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Testing Fuses

How to Test Fuses Using a Multi-meter

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Types of Fuses

Types of Fuses

Photo: Timothy Thiele

When the circuit in your home quits working and you suspect that it is likely a blown fuse, you can test that theory by using a multi-meter for testing fuses. By setting the selector switch to ohms and setting it on a lower range, you can test the resistance between the two points of the fuse. This will measure the resistance of the fuse link, if intact. when working with anything electrical, shut the power off to the device that you'll be working on and check with a tester to make sure it is not live.

Fuses come in different styles, cartridge and screw-in. The Ferrule-type cartridge fuse are generally used for the main feeder and range protection. Normally, range feeds will have 50-amp fuses and the main fuses are generally 60 amps, being more common to older homes. Plug fuses screw in and come in 15, 20, and 30-amp ratings. These fuses supply the branch circuits in your home to run lights, outlets, and appliances. Learn how to test each of these fuses below.

  1. Testing Plug Fuses
    Plug fuses can come in three types: standard, tamper-proof, and time-delay. The tamper-proof style is better known as Edison-based fuses that have special adapters that screw into the existing fuse holder. It has a smaller, plastic threaded sides that have different depths for each sized fuse. This means that you cannot use a 30-amp fuse in a 15-amp base. The standard plug fuses could be interchanged at will. This exposed the home's wiring to over-sized protection for the undersized wiring.
  2. Testing Cartridge Fuses
    Cartridge type fuses come in different styles also. The ferrule-type fuse is a cylinder-looking fuse that has amperage ratings up to and including 60 amps. Knife-blade cartridge fuses can handle loads from 60 up to 600 amps. These fuses can easily be installed and replaced using a fuse puller.

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