SSCE Past Questions: Practical – SS3 Solar Photovoltaic Installation & Maintenance Lesson Note (Second Term)

Practical problem solving in solar installation is finding the cause of a fault by checking the system step by step with the right tools, such as a multimeter, and then choosing or correcting equipment to suit the site.

Behavioural objectives

By the end of the lesson, students should be able to:

1. investigate a system whose battery runs low at night by checking the load, the battery voltage and shading;
2. trace a “no charging” fault by checking the fuse, cable continuity and panel voltage;
3. select the panel type, controller and panel direction for a small, partly shaded roof;
4. explain an inverter overload to a customer and carry out the reset procedure;
5. identify the main solar tools and state their uses.

How do you solve a solar practical problem?

Solve a practical problem by testing the system in a fixed order, starting with the simplest check.

1. Read the scenario: note the symptom, such as a low battery alarm, 0.0 A or a beeping inverter.
2. List possible causes: think of the load, the battery, the wiring, the panels and the controller.
3. Check the simplest cause first: look for a blown fuse, loose wire or shaded panel before using tools.
4. Test with the right tool: use the multimeter to measure voltage or test continuity.
5. Correct the fault: replace, tighten or reconnect the faulty part.
6. Retest and explain: confirm the system works, then tell the customer what went wrong.

What safety rules apply during solar practical work?

Safety rules protect the technician from electric shock, burns and fire.

• Switch off first: isolate the load and the breakers before touching any wire.
• Treat panels as live: panels produce voltage whenever there is light.
• Use insulated tools: never let a metal tool touch both battery terminals.
• Wear protection: use gloves and eye protection, especially near lead-acid batteries.
• Check polarity: connect positive to positive and negative to negative.

How is a multimeter used in solar fault finding?

A multimeter is a hand-held instrument that measures voltage, current and resistance, and tests continuity.

What is the energy chain in a solar system?

The energy chain is the path that power follows from the panels to the appliances.

Case study 1: why does the battery run low at night?

A battery runs low at night when the load is too high, the battery is weak, or the panels do not charge it fully.

• Scenario: a rural health centre has 4 solar panels and 2 large batteries.
• Complaint: the vaccine fridge stays on all day, but at 2:00 AM the “Low Battery” alarm beeps and the lights go dim.
• Task: investigate the fault using your tools.

Step-by-step solution

1. Check the load: list everything plugged in. A television or electric kettle added without telling the installer drains the battery too fast.
2. Test the battery voltage: use a multimeter on the DC voltage setting. A full 12 V lead-acid battery rests near 12.6 V.
3. Read the drop: if the voltage falls to about 10.5 V soon after sunset, one battery is likely faulty or has a dead cell.
4. Check for shading: look at the panels at about 4:00 PM. A tree branch shadow can sharply reduce the power a panel produces.

Case study 2: what causes a “no charging” fault?

A “no charging” fault is a fault in which the controller shows 0.0 A flowing to the battery although the sun is shining.

• Scenario: the sun is bright in Kano, but the charge controller screen shows 0.0 A going into the battery.
• Task: find the break in the energy chain.

Step-by-step solution

1. Check the fuse or breaker: inspect the fuse box between the panels and the controller. A power surge may have blown the fuse to protect the system.
2. Test cable continuity: switch off the circuit and use the continuity setting that beeps. No beep means a wire has snapped or been chewed by a rodent.
3. Measure panel voltage (Voc): disconnect the panels and measure at the wires. A reading of 0 V points to a problem on the roof, often a loose MC4 connector.

Case study 3: how do you install solar in a tight space?

In a tight, partly shaded space, choose high-efficiency panels, an MPPT controller and a south-facing position.

• Scenario: a small shop in a crowded market has a very small roof, partly blocked by a taller building next door.
• Task: select the best equipment for this site.

What are monocrystalline and polycrystalline panels?

• Monocrystalline panel: a panel made from a single crystal of silicon, usually dark in colour.
• Polycrystalline panel: a panel made from many silicon crystals joined together, usually blue.

What are PWM and MPPT controllers?

• PWM controller: a simple, cheaper controller that switches the charging current to the battery.
• MPPT controller: a controller that tracks the panel’s maximum power point to get more energy from the panels.

Step-by-step solution

1. Panel choice: recommend monocrystalline panels because space is small and they give more watts per square metre.
2. Controller choice: use an MPPT controller because the tall building may cause partial shading.
3. Positioning: use a compass to make the panels face south. Nigeria lies north of the equator, so south gives the longest sun exposure.

Case study 4: why is the inverter beeping?

An inverter beeps continuously with a red “Fault” light when the load is more than its rated capacity, which is called overload.

• Scenario: a house inverter gives a continuous beep and a red “Fault” light while the owner is ironing clothes.
• Task: identify the error and explain it to the customer.

Step-by-step solution

1. Identify the overload: an iron produces heat and draws a large current. The demand was higher than the inverter’s capacity, for example 2000 W drawn from a 1500 W inverter.
2. Reset the inverter: switch off the iron, turn off the inverter, wait 30 seconds, then turn it back on.
3. Educate the customer: advise them to read the wattage label on each appliance.
4. Give usage advice: use high-heat items such as heaters, irons and kettles one at a time, or when the sun is at its peak.

Which tools should you know for the SSCE practical?

You may be asked in the SSCE practical to identify a tool or explain its use.

What final tip helps in the practical exam?

Always mention tight connections, because a loose wire is a fire risk.

• Loose connection: it resists current and heats up.
• Result: the heat can melt insulation and wires.
• Prevention: tighten every terminal and crimp every MC4 joint firmly.

Evaluation

1. State the three checks you make when a battery drains before morning.
2. Which multimeter setting is used to test a cable, and what does it tell you?
3. Why are monocrystalline panels and an MPPT controller suitable for a small, partly shaded roof?
4. Why did the inverter beep while the owner was ironing?
5. State the use of a hydrometer.

Assignment

A charge controller shows 0.0 Amps although the sun is shining. List, in order, the three checks you would make to find the fault, and explain each in one sentence.