Consumer protection

Circuit protection for loads on board

Every cable in the onboard system is fused according to its cross-section. In this way fuses and circuit breakers protect cables and loads against short circuit, overload and cable fire, in compliance with ISO 13297.

In brief: The main fuse sits no more than 17.8 cm from the positive post (ABYC E-11), ideally directly on the post. Behind it, every circuit is fused individually at the switch panel or distributor, matched to its cross-section.

What ISO 13297 requires for fusing

• All cables leaving the battery are fused according to their cross-section.
• The main fuse sits as close as possible to the battery; the section before it is unprotected and is routed short and mechanically protected.
• Downstream circuits with a smaller cross-section get their own fuses at the switch panel or distributor.

How each load is protected

Circuit breaker, strip fuse or bolt-down fuse?

Circuit breakers can be reset after tripping and are suitable for safety-relevant loads and the feed to the switch panel. Strip fuses are proven and inexpensive. SHB bolt-down fuses are made for high currents directly at the post. With lithium batteries, only SHB or Class T fuses are permitted at the post.

The cable configurator calculates which fuse suits your cross-section. All designs compared: Fuses on boats.

Frequently asked questions

Where is the main fuse installed?

No more than 17.8 cm from the positive post, ideally directly on the post. This keeps the unprotected cable section as short as possible.

How is the right fuse size determined?

By the cross-section of the cable: the rated current is above the continuous current of the load and below the current-carrying capacity of the cable. The fuse protects the cable, not the device.

Do bilge pumps need separate fusing?

Yes. Bilge pumps and other safety-relevant loads are connected directly to the battery and have their own fuse so that they also work with the main switch off.

Does ISO 13297 also apply to motorhomes?

The standard applies to small craft. Its principles – main fuse close to the battery and every cable fused according to its cross-section – apply equally to motorhomes and expedition vehicles with 12 V or 24 V systems.