List of top seven appliances used for heating:- 1. Non-Pressure Type Water Heater 2. Electric Iron 3. Electric Radiator 4. Immersion Heater 5. The Electric Toaster 6. Soldering Iron 7. Electrode Boiler 8. Hot Air Circulator.
Appliance # 1. Non-Pressure Type Water Heater:
The geyser is a non-pressure type water heater. It supplies the hot water continuously to wash basins and bath rooms. The non-pressure water heater has two vessels. The inner vessel containing water is made up of tinned copper. The outer vessel is made of steel and enameled on outside. Between the inner and outer vessel space is filled with insulating material such as glass wool.
At the bottom of inner vessel heating element and thermostat are fixed. Cold water pipe is connected to the permanently open bibcock. When hot water pipe valve is opened, hot water comes out by principle of displacement. Hot water pipe takes water from upper part of vessel as shown in Fig 3.3.
This prevents emptying of inner vessel by symphonic action. Safety vent is provided at the top to prevent build-up of high pressure. The storing capacity is in the range of 25 to 100 litres. Geysers are rated at 1000 to 1500 W. Electric circuit of geyser is shown in Fig. 3.4.
Appliance # 2. Electric Iron:
The electric iron is extremely popular and widely used domestic electric appliance. Electric iron has various parts such as sole plate, pressure plate, heating element, cover plate, handle etc. In some electric irons pilot lamp is provided to indicate that iron is ‘ON’. There are two types of electric iron ordinary or non-automatic and automatic iron.
In automatic iron thermostat assembly is used which consists of bimetallic strip to operate a switch. The bimetallic strip is connected in series with resistance element. The bimetallic strip is situated in the cavity formed in the pressure plate. Two springs contacts are held together with certain pressure which is regulated by the position of the temperature adjusting knob.
For cotton clothes, large heat is needed whereas for silk and woollen less temperature is needed. This can be achieved by adjusting the temperature knob. The pilot lamp connected in the automatic iron shows whether the iron ‘on’ or ‘off’. The electrical iron is available from 450 W to 600 W.
Appliance # 3. Electric Radiator:
The function of electric radiator is to give heat without producing fumes, smoke and dirt. Moreover it converts all the electrical energy into heat energy. Main type of radiator is reflector radiator.
The element consists of nichrome wire coil wound on a conical ceramic former, which has threaded base screwed into a corresponding socket in the parabolic reflector.
Appliance # 4. Immersion Heater:
The immersion heater is used for water heating in winter season by immersing directly in water. It is made of chromed iron in which the heating element is placed. Insulation is provided around the heating element so that it may not touch the pipe. This method of heating gives highest efficiency since there is no loss of heat to the atmosphere. They are available in the range of 500 to 2000 W.
Appliance # 5. The Electric Toaster:
Electric Toaster has two heating elements of nichrome wire mounted vertically with a space between, into which the slice of bread is inserted. A thermostat regulates the temperature and degree of toasting. The specification of sandwich Toaster is 230V AC and 60W.
Appliance # 6. Soldering Iron:
The main part of soldering iron is element made of nichrome wire wound on rectangular strip of mica and-stack together. The entire stack is in packet tightly into a metal container. The container is open at the handle end for connections of the elements.
The soldering tip is wedge-shaped made of copper. The tip is fixed in the end of metal tube with the help of screw. The two leads of heating element is connected to supply terminals. A wooden or plastic handle is provided for properly holding the soldering iron when in use.
When a current is passed through the element, it becomes hot and heat is conveyed to tip for soldering the wires. The soldering iron available from 25 watts to 75 watts generally.
Appliance # 7. Electrode Boiler:
In electrode boiler voltage is applied to electrodes in water produces heat. This is because, for the electric current passing through the water, a resistance is offered by water and heat is produced. The tank used for electrode boiler is solidly earth and connected to the ground.
A circuit breaker is provided for automatic make or break of supply with over current protective device. Indicator lamps are also used to know whether it is, ‘ON’ or ‘OFF’ from a distance.
Appliance # 8. Hot Air Circulator:
The hot air circulator consists of a number of heating elements connected in such a manner that it gives certain amount heat. The amount of heat produced depends upon the I2R losses produced in the heating coils. The hot air from the heating coils is flown out by the fan. The amount of heat is controlled by the selector switch having low, medium or high ranges.
Thermostat Control Circuit:
This is one of the most important items in the automatic heating appliances. In thermostat a bi-metallic strip is used to operate the switch. Generally bi-metallic strip is connected in series with the resistance element.
A bi-metallic strip consists of two strips of different metals having different co-efficient of expansion, securely fastened together. If such a composite strip is heated, it begins to curve towards the metal having lower co-efficient of expansions of two metals. On cooling, the bi-metallic strip comes to its original position. Fig 3.11 shows the thermostat – Bimetal Type.