Scan the text and say how the wiring system must be protected from excessive current

Electric wiring is the system of wires and cables that distributes electricity throughout a home, store, factory or other building. Main cables run vertically in open shafts with branches at each floor. One of the most important tasks of such wiring is to supply electricity for lighting. It may also have to supply electricity to operate air conditioners, electric stoves, washing machines, and many other appliances. In some houses, electricity also provides heat. A wiring system should be designed to meet all the expected demands for electric power at the least cost.

The wires are usually copper, although aluminum is also used, and are covered with thermoplastic insulation. The wires must be contained in conduit, which is either metal or plastic tubing.

Before construction starts, the builder determines the location and type of wiring. Wires vary in size, depending on the equipment in the house and how far the current must travel. Standard wiring is designed for 110 volt current. But builders often specify heavy-duty, 220-volt wiring if large electrical appliances, such as a stove and a water heater, or an air conditioning system are installed.

Electricians install wiring while carpenters build the frame. Wiring is done in a series of circuits. Each set of wires has several outlets. Electricians often place the wiring for a furnace on a separate circuit. This keeps the furnace running in case another circuit breaks down.

Electric wiring is designed to carry a known current. The wiring system must also be protected from excessive current by fuses. A fuse box usually holds all the fuses. If too much current flows through a wiring circuit, the wiring becomes overheated, which may result in a short circuit or even a fire. Electricians often install another protective device called a circuit breaker, instead of a fuse box. If the circuit becomes overloaded, the circuit breaker automatically cuts off the current.

Planning and installing electric wiring involves many factors. One of the most important is the safety factor. Short circuits resulting from inadequate and improperly installed wiring are a common cause of fires. Most countries set a minimum standard for acceptable wiring. It includes rules for the installation and construction of electrical outlets and appliances to eliminate fire hazards. Other factors include the various wiring methods and kinds of wire that may be used, and planning how to route the wires through a building.

Notes:

fuse – предохранитель

Section II. Lexical - Grammar Tests.

Для того чтобы правильно выполнить контрольные работы, необходимо усвоить следующий грамматический материал:

1. Инфинитив(Infinitive).Употребление инфинитива для выражения цели. Инфинитив в функции определения.

2. Употребление местоимения it и one. Эмфатическая конструкция it is… that.

3. Основные типы придаточных предложений. Союзное и бессоюзное подчинение.

Test 1. Heating

Heating systems may be classified as central or local. Central heating is often used in cold climates to heat private houses and public buildings.

Central heating systems have automatic controls, with a thermostat to regulate the temperature of the rooms heated by the system. The thermostat turns on the system when the temperature drops below the setting of the thermostat.

Another automatic control turns off the central heating system if any part of it becomes dangerously overheated. Still another control prevents the system from starting unless it can start safely.

There are two main kinds of central heating systems (1) direct and (2) indirect. They differ in the way they distribute heat. A direct system circulates the warm air throughout the area being heated. An indirect system circulates steam or hot water through pipes to convectors or radiators, which give off heat.

Warm-air heating. A warm-air heating system warms the air in a furnace and then forces it through a system of ducts to each room. Another system of ducts carries cool air from the rooms back to the furnace. An electrically driven blower in the furnace moves the air through the ducts, and filters remove dust particles from the air.

Steam and hot-water heating systems.

The pipes carrying steam or hot water are smaller than warm-air ducts and thus take up less space. Automatic valves can control the amount of hot water or steam flowing to convectors more easily than they can control warm air.

Steam heating works much like hot-water heating, except that water changes to steam in a boiler. The steam passes to convectors, where it gives up its heat to the room and becomes liquid again. The water then flows back to the boiler.

Radiant heating.

Radiant heating is a method of equalizing temperature within a room.

A continuous loop of hot-water pipe or electric cable is installed in the ceiling or floor. Heat radiates from these pipes and keeps the room temperature nearly the same from floor to ceiling. Radiant heat provides comfort at a lower room temperature than other heating systems.

Radiant electric heating uses a cable that produces heat from electricity. The cable radiates heat to the room and may be installed in the ceiling or floor or along the skirting board. A thermostat controls the amount of heat produced by the cable.

Heat pumps.

A heating system that uses a heat pump operates much like a warm-air system. But the heat pump uses a condenser, evaporator, pump, and other equipment to get heat from outside air or the ground and ''pump'' it into the building.

Notes:

furnace - печь, топка

duct - канал, проход

blower - вентилятор

Test 2. Plumbing

Plumbing is a system of pipes that carries water into and out of a building.

A plumbing system consists of two separate sets of pipes, a water supply system and a drainage system.

The water supply system. Water for a plumbing system comes from two sources: (1) rivers and lakes, and (2) wells and reservoirs. Cities and towns draw water from these sources and pipe it to treatment plants, where it is purified. The purified water flows through large pipes called mains, which run under the streets. The mains connect with smaller pipes known as supply pipes, which lead into each building.

The water supply of every building has a shut-off valve. The shut-off valve normally remains open, permitting water to enter the building. The valve can be closed to turn off the water in order to repair the pipes or fixtures or in case of some other emergency.

Within a building pipes distribute water to the various plumbing fixtures and appliances, each with a valve to hold back the water until it is needed. With a direct system, cold water is taken directly to all the cold taps, to appliances using cold water, and to a water heater which is powered by either gas or electricity.

In an indirect system, cold water at mains pressure is piped to the cold tap at the kitchen sink to guarantee a pure supply for drinking and cooking. It is also piped to a high-level cold water storage tank. From there, water is distributed by gravity (natural flow) to other cold taps and appliances, and to a hot-water cylinder which is heated either directly by electricity or by a central heating system.

The drainage system. After water has been used, it flows out of the building through the pipes of the drainage system. This system also carries away solid waste from sinks, toilets, waste disposal units, and other fixtures and appliances.

The drainpipes from the fixtures and appliances slant downward, carrying water and sewage to a vertical pipe called the soil stack. T he soil stack empties into a main drain beneath the building. This drain leads to a sewer or septic tank outside the building. The top of the soil stack extends up through the roof of the building, where it is vented to the open air.

In many communities, sewage flows from the main drain of each building into an underground system of pipes that carries it to a sewage treatment plant. The plant treats the sewage water and reduces the bacteria in it. The water can then be poured into a river or other body of water with minimum damage to the waterway.

Notes:

plumbing – водопроводно-канализационная сеть

plumbing fixtures – сантехника ( в доме)

slant downward – располагаться под наклоном

UNIT IV