Guard houses against an electric fire
In recent years, more and more electric appliances were installed and used by families, such as the air conditioner, micro-wave oven and VCD player, etc.. And all this raises the consuming electric total power. In our country, the power supply lead of the commonly residential building’s house is designed to bear 6 to 10 amperes, and the total load can’t exceed 1000 to 1500 watt-hours. When the total load exceeds 2000 watt-hours, the possibilities of fire caused by short circuit and the ammeter burnt do exist. From the analysis of fires that has happened in recent two years in Shanghai, about half of the fires were caused by the overloaded short circuit and the poor contact, etc.. Then how to use the electricity in safe in residential houses? I think that the key is to do well the following points:
1. The layout of switchboard. The switchboard has a fuse box, and the fuse box has installed a fuse wire. When the numerical value of the electric current that passes through the fuse wire exceeds the safety value limits, the fuse wire will fuse. Therefore, never arrange the switchboard above the combustible goods so as to prevent the broiling melted drops from lighting the goods. The fusing current of fuse wire is always 1.5 to 2.0 times as much as the rated current. When the electricity is normally being used in houses and the total power of all electric appliances can not exceed 1100 watt-hours, the fuse wire of 5 amperes is just good. When the current that passes through exceeds 7 amperes, the fuse wire will fuse automatically so as to reach the purpose of protection. If the chosen fuse wire meets the standards and yet often fuse the electric current or the electric appliances often sounds a little, we should search the reason in time so as to eliminate the hidden dangers. Do remember not to substitute the fuse wire with the thick one or even the copper wire and the iron wire, and it will not play the role of protection. The choice of monophase watt-hour meter should also be based on the total electric power. As long as the total power can be guaranteed not to exceed its own rated current of ammeter, it will be right. In addition, if the condition permits, the house can also be installed with the earth leakage protective device. Once an accident of electric shock occurs, the device can operate in time and cut off the current.
2. The choice of electrical wire. At present, the circuitries used in many houses are laid several decades ago or even earlier, and can’t meet the requirements of modern household electrification. Firstly, the insulating layer of wire has been gradually loosing and aging for being used for several decades, and this will lead to leak slightly. The leakage will also lead to a serious consequence of a fire caused by the short circuit. As a result, the electric wire should be changed regularly. Furthermore, the electric load has a requirement for the wire. If the total amount of consuming electricity is under or equals to2200 watts (10 amperes), when using the light, TV and air conditioner and other appliances at the same time, it will be overloaded to use a 500 watts electric iron and will also become very dangerous to use one more micro-wave oven. Under the circumstance of overloading, the aging speed of wire insulating layer will become fast. If the heat released by electric core makes the temperature of insulating layer exceed 250ºC, the electric wire will catch a fire. Therefore, the choice of electric wire must be based on the electric current. At last, the right style of lead will be chosen according to different conditions. In a dry house, the common insulating lead can be adopted, while in a moist house, the insulating lead with a protective layer should be adopted, such as the wire with an aluminum layer and the wire with a plastic sheath, etc.. To those electric equipments, which are often moved, the soft wire should be adopted, and so on.
3. The reasonable layout of electric wire. Soon after one resident entered into and lived in his house which had been just decorated, the house caught a fire. Through investigations, the reason was found that when decorating, the navvy directly laid the electric wire in the dado, and the short circuit lighted the dado. If the electric wire is laid visibly, its insulating layer should be avoided being damaged. When going through the combustible surface, the electric wire should be pulled on an lightweight anti-flaming sheath. In the house with suspended ceiling, the electric wire in the suspended ceiling should be the wiring in metal pipe. In order to avoid being damaged, the electric wire that need to go through the wall should be protected in the hard plastic pipe, and the two ends should protrude about 1 cm from the wall.
4. Use the household electric appliances properly. After using of TV and radio-recorder, etc., you should not only turn off their switches, but also pull out the power plugs. The reason is that the power switches of many kinds of electric appliances are designed near the margin of transformers, and the inner loops of transformers will lead to short circuit or be carbonized with the insulating layer once the plugs are not pulled out, then the fire breaks out. In addition, the capacitance and the voltage fluctuate greatly in our country. When being in the low-lying valley of consuming electricity, the power pressure of 220 volts can reach a maximum value of 250 volts. This will lead to a phenomenon that some electric appliances will be burnt, which don’t have the capacitors with enough pressure value. Therefore, the voltage stabilizer should be installed additionally in this kind of circuit.