3.3 Fire Guidance, Grid Codes and Manufacturer Instructions

Quick Answer: The remaining LO1.1.1(b) titles are RC62 (fire-safety recommendations aimed at insurers and the fire service), manufacturer's instructions (install to them; MCS wins a conflict unless performance, safety and durability are proven no worse), and ENA Engineering Recommendations G98, G99 and G100 (connection and export/import limitation). G98 is fully type-tested micro-generators up to and including 16 A per phase, connect-and-notify. G99 is other parallel generation and needs prior application. G100 is export and import limitation. MGD 005 remains the shade procedure, not a wiring reg.

RC62 — fire guidance, not a wiring regulation

RC62 Recommendations for fire safety with photovoltaic panel installations is a RISCAuthority / Fire Protection Association joint code, produced with MCS and Solar Energy UK input. The 2922 handbook lists it under non-statutory guidance. It is insurer- and fire-service-oriented. It is not BS 7671, not Approved Document B, and not a substitute for a fire risk assessment under the Regulatory Reform (Fire Safety) Order 2005 (or the Scottish and Northern Ireland equivalents).

RC62's focus is larger commercial and public rooftops, but the control ideas transfer to any occupied building an electrician will actually meet on 2922 — including schools. Four themes come up again and again:

• Access. Keep roof edges, valleys, hatches and fire-fighting routes clear. High-density covering that stops the fire service venting or walking the roof is a RC62 problem, not a yield optimisation. IEC TR 63226 is cited for array layout against compartment walls; RC62 also expects a structural view of extra roof load, including ballast and rainwater ponding.
• Labelling. The presence of PV is not always obvious from the ground. RC62 expects prominent "PV on the roof" information for the Fire and Rescue Service, isolation-point identification, and site information at a reception or gate. That sits with BS 7671 712 notices, not instead of them.
• DC isolators. Modules remain live in daylight. RC62 discusses firefighter access to DC isolation, fire-service switches on some commercial designs, and the uncomfortable fact that a large share of historic PV fires involved DC connectors, inverters and DC isolators (the BRE 2017 split is widely quoted as about 84% of PV-related fires). Poorly made or mixed-brand connectors and waterlogged isolator enclosures are fire problems as well as electrical ones. RC62 even discusses eliminating separate DC isolators where the inverter already provides a suitable integrated isolator — that is a risk-control discussion, not a licence to ignore 712 isolation requirements.
• Inversion of roof fire performance. New rooftop PV, including panels and fixings, shall not lower the fire performance or classification of the roof. Combustible or partly combustible roofs need a fire-resistant covering if they cannot be avoided. In-roof systems need the correct fire qualification under the Building Regulations. That is the "inversion" idea in exam language: the array must not turn a compliant roof into a worse roof.

RC62 also expects early conversation with the insurer and, where the building warrants it, with the local fire authority. Individual insurers may demand more than RC62. Treat RC62 as the shared checklist, not as a promise that every underwriter will accept the same layout.

Manufacturer's instructions — MCS 5.4

LO1.1.1(b) lists manufacturer's instructions as non-statutory guidance. MIS 3002 5.4.1 says all equipment should be installed in accordance with its manufacturer's instructions. Torque values, connector families, ventilation clearances, roof-hook gauges, inverter wall-mount envelopes and battery environmental limits are not optional folklore. They are how that listed product stays inside its certificate.

5.4.2 is the conflict rule you must be able to state. If the manufacturer's instructions conflict with the MCS standard, the MCS standard takes precedence, unless it can be proven that system performance, safety and durability are no worse than if the MCS requirements were followed. That is a high bar. "The sales engineer said we could skip the MCS 012 kit" is not proof. A written demonstration that the alternative is no worse on those three tests is the only MCS route around the standard.

Do not invert 5.4. Manufacturer first is the default installation behaviour. MCS first is the default conflict behaviour. BS 7671 still sits above both on electrical requirements, as 5.2.2 already taught.

