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Domestic EESS, island mode and island mode isolator

Downdraft

Hello,
I need some help please Slight smile

I am trying to understand if an 'Island mode' isolator is required for this particular inverter design.

The Solar PV Hybrid inverter has an 'EPS' (emergency power supply) output that we would like to use.
The inverter has an internal N-PE Bond relay.
In connected mode this takes its power direct from the grid.
In island mode the Hybrid inverter will have disconnected from the grid as per G98/99, and then the EPS is supplied from PV and/or battery.

So if the inverter is designed to disconnect from the grid during grid loss/outside protection limits is either an Automatic or manual changeover switch required?

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    Do you plan on having EPS output power supply a dedicated consumer unit, independently connecting your essential circuits, separate from the main household consumer unit ?

  • 0 in reply to AMK

    The inverter’s EPS output, active during both normal operation and island mode, inverter creates a neutral-earth bond in power cuts. The EPS connects to a 100 mA time-delayed RCD, feeding a dedicated consumer unit with RCBOs for essential circuits, independent of the main household consumer unit. The other option is using a Gateway for complete installation backup.

  • 0 in reply to AMK

    Yes this is correct :)

  • 0 in reply to AMK

    Thank you and this confirms my understanding - if the EPS output is only supplying dedicated CU/circuits then we can rely on the inverter to disconnect and isolate from the grid in island mode.




  • 0 in reply to Downdraft
    Downdraft said:
    then we can rely on the inverter to disconnect and isolate from the grid in island mode.

    I would caution, that I have been made aware that some inverters do not disconnect from the grid using devices that BS 7671 would recognize as providing 'isolation'. See Regulation 826.1.1.1, last para, which states 'A switching device suitable for isolation according to Chapter 53 shall disconnect all live conductors from the public distribution network.'

    It's also worth remembering the provision in Regulation 21 of ESQCR [Regulation 22 of ESQCR(NI)] which conains the requirement that 

    21.  Where a person operates a source of energy as a switched alternative to a distributor’s network, he shall ensure that that source of energy cannot operate in parallel with that network and where the source of energy is part of a low voltage consumer’s installation, that installation shall comply with British Standard Requirements. 

    (British Standard Requirements means BS 7671 in the ESQCR.)

  • 0 in reply to gkenyon

    Hi Graham. Is this the best way to ensure compliance to check the inverter model on the ENA Type Test Register (via the Energy Networks Association website) for G98/G99 certification. Also perhaps, contact the manufacturer, ask Does their  inverter provide Chapter 53-compliant isolation per 7671 Reg 826.1.1.1 & ESQCR Regulation 21.  Do you have any additional advice or steps we should consider?

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  • 0 in reply to gkenyon

    Hi Graham. Is this the best way to ensure compliance to check the inverter model on the ENA Type Test Register (via the Energy Networks Association website) for G98/G99 certification. Also perhaps, contact the manufacturer, ask Does their  inverter provide Chapter 53-compliant isolation per 7671 Reg 826.1.1.1 & ESQCR Regulation 21.  Do you have any additional advice or steps we should consider?

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