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Mercury 5 x 20mm F6.3A Quick Blow Fuses - 250V

£149
The RRP is the manufacturer's recommended retail price of the item.
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Description

The Mercury F6.3A is a 5 x 20mm quick blow cartridge fuse with a 250V rating and a 6.3A breaking threshold. The glass body with nickel-plated brass end caps houses a fine-gauge wire that melts within milliseconds when current exceeds the rated 6.3A, disconnecting the circuit before downstream components overheat or fail.

Designed for equipment protection in AV amplifiers, powered speakers, DJ mixers, lighting controllers, and other mains-powered audio and electrical gear where rapid fault isolation is critical, the quick blow construction prioritises speed over inrush tolerance. This makes the fuse suitable for resistive loads and circuits where startup current spikes do not exceed the 6.3A threshold. For circuits with higher inrush (motors, transformers, capacitive PSUs), a time-delay or slow-blow fuse may be more appropriate.

The 5 x 20mm dimension is an international standard IEC format, making these fuses compatible with the majority of UK and European equipment using cartridge-style fuse holders. The glass body allows visual inspection of the internal wire, so a blown fuse can be identified without a continuity meter. Each fuse weighs approximately 1g and the nickel-plated brass caps provide corrosion resistance and reliable contact within spring-loaded holders.

Frequently Asked

What does 'quick blow' mean?

Quick blow (also called fast-acting or F-type) means the fuse responds to overcurrent within milliseconds. When current exceeds 6.3A, the internal wire melts almost instantly, cutting power to protect downstream components. This differs from slow-blow or time-delay fuses, which tolerate brief current spikes without breaking.

What equipment uses 5 x 20mm fuses?

The 5 x 20mm format is standard in audio amplifiers, DJ equipment, powered speakers, lighting controllers, bench power supplies, and many mains-powered electrical devices. Check your equipment's fuse holder or manual to confirm the required size and rating before replacing.

Can I use this to replace a 5A or 10A fuse?

No. Fuse ratings must match the equipment specification. Using a 6.3A fuse in a circuit designed for 5A risks under-protection; using it in place of a 10A fuse means the fuse will blow prematurely under normal load. Always replace with the exact amperage rating specified by the manufacturer.

How do I know if the fuse has blown?

The glass body allows visual inspection. A blown fuse shows a broken or discoloured internal wire, and the glass may be blackened by the arc. If the wire appears intact and continuous, test with a multimeter in continuity mode to confirm.

Shipping & Returns

Free worldwide delivery

Free worldwide delivery on all orders over £99. International orders for third-party brand products may be subject to an additional courier surcharge based on volumetric weight, particularly on larger lighting fixtures — if a surcharge applies, our team will email you with the amount before dispatch and you can proceed or cancel for a full refund. See full delivery terms.

Returns

30-day returns window from delivery. As all our products are electrical or lighting goods, returned items must be inspected and recertified by a qualified electrician before resale — the cost of this inspection (25–40% of the item value) is deducted from your refund. Customers pay return shipping. Made-to-order, special-order and clearance items cannot be returned. See full returns policy.

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    Description

    The Mercury F6.3A is a 5 x 20mm quick blow cartridge fuse with a 250V rating and a 6.3A breaking threshold. The glass body with nickel-plated brass end caps houses a fine-gauge wire that melts within milliseconds when current exceeds the rated 6.3A, disconnecting the circuit before downstream components overheat or fail.

    Designed for equipment protection in AV amplifiers, powered speakers, DJ mixers, lighting controllers, and other mains-powered audio and electrical gear where rapid fault isolation is critical, the quick blow construction prioritises speed over inrush tolerance. This makes the fuse suitable for resistive loads and circuits where startup current spikes do not exceed the 6.3A threshold. For circuits with higher inrush (motors, transformers, capacitive PSUs), a time-delay or slow-blow fuse may be more appropriate.

    The 5 x 20mm dimension is an international standard IEC format, making these fuses compatible with the majority of UK and European equipment using cartridge-style fuse holders. The glass body allows visual inspection of the internal wire, so a blown fuse can be identified without a continuity meter. Each fuse weighs approximately 1g and the nickel-plated brass caps provide corrosion resistance and reliable contact within spring-loaded holders.

    Frequently Asked

    What does 'quick blow' mean?

    Quick blow (also called fast-acting or F-type) means the fuse responds to overcurrent within milliseconds. When current exceeds 6.3A, the internal wire melts almost instantly, cutting power to protect downstream components. This differs from slow-blow or time-delay fuses, which tolerate brief current spikes without breaking.

    What equipment uses 5 x 20mm fuses?

    The 5 x 20mm format is standard in audio amplifiers, DJ equipment, powered speakers, lighting controllers, bench power supplies, and many mains-powered electrical devices. Check your equipment's fuse holder or manual to confirm the required size and rating before replacing.

    Can I use this to replace a 5A or 10A fuse?

    No. Fuse ratings must match the equipment specification. Using a 6.3A fuse in a circuit designed for 5A risks under-protection; using it in place of a 10A fuse means the fuse will blow prematurely under normal load. Always replace with the exact amperage rating specified by the manufacturer.

    How do I know if the fuse has blown?

    The glass body allows visual inspection. A blown fuse shows a broken or discoloured internal wire, and the glass may be blackened by the arc. If the wire appears intact and continuous, test with a multimeter in continuity mode to confirm.

    Shipping & Returns

    Free worldwide delivery

    Free worldwide delivery on all orders over £99. International orders for third-party brand products may be subject to an additional courier surcharge based on volumetric weight, particularly on larger lighting fixtures — if a surcharge applies, our team will email you with the amount before dispatch and you can proceed or cancel for a full refund. See full delivery terms.

    Returns

    30-day returns window from delivery. As all our products are electrical or lighting goods, returned items must be inspected and recertified by a qualified electrician before resale — the cost of this inspection (25–40% of the item value) is deducted from your refund. Customers pay return shipping. Made-to-order, special-order and clearance items cannot be returned. See full returns policy.