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What DC and AC isolation does a rooftop PV system need?

Short answer

Provide a means to isolate the PV array DC from the inverter and an AC isolator for the inverter, lockable in the off position, rated for their duty. DC isolators must be DC-rated for the maximum string voltage and current. Test and record both at commissioning, then check them at each maintenance visit for damage and water ingress.

Last checked 24 September 2026 · 1 source

In more detail

  • MIS 3002 App E records array isolator rating (A, V), location and functional check.
  • MIS 3002 App F: functional check, damage and ingress of AC and DC isolators at intermediate/full visits.
  • MIS 3012 cl.3.5.35: battery isolation as close as practicable to its output terminals; cl.3.5.20 DC-rated equipment.
  • Detailed BS 7671 712 isolation clauses and IET CoP isolator placement not re-read (paywalled).

The facts, dated

  1. 01
    Batteries need isolation as close as possible to output terminals — cl.3.5.35

    standard · UK · checked 24 September 2026 · MCS

Sources

Last checked: 24 September 2026