ENA G98, G99 and G100 — names and roles only

The Energy Networks Association (ENA) Engineering Recommendations are the Great Britain distribution-connection rules for generation that runs in parallel with a licensed DNO network. They are not IET Wiring Regulations. MIS 3002 5.1 requires MCS contractors to apply:

• G98 where the installation is a fully type-tested micro-generator with aggregate registered capacity up to and including 16 A per phase
• G99 where the installation is other parallel generation (including anything that is not G98-compliant, and anything above the 16 A per phase aggregate)
• G100 where export or import is to be limited

Do not skip the 16 A definition. In G98, 16 A per phase is the aggregate registered capacity of the micro-generating plant on that customer's installation — including electricity storage that can operate in parallel. It is not "the inverter nameplate if we ignore the battery." MIS 3002 even flags the trap: a 3 kW PV inverter and a 3 kW battery on the same single-phase supply can push the theoretical combined output through the 16 A door, in which case G99 applies. The arithmetic that converts 16 A at 230 V into kilowatts, and the worked "is this still G98?" examples, belong to a later chapter. Learn the definition here; do not invent a 2922 shortcut that ignores storage.

Process, kept short:

• G98 is connect-and-notify. The installer connects a qualifying fully type-tested micro-generator and notifies the DNO (typically within 28 days of commissioning). You do not sit in a G99 application queue for a straightforward qualifying G98 job.
• G99 is prior application. Other parallel generation needs DNO agreement before connection. Fast-track exists for some smaller G99 jobs; it is still not G98.
• G100 is the technical recommendation for customer export and import limiting schemes. It is used with G98 or G99 when the installed capacity would otherwise exceed the agreed export (or import) limit. G100 is not a shade guide and not a substitute for type-testing.

The MCS contractor, not the 2922 candidate as a private individual, is the party MIS 3002 names for G98/G99 notification.

MGD 005 again — shade procedure, not a wiring reg

The handbook lists MGD 005 Solar PV Shade Evaluation Procedure in the same LO1.1.1(b) bullet list as RC62 and G98. That placement causes mix-ups. MGD 005 tells you how to evaluate shade so the SF term in kWp × Kk × SF is defensible. It does not tell you how to earth an array frame, how to label a DC isolator, or how to notify a DNO. If a 301 stem mentions sunpath diagrams, near shading or a shade factor, MGD 005 is in play. If it mentions 712 notices, G98 thresholds or RC62 firefighter access, leave MGD 005 on the desk.

Scenario: insurer asks for an RC62-informed layout on a school roof

A maintained school wants 40 kWp on a pitched classroom block. The insurer's surveyor emails: "Layout to RC62, please." You already know 40 kWp is inside MIS 3002's 50 kWp DC scope. RC62 now adds a property-protection overlay:

• confirm the roof covering will not lose fire classification once the array and fixings are on it
• keep access for maintenance and for the Fire and Rescue Service — edges, a walking route, no wall-to-wall carpet of modules over every compartment line
• put PV identification and isolation information where firefighters will actually find it, in addition to 712 equipment labels
• treat DC connectors and isolators as fire-critical components: same-manufacturer mating, no mixed connectors, enclosures that will not fill with rain
• invite or at least inform the local fire service on a school, where occupancy and evacuation change the risk picture
• keep manufacturer instructions for the chosen MCS 012 kit and MCS 005 modules, and do not "improve" a hook spacing in a way that fights either the manufacturer or MIS 3002 5.4.2

G98 versus G99 on that school still turns on aggregate 16 A per phase including any storage, not on whether the insurer liked the site plan. Work that threshold properly in the later grid chapter; do not guess it from the RC62 drawing.

The stack below is the LO1 hierarchy in one picture. It is not "always obey the lowest box." Statute always binds. Between the IET Code of Practice and BS 7671, latest BS 7671 wins (MIS 3002 5.2.2). Between manufacturer instructions and MCS, MCS wins unless performance, safety and durability are proven no worse (5.4.2).