Fuses play a critical role in electrical systems, protecting against potentially dangerous overloads and short circuits. From home wiring to large industrial equipment, the right type of fuse helps safeguard electrical circuits and devices. Here is an in-depth look at the major fuse types used across the UK.
Table of Contents
What Are Fuses and How Do They Work?
A fuse is a safety component designed to interrupt electrical flow when a circuit is overloaded. It contains a thin wire or strip of metal that melts and breaks if current exceeds the fuse’s rated amperage, thereby cutting power to the circuit.
Once a fuse blows, it must be replaced with a new one for the circuit to function again. Replacing blown fuses with the proper type and rating restores protection against overloads.
Fuses are available in a range of shapes, sizes, voltage/amperage ratings, and response times to suit various applications. But they all function on the same basic principle of using a sacrificial piece of metal engineered to melt under excessive current. This self-destructing action helps prevent damage higher up the electrical chain.
Common fuse applications include:
- J type fuses in control panels and equipment
- Cartridge fuses protecting motors and large appliances
- Blade fuses in automotive applications
- Plug fuses built into appliance plugs
- Wired fuses on PCB assemblies and electronic devices
- High voltage fuses on transmission lines
Fuse Standards and Markings
All fuses sold in the UK must adhere to British and/or European standards that indicate:
- Rated voltage (V)
- Rated current (A)
- Type designation per IEC 60269 or BS 88
- Manufacturer/brand identification
- Approval marks like ASTA or BEAB
Fuse ratings are provided in amps, indicating the maximum current they can safely sustain. Standard values are 2A, 3A, 5A, 10A, 15A, 20A, 25A, 30A, 45A, 60A. But other specialty ratings exist too.
Voltage ratings for commonly used fuses in UK mains electrical systems are 250V or 500V.
Proper fuse selection means choosing a type and amp rating suitable for the protected circuit. Amp rating should be slightly higher than maximum expected current draw. And voltage rating must be equal to or greater than supply voltage.
Fuse Types Used in the UK
There are numerous fuse designs and formats developed over the decades. But these are among the most prevalent fuse types used in UK electrical infrastructure, equipment and appliances:
BS 1362 Plug Fuses
These small cylindrical fuses are built into the plugs of portable appliances like kettles, laptop chargers and electric shavers. They fit into a fuse holder compartment in the plug between the live and neutral prongs. Available ratings are 1A, 2A, 3A, 5A, 10A, and 13A.
BS 1363 Fuse Links
Also called in-line fuses or kitkat fuses, these slender cylindrical fuses have metal caps at both ends allowing wire connection. They are used to protect cables, appliances and electronic devices, and are available from 2A to 45A. Common ratings are 3A, 13A and 15A.
Cartridge Fuses
Cartridge fuses feature a cylindrical body capped with metal contact ferrules or blades for screw-in mounting. Ratings range from 15A to 200A. They are used in control panels, motors, pumps, appliances and industrial equipment. Popular sub-types include:
- Class CC – Fast-acting for general purpose circuits up to 60A
- Class G – Time-delay for motors starting up to 16A
- Class H – Time-delay for motors starting up to 200A
- Class K – Very fast-acting for safety circuits up to 60A
- Class R – Time-delay for motors starting up to 200A
High Rupturing Capacity (HRC) Fuses
These heavy duty cylindrical fuses are rated from 60A to 800A+ and are designed to safely break high short circuit currents in industrial applications down to 1000V. They feature glass tubes or ceramic bodies to extinguish the intense arcing when interrupting dangerous overcurrents.
Blade/Bolted Fuse Links
Consisting of a flat metal strip with bolted end caps, these allow easy large cable connections up to 600A. They are used for workshop equipment, generators, distribution panels, commercial HVAC and other heavy load applications. J, RK1 and RK5 types are common.
Diazed Fuse Links
Similar to blade fuses but with a notch that fits specialized diazed fuse carriers. This allows tool-free installation/replacement. Common for fused disconnect switches and motor control up to 690V and 1200A.
Switch Fuse Units
These combine a fuse link with a switch in a single housing. They allow combined isolation and protection in one device. Used in distribution boards and control panels up to 800A.
MCB Fuse Links
Miniature circuit breaker (MCB) fuses provide adjustable magnetic overcurrent protection in a compact housing. Used in control panels, machinery and switchboards up to 125A. Combination MCB/fuses also exist.
Semiconductor Fuses
Designed to protect sensitive electronic equipment, these very fast acting fuses can clear overloads and faults in less than 0.003 seconds. Protect voltage sensitive devices down to 125VDC.
