1. Before You Start: Safety Fundamentals

Solar DC systems are always live when light hits the panels — you cannot turn them off the way you switch off mains power. This demands a different mindset from conventional electrical work.

The Non-Negotiable Safety Rules

1. Never work alone. Always have a second person present when working on live DC circuits or working at height on roofs.
2. Cover panels before wiring. Before connecting any DC cable, cover all solar panels with an opaque tarpaulin or cardboard. Covered panels produce no current — uncovered panels are always live in daylight.
3. Use insulated tools. All tools used on DC circuits (screwdrivers, pliers, wire strippers) must be rated for the voltage of the system.
4. Verify polarity before connecting. Reversed polarity on DC circuits destroys charge controllers, inverters, and batteries — often without a visible fault. Always measure with a multimeter before making any final connection.
5. Never short a battery. Even a brief short across a battery bank can weld metal, cause explosion, and cause serious burns. Always fit the main fuse as the very last step before energising the battery circuit.
6. Label everything. Every cable, every terminal, every fuse must be labelled with voltage, polarity, and circuit identity. Future maintenance technicians — and future you — depend on it.

Required Personal Protective Equipment (PPE)

• Safety glasses (sparks from accidental shorts)
• Insulated gloves rated for DC voltage
• Non-conductive footwear
• Hard hat and safety harness for roof work above 2 metres
• Multimeter for polarity and voltage verification

2. Installation Sequence — The Correct Order

A solar system must be installed in the correct sequence to avoid damaging components and ensure each stage can be safely tested before the next begins.

1. Install mounting structure (roof or ground)
2. Mount panels on structure — leave covered
3. Route and secure all DC cables (panels to controller)
4. Install charge controller, inverter, battery enclosure in equipment room
5. Connect battery bank internally (series/parallel wiring) — leave main fuse out
6. Connect MPPT charge controller to battery (fuse still out)
7. Connect inverter to battery (fuse still out)
8. Wire AC output from inverter to distribution board (breakers off)
9. Connect DC cable from panels to charge controller — verify polarity first
10. Install all protection fuses and breakers
11. Remove panel covers — system energises
12. Commission: verify charging, test AC output, check all protection devices

3. Mounting Structure Installation

Metal Sheet Roof (Most Common in Sub-Saharan Africa)

1. Locate purlins: Tap the roof to find the timber or steel purlins beneath. All mounting bolts must go into purlins — not just the thin metal sheet which cannot support load.
2. Mark fixing positions: Rails run perpendicular to the panel’s long axis. Space rails to manufacturer specifications — typically 600–900mm apart for portrait mounting.
3. Drill and seal: Use a step drill for clean holes through metal roofing. Apply butyl rubber sealant or EPDM gasket on every bolt before tightening. Leaks are the number one long-term complaint from roof mount installations in Africa’s rainy seasons.
4. Install rails: Aluminium extrusion rails attach to roof hooks or L-feet via stainless steel bolts. Aluminium-to-steel contact requires isolation tape to prevent galvanic corrosion.
5. Bond rails to earth: The mounting structure must be electrically bonded and connected to earth as part of the lightning protection system (see Section 6).

Concrete Slab / Flat Roof

Two options for flat roof or concrete slab: ballasted frames (no penetration, weighted down) or anchor bolts (penetrate slab, structurally fixed). In most of Africa where high wind speeds are a risk (coastal zones, highland regions), anchor bolting is preferred. All penetrations must be waterproofed with appropriate roofing sealant.

4. Panel Wiring: MC4 Connectors & String Assembly

Solar panels connect to each other and to the charge controller using MC4 connectors — the industry-standard weatherproof DC connector used globally. MC4s are polarised (male/female) and lock with an audible click. They are rated for outdoor UV and weather exposure for the full 25-year panel life.

Series Wiring (Increases Voltage)

Connect the positive (+) output of one panel to the negative (−) of the next. The string voltage equals the sum of individual panel voltages. The current remains the same as a single panel.

Example: 2 × 400W panels with Vmp 40V in series → String Vmp = 80V, current = single panel Imp (~10A)

Parallel Wiring (Increases Current)

Connect all positive outputs together and all negative outputs together using MC4 branch connectors (Y-connectors). Voltage stays the same as a single panel; current multiplies.

