Over-fused means that the amperage rating of a fuse or breaker exceeds the amperage rating of the wiring in the circuit, or exceeds the amperage rating by a manufacturer for an appliance on the circuit. The main purpose of a an overcurrent device is to prevent overheating when too much current is flowing through the wiring; so, when properly sized, it trips to disconnect the circuit before the hot wires start a fire.
In ordinary residential installations, there are standard matches between copper wire size and breaker rating, such as 15-amp breaker and #14 wire, 20-amp and #12, 30-amp and #10, and so forth. Larger wires can carry more current. But special situations may require derating the wiring (upping to a larger size), and an electrician will know when these kick in.
• • • • • • • • • • • • • • • • • • • • • • • • • • •
Here’s links to a collection of our other blog posts about ELECTRICAL WIRING:
• Which house appliances need a dedicated electrical circuit?
• Can a short circuit cause a high electric bill?
• What is the maximum spacing requirement for securing NM-cable (nonmetallic-sheathed cable)?
• Is it alright to just put wire nuts on the end of unused or abandoned NM-cable or wiring?
• What causes copper wires to turn green or black in an electric panel?
• What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?
• Why is it unsafe to bond neutral and ground wiring at subpanels?
• Should I get a lightning rod system to protect my house?
• Why is a strain relief clamp necessary for the cord connection to some electric appliances?
• Does a wire nut connection need to be wrapped with electrical tape?
• What is the minimum clearance of overhead electric service drop wires above a house roof?
• What are the requirements for NM-cables entering an electric panel box?
• What is the color code for NM cable (Romex®) sheathing?
• Why are old electrical components not always "grandfathered" as acceptable by home inspectors?
• How can I find out the size of the electric service to a house?
• Can old electrical wiring go bad inside a wall?
• What is an open electrical splice?
• What are the most common electrical defects found in a home inspection?
• What is the life expectancy of electrical wiring in a house?
• What is an "open junction box"?
• How dangerous is old electrical wiring?
• What is a ground wire?
• I heard that aluminum wiring is bad. How do you check for aluminum wiring?
• What is "knob and tube" wiring?
• What is the code requirement for receptacle outlets in a closet?
Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.