Electrical Dangers Explained
Statistics show that electrical equipment can cause fires.
While some appliance and equipment fires occur through the misuse by the person using the appliance or piece of electrical equipment, a more prevalent factor is component fatigue.
Design and / or manufacturer faults are also common fire causes which is reflected in the number of recall notices issued.
The information below can assist in identifying how fires can originate, particularly from electrical appliances.
Air Conditioners that are operating continuously in a dusty environment can cause fires because the dust can settle over electrical components such as capacitors and cause tracking faults.
The top plastic surface of the capacitor can also break down thermally leading to a tracking fault.
The older generation of fax machines generate a lot of heat on standby mainly because they have a thermal print head.
If the fax machine is covered with a combustible material and the heat from the print head cannot dissipate a fire could occur.
Hot Water Heaters
The main cause of fires from hot water heaters is moisture contacting the electrics. Because of corrosion, heaters can leak from several areas such as around the elements or from the water inlets and outlets.
In some instances, the polyurethane insulation that is blown into the heater jacket during manufacture is found very close to the electrics and provides a nearby readily combustible material that can ignite and then smoulder for hours.
Heaters use large currents and so the fire risks associated with large currents apply.
Electric heaters that are fan forced can cause a fire if some combustible material such as plastic wrap is sucked into the heater. The element can become detached through rough handling and later ignite the plastic casing. If the inlet air is partially restricted and the over-temperature sensor is not affected by the restriction the element can overheat and ignite the plastic casing.
The fire risks associated with radiant heaters are that a combustible material is left too close to the heater or the heater falls over and ignites the floor coverings.
Television Sets and Computer Monitors
There have been several recalls for television sets and computer monitors in recent years mainly because of soldering defects and faults in the transformers. These soldering defects are called dry joints and are caused by the solder failing to run correctly during manufacture, which leaves a high resistance pathway which progressively worsens with use.
Television sets are manufactured using fire rated plastics that do not easily ignite. However because so many different plastics are used in the manufacture of a television set and their fire ratings vary, it is still possible for electrical faults to cause a television set to catch fire.
Refrigerators & Freezers
Freezers and refrigerators can cause fire if they have been left sitting on their power leads. There is also a fire hazard associated with the door seal elements. If water does penetrate the door seal then a short circuit can be created resulting in a hot spot that can ignite the plastic door seal. Evidence of hot spots in the element can sometimes be detected before a fire due to the unusual odours produced by the pyrolysing door seal inside the refrigerator.
Moisture problems with refrigerators arise when the drain tube from the freezer becomes blocked. If the tube is blocked and the freezer goes into the defrosting cycle, the water can then run out of the front of the refrigerator and reach the electrics underneath to cause a fire.
Modern refrigerators use waste heat to evaporate the defrost water on a tray mounted above the motor. Older refrigerators sometimes have a plastic tray embedded with elements to evaporate the defrost water. If the drain valve becomes blocked this tray can over heat and over a long period of time can start to crack and expose the elements. When the blockage clears, water fills the tray and a short circuit and fire can occur because of the exposed elements.
Kettles and Urns
Failure of the safety cut-out device on kettles and urns is the most common reason these appliances cause fires.
However, as the electrics are normally located underneath the water reservoir any leaks will allow water to reach them, possibly causing a fire.
Power Strips & Extension Leads
The larger the current flowing through a power strip or extension lead, the greater the risk of fire because of poor connections or due to thermal breakdown of the insulation.
Extension leads exposed to moisture at a point well away from the power socket can cause a fire back at the socket.
If extension leads are exposed to an outdoor environment, rain water can run back along the lead and reach the power socket and cause a fire.
Lights emit heat that can ignite some nearby combustible material and lead to a fire. High wattage incandescent lights generate significant heat that can damage the socket and associated wiring causing a short-circuit which may lead to a fire.
The ballast in fluorescent lights can overheat due to internal short-circuiting and ignite combustible ceiling materials.
Quartz halogen lights have a filament that is very hot and if the globe is not installed horizontally or there is finger grease present, the globe can break and the hot filament may ignite combustible materials below.
Down lights also generate significant heat and if the top of the down light is covered by insulation, the insulation can ignite. Down lights installed in bathrooms are susceptible to moisture accumulating at the terminals which can lead to short-circuits.
A fire hazard has been identified associated with wheat bags heated in microwave ovens. Microwave ovens emit radiation that will excite water molecules. If there is no moisture available, other less volatile molecules will absorb the radiation and start to heat.
Therefore any material which has dried out can overheat and ignite in a microwave oven. Also, any metal objects inside a microwave oven can cause severe sparking which could lead to a fire.
Recalls of cooling fans have involved a hazard associated with a capacitor overheating which caused the plastic casing near the capacitor to ignite.
Problems with fan motors are common, however fires originating from motors are rare because the motors are well ventilated and the heat generated from a fault is readily dissipated.
Sink Disposal Units
Sink disposal units do not normally present a fire hazard because many are equipped with overload devices that cut the power if the motor becomes seized.
However, the power for most “sinkerators” is supplied from a power outlet installed under the sink and these sockets are susceptible to moisture, particularly if there is a leak at the back of the sink.
Stoves and Ovens
Stoves and ovens are normally made of non-combustible materials that significantly reduce the fire hazard.
However, if a combustible material such as a towel or some cooking oil is left on the stove or in the oven and there is a fault with a controller, fire can occur.