Battery Fuses
Provide short circuit protection for automotive and deep cycle batteries. Available in a variety of sizes and voltage ratings. Some feature built-in voltage/current meters.
Fuse Operation and Standards
Fuses are designed to operate within strict standards to properly protect circuits across typical applications. Key operating parameters include:
Voltage Rating
- Must equal or exceed supply voltage
- Common values: 32V, 63V, 125V, 250V, 480V, 600V, 1000V
Current Rating
- Amp rating slightly above max expected load
- Common values: 0.5A, 1A, 2A, 3A, 4A, 5A, 7A, 10A, 15A, 20A, 25A, 30A, 40A, 50A, 63A, 80A, 100A, 125A
Interrupting Rating
- Maximum current that can be safely interrupted
- 25kA, 50kA, 100kA+ common for high capacity fuses
Speed/Operating Time
- Time from overload detection until fuse blows
- Very Fast = <0.1s, Fast = <2s, Time Delay = 2-120s
Breaking Capacity
- Max current fuse can break without arc flash damage
- Ranges from 10kA for electronics to 200kA+ for high power
Melting I2t Value
- Energy needed to melt fuse element, dictating time/current blow characteristics
Certifications
- ASTA, BEAB, CSA, UL, IEC – verify compliance with standards
Fuse selection depends on matching electrical characteristics and performance to your circuit requirements.
Fuse Holders, Carriers and Bases
To safely install and access fuses, a range of compatible fuse holders exist:
- Fuse holders – Enclose end cap type fuses in water-tight plastic housing with screw terminals
- Open style carriers – Clamp to open end cap fuses for mounting on rails
- Fused rotary disconnects – Allow disconnecting power and accessing fuses with handle
- Fuse bases – Hold cartridge fuses and have screw terminals for wire connections
- Diazed fuse carriers – Snap-in style holders specific for diazed fuses
- Fuse blocks – Hold multiple cartridge fuses and include protective cover
- Fuse cutouts – Hinged enclosure for blade type fuses on poles and transformers
- Fuse plugs – Accept BS 1362 cylindrical plug fuses
Proper fuse holders securely enclose and protect fuses while allowing safe fuse access and replacement.
Why Are Fuses Important for Electrical Safety?
Fuses play several crucial protective roles that make them indispensable safety components:
Overload Protection
- Melts fuse element if current exceeds rating for sustained time
- Prevents motor/transformer/wire overheating damage
Short Circuit Protection
- Blows quickly if short circuit sensed
- Stops dangerous high currents from arcs/fire
Voltage Spike Protection
- Opens rapidly in reaction to voltage spike
- Protects sensitive electronics from damage
Fault Protection
- Clears faults like arc faults and ground faults
- Prevents electrocution/shock risks
Surge Protection
- Sacrificially burn out from sudden surges
- Saves rest of electrical system from harm
Circuit Isolation
- Blown fuse fully isolates protected circuit
- Allows safe maintenance/repair of devices and wiring
Choosing fuses with characteristics matched to your specific electrical system and components helps maintain safety and uptime.
Fuse Troubleshooting Tips
When a fuse blows, it is typically due to an underlying issue needing correction rather than a faulty fuse. Some troubleshooting tips include:
- Identify and repair the failure or fault before replacing fuse
- Replace with same type and rating as original fuse
- If fuse keeps blowing, the circuit likely needs re-evaluation
- For consistent blown fuses, check for loose wiring, overloaded circuits, mismatched loads and ground faults
- Use a multimeter to check for abnormal voltage/current readings
- Test fuse with continuity checker or multimeter to confirm open circuit
- Eliminate added load on circuit and see if issue stops
- Upgrade to a higher rated fuse if demanded load exceeds fuse capacity
Replacing a blown fuse without addressing the root cause will result in more blown fuses or potentially an electrical fire if the circuit is overloaded.
Consult the Experts
Choosing the optimal fuse type for your specific application requires an in-depth understanding of fuse capabilities and electrical system needs. The professionals at Cable Services Ltd have the expertise to recommend the ideal fuses and accessories to safely protect your critical equipment and facility electrical networks. With decades of experience and advanced technical knowledge, they provide valued guidance you can trust.
Rely on Cable Services Ltd for all your fuse supply, replacement and protection needs. Their extensive inventory includes fuse links, holders, bases and other fuse accessories from leading brands meeting UK and European standards. Receive knowledgeable support to keep your electrical systems properly protected 24/7.
