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Mercury 5 x 20mm T630mA Slow Blow Fuses - 250V

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

The Mercury T630mA is a 5 x 20mm slow blow fuse rated at 630mA and 250V, designed to protect low-current electronics that experience brief startup surges without blowing on normal transient spikes. The time-delay element inside the glass body allows short bursts of overcurrent to pass while still interrupting sustained faults within milliseconds.

Slow blow fuses are used in power supplies, audio amplifiers, LED drivers, motor controllers and precision measurement equipment where inrush current on power-up can be several times the normal running current. A standard fast-acting fuse would blow during normal startup in these circuits, while a slow blow fuse rides out the surge and protects against genuine faults. The 5 x 20mm size is an IEC standard fitting common in Euro-style equipment and many mains-powered devices.

Each fuse has nickel-plated brass end caps and a clear glass body, allowing visual inspection of the filament to confirm whether the fuse has blown. The 630mA rating suits circuits drawing up to approximately 0.5A continuous, with headroom to tolerate brief peaks during switching or motor starting. The 250V AC rating covers standard UK mains-derived supplies after transformer or rectification.

Frequently Asked

What does 'slow blow' mean?

A slow blow (or time-delay) fuse tolerates brief overcurrent surges without blowing, but will still interrupt sustained faults. This makes them suitable for circuits with high startup current, like transformers and motors, where a fast-acting fuse would blow during normal power-up.

What equipment uses 5 x 20mm fuses?

This size is common in mains-powered audio equipment, small power supplies, LED drivers, older test equipment, and many European-designed devices. Check your equipment's manual or the blown fuse's markings to confirm the size and rating needed.

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

No. Fuse type (fast or slow) is chosen to match the protected circuit's characteristics. Using the wrong type can result in nuisance blowing (fast in place of slow) or delayed protection during faults (slow in place of fast). Always replace with the same type specified by the equipment manufacturer.

Are these sold individually or in packs?

Check the product listing above for pack quantity. Mercury fuses are typically sold in packs of 10 or more for trade and maintenance use.

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 T630mA is a 5 x 20mm slow blow fuse rated at 630mA and 250V, designed to protect low-current electronics that experience brief startup surges without blowing on normal transient spikes. The time-delay element inside the glass body allows short bursts of overcurrent to pass while still interrupting sustained faults within milliseconds.

    Slow blow fuses are used in power supplies, audio amplifiers, LED drivers, motor controllers and precision measurement equipment where inrush current on power-up can be several times the normal running current. A standard fast-acting fuse would blow during normal startup in these circuits, while a slow blow fuse rides out the surge and protects against genuine faults. The 5 x 20mm size is an IEC standard fitting common in Euro-style equipment and many mains-powered devices.

    Each fuse has nickel-plated brass end caps and a clear glass body, allowing visual inspection of the filament to confirm whether the fuse has blown. The 630mA rating suits circuits drawing up to approximately 0.5A continuous, with headroom to tolerate brief peaks during switching or motor starting. The 250V AC rating covers standard UK mains-derived supplies after transformer or rectification.

    Frequently Asked

    What does 'slow blow' mean?

    A slow blow (or time-delay) fuse tolerates brief overcurrent surges without blowing, but will still interrupt sustained faults. This makes them suitable for circuits with high startup current, like transformers and motors, where a fast-acting fuse would blow during normal power-up.

    What equipment uses 5 x 20mm fuses?

    This size is common in mains-powered audio equipment, small power supplies, LED drivers, older test equipment, and many European-designed devices. Check your equipment's manual or the blown fuse's markings to confirm the size and rating needed.

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

    No. Fuse type (fast or slow) is chosen to match the protected circuit's characteristics. Using the wrong type can result in nuisance blowing (fast in place of slow) or delayed protection during faults (slow in place of fast). Always replace with the same type specified by the equipment manufacturer.

    Are these sold individually or in packs?

    Check the product listing above for pack quantity. Mercury fuses are typically sold in packs of 10 or more for trade and maintenance use.

    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.