ACV Slow-blow fuse 5476C011

The ACV Slow-blow fuse 5476C011 is a 12.5 A, 6.3 mm fuse with a slow-blow (time-lag) characteristic, designed for use in ACV boilers. It fits models including the HeatMaster 45 TC Smart ME Prestige Solo MK2 and HeatMaster 45 TC. This fuse protects control boards, ignition transformers, and low-voltage circuits from overcurrent and short circuits. Its slow-blow action tolerates brief inrush currents during start-up, preventing nuisance trips.

When selecting a fuse of this type, match the physical dimensions (e.g., 6.3 x 32 mm), current rating, and speed (slow-blow) to the original. Verify the voltage rating on the fuse body is at least the circuit voltage. Never use a higher current rating or faster speed, as this compromises protection. Always investigate the cause of a blown fuse before replacement.

A blown fuse of this kind typically results from a shorted component or failing transformer, causing the boiler to lose power to protected circuits. Symptoms include the boiler failing to start, control board not powering up, or ignition transformer not operating. Check the fuse continuity and inspect for visible damage or discoloration.