Fire safety for UK commercial solar installations

Very rarely and almost always from installation defects — DC connectors not fully mated, isolator water ingress, unsupported cabling or roof-membrane damage. RISCAuthority statistics put annual UK solar-fire incidents in the low hundreds against ~1.5m installations. Following MCS 3007 and BRE 489 essentially eliminates the risk.

For new commercial installs, insurers routinely expect a firefighter-accessible DC isolator at the array as well as at the inverter, plus rapid-shutdown functionality on any building over four storeys or with public access — increasingly a de-facto standard on all commercial roofs.

The roof-cover fire classification must remain compliant with the panels installed. On combustible substrates (some older single-ply and warm-roof systems) BRE 489 requires either a non-combustible sub-layer, air-gap detail or a re-tested roof buildup. A competent installer confirms this at survey.

AFCI is a mandatory US requirement (NEC 2011+) and now standard in Tier-1 commercial inverters (SMA, Sungrow, Huawei, Fronius). We specify it on all UK commercial projects; it detects and disconnects a DC arc-fault typically in <2 seconds.

Ideally at design stage: supply a single-line diagram showing DC isolator locations, inverter positions and rapid-shutdown zones. Insurers increasingly want an MCS installation certificate plus workmanship-warranty proof at renewal; some now require an annual thermographic scan on installations over 250 kWp.