Solar PV Commissioning and Handover: MCS Commissioning Checklist, Handover Pack and Monitoring Setup

Summary

Commissioning and handover are the final steps of every solar PV installation, but they are also the most frequently rushed. Incomplete commissioning means faults are not detected at installation; poor handover means the customer can't use their system effectively. Both reflect on the installer's reputation and professional standing.

MCS 001 specifies minimum requirements for commissioning documentation and customer handover. BS EN 62446 specifies the electrical tests. This article provides a practical checklist for both.

Key Facts

• BS EN 62446 — the international/British standard for grid-connected PV system documentation and commissioning tests; the definitive commissioning test reference for UK solar PV
• MCS installation certificate — issued by the installer after commissioning; lodged on the MCS database within 10 days of commissioning; the primary document for SEG applications
• EIC (Electrical Installation Certificate) — issued for the AC side of the installation (new circuit from inverter to consumer unit); required under BS 7671 Part P
• G98 notification — DNO notification for systems ≤3.68kW export capacity; must be submitted within 28 days of connecting to the grid; see dno g98 g99 applications
• Anti-islanding test — confirms the inverter disconnects when the AC grid supply is removed; a safety requirement (prevents the solar system energising a dead grid circuit); typically tested by briefly opening the AC isolator and confirming the inverter shuts down
• String Voc measurement — measure and record open-circuit voltage of each string at the inverter; compare to calculated Voc from panel spec; a significant discrepancy indicates a wiring fault or panel problem
• Insulation resistance (DC) — measured on DC circuits between live conductors and earth (disconnected from inverter); minimum >1MΩ; typically much higher on new cables
• Monitoring app setup — the customer's inverter monitoring account (Fronius Solar.web, SolarEdge monitoring, Enphase Enlighten, Solis Cloud, etc.) should be set up and demonstrated at handover
• Handover documentation — the complete package of documents provided to the customer at handover; must include all MCS-required documents
• MCS workmanship warranty — minimum 2-year workmanship warranty from the installer, required by MCS 001
• System performance estimate — the expected annual yield (kWh) must be communicated to the customer; typically from PVGIS calculation (see solar pv system sizing)

Quick Reference Table: Commissioning Tests (BS EN 62446)

Detailed Guidance

Pre-Energisation Tests

Before connecting the inverter to the AC supply or the DC string to the inverter, complete all DC-side tests:

Step 1: Visual inspection Walk the roof and cable routes:

• All panels correctly seated on rails; clamps torqued
• DC cables correctly routed; protected from damage; not loose
• MC4 connectors fully clicked together (listen for click; pull test)
• Array earthing bond connected to mounting rails
• DC cable entry into building fire-stopped or sealed
• Labelling: DC isolator labelled "WARNING — DUAL SOURCE ISOLATION REQUIRED"; consumer unit labelled for the new generation circuit

Step 2: DC polarity At each string input (at the inverter or at the string combiner if fitted), measure polarity with a multimeter:

• Connect the red probe to the positive MC4 and the black probe to the negative MC4
• Result should be a positive DC voltage (approximately Vmpp × number of panels in series)
• A zero reading: open circuit in the string (check all MC4 connections); a negative reading: reversed polarity in the string (check panel connection sequence)

Step 3: String Voc With all panels in the string connected and the string disconnected from the inverter, measure the open-circuit voltage of each string:

• Expected value: panels in series × Voc_per_panel (STC, adjusted for temperature if not at 25°C)
• At 15°C ambient (typical UK installation): Voc increases slightly (~3–5%) above STC value
• A low Voc reading indicates a faulty panel or missing panel in the string; a very low reading indicates a short circuit in one panel

Record the measured Voc for each string in the commissioning report.

Step 4: DC insulation resistance Disconnect the inverter from the DC strings. Measure insulation resistance using a 500V DC megger:

• L+ conductor to earth (PE): should be >1MΩ (typically >200MΩ for new cables)
• L- conductor to earth (PE): should be >1MΩ
• L+ to L-: should be >1MΩ (tests for internal short in panels)

Values significantly below 1MΩ indicate insulation damage, water in a connector, or a panel defect. Investigate and rectify before connecting to the inverter.

Step 5: Earth bond continuity Using a low-resistance ohmmeter, measure from the mounting rail or panel frame to the Main Earthing Terminal (MET) at the consumer unit. Record the value; it should be <1Ω.

Inverter Commissioning

Step 1: Connect DC strings to inverter Connect the DC string MC4 connectors to the inverter DC inputs. Set the inverter's DC isolator to the off position before connecting; close the DC isolator and confirm the inverter's DC input LEDs activate.

Step 2: Connect AC supply Switch on the RCBO in the consumer unit feeding the inverter. The inverter will begin synchronising with the grid. Most inverters perform a 2–5 minute synchronisation period (checking grid voltage and frequency) before beginning to export. This is normal.

