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Isolation of Solar PV

sparkiemike

I came across a small (2 panels) Solar PV installation where the inverters on are the "micro-inverters", i.e. each panel has a integrated micro-inverter so effectively the panels deliver AC power into the property.

On this installation there was only a single AC isolator near the consumer unit. In the loft there was no isolator, just a junction box where the the cables come into the roof. I would have expected an isolator instead of the junction box, for maintenance and so the circuit could be tested & inspected upto the panels.

Does a single isolator in this situation comply with the regs and specifically 712.537.2.1.1? "To allow maintenance of the PV converter, means of isolating the PC converter form the DC side and the AC side shall be provided"

It seems it does but does not seem right.

Parents
  • 0

    Interesting. Microinverters tend to be connected directory to each panel - and the DC connectors (e.g. MC4) tend not to be rated for breaking d.c. currents (even at extra low voltages, d.c. arcs can be hard to extinguish). My PV (string) inverter came with instructions always to operate the a.c. side isolation first - I understand that the theory was that with the inverter shut down no current was drawn through the d.c. side even though the d.c. voltage was still present - making it then safer to operate the d.c. isolator.

    So short of covering the panel, I guess the only approach would be to isolate the a.c. side first, then unplug with a d.c. (extra low) voltage present but no d.c. current flowing. Akin to isolation by disconnecting wires rather than operating a device in table 537.4.

       - Andy.

Reply
  • 0

    Interesting. Microinverters tend to be connected directory to each panel - and the DC connectors (e.g. MC4) tend not to be rated for breaking d.c. currents (even at extra low voltages, d.c. arcs can be hard to extinguish). My PV (string) inverter came with instructions always to operate the a.c. side isolation first - I understand that the theory was that with the inverter shut down no current was drawn through the d.c. side even though the d.c. voltage was still present - making it then safer to operate the d.c. isolator.

    So short of covering the panel, I guess the only approach would be to isolate the a.c. side first, then unplug with a d.c. (extra low) voltage present but no d.c. current flowing. Akin to isolation by disconnecting wires rather than operating a device in table 537.4.

       - Andy.

Children
  • 0 in reply to AJJewsbury

    Pretty well what the Enphase instructions say for their microinverters for disconnections.

    See this page for an example NHS installation done with these microinverters - so its not just domestics.

    The picture also show the DC input leads to the micro inverter. These two connect directly into the output leads from the solar panel.

    The AC output socket from the microinverter is the one immediately below the DC input for which Enphase supply the plug and a section of AC two core H07RN-F lead for onward connection to your AC side via a weatherproof JB.

    www.thesolarpeople.co.uk/.../

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