MEP · 14 checks

Solar / PV Installation
QA inspection checklist

Solar panel and photovoltaic system installation quality audit.

Every check below carries what good looks like, when it passes, the standard it comes from and the defects that usually fail it. That guidance is what turns a tick-box into an inspection.

Mounting & Structure

  1. 1.
    Roof structure assessed and adequate for loading
    What to look forStructural assessment by competent person prior to install — covers dead load (panel + frame), wind uplift (BS EN 1991-1-4), snow (BS EN 1991-1-3). Existing roof structure capacity verified. Reinforcement (if required) installed.
    Acceptable whenPer BS EN 1991-1-3 (snow) / BS EN 1991-1-4 (wind) / MCS MIS 3002: roof structure verified to take additional dead and live loads. Calculations by chartered structural engineer for non-standard installs.
    StandardMCS MIS 3002:2024 — Solar PV system installation. BS EN 1991-1-3 / 1991-1-4 (Eurocode 1 loads). BRE Digest 489.
    Common defectsNo structural assessment — overload risk on old roofsWind uplift calculation done with wrong terrain categorySnow load forgotten in northern UK / hill sitesReinforcement designed but not installedConcentrated load on rafters not designed for it
  2. 2.
    Mounting rails aligned and secure
    What to look forRails aligned with set-out, level along length (allowing for roof pitch). Fixed to roof structure (rafter or purlin) — not battens or board. Fixing pattern and quantity per manufacturer wind calculation.
    Acceptable whenPer MCS MIS 3002 / manufacturer mounting kit: fixings into rafter / purlin only; spacing per wind zone calculation; rail level ±5 mm in 10 m. Stainless or galvanised steel components.
    StandardMCS MIS 3002. Manufacturer mounting system specs (Schletter, K2, IronRidge, Solfit).
    Common defectsFixing into batten or boards — pull-out under windInsufficient fixings for wind zoneRail not level — panels twistWrong stainless grade — galvanic corrosionMounting kit improvised from generic parts
  3. 3.
    Waterproofing maintained at fixing points
    What to look forRoof penetrations sealed — flashing kit, EPDM gasket, lead flashing, or proprietary "AlphaFlash" / Solar Mounts type. Existing tile/slate replaced with manufacturer roof hooks. No reliance on silicone sealant alone.
    Acceptable whenPer MCS MIS 3002 / NFRC: each penetration weatherproofed by approved means — flashing kit lapped under tile above and over tile below. No mastic-only seals. Lead minimum Code 4.
    StandardMCS MIS 3002. NFRC Solar Roof Best Practice.
    Common defectsMastic-only seal — leaks within 1 winterLap reversed — water enters under flashingTile broken not replaced — leak pathLead under-spec (Code 3 in exposed)Roof hook without flashing — direct rain entry
  4. 4.
    Panel orientation and tilt angle correct
    Record: Tilt (degrees)
    What to look forPanel orientation (azimuth) and tilt match the SAP / yield calculation. Typical UK best at south-facing 30-40° tilt. Flat-roof systems with ballast or fixed tilt frames at design angle. Shading from chimneys / vents avoided.
    Acceptable whenPer MCS MIS 3002 / SAP Appendix M: orientation and tilt per design yield calc. Shading from objects within 20 m considered. Inter-row spacing on flat roof to avoid self-shading at low sun.
    StandardMCS MIS 3002. SAP 10 Appendix M (PV calculations). MCS Microgeneration Installation Standard.
    Common defectsPanel orientation east/west when south specified — yield down 25%Tilt > 45° — no advantage in UK, more wind loadPanels under tree / chimney shadow — partial-shade reduces outputInter-row spacing too tight — shadowingYield calc not actually delivered

