Fuses perform the same function as a breaker, except when a
fuse blows, it has to be replaced.
There are cartridge fuses and screw-in fuses. Cartridges
look kind of like a shotgun shell. They mount in a little rack that pulls in
and out of a bracket Screw-in fuses screw in and out like light bulbs. Some
have a glass window on top and metal threads on bottom. A fuse blows; its internal metal strip breaks
and the window may get discolored. Be sure to replace a fuse with the exact
same amperage-rated fuse. Fifteen and 20 amp fuses are the most common size
ratings. Some fuses have a smaller screw base and are called "non-tamper
able, type-S" fuses. The threads vary in size so they can't be accidentally
replaced by another type. When you install a fuse, screw it in snug, then give
an extra 1/4-turn to make a solid connection. Other fuses are rated as
"slow-blow" or "time delay." They take a little longer to
blow and are made to withstand short, extra surges of power -- like a motor
starting. When buying replacements, be sure to get the right fuse types. It's
also a good idea to get a couple extra fuses of each type to keep on hand when
working on circuits.
