2.Active vocabulary: Text 2 Hot water installations

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Hot water can be produced in various ways, but in modern buildings it should be a safe and efficient part of the normal plumbing installations. This section examines the methods for supplying hot water to sinks, baths, basins and showers in do­mestic environments.

Three types of electric appliances heat water:

1. immersion heaters;

2. electric boilers;

3. electric geysers.

An immersion heater is an electric element in a storage cylinder, which heats the water to a pre­set temperature. When the hot water is used, then the immersion heater heats up the new supply of cold water to the pre-set temperature. The immer­sion heater has a thermostat, which senses the temperature of the water and switches the electric­ity supply on and off as required.

The hot water is supplied from the top of the cylinder and cold water enters the bottom. This ensures that the hottest water is available for use. Cylinders fitted with insulation jackets retain heat longer and save energy.

An electric boiler is a separate appliance for heating water in a storage tank. A primary pipe circuit links the boiler with the storage cylinder. The boiler heats the water in the primary circuit, which gets hotter and hotter. While it passes through a coil in the storage cylinder, the heat transfers to the cold water in the cylinder. When the water in the cylinder reaches a pre-set temperature, then a thermostat switches off the electricity supply to the boiler. As hot water is used and the temperature of the remaining water drops, then the thermostat switches on the electricity again and the boiler heats up more water.

An electric geyser makes hot water by convert­ing cold water to hot as it is needed. When a tap is turned on, water flows through a coiled pipe, which is covered by a heating element. Turning the tap switches on the current to the heating element, which heats the water as it flows past. The flow of water is fairly slow so this type of fitting is best suited to a single location such as a basin or sink.

The pipework for hot water systems Cold water enters the hot water cylinder at the bottom of the tank (Figure 18.6). The source may be:

1. a direct down service from the cold water stor­age tank;

2. a supply from a cylinder on a solar heating circuit.

The various fittings that use hot water draw it off from the top of the cylinder in a series of branch pipes. When you turn on a tap the water comes out under pressure which is created by a head of water between the tap and the level of water in the cold water tank.

Figure 18.6 Parts of a hot water tank.

The pipe at the top of the cylinder also acts as an expansion pipe so that any water that is pushed out of the system as the temperature rises falls back into the cold, storage tank .-This is a safety valve for the system. If the thermostat fails on the immersion heater, and the water boils, then steam will escape from the expansion pipe into the cold tank.

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