Electrical

  1. 5.
    DC cabling correct type and size
    What to look forSolar DC cable (typically TUV-certified single-core 4-6 mm² double-insulated). UV-stable jacket. Cable rated for outdoor use, fire performance Cca-s1b,d1,a1 per Construction Products Regulation. Size per voltage drop calculation (typically ≤ 3% across array to inverter).
    Acceptable whenPer IET Code of Practice for Grid-Connected Solar PV / BS 7671 Section 712: DC cable double-insulated, UV-resistant, fire performance Cca for indoor runs. Voltage drop ≤ 3% to inverter at design current.
    StandardBS 7671:2018+A2:2022 Section 712 (PV systems). IET Code of Practice for Grid-Connected Solar Photovoltaic Systems. MCS MIS 3002.
    Common defectsStandard PVC cable used — UV degrades, insulation failsCable size too small — voltage drop > 3%Cable in conduit hot zone — insulation breaks downConnectors mismatched (MC4 from different manufacturers)Cable run alongside AC without segregation
  2. 6.
    Inverter installed and accessible
    What to look forInverter mounted in well-ventilated location. Manufacturer-recommended clearances around. Status display readable. AC and DC isolators within 1 m. Cable management tidy. IP rating per location (IP65 if outdoor).
    Acceptable whenPer MCS MIS 3002 / manufacturer: mounted ≥ 200 mm from any wall, vent space above per manufacturer; ambient -25 to +60°C operating; access for service. AC / DC isolators within reach.
    StandardMCS MIS 3002. Manufacturer installation manual. BS 7671 Section 712. G98 / G99 Engineering Recommendations.
    Common defectsInverter in cupboard with no ventilation — overheat shutdownNo clearance for serviceInverter outdoors without IP65 rating — water ingressAC / DC isolators distant — emergency isolation hardDisplay not readable from standing height
  3. 7.
    AC connection to distribution board correct
    What to look forAC connection on its own dedicated breaker on consumer unit. RCBO / MCB rating per inverter output. Cable size per BS 7671. Labelled "Solar PV — do not isolate".
    Acceptable whenPer BS 7671 Section 712: dedicated final circuit; OCPD per inverter manufacturer; cable size per current; "Do not switch off" warning label. AC isolator within 3 m of inverter.
    StandardBS 7671:2018+A2:2022 Section 712. ENA G98:2019 (single-phase, ≤ 16 A) / G99:2018 (larger systems).
    Common defectsConnected to ring main — non-compliantNo dedicated breakerWrong OCPD rating — nuisance trips or insufficient protectionNo warning label — inverter switched off, AC remains energisedAC isolator not present
  4. 8.
    Earthing and lightning protection installed
    What to look forFrame earthed via dedicated earth cable to main earth bar (10 mm² minimum typical). Equipotential bonding between rails / panels. Lightning protection per BS EN 62305 if at risk (e.g. exposed sites, > 20 m height).
    Acceptable whenPer BS 7671 / IET CoP / BS EN 62305-3: earthing conductor size per fault current; lightning risk assessment for class of LPS. Surge protection devices Type 2 or Type 1+2.
    StandardBS 7671:2018+A2:2022. BS EN 62305-3:2011 — Lightning protection. IET Code of Practice for Solar PV.
    Common defectsFrame not earthed — fault current returns through DC cablingNo equipotential between rows — different earth potentialsLightning risk assessment skippedNo surge protection on inverter inputEarth cable size too small for fault current
  5. 9.
    DC isolator accessible at roof level
    What to look forDC isolator (firefighter switch) accessible without entering loft / scaffold. Located at the inverter and at roof level (or string isolator near array). Switch labelled "DC ISOLATE BEFORE ENTERING LOFT".
    Acceptable whenPer BS 7671 Section 712 / IET CoP: DC isolator at the inverter and accessible firefighter switch at array. PV array isolation must disconnect both poles. Lockable in OFF position.
    StandardBS 7671 Section 712. IET Code of Practice for Solar PV.
    Common defectsNo DC isolator — fire risk to firefightersIsolator in loft only — no roof-level accessSingle-pole isolator — second pole still liveNot lockable — risk of restoration during workLabel missing or unclear

