The objective of this activity is to practise the comprehension of a written text and write the answers in well-structured and complete sentences.
Read the following text and answer the questions below.
HVAC stands for Heating, Ventilation and Air Conditioning. It is a generic term which refers to a system whose main function is to contribute to the environmental comfort of a house or a building by providing the desired conditions of temperature and air circulation.
The HVAC systems are very important in large industrial and office buildings as well as in buildings where the temperature and humidity must be carefully regulated, as for example in greenhouses or aquariums. The design of HVAC systems in large buildings corresponds to the field of mechanical engineering. In a home, the HVAC service is provided by the central heating, heat pumps and air conditioning units.
HVAC units like central heating or air conditioning imply the installation of separate units for heating or cooling a home. In central heating, the heat is generated in a central boiler, which heats water and distributes it through pipes to radiators placed around the house. In air conditioning systems, the basic device is the air conditioner, which is a machine designed to change the temperature and humidity of the house using a refrigeration cycle. In this process, heat is absorbed from indoors and transferred to the exterior of the house. The installation of HVAC units requires the installation of a variety of elements like central boilers, radiators, pumps, air conducts, pipes, air conditioners, air conditioning units, etc. We can in part avoid such complexity by including a reversing valve in an air conditioning installation. This valve automatically changes from heating in winter to cooling in summer, so a house can be heated and cooled using the same equipment instead of using two separate systems.
A good solution for heating and cooling a house in a simple and highly efficient way is by installing a heat pump. A heat pump is an electrical device which works very much like an air conditioner, moving hot and cold air from one place to the other to cool or heat a place. The biggest advantage of a heat pump is that there’s no need to install separate heating and cooling systems. Heat pumps are also cheaper and more efficient than standard HVAC units because they only move heat from one place to the other instead of creating it by heating water. This also makes heat pumps more energy saving than other systems because they require very little energy to operate. And they are certainly cheaper to install and maintain.
The most common type of heat pump is the air-source pump. The working is very simple. A unit installed outside the building takes the outside air. A system of fans, coils and a compressor transforms the air into hot vapor which passes to a unit installed inside the building and is then distributed through the house by air conducts. A reversal pump installed on the compressor allows the system to reverse the process and instead of taking the heat from outside, it takes the inside heat and expels it outside, as an air conditioner does.
Air-source pumps are the most common type, but there are others, like the ground-source pump, which absorbs the heat from the ground and transfers it inside a house, and the absorption pump, which is similar to an air-source pump, but using natural gas or solar power instead of electricity.
As we said before, the main advantages of heat pumps are that they have the heating and cooling functions in a single system, they are cheaper because they consume less energy and therefore they are also more friendly to the environment. But they might also have some disadvantages. In very cold climates, heat pumps are not as efficient as in moderate climates because the system needs more energy to absorb and distribute the little heat that is available outside. When the difference in temperature between the inside and the outside of a house is very big, the system might even stop if it reaches a point of saturation. On the other hand, the heat produced by heat pumps is not so intense as the heat produced by the central heating.
- What is the definition of HVAC systems, according to the text?
- Give three examples of home HVAC systems.
- How does a central heating system work in order to heat a home?
- How can we simplify the installation of an HVAC system?
- Which are the advantages and disadvantages of heat pumps?
The objective of this activity is to practise the use of the modal verb can to express ability in the present and in the past.
Write 6 things that you can or can’t do now.
Now say 6 things that you could or couldn’t do when you were a child.
The objective of this activity is to practise the use of the modal verbs may or might to express possibility.
Say 6 things that may or may not happen if the following situation comes true, as in the example. Remember that may and might have the same meaning, but with might, the possibility is seen as more remote.
If the economic crisis continues for a long time, …
Example: We may have lots of problems.
The objective of this unit is to practise the use of the modal verbs must and should to express obligation.
Remember that the modal verb must is used to express a strong obligation, usually, but not always, established by the law. Say 6 things that you must or mustn’t do.
On the other hand, the modal verb should is used to express a moral obligation, that is, an action which is not prohibited, but it is advisable to do. Now say 6 things that you should or shouldn’t do to learn English.
The objective of this activity is to practise the use of the future to make predictions.
Imagine our world in 100 years’ time. Make 6 predictions. Begin like this:
In 100 years’ time, I think that …
The objective of this activity is to practise the use of the future to express your plans.
Write 6 plans that you have made for next year. Begin like this:
Next year …
The objective of this unit is to practise the use of the imperative form and the connectors to write an appropriate text giving instructions.
Write a text with the appropriate instructions in case of fire in the house. Remember to use the imperative form of the verb and the correct connectors to link different ideas.