Why they are dangerous, how to find them, and how to protect yourself against them.
Like in the movies, short circuits are when electrical things go bang.
A dramatic flash, crack, buzz, or even explosion are symptoms of short circuits in the home.
This post will discuss what a short circuit is, why they occur, where to find them, and how to protect yourself from them.
What Is A Short Circuit?
A short circuit occurs when the live phase wire makes contact with the neutral wire, effectively creating a ‘short circuit’ or an easier path for the energy to flow back to earth. A ground fault is also technically a short circuit.
When this happens a lot of energy is released, especially if there is a distribution transformer nearby.
This energy is released both as heat and electrical current and it can appear as a dramatic flash, crack, buzz, or even explosion in the equipment or cable containing the short circuit.
Can a Short Circuit Cause A Fire?
Yes, a short circuit can cause a fire. In fact, they are a major cause of house fires and damage to electrical equipment. If a short circuit isn’t interrupted and stopped by a circuit breaker, it will continue to crack and buzz eventually causing a fire.
This happens because the amount of energy released can cause things surrounding the short circuit to heat up, melt and begin to catch on fire. This might include the wire insulation, electrical fittings and anything adjacent such as wall insulation, or the building structure.
As most of the wiring is hidden behind wall cavities, in ceilings or under floors it can be difficult to see or detect a fire about to occur.
This is why regulations exist about having correctly rated circuit breakers in the home designed to operate within a specified time frame to stop a short circuit, if one occurs, and prevent a fire.
Where Do Short Circuits Occur?
In the home, short circuits can occur anywhere there is a phase and neutral. T
This can be at any point of the electrical circuit including the wiring located in the walls, ceilings, underfloor.
A short circuit can also occur at any electrical fitting or appliance where the wiring connects such as:
- Light fittings
- Light Switches
- Power Outlets
- Switchboards
- Heaters
- Extension Cords
- Fans
- Water pumps
- Dishwashers
- Dryers
- Fridges
- Ovens
- Spa Pools
- Microwaves
- Multiboards
This is just to name a few. Short circuits can appear in many more appliances.
Why Do Short Circuits Occur?
Short circuits occur because the phase wire has come in contact with the neutral wire.
In our experience here are common reasons for why this happens:
- Wear and tear of electrical fittings.
- Careless, incorrect wiring by someone, even Electricians.
- Cable damage due to sharp objects, such as nail plates rubbing against cables in the ceiling.
- Rodent chewing of cables in the wall or ceiling.
- Rodents making nests behind switches and power outlets.
- Other vermin, such as ants or bugs shorting the circuit out.
- Water intrusion into electrical fittings or cable like outdoor lights.
- Sun UV degradation of the structural integrity of the electrical fitting.
- Using an appliance incorrectly, such as heating a hot water cylinder without water causing the element to eventually short out.
- Using old and dangerous switches and outlets which have been outlawed.
- Using an appliance which doesn’t meet safety regulations.
There are many other possible scenarios which could cause a short circuit not included in the list above.
What Does A Short Circuit Look Like?
A short circuit looks like a burnt and melted wire or electrical fitting. You may notice it smells like burnt plastic, ‘fishy’ or like ‘ozone’. You might have a tripped circuit breaker in your switchboard.
How To Find A Short Circuit With A Multimeter
A multimeter is not the best tool for finding a short circuit in a length of cable. The best way to test for a short circuit is with an insulation resistance tester or ‘Mega’. An insulation resistance tester will tell you if a connection exists between the phase and neutral by applying a voltage between them and testing the insulation of the wires.
How To Protect Yourself From Short Circuits
A short circuit needs to be stopped as soon as possible to prevent a fire from occurring.
This means cutting off the electrical supply to the short circuit, cancelling it out.
This is done automatically via circuit breakers in your switchboard.
Circuit breakers, by law, are designed to disconnect the power within 0.4 seconds in the event of a short circuit. This helps prevent much of the damage such as fires from happening. It may even save you needing to buy new equipment.
While this is the ideal scenario, by law, it needs a few things in place for the circuit breaker to do its job which I will discuss below.
Good Connection To Earth
Your electrical system needs a good earth. This earth might be a ground electrode outside your house, or it might be provided to you by your power company. Without a good earth, your circuit breaker won’t trip either in time to prevent a fire or at all, if there is a short circuit.
In essence, a good earth means a low resistance path for fault current to travel. If the resistance is too high, not enough current will flow to cause the circuit breaker to trip.
Here is what a good earth looks like:
- Correct earth cable size. If the earth cable is small, then resistance will be too high to trip the breaker.
- Good connection at the earth electrode and switchboard. If it is too tight or too loose then resistance will be too high to trip the breaker.
- Good ‘earth’. Depending on the composition of the ground outside, your earth may be naturally good or bad. Some types of dirt provide a better earth than others. For example, clay is better than volcanic ‘pumice’ soil.
Correctly Rated Circuit Breaker
A circuit breaker needs to be correctly rated for the short circuit fault current of the circuit. This is the maximum amount of energy the circuit breaker can handle in a short circuit. If the short circuit fault current is too high, it will simply melt the circuit breaker.
Correct Polarity
This means ensuring the phase wire goes where the phase is supposed to go and the neutral goes where the neutral is supposed to go. If you were to get them around the wrong way, chances are that the appliance will still work, but your chance of getting a shock increases. Making sure polarity is correct is the best way to avoid this.
Change Out Old Electrical Fittings
The best way to protect yourself from short circuits is to change out old and worn out fittings. This will refresh the area as well as make it safer.
Waterproof Outdoor Or Wet Area Electrical Fittings
Use the correctly IP rated electrical fittings in wet areas or use low voltage supplies.
Pest Control
Keeping on top of vermin and rodents is a good way to protect the integrity of your electrical wiring and fittings.
Hire Expertise
Finally, ensure that whoever is working on your electrical system is experienced and qualified to do so.
Next Steps
We Fix Faults is all about diagnosing and troubleshooting common electrical faults around the home. If you liked this guide check out some of our other posts and subscribe to our email list.