Use this as an owner’s verification checklist, not a wiring guide. Ask for the as-built diagram, protection schedule and commissioning records; match them to what was installed; and use qualified personnel for electrical testing. Solar DC can remain energised in daylight even when the AC supply is off.
Review solar electrical safety without turning it into a DIY high-voltage job
1. Ask for the single-line diagram and protection schedule
You should be able to see how modules, strings, inverter, AC connection, isolation, earthing and surge-protection devices fit together.
2. Match the design to the installation
Model numbers, cable routes, isolators, protection devices and earthing conductors on site should correspond to the approved design or a documented as-built drawing.
3. Request test and commissioning records
Ask what electrical tests were performed, who performed them, the instruments or standards used, and the signed acceptance record.
4. Inspect visually from safe locations
Look for damaged enclosures, loose visible conduits, exposed conductors, water ingress or corrosion. Do not open inverter or DC combiner compartments unless qualified and authorised.
5. Escalate defects before normal operation
If protection is missing, visibly damaged or undocumented, obtain qualified inspection and written remediation instead of improvising a repair.
What earthing and surge protection actually do
Earthing provides a controlled protective path and helps exposed conductive parts remain at safer potentials under fault conditions. Surge protective devices limit transient overvoltage reaching equipment. They solve different problems, and neither substitutes for correct cable sizing, isolation, overcurrent protection, lightning-risk design or workmanship.
The exact arrangement depends on inverter type, system architecture, local electrical rules, the building’s lightning-protection system and manufacturer requirements. A generic internet diagram should not be used as an installation drawing.
The handover documents that make safety maintainable
| Record | What it lets you verify | Red flag |
|---|---|---|
| Single-line or as-built diagram | How DC and AC sides connect and where protection sits | No drawing, or drawing does not match the site. |
| Equipment schedule | Exact inverter, module, isolator and protection models | Undocumented substitutions. |
| Earthing/protection test record | What was tested at commissioning and by whom | Only a verbal “earthing is done.” |
| Warranty and datasheets | Installation constraints and replacement compatibility | No serial numbers or accessible terms. |
| Shutdown instructions | How authorised persons isolate the system safely | No labelled isolation points or owner instructions. |
Questions to ask the installer instead of guessing a resistance number
- Which earthing arrangement did you design for this site, and why?
- How does the inverter manufacturer require protective earthing to be connected?
- What surge-protection devices are installed on the DC and AC sides, and what design basis was used?
- Does the building have an existing lightning-protection system, and was coordination reviewed?
- What commissioning tests were performed, and can I have the signed results?
- What inspection interval does the manufacturer or installer recommend for this exact system?
Safe owner checks
You can verify labels, documentation and obvious physical condition without touching live parts. From safe access points, look for broken conduits, loose external cable supports, cracked enclosures, obvious water entry, heavy corrosion, burn marks or repeated inverter protection faults. Photograph changes over time for service personnel.
After lightning, flooding, roof work or a major surge
Do not automatically restart a visibly damaged system. Roof work can disturb bonding, conduits or module wiring; water can affect enclosures; and a surge can damage protective devices without an obvious external failure. Ask for a targeted inspection and keep the service report.
For a warranty or workmanship dispute, preserve the original design, as-built drawing, commissioning records, dated photos, inverter logs and the technician’s written diagnosis.