Shocksafe Cylindrical Vertical 5x20mm PCB Fuse Holder PTF-45 10 Amps 250 Volt With Screw Cap 10 mm Pin Spacing

Do I have bad fuses, or bad PCB fuse holders?

My fuse holder has melted, even though the fuse has not blown, does this mean my equipment is faulty and drawing too much current?

If the fuse itself has not blown but the fuse holder has melted, it indicates that the equipment is not drawing excessive current, rather that the fuse holder was making poor contact with the fuse. Heating in an electrical circuit is always caused by current flowing through a resistance. If there is significant resistance in the contact between fuse and fuse holder, current well below the fuse rating can cause enough heating to melt the fuse holder.

This heating may not always be immediate. Whilst the initial resistance may be lower and the initial heating may not be enough to melt the fuse holder, the heating can cause oxidation of the metal connections, leading to increased contact resistance. This accelerates the heating effect until there is an “avalanche” of rapidly increasing heating/increasing resistance, leading to what may appear to be a sudden failure even some time after installation.

The simple answer is- if the fuse has not blown the equipment is not drawing too much current.

Always use good quality fuses and fuse holders. Whilst the popular automotive blade type fuses and holders may be OK at lower currents, Eg 5-10A, for higher currents (20A or more) it is essential to use good quality fuses and fuse holders, for example “Maxifuse”, “Megafuse” or “MTA” Midi fuse style products.