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The Different Types of Fuses
Home » Electrical Supplies » Fuses » The Different Types of FusesWhile automobiles employ small blade fuses and certain instruments require sub-miniature fuses, most residential fuses are either plug fuses or cartridge fuses, and the difference is immediately noticeable.
• Plug Fuses: Plug fuses are short fuses that look somewhat like a mushroom. To insert a new plug fuse, simply hold the head of the fuse and screw the base into the fuse outlet, thus “plugging” the hole. Most plug fuses are designed for circuits rated for 125 volts or less; thus, in many buildings, they protect the lighting and wall outlets in buildings. In addition, plug fuses have a low maximum capacity for amps; often, they can only handle fifteen or twenty amps.
• Cartridge Fuses: Cartridge fuses can be several different lengths, but they are always cylindrical. They are useful in all types of buildings, and they can handle a larger electrical current than do plug fuses, so they are used for different circuits. Depending on the type of cartridge, these fuses work on circuits rated for 250 or 500 volts, and they have a capacity of approximately six hundred amps.
The second primary difference between fuses refers to the time it takes an electrical current to melt the metal element in the fuse. Time delay fuses (also known as slow blow or time lag fuses) take a long time to melt, so they will not trip on momentary overloads. These fuses conveniently protect against tripped fuses caused by items such as incandescent lamps that require a rush of electricity when you first turn them on. On the other hand, fast-acting (F) and very fast-acting (FF) fuses melt quickly, and are useful for protecting semiconductor devices and other sensitive items. Most residential fuses, however, should be time delay fuses.
Third, examine the breaking capacity of a fuse. The breaking capacity refers to the maximum current that the fuse can interrupt. Residential fuses usually have a breaking capacity of at least ten thousand amps, but larger power systems require a breaking capacity of two hundred thousand amps or more.
When you don’t know which type of fuse to buy, simply match the fuse you currently have to the fuses in the store. Your fuse box and your circuits are designed to match a particular type of fuse, and unless you consistently have problems with a certain fuse, you should continue using the same type. If, however, you have to choose between seemingly identical fuses, and only one of them refers to itself as “UL listed,” choose that one; Underwriters’ Laboratories (UL) has tested it for fire prevention.
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