The diagram below shows how a central heating system in a house works.

Summarise the information by selecting and reporting the main features, and make comparisons where relevant.
 
Write at least 150 words.

Sample Answer 1:

The given diagram shows how a central heating system of a house works. As is observed from the illustration, the central heating machine comprises several mechanical aspects and forms a complex system.

According to the given illustration, for the central heating machine to work the cold water supply is required and this water flows to the storage tank and the overflow pipe is there to store the excess water in storage. The water is passed through a boiler which is either gas or oil driven and a pump is connected with it. The radiators are connected with the boiler and these radiators are made of small tubes. When the cold water passes through the pump and boiler, it gains temperatures and become hot water and from the water taps, the house members get hot water. Thus the whole system that covers the house keeps it warm.  

In summary, the central heating system mainly works by flowing water through the house and increasing the temperature of it.

Model Answer 2:

The given picture illustrates how a central heating system operates in a typical house in order to keep internal climate and tap water at a pre-set temperature. The process runs through two stages, starting at a transitory state until reaching a steady state.

In the transitory stage, the main goal is to fill the heater´s piping circuit up with water. Initially, cold water is taken from the local water utility supplier and passed through a boiler, which is a device designed to exchange energy between burned fuel (gas or oil) and water, this fluid is then pumped through some tubes and radiators, which are equipment used for exchanging temperature between the running fluid and the air inside the house. Finally, water reaches back to the boiler. The amount of water taken from the utility service has a specific volume according to an engineering design, this stage continually repeats until the water gets a predefined temperature.

Once the system has reached the pre-set temperature, that is when it gets to steady state, thanks to the high pressure on the piping circuit, water is transported to a storage tank from the boiler, after the storage tank is completed, water runs down to a sink and when the pressure again is high enough, water deviates towards a spare water tank which functions as a water reserve for when the service is interrupted.

[Written by – Sebastián Gómez Vidal]