Home Wiring 101: Dealing with Circuit Breakers and Fuses

15, 20, and 30 amp plug type fuses.
15, 20, and 30 amp plug type fuses.

How to Replace a Blown Fuse

Unlike circuit breakers, fuses can’t be reset and must be replaced when they burn out.

To replace a plug type fuse:

  • Unplug Electrical Devices: If the fuse blew because the circuit was overloaded, turn off or unplug electrical devices on the circuit before replacing the fuse to prevent it from blowing again.
  • Locate Blown Fuse: Look in the window of each fuse at the metal strip inside. The metal strip on a blown fuse will be melted in two. Often the window of the blown fuse will be discolored or blackened as well.
  • Remove Blown Fuse: Unscrew a blown fuse by turning it in a counterclockwise direction. To prevent electrical shock, do not touch or insert tools inside the fuse plug socket.
  • Install New Fuse: Screw a new fuse of the same type and amperage as the blown fuse in the fuse socket in a clockwise direction. There are two types of threads for plug fuses, so make sure you have the right one for the socket.
  • Test Circuit: Turn on a light fixture or lamp on the circuit to make sure the circuit has power.

Electrical circuits that draw a lot of current, such as those for appliances, use cylindrical cartridge type fuses mounted behind pullout blocks in the fuse box.

To replace a cartridge type fuse:

    Cartridge fuse.
    Cartridge fuse.

  • Unplug Electrical Devices: If the fuse blew because the circuit was overloaded, turn off or unplug electrical devices on the circuit before replacing the fuse to prevent it from blowing again.
  • Remove Pullout Block: Pull on the handle to remove the entire pullout block from the fuse box.
  • Remove Blown Fuse: Remove the blown fuse from the pullout block. A fuse puller tool makes removing cartridge type fuses easier and prevents damage to the fuse.
  • Install New Fuse: Insert the new cartridge fuse, and push the pullout block back into the fuse box.
  • Test Circuit: Try turning on a light fixture or lamp on the circuit to make sure the circuit has power.

Barbara Johnson works in real estate and enjoys finding her clients the perfect homes. She writes on a number of topics ranging from pest control in Long Island to the best home improvement projects for real estate value.

Further Information


  1. Since my husband passed away and I’m the only one in the house, I’ve been switching off the breaker for the hot water heater. I’m gotten mixed messages if this is ok. Someone just told me I could wear out the switch if I do this too often. Am I making a mistake switching off the water heater at the box for a day or two?

  2. The first para could be easily misconstrued and it states: “An electrical service panel is a metal box mounted on a wall or on the outside of your house which contains either circuit breakers or fuses to control the wiring in your home.”

    For all homes I’ve ever seen the circuit breaker box is never outside. What is outside is the meter box, and most commonly the circuit breaker box is directly behind it on an interior wall. It is not too far away since it is a high power wiring.

    I’d like to suggest one diagnostic approach if early conclusion is a defective breaker, remove it with main power switch off, and replace it with another one in the paned with the same amp rating. This also goes for old fashioned fuses where it only needs to be unscrewed from the fuse socket.


    • Hi Rusty,
      Most breaker panels are located inside a house, but they can be mounted outside if a NEMA Type 3R enclosure is used. The house I used to live in had a combination meter and breaker box mounted on the outside wall.

  3. ABOUT THE SWITCHING HOT WATER HEATER off & on (to save electricity)…Whats the pros & cons on that ???? It saves about $20 mo. on electric bill. Whats a better way to go ?????WE have enough HOT water for 2 days.Turn on for 1 hr….then off again.

    • Paula and Janie,
      Circuit breakers are not designed to act a regularly used on/off switch, and doing so will cause the breaker to wear out prematurely over time. If the water is hotter than necessary, start by turning the breaker to the water heater off and then turning the thermostat on the hot water heater down to 110 to 120 degrees. Another option is to have a switch rated for the number of amps the water heater draws installed in the electrical line that powers the water heater.

  4. My A/C outside unit fan motor went out. I had a license service company replace the motor. It ran all summer long never shutting it off. Finally it cooled down in sept., turn thermostat off. I notice the outside fan unit did not turn off. I now think it never did cycle off. Our electric bill was higher than normal. Anyway, had to shut it off by breaker switch. It has always shut off by thermostat and the only thing that changed was the replacement motor. I called service company and she said it was 4 months ago and I said yes we never shut it off. I asked her to ask the guy who installed it if he could had crossed wired something. She asked and called back and said its a possibility but if it is not our fault the 90 service fee will be charged. I don’t trust this company, I feel that they would make up something to keep from owning up. Also if the unit never cycled off that new motor ran 24/7 and its life expectancy is now less. Is there a way I can look at wiring and know if it was miswired?

  5. I am glad that you mentioned to be dry and stand on a dry surface when working with electrical panels. This is not something I would have considered. I have an unfinished basement that I am working on and I do not feel comfortable working on the electrical wiring by myself. Finding an electrician will make finishing these renovations a lot easier.

  6. The other day my brother mentioned he would like to to have a circuit break installed in his new home. I will remind him to switch off the power source before he engages.

  7. I have an old house (built in 1971) it has a mixture of cartridge fuses and plug in (screw in fuses). All outlets seem to work well except for my dryer which keeps blowing my dual cartridge fuse. I have two 15-amp cartridge fuses for the dryer (so a total of 30 amps) but it still keeps blowing.
    Question #1 – Is there a way to replace the cartridge fuse holder with a screw in fuse holder?
    Question #2 – Is there a way I can replace all the fuses with a circuit breaker type system without replacing the wiring in the house given that the house is probably the older aluminum wiring ?

    • Hi, Rayman,
      We’ve tried contacting you to appear on the Today’s Homeowner Radio Show, but we haven’t heard back.
      No worries! We’re still happy to help. Connect one-on-one with a home improvement pro immediately through JustAnswer, a Today’s Homeowner partner, right here: http://justanswer.9pctbx.net/c/2342074/565926/9320
      Good luck with your wiring project!


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