Cooper Bussmann MDQ-4 Cartridge Time Delay Fuse 4A

Product Description

The COOPER BUSSMANN MDQ-4 is a miniature cartridge time-delay fuse rated at 4 amps, designed to protect low-current circuits from sustained overloads without nuisance tripping on brief inrush surges. The glass body measures 1.25 inches in overall length and 0.25 inches in diameter, fitting standard mini fuse holders used across HVAC control circuits, small appliances, and light commercial equipment. It uses a dual-element construction that separates the time-delay function from the fast-blow overcurrent response, giving equipment the startup current it needs while still providing reliable short-circuit protection. Licensed electricians and HVAC technicians are the primary installers.

The MDQ-4 is suited for residential and light commercial applications where a 1/4-inch by 1-1/4-inch cartridge fuse position is specified. Common installations include HVAC control boards, transformer secondary circuits, and instrumentation panels that require a time-delay characteristic to accommodate motor or transformer inrush. The glass body allows visual inspection of the element without a fuse tester, which speeds troubleshooting in the field. This fuse is sold individually but must be ordered in multiples of 5.

Key Features

• Time-delay dual-element design tolerates inrush current without nuisance opens
• 4 amp rating suits low-current control and instrumentation circuits
• Glass body allows quick visual continuity check without instruments
• Mini cartridge form factor: 1.25 inches OAL, 0.25 inches diameter
• UL Listed 248-14 and CSA Class 1422-01 Component Accepted
• UNSPSC Code 39121605 for procurement and catalog alignment

Compatibility

Designed as an OEM-style replacement for miniature cartridge fuse positions requiring a 1/4-inch by 1-1/4-inch time-delay glass fuse at 4 amps.

Installation Notes

Installation should be performed by a licensed electrician or qualified HVAC technician following applicable NEC requirements. Always de-energize and lock out the circuit before replacing a fuse. Confirm the replacement fuse amperage and time-delay rating match the equipment nameplate or schematic before reinstalling. Never substitute a fast-acting fuse where a time-delay type is specified, as nuisance opens or equipment damage may result.