What they are, why they occur, and how to protect yourself from them.
Electrical overloads in a domestic household scenario can be a nuisance, but also indicate serious electrical issues beneath the surface. Like short circuits and ground faults, electrical overloads are protected against using circuit breakers.
This post will go into what electrical overloads are, why they occur and how to protect yourself and loved ones from them.
What Is An Electrical Overload?
An electrical overload is a type of electrical fault where too much electrical current is drawn than the cable can provide.
The amount of ‘power’ that can be drawn from a cable is limited by its size, or cable surface area. For example, a thicker cable can carry more current without heating up.
If the cable is too small for the electrical demand of the circuit, the cable will heat up and continue to heat up until a potential fire starts.
Can An Electrical Overload Cause A Fire?
Yes, electrical overloads can and do cause fires. As mentioned above, cables and electrical fittings will heat up until they eventually melt. Households are protected from overloads by miniature circuit breakers, also known as MCB’s.
Where Do Electrical Overloads Occur?
Electrical overloads can occur at any point in the circuit containing the electrical device or appliance drawing electrical current.
- If two cables of different sizes are used, the overload will melt the smaller cable first.
- If an electrical fitting, such as an outlet or switch has a lower current rating than the cable, the electrical fitting will melt first. For example, a 10A rated power outlet on 20A cable will melt the outlet first before the cable.
- Poor cable connections will generally melt first. These terminations will be located in the appliance, in the switch, in the power outlet, or in the circuit breaker.
Why Do Electrical Overloads Occur?
Overloads happen for a range of reasons. In our experience, here are common reasons why overloads occur.
- Multi Boxes with too many appliances plugged in. Multi boxes are notorious for tripping breakers. The reason is that the appliances plugged in draw too much current from the circuit than the cables are designed for.
- Motors. When a motor starts up, it will draw 7 to 10 times the normal operating current. This will definitely overload and trip your standard domestic C type breakers. The solution for this is to install motor rated ‘D’ type circuit breakers to account for the high currents from motors.
- Older House. Older houses tend to have smaller cable installed. This smaller cable can lead to overloads with modern appliances.
- Cheap Wiring. Houses wired on the cheap will tend to have used smaller cable linking too many outlets and switches. This is very common and will definitely cause circuit breakers to trip on overload.
What Does An Electrical Overload Look Like?
If a breaker hasn’t tripped, here is what an electrical overload will look like:
- Lights will dim or flicker.
- Appliances will feel warm.
- Outlets will feel warm or hot.
- Walls containing wiring will feel warm.
- Appliances will seem like they have ‘less power’ or don’t work as they should.
- Appliances will shut off.
These are the main things you will notice if there is an overload, but there are others you might experience not covered above.
How To Protect Yourself From An Electrical Overload
An electrical overload is caused by too much current being drawn through a too small cable, fitting, or connection.
By law, overload protection must be included in your home electrical system.
There are several things you can do to protect yourself and your family from domestic electrical overloads.
Increase The Cable Size
If the electrical demand from the circuit is too high, the solution is to install a bigger cable. For example, if the circuit has cable sized at 1.5mm2 consider updating it to 2.5mm2.
Create Dedicated Circuits
In cheaply wired houses you will often find too many outlets on a single circuit. This is done to save money. The solution is to break these up into separate circuits going back to the switchboard.
Use Correct Sized Circuit Breakers
If the circuit breaker current is too small for the cable size then the breaker will nuisance trip.
However, if the circuit breaker current is too big it won’t trip at all. This is a dangerous fire risk because the overload won’t trip the circuit breaker.
Use Correct ‘Trip Curve’ Breaker
You need to consider the types of appliances running on the circuit. For example, if you have motors, you should use ‘D curve’ breakers. These breakers will take into account motor start currents. If you used a domestic ‘C curve
Next Steps
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