Aschematic diagram of the internal workings of a pod-type thermostat. This type is used in appliances that have a variable temperature control. It consists of an oil-filled pod connected to the switch by a capillary tube. When the oil in the pod is heated or cooled, it expands or contracts in the tube and operates a diaphragm. The diaphragm acts on the switchgear thus breaking the circuit and in this instance, ‘making’ the other. The cooling oil contracts, pulling the switch the opposite way — back to its original position; the process repeats if temperatures change. Read the rest of this entry »
Many household appliances have some means of governing the temperature at which they operate. Examples include the regulation of high temperature ovens and heaters by switching elements on or off and, at the other end of the scale, the control of low temperatures in refrigerators and freezers by turning the compressor motor on or off.
A thermostat is an automatic device for regulating temperature. They range in type from the simple single action switch, which turns off or on at one pre-set temperature, to the fully adjustable type, which can be adjusted within a given range. Read the rest of this entry »
These are among the most frequently used items in the home. Generally, they are very reliable, but when a problem does occur, it is usually at the most inconvenient time. Over the years, ovens and hobs have become increasingly complex with the addition of digital timers, touch controls and other refinements.
It is essential to remember that these appliances are connected directly to the mains supply and, as with any repair, cleaning or service, must be completely isolated. In this instance, the main double-pole isolation switch for the appliance must be switched off and also the fuse for the cooker/hob circuit removed from the main distribution board. If an MCB is fitted in place of a fuse, ensure it is in the off position. Do not proceed with any repair or service if both these requirements are not met and also make sure you advise others who may use the switch of your intentions. Read the rest of this entry »
The humble kettle has been given a new image in recent years. Simple versions consisting of only a container with a heating element fixed inside are still available, but for many years the trend has been towards the automatic kettle that turns off once the water has boiled.
Some more recent models have been further improved with high-speed elements and spout filling. The latest jug version combines all the features of a modern kettle with the added feature of the handle’s being positioned on the side, so that the user avoids the steam when pouring.
As with irons, cable damage through wear and tear and misuse tends to be a common fault. Cordless kettles and jugs preempt this problem. They are similar to cordless irons in that they require a power base that has its own mains lead. When the cordless kettle is placed on its base, electrical contact is made to its heating element. The operation from then on is like any other automatic kettle. Read the rest of this entry »
The toaster is another appliance that uses heating elements and, in most instances, a bi-metal strip thermostat to control the length of time the bread is exposed to them. This, in turn, relates to the degree of browning required by varying the position of the bi-metal contact points. When bread is inserted, a latched spring system is actuated to hold the bread carrier in place. At the same time, it makes a switch contact to supply power to the elements. The heat from the elements toasts the bread and also heats the bi-metal strip, causing it to bend. Read the rest of this entry »
