Fuse Size Calculator: How to Choose the Right Fuse for Your Campervan

Angela Devaney

Selecting the correct fuse size is critical when designing or upgrading your campervan’s electrical system. The wrong fuse can cause serious issues like overheating, damaged devices, or even fire hazards. To help simplify the process, we’ve developed a Fuse Size Calculator that takes the guesswork out and ensures your system is properly protected.

Why Fuse Size is Important

Fuses are the first line of defence in protecting your electrical system. They stop the current if it exceeds safe limits, preventing damage. In a campervan, where multiple devices share a power system, this is even more essential.

If your fuse is too small, it will blow too often, causing disruption. Too large, and it won’t blow when needed, putting your system at risk.

Read more: The role of fuses & breakers in a campervan’s electrical system

Fuse Size Calculator

Enter your device’s current rating, the circuit’s wire size and your location to calculate the appropriate fuse sizes

Approximate Fuse Sizes

How the Fuse Size Calculator Works

Our Fuse Size Calculator makes choosing the right fuse simple. You just need to enter your device amps, select the wire size, and choose your location. The calculator provides three fuse sizes:

  1. Minimum Fuse Size – The smallest fuse that can handle the device's current safely without blowing unnecessarily.
  2. Recommended Fuse Size – Provides a 25% margin for minor fluctuations in current but still protects your wiring.
  3. Maximum Fuse Size – Based on your device, wire size and location, ensuring your wiring can handle the current without overheating. If the Maximum Fuse Size is smaller than the Recommended Fuse Size, your wire size is likely too small for the device.

🔒 Maximum Fuse Size = Safety Limit

The Maximum Fuse Size provided by the calculator is the upper safety limit for your wiring. If your Recommended Fuse Size exceeds this, it’s a sign that your wire is too small. Upgrade to a thicker wire to ensure safety.

Calculate the correct wire gauge with our DC Wire Size Calculator.

Rounding: Why You Should Never Round Down

Sometimes, the exact size calculated may not be available, so rounding is necessary. It’s essential to understand how to round safely.

  • Rounding Up: It’s generally safer to round up to the next available fuse size, as long as this doesn’t exceed the Maximum Fuse Size. This ensures the fuse won’t blow unnecessarily while still offering protection.
  • Rounding Down: Do not round down. Rounding down can cause the fuse to blow under normal operation, leading to constant fuse replacements and unnecessary frustration.

❌ Avoid Rounding Down

Rounding down can cause your fuse to blow unnecessarily, even under normal conditions. Always round up to the next available size—but be sure not to exceed the Maximum Fuse Size.

Follow Manufacturer Guidelines

While our Fuse Size Calculator provides reliable recommendations, it’s important to always follow the manufacturer’s fuse size guidelines. Many devices come with specific fuse recommendations tailored to their operation.

🛠️ Manufacturer Recommendations First

Always follow the specific fuse size recommendations provided by the manufacturer. The calculator gives general guidance, but manufacturer recommendations are customised for your device’s safe operation.

Location-Specific Maximum Fuse Sizes

Different regions have varying standards for electrical systems. Our Fuse Size Calculator adjusts the Maximum Fuse Size according to these standards, ensuring your system is compliant no matter where you are—whether in the UK, Europe, US, Australia, or Canada.

🌍 Regional Safety Standards Matter

Electrical standards vary by region. Our calculator automatically adjusts the maximum fuse size based on your location, ensuring your system is safe and compliant whether you’re in the UK, Europe, US, Australia, or Canada.

How to Use the Fuse Size Calculator

  1. Enter Device Amps: Input the amount of current your device draws (usually found on the device label or in the manual).
  2. Select Wire Size: Choose the wire size (AWG or mm²) used in your campervan’s electrical system.
  3. Select Location: Choose your location to apply the correct regional standards for maximum fuse sizes.

Once the information is entered, the calculator provides the Minimum, Recommended, and Maximum fuse sizes, ensuring that your system remains protected.

Example:

If you’re using a fridge that draws 10 amps with 10 AWG wire in the UK, the calculator might suggest:

  • Minimum Fuse Size: 10A
  • Recommended Fuse Size: 13A (rounded up)
  • Maximum Fuse Size: 14A (based on UK standards for 10 AWG wire and not exceeding 40% of the device's current rating)

If the Recommended Fuse Size exceeds the Maximum Fuse Size, it’s a sign that your wire size is too small, and you’ll need to upgrade.

Why Correct Fuse Sizing is Essential

Using the wrong fuse size can lead to:

  • Frequent blown fuses: A fuse that’s too small will blow too often, even under normal usage.
  • Overheated wiring: A fuse that’s too large won’t blow when necessary, allowing wires to overheat and potentially cause fires.
  • Damaged devices: Fuses don’t just protect wires, they also protect devices from overcurrent damage.

Conclusion

Selecting the right fuse size for your campervan’s electrical system is critical for safety and reliability. Our Fuse Size Calculator makes the process easy, giving you precise recommendations based on your device amps, wire size, and location. Remember to round up, but not beyond the Maximum Fuse Size, and always follow manufacturer recommendations when provided.

Angela Devaney - Expert in RV & Campervan Electrics - Mowgli Adventures

Angela Devaney

Angela Devaney, a former IT project management professional, embarked on an adventurous journey of full-time travel, which included touring West Africa in a converted overland truck and converting an ex-military 4x4 Sprinter van into a camper for a five-year South American expedition. She now utilizes her hands-on experience to create practical van life advice as a full-time digital media producer, reaching over a million users annually through her YouTube channel, blog, and newsletter. Angela also lends her expertise as the editor-in-chief of the Campervan Electrics Handbook.

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