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Mercury 5 x 20mm T6.3A Slow Blow Fuse - 250V Time-Delay

£149
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Description

The Mercury T6.3A is a slow blow fuse in a 5 x 20mm glass cartridge body with nickel-plated brass end caps, rated at 250V AC. The time-delay element inside the glass tube allows brief inrush currents to pass without blowing while still protecting the circuit from sustained overloads above 6.3A.

Designed for equipment with moderate startup currents such as small motors, power supplies, transformers and audio amplifiers, the slow blow characteristic prevents nuisance blowing during the initial energisation period when inductive loads briefly draw several times their running current. Once the equipment is running and current stabilises below the 6.3A rating, the fuse holds indefinitely. If a fault causes sustained overcurrent, the fuse element melts and breaks the circuit.

The 5 x 20mm dimension is a standard cartridge fuse size found in panel-mount fuseholders, inline cable fuseholders and PCB-mount fuse clips across consumer electronics, industrial control panels and lighting equipment. The glass body allows visual inspection of the fuse element — a broken or discoloured element indicates the fuse has blown. These fuses comply with IEC 60127 safety standards for low-voltage fuses in equipment.

Frequently Asked

What does 'slow blow' mean?

Slow blow (also called time-delay or anti-surge) fuses are designed to tolerate brief current spikes above the rated value without blowing, while still protecting against sustained overloads. This is useful for equipment with inductive loads like motors or transformers that draw several times their normal current for a fraction of a second when first powered on.

Can I replace a fast-blow fuse with a slow blow?

Not without understanding the circuit requirements. Fast-blow fuses provide tighter overcurrent protection and are specified where immediate cutoff is needed for sensitive components. Replacing a fast-blow with a slow blow may allow damaging currents to persist longer than the circuit was designed for. Replace fuses with the same rating and time-delay characteristic unless you know the circuit can safely accept the change.

What does T6.3A mean?

T indicates time-delay (slow blow) characteristic. 6.3A is the continuous current rating — the maximum current the fuse can carry indefinitely without melting. The fuse will tolerate brief spikes above 6.3A but will blow if overcurrent is sustained.

Are these suitable for DC circuits?

These fuses are rated at 250V AC. Using them in DC circuits is possible but the DC voltage rating is lower than the AC rating due to arc suppression differences. For DC applications consult the manufacturer datasheet to confirm the appropriate voltage deration.

Shipping & Returns

Delivery UK delivery is £14.99, and delivery is free on all orders of £99 or more, in the UK and internationally.

Returns If you change your mind, you have 14 days from delivery to tell us, and a further 14 days to send the goods back. Return postage for a change-of-mind return is paid by you. Change-of-mind returns are subject to an inspection and handling deduction. See our full returns policy.

To arrange a return, call us on 020 8149 5199 or use our contact page.

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    Description

    The Mercury T6.3A is a slow blow fuse in a 5 x 20mm glass cartridge body with nickel-plated brass end caps, rated at 250V AC. The time-delay element inside the glass tube allows brief inrush currents to pass without blowing while still protecting the circuit from sustained overloads above 6.3A.

    Designed for equipment with moderate startup currents such as small motors, power supplies, transformers and audio amplifiers, the slow blow characteristic prevents nuisance blowing during the initial energisation period when inductive loads briefly draw several times their running current. Once the equipment is running and current stabilises below the 6.3A rating, the fuse holds indefinitely. If a fault causes sustained overcurrent, the fuse element melts and breaks the circuit.

    The 5 x 20mm dimension is a standard cartridge fuse size found in panel-mount fuseholders, inline cable fuseholders and PCB-mount fuse clips across consumer electronics, industrial control panels and lighting equipment. The glass body allows visual inspection of the fuse element — a broken or discoloured element indicates the fuse has blown. These fuses comply with IEC 60127 safety standards for low-voltage fuses in equipment.

    Frequently Asked

    What does 'slow blow' mean?

    Slow blow (also called time-delay or anti-surge) fuses are designed to tolerate brief current spikes above the rated value without blowing, while still protecting against sustained overloads. This is useful for equipment with inductive loads like motors or transformers that draw several times their normal current for a fraction of a second when first powered on.

    Can I replace a fast-blow fuse with a slow blow?

    Not without understanding the circuit requirements. Fast-blow fuses provide tighter overcurrent protection and are specified where immediate cutoff is needed for sensitive components. Replacing a fast-blow with a slow blow may allow damaging currents to persist longer than the circuit was designed for. Replace fuses with the same rating and time-delay characteristic unless you know the circuit can safely accept the change.

    What does T6.3A mean?

    T indicates time-delay (slow blow) characteristic. 6.3A is the continuous current rating — the maximum current the fuse can carry indefinitely without melting. The fuse will tolerate brief spikes above 6.3A but will blow if overcurrent is sustained.

    Are these suitable for DC circuits?

    These fuses are rated at 250V AC. Using them in DC circuits is possible but the DC voltage rating is lower than the AC rating due to arc suppression differences. For DC applications consult the manufacturer datasheet to confirm the appropriate voltage deration.

    Shipping & Returns

    Delivery UK delivery is £14.99, and delivery is free on all orders of £99 or more, in the UK and internationally.

    Returns If you change your mind, you have 14 days from delivery to tell us, and a further 14 days to send the goods back. Return postage for a change-of-mind return is paid by you. Change-of-mind returns are subject to an inspection and handling deduction. See our full returns policy.

    To arrange a return, call us on 020 8149 5199 or use our contact page.