What is the importance of fuses in a house?

Answer 1

The cable between the plug and appliance is vulnerable to physical damage, which can lead to a breakdown of insulation between the internal conductors (live, neutral and earth) causing a short-circuit current to flow. Without the fuse in the plug this could lead to fire. The fuse senses the short-circuit current and interrupts it before damage can occur.

Answer 2

It protects the house from fires which could otherwise start if too much power would cause the wiring to heat up. With fuses, the fuse goes before anything else happens.

The safety function of your house fuse is to prevent fire.

Here is how they work.

Every wire is rated to conduct a certain maximum number of amperes. For example, a 14 AWG wire normally used in house wiring is rated at 15 amperes. What this reflects is that this wire will not overheat if you can limit the current to just 15 amperes. Because of it's insulation and the normal ambient temperature and cooling environment in house wiring, it has been determined that this 14 AWG wire will not exceed a temperature that may ignite adjacent materials or it's own insulation - provided that you do not exceed the 15 ampere limit.

All wire (except superconducting wire) has resistance to electrical current flow. This leads to resistive heating in wires in accordance with the power law P=I2R. When applied on a per foot basis, one can appreciate that if a wire has a resistance of 0.0025 ohm/foot, then a 15 ampere current would produce 225x0.0025 watts or 0.56 watts in that 1 foot length. Not to worry. No fire.

The house fuse prevents the current from exceeding the rated current of the wire.

This is why it is important to size the fuse in accordance with the house wire gauge that it is protecting. For example, you must not use a 20 ampere fuse if the circuit is wired with 14 AWG. Nor should circuit breakers be similarly oversized.

Answer 3

The main fuse protects the supply outside the house from faults inside the house, and it is placed at the point where the supply enters from outside.

In the UK the supply company owns the main fuse which is called a cut-out and the company must be called when it blows.