Example: 2 parallel strings of 2 panels → Vmp = 80V, current = 2 × 10A = 20A

MC4 Crimping — Do It Right

• Use only the correct MC4 crimping tool — pliers will produce a connection that looks correct but fails under vibration and weather cycling
• Strip cable insulation to exactly the depth of the MC4 pin (typically 7–9mm) — too short causes a high-resistance joint; too long exposes bare conductor
• After crimping, conduct a pull test: the cable should not pull free from the pin with moderate hand force
• Never mix MC4 brands in the same connection — different brands have slightly different tolerances and an imperfect seal can cause arcing and fire

5. DC Cable Routing & Management

Good cable management is not cosmetic — it protects cables from physical damage, UV degradation, rodent attack, and makes future fault-finding possible.

Routing Best Practices

• Use UV-rated conduit for all outdoor runs. Solar DC cable is UV-resistant itself, but exposed cable on a roof will degrade faster than conduit-protected cable and is vulnerable to bird or animal damage.
• Avoid sharp bends. Cable bend radius should be at least 6× the cable diameter to avoid insulation cracking over time.
• Keep positive and negative cables together. Running + and − cables separately creates a large current loop that acts as an antenna for lightning-induced surges. Always bundle or twist + and − together.
• Secure every 300–400mm on horizontal runs, every 500mm on vertical runs. Unsecured cables flap in wind, wearing through insulation at contact points.
• Enter the building through a properly sealed cable entry. Roof penetrations must be sealed against both water and insects — in Africa, termites entering through an unsealed cable hole can destroy structural timbers within a season.

Labelling Standard

Label each cable at both ends with: Circuit identity (e.g. “PV STRING 1 +”), Voltage, and installation date. Use UV-resistant cable markers or heat-shrink label sleeves — standard paper labels turn to mush in 12 months of African humidity.

6. Earthing & Lightning Protection

Lightning is a serious and common hazard across much of Africa. A direct strike on an unprotected solar array will destroy the entire system and can cause fire. Proper earthing and surge protection is not optional in African installations — it is essential.

Earthing the Array Structure

1. Bond all mounting rails together with a continuous 6mm² green-yellow earth cable.
2. Connect panel frames to mounting rails via the panel frame earth lug (present on all IEC-certified panels).
3. Run earth cable from array structure to a ground rod (copper-clad steel rod, minimum 1.2m long, driven into moist soil. In dry regions, surround with a water-retention earthing compound like bentonite).
4. Earth the negative DC bus of the system at the charge controller (for non-isolated systems) or at the inverter earth terminal.

Surge Protection Devices (SPDs)

Even without a direct strike, a nearby lightning strike induces a voltage surge that travels down cables and destroys electronics. Install:

• DC SPD (Type 2) on the PV array input — at the point where cables enter the building from the roof
• DC SPD at the charge controller input — second line of defence protecting the controller
• AC SPD at the distribution board — protects all connected appliances from surges on the inverter output

SPDs are relatively inexpensive (KES 3,000–8,000 each) but protect equipment worth 100× more. They are non-negotiable in high-lightning areas such as the East African highlands, Zambia, Zimbabwe, and the West African coastal belt.

7. Battery Room Setup & Safety

Location Requirements

• Cool: Every 10°C rise in battery temperature above 25°C approximately halves lithium battery cycle life. Avoid locations that exceed 40°C — do not install in an enclosed metal room with no airflow in a tropical climate.
• Ventilated: Even LiFePO4 batteries require ventilation for heat dissipation. Lead-acid batteries additionally produce hydrogen gas during charging — a 4% hydrogen/air mixture is explosive. Lead-acid battery rooms must have dedicated ventilation to the outside and all electrical equipment in the room must be rated for explosive atmospheres.
• Dry: Moisture causes terminal corrosion, insulation degradation, and shorts. Never install batteries directly on concrete floors — use a raised battery rack or rubber matting.
• Secure: Battery banks have significant resale value and are a target for theft in some regions. Install in a lockable room or cabinet.
• Accessible: Terminals and connections must be accessible for regular inspection and maintenance without requiring dismantling.

8. System Commissioning — First Power-Up Procedure

Commissioning is the structured process of bringing the system to life safely and verifying every function before handing it over to the customer.

