Choosing or replacing a fuse: check more than the amp rating
A fuse is intended to protect wiring and equipment when a fault current occurs. Never bridge a blown fuse. Find the cause first and replace it only with a type assessed for the same application.
Check these seven points
- Normal current and inrush. Determine operating current and motor, transformer or capacitor inrush. Do not select from one universal percentage.
- Time-current characteristic. Match fast, time-delay or another characteristic to the datasheet curve and to what the load and wiring can withstand.
- Voltage rating and AC/DC. The fuse voltage rating must cover the circuit voltage. Verify whether the exact type is rated for AC, DC or both.
- Interrupting rating. Breaking capacity must suit the prospective fault current at the fuse.
- Temperature and derating. Ambient temperature, holder, mounting and continuous load affect current-carrying capability.
- Size, holder and approvals. Check dimensions, termination, holder rating and applicable standards or approvals.
- Exact replacement. Follow the equipment manufacturer's instructions and match current, voltage, characteristic, breaking capacity, size and approvals.
An RCD and a fuse have different jobs
A fuse or circuit breaker protects against overcurrent and short circuit. An RCD detects residual current and can provide additional protection against electric shock. Neither replaces the other.
The required RCD and its type depend on the installation, circuit, country and current standard. For fixed mains installations, use the applicable installation rules and qualified electrical expertise. This article is not installation approval.
Search the fuse and fuse-holder results only after checking the original part number, equipment instructions and full datasheet.
