Selecting the correct breakers and fuses for your solar installation is one of the most important steps to protect your batteries, inverter, charge controller, and wiring from fire hazards, short circuits, and overloads.

Unfortunately, many solar systems in Nigeria and across Africa fail because the installer picked the wrong protection devices—or used none at all.

This guide explains exactly how to choose the right breaker or fuse size for every part of your solar system:

• Between panels and charge controller
• Between charge controller and batteries
• Between batteries and inverter

Let’s break it down in a simple, practical way.

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Why Breakers and Fuses Are Important in Solar Systems

They help prevent:

• Overcurrent (too much current causing heat)
• Short circuits
• Fire outbreaks
• Battery and inverter damage
• Melted cables
• System shutdown during faults

Without proper breakers, a single wiring mistake or surge can destroy your entire setup instantly.

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1. Selecting Breakers for Solar Panels → Charge Controller

Step 1: Find the panel’s short-circuit current (Isc)

This value is printed at the back of the panel.

Example:

• A 550W panel has an Isc of 13A.

Step 2: Add 25% safety margin

13A × 1.25 = 16.25A

Step 3: Select the nearest breaker size

Use a 20A DC breaker.

String Rules:

• Panels in series: Use the same Isc as one panel.
• Panels in parallel: Multiply Isc by number of strings.

Example:
3 strings of 550W in parallel:
13A × 3 = 39A
39A × 1.25 = 48.75A → Use a 50A DC breaker.

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2. Breaker Between Charge Controller → Battery Bank

Use the charge controller’s maximum output current rating.

Example:

A 60A MPPT produces a maximum of 60A.

60A × 1.25 = 75A

→ Use a 70A or 80A DC breaker.

NOTE:

Never use an AC breaker here.
Always use DC-rated MC4, MCB, or rotary breakers.

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3. Breaker Between Battery Bank → Inverter

This is the most important breaker in the system.

Formula:

Breaker Size = Inverter Power (W) ÷ Battery Voltage ÷ 0.8

The 0.8 factor accounts for efficiency losses.

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Example 1: 1.5kVA inverter (24V battery)

1500W ÷ 24V ÷ 0.8 = 78A

→ Use an 80A or 100A DC breaker.

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Example 2: 3.5kVA inverter (24V)

3500W ÷ 24V ÷ 0.8 = 182A

→ Use a 200A DC breaker.

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Example 3: 5kVA inverter (48V)

5000W ÷ 48V ÷ 0.8 = 130A

→ Use a 150A DC breaker.

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4. Breakers for AC Output (Inverter → House)

Use standard AC MCBs based on load.

• 1.5mm cable → 10A breaker
• 2.5mm cable → 16A/20A breaker
• 4mm cable → 32A breaker

This protects the house wiring from overloads.

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5. Should You Use Breakers or Fuses?

✔ Use breakers when:

• You want easy reset
• For panels, batteries, and inverter main line
• For frequently accessed areas
• For professional installations

✔ Use fuses when:

• Budget is low
• DC breakers are unavailable
• You want protection for individual strings
• You need fast-blow protection (for sensitive devices)

Both are acceptable as long as you size them correctly.

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6. Best Type of Breakers to Use in Solar Systems

DC Breaker Recommended Types:

• MC4 in-line breakers
• DC rotary isolators
• DC MCBs (63V DC, 125V DC, 250V DC, 500V DC depending on system)
• NH DC fuses for high current setups

Never Use These:

• Normal AC breakers on DC lines
• Chinese “no-label” breakers
• Breakers without Isc ratings

Always buy solar-rated breakers with clear voltage and current rating.

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7. Summary Table: Recommended Breaker Sizes

Location	Calculation Basis	Typical Breaker
Panels → MPPT	Isc × 1.25	15A–50A DC
MPPT → Battery	Controller max output × 1.25	60A–100A DC
Battery → Inverter	W ÷ V ÷ 0.8	80A–200A DC
Inverter → AC Loads	Cable size	10A–32A AC

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Final Advice

Always oversize breakers slightly but never oversize cables.
Breakers should trip before a fire starts—not after something has melted.

If unsure, always consult a certified solar technician for safety.