverter its own RCD is a good idea.


    There will need to be an isolator between the CU and the inverter.  It might make things easier to get that in place in advance.
  • 0
    If the PV system is going to be connected under G98 (G83 as was) then you're limited to 16A/phase anyway - so in theory a 16A rather than 20A MCB should do.


    Actually it's quite common for the sum total of the panels to exceed the rating of the inverter by a small margin - under UK skies a 4kWp nominally rated panels are unlikely ever to produce more than 3.68kW (16A @ 230V) - and it's generally more efficient to run a smaller inverter closer to capacity than a larger inverter that'll always have capacity to spare.


       - Andy.
  • 0
    20A MCB B type(3 - 5 In) is appropriate. Surge arrestor is recommended as panels and array generally installed on roof. You should check the shielding from surround buildings. You know, one panel is being shadowed, overall performance within one array will draft down. You can think about oversizing panel
  • 0
    You may also find that the inverter will provide power for several tens of seconds after the mains fails. If you do not have double pole rcds / a separate CU for the solar, you may find that the CU will remain live and some loads still on, after an rcd trip. 


    Regards,


    Alan.
  • 0
    The PV installer usually installs a seperate 2 or 4 way cu with a type A or B RCD exclusively for their kit as part of the installation package, along with a seperate rotary 20A isolator.

    I would consult with the PV installer first - no need to duplicate kit un-necessarily.

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