Step 3: Verify grid connection and generation Confirm:

• Inverter display shows AC voltage (approximately 230V) and grid frequency (approximately 50Hz)
• Inverter begins generating (DC input power and AC output power visible on display or app)
• No error codes displayed

Step 4: Anti-islanding test With the system generating:

1. Open the main isolation at the consumer unit (turn off the main switch) or open the dedicated generation circuit MCB at the consumer unit — this simulates a grid outage
2. Observe the inverter: it must shut down within the required time (typically within 2 seconds, per G98 protection settings)
3. Re-energise the consumer unit; the inverter should restart and re-synchronise

Record the result in the commissioning report.

Step 5: Inverter protection settings (G99 or commercial installs) For G99 installations or where specific DNO protection settings were required in the approval, confirm the inverter's under/over voltage and under/over frequency settings match the approved settings. Most inverters allow these to be read from the configuration menu.

G98 DNO Notification

Submit the G98 notification via the DNO's online portal on the day of commissioning or within 28 days. Required information:

• Installation address
• Inverter make and model (must be on the G98 type test register)
• Panel make, model, and total kWp
• Total export capacity (inverter AC rating, confirming ≤3.68kW)
• Date of connection
• Installer contact details and MCS number

Save the submission confirmation for the customer handover file.

MCS Installation Certificate

Log into the MCS certification body's portal (NAPIT, NICEIC, BSI, etc.) and complete the MCS installation certificate:

• System address
• Panel make, model, number, kWp
• Inverter make, model, capacity
• Mounting type and orientation
• Tilt angle
• MCS installer number
• Commissioning date
• Estimated annual yield (kWh)

Submit the certificate. It will be lodged on the MCS public database automatically. Provide the certificate number to the customer — they need it for SEG applications.

Deadline: Within 10 days of commissioning.

Customer Handover

Handover pack contents (MCS 001 requirement):

1. MCS installation certificate (copy)
2. EIC (copy)
3. G98 notification confirmation
4. Inverter user manual and warranty documents
5. Panel product datasheet and warranty documentation
6. Mounting system documentation
7. Expected annual yield (kWh) from system design
8. MCS 2-year workmanship warranty statement
9. Installer contact details for warranty claims
10. SEG information sheet (how to apply; see solar pv export tariff sei)

Monitoring app demonstration: Set up the customer's account on the inverter monitoring platform and demonstrate:

• How to view live generation (current kW output)
• How to view historical generation (daily, monthly, annual kWh)
• How to recognise normal vs abnormal system behaviour
• How to contact the installer if a fault is suspected

Customer briefing: Explain:

• The system will not generate on cloudy days (reduced, not zero — reassure customers)
• The inverter is normal if it shuts down at night (no AC generation: the inverter disconnects from the grid in the absence of DC input)
• Export metering: the smart meter from their energy supplier is the reference for SEG payments
• Annual checks: advise the customer to review their monitoring platform annually and contact the installer if annual generation is significantly below the estimated figure

Frequently Asked Questions

Does the MCS certificate have to be lodged before the customer can apply for SEG?

Yes. The SEG supplier checks the MCS database when processing the customer's application. The certificate must be lodged on the database (not just issued to the customer) for the supplier to verify eligibility. The 10-day lodging deadline is therefore commercially important — if the customer wants to apply for SEG promptly, the certificate should be lodged as soon as possible after commissioning.

What if I can't complete all BS EN 62446 tests on the day (e.g., generator test during power cut)?

Document what was tested and what was deferred. Deferred tests should be completed at the earliest opportunity (typically within 5 working days). The MCS installation certificate should not be lodged until all commissioning tests are satisfactorily completed.

Is the G98 notification really required within 28 days, even for a small 2kWp system?

Yes. The 28-day deadline applies to all G98-qualifying installations regardless of size. There is no minimum threshold below which notification is waived. Submit it on the day of commissioning where possible.

Regulations & Standards

• BS EN 62446-1:2016 — Grid connected photovoltaic systems — minimum requirements for system documentation, commissioning tests, and inspection

• MCS 001 — MCS Installer Standard; commissioning and handover requirements

• ENA G98 Issue 1 — G98 notification requirements; 28-day rule

• Building Regulations Part P — EIC requirement for AC circuit work

• BS 7671:2018+A2:2022 Section 712 — PV system testing requirements

• BS EN 62446 via BSI — commissioning test standard

• MCS installer guidance — mcscertified.com — MCS 001 commissioning requirements

• ENA G98 — energynetworks.org — DNO notification process

• mcs certification solar — MCS certification background

• dno g98 g99 applications — DNO notification process

• building regs part p solar — Part P EIC requirements

• solar pv earthing and bonding — DC circuit testing requirements

• solar pv export tariff sei — SEG application guidance for customers