PV System Maintenance II – SS2 Solar Photovoltaic Installation & Maintenance Lesson Note (Second Term)

Troubleshooting a PV system means finding and fixing faults by following the path of power: Sun, panels, controller or inverter, batteries and appliances. The technician asks the owner what happened, checks the inverter, breakers and fuses, tests the panels and batteries with a multimeter, and replaces broken parts only after switching off the power in the right order.

Behavioural objectives

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

• Describe the path of power and use it to start troubleshooting.
• List the first checks to make on a system with no power.
• Use a multimeter to test a string of panels and explain the readings.
• Identify the signs of a bad battery.
• State the power down sequence and the correct order for connecting and disconnecting battery cables.

What is the mindset of a troubleshooter?

Troubleshooting is like being a detective. Do not start by pulling wires. Follow the “Path of Power”: Sun → Panels → Controller/Inverter → Batteries → Appliances.

The first question

Always ask the owner, “What exactly happened?” The answer points to the likely cause:

• Did it stop working suddenly during a rainstorm? (Could be lightning or a leak.)
• Did it slowly get weaker over weeks? (Could be dust or a dying battery.)
• Did it stop right after someone plugged in a big freezer? (Overload.)

What should you check when the system is completely dead?

If the house has no power at all, start at the “brain” of the system, the inverter.

1. Check the screen: Most modern inverters show an error code (like E01 or F05). Look up the code in the manual.
2. Check for a tripped breaker: Look at the distribution box. Often, a “fault” is just a circuit breaker that flipped “OFF” because of a power surge. Flipping it back may solve the problem.
3. Check for blown fuses: If a fuse has melted, the “bridge” for electricity is broken. Find out why it blew (usually an overload) before replacing it.

Safety rule: Never replace a fuse with a piece of copper wire. This is a fire hazard. Always use a fuse with the same amp rating.

How do you troubleshoot the solar array (DC side)?

If the batteries are not charging but the sun is bright, the problem is on the roof. There are two ways to test.

• Visual inspection: Look for “hot spots” (brown burn marks) on the panels. This happens if a cell is cracked.
• Using the multimeter: Disconnect the string of panels and measure the voltage.
  1. If you expect 100V but see 0V, there is a broken wire or a loose connection in a junction box.
  2. If you see 40V, one of the panels in the string might be faulty or shaded.

How do you recognise a bad battery?

Batteries are usually the first thing to fail in a solar system. Look for these signs:

1. Fast charge and fast discharge: If the battery voltage jumps to “Full” after only 10 minutes of sun, but dies 5 minutes after the lights come on at night, the battery is sulphated or dead.
2. Swelling: If the sides of the battery look bulging or “pregnant,” it has been overcharged or exposed to too much heat. Warning: Swollen batteries can be dangerous. Disconnect them immediately.
3. Low voltage: Use your multimeter. A “12V” battery that reads 10V even after a day of sun is likely damaged beyond repair.

How do you replace components safely?

When you find a part that is truly broken, switch off the system in the correct order before you replace it.

The “power down” sequence

1. Turn off the AC output (load).
2. Turn off the PV input (panels).
3. Turn off the battery switch.

In short, work from the house back to the batteries.

Replacing a battery

• Always disconnect the negative (-) cable first.
• When installing the new battery, connect the positive (+) cable first. (Think: “Positive is the first to arrive, last to leave.”)

Final check

After replacing a part, do not walk away. Stay for 15 minutes. Check whether the connections are getting hot, and make sure the inverter screen shows that power is flowing again.

Evaluation

1. Write down the path of power in a solar PV system.
2. Give three checks to make when a house has no power at all.
3. Why must you never replace a fuse with copper wire?
4. A string of panels should read 100V but reads 0V. What are the likely causes?
5. State the order for turning off a PV system, and the cable to disconnect first when removing a battery.

Assignment

A customer says the batteries are not charging although the sun is bright. Write a short troubleshooting plan that says what you would inspect, what you would measure with the multimeter, and what the readings would tell you.