How to Replace a Blown Plug or Cartridge Fuse
It is important to know which type of fuse you are replacing. A plug fuse is shaped like a short cylinder with a diameter that is slightly larger than a quarter. One end screws into the circuit like a light bulb, while the other is partially clear so you can determine the condition of the fuse. The partially clear end of a plug should be easily located when you open the circuit box. Most plugs service 120 V circuits and are rated for 15, 20, or 30 amps.
Cartridge fuses are cylinders that are both longer and narrower than plugs. When you open the circuit box, you will have to pull out individual boxes to replace a cartridge. Cartridges are used to service 240 V circuits and have a range of ratings from 30 to 100 amps. Both types of fuses are found in a typical circuit box.
Replacing a blown plug is easy. You should be able to spot the blown plug by looking at its clear top. How the plug failed is also a good indicator on what you need to fix in order to stop any more from being blown. A melted piece in the clear top indicates that the circuit was overloaded. A discolored blown plug indicates that there was a short circuit that caused the failure.
When you have located the blown plug, unscrew it carefully, being sure only to touch the clear end of that is insulated to protect you. After it is completely removed, replace it with a plug made to handle the same number of amps as your blown plug.
A cartridge is slightly more difficult to fix. First, you must remove the fuse block that houses the cartridge fuse. To complete this step, grab onto the handle of a single box and pull towards you.
Next, you will need a fuse puller to remove the blown cartridge fuse. This inexpensive tool can be purchased at most home improvement stores and is well worth the cost. It works similarly to a set of pliers, making the cartridge easy to remove.
The suspected blown cartridge should be tested using a continuity tester. If the tester glows, that cartridge does not need to be replaced. If your continuity tester does not glow, replace the cartridge with an identical new cartridge fuse.
Replacing a blown plug or cartridge fuse may make you a little apprehensive the first few times, but it is an easy and essential skill to master. Keep in mind that you should not have to regularly replace a fuse. If you find that you are often heading out to your circuit box, call an electrician who can fix the underlying problem.
