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Where can a PV array be connected?

Chris Pearson

I suspect that a PV array would normally be connected between the meter and the first DB, but can it be connected more peripherally please?

The most suitable area of roof is at the opposite end of the premises from the electrical origin. However, there is a small DB with spare ways adjacent to the loft space. It supplies one lighting and one socket circuit and is seldom significantly loaded. The distribution circuit from the main DB is 16 mm² singles (with the live conductors being sheathed). As far as I can see, it travels through under-floor voids and is boxed in with other services as it ascends in a bathroom so RCD protection is not required. If the inverter can be situated in the loft space then only a short length of AC cable would be required.

This is what I have in mind.

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  • 0

    It cannot be assumed a protective device in a consumer unit can be back fed, it definitely could be an issue with an electronic RCBO.

    Also if an RCD is required for additional protection it has to be double pole, so a single pole RCBO would not be permissible.

  • 0 in reply to Sparkingchip

    So long as the inverter stops generating when synchronisation with the mains is lost, the question of which way the current is flowing it not so important. When the thermal part or the RCD part causes contacts to open, the inverter side is safe, after the shut off time.

    But that will be longer than the breaking time alone so ADS times need a re-visit.

    It is much more serious with an inverter capable of island operation, as then the side you may expect to be dead may still be very much alive but just out of phase .

    Mike

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  • 0 in reply to Sparkingchip

    So long as the inverter stops generating when synchronisation with the mains is lost, the question of which way the current is flowing it not so important. When the thermal part or the RCD part causes contacts to open, the inverter side is safe, after the shut off time.

    But that will be longer than the breaking time alone so ADS times need a re-visit.

    It is much more serious with an inverter capable of island operation, as then the side you may expect to be dead may still be very much alive but just out of phase .

    Mike

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  • 0 in reply to mapj1
    mapj1 said:
    so ADS times need a re-visit

    If the cables went all the way back to the origin, they might have to be pretty substantial to meet the minimum Zs; but if they went only part way wouldn't that issue go away? Put another way, you would want the inverter supply to have an R1 + R2 at a comparable value to Ze, which may be difficult to achieve.

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