Pre-Energisation Checklist

• ☐ All DC cables labelled and polarity verified with multimeter
• ☐ All connections torqued to manufacturer specification (under-torqued terminals arc and overheat; over-torqued terminals crack)
• ☐ Battery bank wiring complete — main fuse NOT yet installed
• ☐ MPPT and inverter connected to battery bus — main fuse NOT yet installed
• ☐ AC distribution board connected to inverter output — all breakers OFF
• ☐ All panels covered
• ☐ Earth continuity test: measure resistance between panel frame and earth rod — should be <1Ω
• ☐ Insulation resistance test: measure insulation resistance of PV array (+) to earth and (−) to earth — should be >1MΩ

Energisation Sequence

1. Install battery main fuse. If spark occurs on connection, stop and investigate — a spark means a fault exists in the circuit.
2. Power on charge controller. Verify it displays battery voltage correctly on the screen/app.
3. Power on inverter in standby mode. Verify battery voltage displayed matches actual measured voltage (±0.5V).
4. Uncover panels gradually (one string at a time). Monitor charge controller display: PV voltage should appear and charging current should register. At solar noon in Africa, you should see close to rated panel current.
5. Enable AC output on inverter. Measure AC voltage at inverter output terminals — should read 220–240V AC, 50Hz.
6. Switch on each AC breaker one at a time in the distribution board. Test each circuit.
7. Test protection devices: Verify the battery management system (BMS) low-voltage cutoff functions by running loads until the BMS trips.

9. Maintenance Schedule

A solar system that is properly installed and regularly maintained will outlast the house it powers. One that is ignored will fail within 3–5 years. Maintenance is simple but must be consistent.

Task	Frequency	What to Check
Panel cleaning	Monthly (or after dust storms / dry season)	Remove dust, bird droppings, leaf debris. Use soft cloth with clean water. Never use abrasive cleaners or high-pressure water directly on panel glass edges.
Visual inspection of panels	Monthly	Cracks, delamination, discolouration (hotspots), damaged frames
Cable and connector check	Every 6 months	Check MC4 connectors for corrosion or loosening. Check conduit fixings. Look for animal damage.
Battery terminal inspection	Every 6 months	Check for corrosion (white/blue powder on terminals — clean with baking soda solution). Check all bolts are at correct torque. For flooded lead-acid: check electrolyte level and top up with distilled water only.
Charge controller & inverter check	Every 6 months	Review system logs for fault codes. Check cooling vents for dust blockage. Verify charging parameters still match battery specs.
Earth rod inspection	Annually	Measure earth resistance (<1Ω). Re-drive rod if resistance has increased (soil may have dried around it).
Battery capacity test	Annually	Fully charge battery, then discharge at rated current to BMS cutoff. Measure actual Ah delivered vs rated capacity. Capacity below 80% of original rating indicates end of life approaching.
Mounting structure check	Annually (before rainy/storm season)	Verify all bolts are tight. Check roof flashings and sealant around penetrations for signs of water ingress.

10. Troubleshooting Common Problems

Symptom	Most Likely Cause	Diagnostic Step	Fix
Panels producing much less than expected	Shading, soiling, or faulty panel	Measure voltage and current of each string individually	Clean panels; identify and bypass shaded string; test/replace faulty panel
Battery not reaching full charge	Undersized array, wrong charge parameters, failing battery	Check charge controller parameters vs battery spec; measure battery voltage at end of charge	Correct charge parameters; if voltage OK but capacity low, battery may be failing
Inverter shuts off under load	Overload, low battery voltage, overheating	Check inverter display for fault code; measure battery voltage under load	Reduce load; check battery health; improve inverter ventilation
Flickering lights / unstable voltage	Loose connection, undersized cable, failing battery cell	Check all terminal connections; measure voltage drop from battery to inverter under load	Tighten connections; upgrade cable; test battery capacity
MPPT showing zero PV input	Covered/shaded panels, open-circuit fault, blown fuse	Check fuses; measure PV voltage at MPPT input terminals	Replace blown fuse; locate open-circuit fault in cable or connector
System works in day but fails at night	Battery undersized or failing; incorrect low-voltage cutoff settings	Check battery state of charge at sunset vs load demand	Reduce night loads; add battery capacity; verify charge controller settings

The Complete Series: Your Solar Design Roadmap

You have now completed the Diaspora Solar Design Series. Here is the full knowledge pathway from concept to confident installation:

1. Why Solar Systems Fail — Understanding the root causes of failure and how to design for longevity from the start
2. Geographic Orientation & Site Assessment — Latitude, tilt angles, true north, Peak Sun Hours across Africa, shading analysis
3. System Sizing & Design Calculations — Energy audit, panel sizing, battery sizing, charge controller and inverter selection, wire sizing
4. Installation, Wiring & Safety (this article) — Mounting, MC4 wiring, cable management, earthing, lightning protection, commissioning, maintenance

If you would like Diaspora Solar to assess your specific site, design a system to your exact needs, or oversee installation in your location, get in touch with our team. We work with diaspora clients to design systems for properties across East and West Africa, with local installation partnerships on the ground.