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What are Screw-in Plug Fuses, Tamper-proof Fuses, and Fuse Adapters?

Electrical Panel Fuses

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Screw-in plug fuses, tamper-proof fuses, and fuse adapters, what are they? They sound so complex, don't they. These are all different things you can find in a fuse panel in your home. But what are each of these used for? Do I have all of them in my home? Both of these are good questions and after further review of this article, hopefully you'll be able to answer these questions.

1. Plug Fuses

Plug and Tamper-Proof Fuses
Photo: Timothy Thiele

Plug fuses are common fuses used in a home's fuse panel. They come in 15, 20, and 30-amp sizes and are screwed into the electrical panel. They control the amount of amperage to the circuit it connects to. Plug fuses control 120-volt circuits that normally feed lighting and receptacle loads throughout your home.

Plug fuses have a metal alloy ribbon inside that carries the current of the circuit. In the case of a short or overload, causing too much current to flow, the ribbon will melt and open the circuit. When this happens, no current can flow and the circuit is disconnected from the power supply. This protects against short circuits and overloads that may damage electrical wiring and cause house fires.

2. 15-amp Plug Fuses

15-amp Plug Fuse
Photo: Timothy Thiele

A 15-amp plug fuse is a screw-in fuse that can handle electrical current up to 15 amps without the fuse blowing. The 15-amp fuse is generally used for house lighting circuits. Through the clear window provided on the face of the fuse, you can see the metal alloy ribbon that carries the current. When the amperage is exceeded, this melts and often blackens the window to indicate the fuse has blown and that it needs to be replaced. This type fuse protects 15-amp circuits and its wiring.

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3. 20-amp Plug Fuse

20-amp Plug Fuse
Photo: Timothy Thiele

A 20-amp plug fuse is a screw-in fuse that can handle electrical current up to 20 amps without the fuse blowing. The 20-amp fuse is generally used for outlet and appliance circuits. Through the clear window provided on the face of the fuse, you can see the metal alloy ribbon that carries the current. When the amperage is exceeded, this melts and often blackens the window to indicate the fuse has blown and that it needs to be replaced. This type fuse protects 20-amp circuits and its wiring.

4. Tamper-Proof Fuses

Tamper-proof Fuses
Photo: Timothy Thiele

Tamper-proof fuses were designed to keep someone from replacing the wrong sized fuse in the fuse base. You see, in the regular plug fuse style bases, you could replace a 15-amp fuse with a 20 or 30-amp fuse. This is where all the trouble started. If your wire was only rated for 15 amps and you put 30-amps of current through it, your wires get hot and start an electrical fire. So to make sure this couldn't happen, the "S" type fuse was developed. Each size tamper-proof fuse will only screw into the proper tamper-proof base. That way, you can't accidentally place the wrong size i the base. These fuses come in 15, 20, and 30-amp sizes also.

5. Plug Fuse Adapters

Plug Fuse Adapters
Photo: Timothy Thiele

If you have an older style fuse panel with standard plug fuses and want to add tamper-proof fuses, simply add plug fuse adapter. These adapters come in 15, 20, and 30-amp sizes. They allow the newer ad safer "S" type tamper-proof fuses to be screwed into the standard bases. simply screw the new "S" type fuse into the base and then screw the whole assembly into the fuse panel socket. Each of these plug fuse adapters is rated for either 15, 20, or 30 amps and is labeled on the inner base of the adapter.

Too often fuses are wrongly replaced and many electrical fires are the result. For your safety, only replace fuses with the appropriate sized fuses. If they are blowing, there is a problem with the circuit or something attached to it.

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