Commissioning

  1. 10.
    String voltage and current within expected range
    Record: Voc / Isc
    What to look forString open-circuit voltage (Voc) and short-circuit current (Isc) measured at irradiance and temperature. Compared with calculated values (panel datasheet × number per string × temp coefficient). Within ±5% expected.
    Acceptable whenPer IET CoP / MCS MIS 3002: Voc, Isc, and operating power measured at commissioning. Voc within 5% of calculated; Isc within 10% allowing for irradiance. Records on commissioning sheet.
    StandardIET Code of Practice for Solar PV. MCS MIS 3002. BS EN 62446-1:2016.
    Common defectsVoc much lower than expected — string broken or wrong panel countIsc much lower — shading, soiling, or wrong panel sizeNo temperature correction in calculationRecords not keptString measurements made off-cloud — irradiance unrepresentative
  2. 11.
    Insulation resistance test passed
    What to look forInsulation resistance (IR) test at 1000 V DC between PV+/PV- and earth. Reading > 1 MΩ for systems > 120 V. Test made before commissioning, in dry conditions. Results retained.
    Acceptable whenPer BS EN 62446-1:2016 / BS 7671: insulation resistance ≥ 1 MΩ for systems > 120 V; ≥ 0.5 MΩ for ≤ 120 V. Test voltage 250-1000 V DC.
    StandardBS EN 62446-1:2016 — PV systems requirements for testing, documentation and maintenance. BS 7671:2018+A2:2022.
    Common defectsIR test not performedReading < 1 MΩ — moisture in connector / cable damageTest in wet conditions invalidWrong test voltageRecords missing
  3. 12.
    Monitoring system operational
    What to look forMonitoring (inverter Wi-Fi, ethernet, or third-party logger) connected to the internet and showing live yield. App or web portal accessible to client. Alarm notifications configured for fault conditions.
    Acceptable whenPer MCS / inverter manufacturer: monitoring active and accessible to client at handover. Alerts for inverter fault, low yield, communications lost. Historical data retained for FIT / SEG metering.
    StandardMCS MIS 3002. Manufacturer specifications.
    Common defectsMonitoring not configured at handoverWi-Fi credentials not handed to clientAlerts not set upClient cannot access portalHistoric data lost on internet outage
  4. 13.
    MCS certificate issued
    What to look forMCS (Microgeneration Certification Scheme) certificate issued by approved installer. Includes installation details, yield estimate, and warranty. Required for SEG (Smart Export Guarantee) eligibility.
    Acceptable whenPer MCS standards: certificate issued via the MCS Installation Database (MID) by a registered installer. Required for FIT / SEG eligibility. Quality of design and install backed by MCS Consumer Code.
    StandardMCS Installer Standards. MCS Consumer Code. Microgeneration Certification Scheme.
    Common defectsInstaller not MCS registered — client loses SEG / FITCertificate not issued at handoverYield estimate wildly optimisticCertificate covers wrong system sizeNo warranty documentation
  5. 14.
    DNO notification completed
    What to look forDNO notification per ENA G98 (≤ 16 A single-phase) or G99 (larger / three-phase). G98 is "connect-and-notify" within 28 days; G99 requires prior approval. Confirmation from DNO retained.
    Acceptable whenPer ENA G98:2019 / G99:2018: G98 notify after install (within 28 days); G99 prior approval before install. Confirmation reference retained for client / future works.
    StandardENA G98:2019 — Microgenerator type approval (single-phase ≤ 16 A). ENA G99:2018 — Generator connection > 16 A.
    Common defectsNo DNO notification — illegal export to gridG99 install made without prior approvalWrong threshold applied (G98 used for system needing G99)Reference number not on documentationDNO approval lapsed before energisation

Questions people ask

What is a solar / pv installation QA inspection for?

To record that the work was checked against the specification before it was covered up or handed over: a pass or fail against each item, a measurement where one matters, and a photo where it failed. It is the evidence a client's quantity surveyor or clerk of works asks for, and the thing that settles the argument at final account.

What standards does this checklist check against?

Each item names its reference. On this checklist that includes MCS MIS 3002:2024, MCS MIS 3002. Manufacturer mounting system specs (Schletter, MCS MIS 3002. NFRC Solar Roof Best Practice., MCS MIS 3002. SAP 10 Appendix M (PV calculations). MCS Microgeneration Installation Standard., BS 7671:2018+A2:2022 Section 712 (PV systems). IET Code of Practice for Grid-Connected Solar Photovoltaic Systems. MCS MIS 3002., MCS MIS 3002. Manufacturer installation manual. BS 7671 Section 712. G98 / G99 Engineering Recommendations.. The contract specification and the approved drawings always take precedence over a general standard; where they say something stricter, inspect to that.

Who signs a QA inspection off?

The person who carried out the check, named and dated, and where the contract calls for it the client's representative as a witness. The signature records that the check was done and what was found. It is not a warranty of the work.

How many items are on it, and do I have to use them all?

14 checks across 3 sections. Delete what does not apply to the job and add anything the specification asks for that is not here. A checklist that has plainly been thought about carries more weight than a long one nobody read.

Is this useful for a subcontractor as well as a main contractor?

More so. The subcontractor is the one who gets asked to come back and open something up. A signed inspection sheet with photos at the time is the cheapest insurance on a construction site.

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