Falls from roofs are among the most serious accidents in Indian construction, and rooftop solar puts people on roofs every day: parapet-less terraces, old tin sheds, asbestos-cement sheets and wet tiles. Add live DC that cannot be switched off in daylight, and 45 °C afternoons. A good crew finishes the job and goes home uninjured, every time. This lesson covers the kit and the habits that make that possible.
The tool kit
Mechanical
- Hammer drill with SDS bits (for RCC anchors), and a cordless drill-driver
- Chemical anchor dispensing gun, cleaning brush and blow pump (holes must be cleaned before injecting)
- Torque wrench (for anchors and module clamps), spanner and socket sets
- Spirit level, measuring tape, chalk line, string line, marker
- Angle grinder with guard (for cutting rails or strip, with a cold-galvanising spray for cut ends)
- Rivet gun and self-drilling screws (for tin sheds)
- Compass and inclinometer (or phone apps you have checked against a real compass)
- Ropes, pulley or hoist for lifting material
Electrical
- MC4 crimping tool and matching unlocking spanners (one connector system per job)
- Cable cutter and wire strippers, including for 4–6 mm² solar cable
- Hydraulic crimper for larger lugs (battery cables, AC above 10 mm²)
- Insulated screwdrivers (1,000 V rated)
- Heat gun and heat-shrink sleeves, cable ties (UV-stable), labels
Test instruments
- Digital multimeter, CAT III 1,000 V DC (or CAT IV for work at the meter)
- DC clamp meter (true DC; an AC-only clamp reads nothing on PV strings)
- Insulation resistance tester, 500 V and 1,000 V test voltages
- Earth resistance tester (three/four-terminal, with stakes and leads)
- Irradiance meter and module thermometer (for commissioning checks)
- Thermal camera, optional but very useful for O&M
- Phase-sequence and socket testers
PPE: what each item protects against
| PPE | Protects against | Notes |
|---|---|---|
| Safety helmet with chin strap | Falling tools, head strikes | Chin strap stops it falling off when you bend over a parapet |
| Safety shoes | Dropped rails and modules, nails, sharp sheet edges | Non-slip soles for tin and tiles |
| Cut-resistant gloves | Module frame edges, sheet metal, rails | Remove for fine electrical work |
| Insulating gloves (Class 0) | DC shock when handling live strings | Inspect before each use for pinholes |
| Safety glasses | Drilling dust, chemical anchor splash, battery acid | Clear lenses, wraparound |
| Full-body harness with double lanyard and shock absorber | Falls from height | Must be connected to a suitable anchor |
| Hearing protection | Hammer drill and grinder | |
| Dust mask (N95) | Concrete and silica dust | |
| Cap, sunscreen, light long sleeves | Sun and heat | Part of PPE in Indian summers |
PPE is the last line of defence. Planning the work (edge protection, safe access, de-energised circuits) comes first.
Working at height
Assess the roof before anyone climbs
- Edges: is there a parapet, and is it at least about 1 m high? A 450 mm parapet stops nobody.
- Fragile surfaces: asbestos-cement and old GI sheets, polycarbonate skylights, plastic water-tank covers. Never step between purlins on a sheet roof; use crawl boards laid across at least three purlins, and walk only along the fixing lines.
- Anchors: where will harnesses attach? Strong structural points (RCC columns, beams, purpose-installed anchors), never a water pipe, a dish antenna or a parapet coping stone.
- Access: staircase to terrace, or ladder? Is the material route clear?
- Weather: wind, rain and thunder forecast.
Ladders
Use the 4:1 rule: for every 4 m of height, the ladder foot is 1 m out from the wall. The ladder must extend about 1 m above the landing so you have a handhold when stepping off, and it must be tied or footed by a second person.
Worked example
A parapet top is 3.6 m above the ground. - Foot distance: 3.6 ÷ 4 = 0.9 m from the wall - Length to the landing: √(3.6² + 0.9²) = √(12.96 + 0.81) = 3.71 m - Plus 1 m above the landing: about 4.7 m, so use a 5 m ladder (or a longer extension ladder), not the 4 m ladder in the van.
Harness use
- Inspect the harness and lanyard before each use: webbing cuts, sun damage, stitching, hooks.
- Anchor above the D-ring where possible, to keep the fall short.
- Use a double lanyard so you are always connected while moving between anchors.
- A harness without a rescue plan is half a plan: someone suspended in a harness needs to be brought down within minutes. Keep a ladder or rescue kit ready and know the nearest hospital.
Handling modules on the roof
- Modern modules weigh about 25–32 kg and are over 2 m long. Two people per module, carried on edge by the frame.
- A module is a sail. Stop lifting and carrying modules when the wind is gusty; a gust can take a person off a roof with it.
- Never stand, kneel or walk on modules; it causes micro-cracks that show up as hot spots later.
- Stack modules on the pallet or on edge against a wall, never face-down on gravel or rebar ends.
Live DC: the hazard you cannot switch off
A string of modules produces its full voltage whenever light falls on it: 400–600 V DC on a typical home system, even on a cloudy morning. Switching off the inverter does not make the string safe.
- Treat all PV cables and connectors as live in daylight.
- Connect modules into strings before connecting the string to anything; make the final connection at the DCDB with the isolator open.
- Never open MC4 connectors under load; open the DC isolator first and check current with a DC clamp meter.
- To work on a string in daylight, cover the modules with an opaque sheet or work early or late with the isolator open and connectors separated.
Heat, rain and lightning
- Heat: in April–June, start early (6:30–7 am), break from about noon to 3 pm, and finish late afternoon. Drink water every 20 minutes, add ORS, rotate tasks, and watch each other for headache, confusion or stopped sweating, which are signs of heat stroke.
- Rain: wet modules, tiles and sheets are slippery; stop roof work in rain and wait for surfaces to dry.
- Lightning: if you hear thunder, get off the roof. Many crews use the "30-30" rule: if the gap between flash and thunder is under 30 seconds, stop; wait 30 minutes after the last thunder before returning.
Key points
- Carry proper DC test instruments: CAT III 1,000 V meter, DC clamp meter, insulation and earth testers.
- PPE includes helmet with chin strap, safety shoes, gloves, glasses and a full-body harness, plus sun protection.
- Survey edges, fragile surfaces and anchors before climbing; never step between purlins on sheet roofs.
- Ladders: 4:1 angle, 1 m above the landing, tied or footed.
- PV strings are live in daylight; never break connectors under load.
- Plan around heat, rain and lightning.
Check yourself
- A ladder must reach a landing 4.8 m high. How far out should its foot be?
- Why is a DC clamp meter needed instead of an ordinary clamp meter?
- What is the safe way to walk on an asbestos-cement sheet roof?
Answers
- 4.8 ÷ 4 = 1.2 m.
- Ordinary clamp meters measure only AC current using a transformer; PV string current is DC and needs a Hall-effect DC clamp.
- Do not walk on the sheets; use crawl boards spanning at least three purlins and stay on the fixing lines, with fall protection.