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What is HVAC?

written by: Haresh Khemani • edited by: Lamar Stonecypher • updated: 11/14/2008

HVAC stands for heating, ventilating, air-conditioning. Many times the letter R is also added to it making it HVAC-R or HVACR.

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    What is HVAC?

    HVAC stands for heating, ventilating, air-conditioning. Many times the letter R is also added to it making it HVAC-R or HVACR. The letter R stands for refrigeration. In some cases the word ventilating is removed from short form making it HACR. Another term similar to HVACR is RAC that stands for refrigeration and air-conditioning.

    HVAC mostly deals with the control of the temperature inside the domestic room, offices, buildings etc. During summers the temperature of the room has to be kept lower than the atmospheric temperature to maintain comfort conditions and at the same time some flow of air has to maintained inside the room so that there is no suffocation.

    Large amount of heat is generated inside the room due to various sources of heat like human beings, windows, walls, partitions, roof, electrical and electronic appliances etc. HVAC involves calculation the total amount of heat generated inside the room. For the large buildings like hotels, theaters, air-ports the total heat generated in all rooms has to be calculated. Along with the heat load calculations, the total amount of air-circulation required inside the rooms or halls of the building has also to be calculated.

    Based on all these calculations, the HVAC designer recommends the size of the air-conditioning system that will required for the whole building or a particular room to maintain the comfort conditions of 25 degree Celsius and 50% relative humidity inside all the rooms. The recommendation of the HVAC designer is very crucial for if the air-conditioning system of lower size is selected, it won’t serve the purpose of cooling the room, while if oversized system is selected the initial and running cost of the system will become very high.

    HVAC also involves maintaining the high temperature inside the room when the atmospheric temperature is very low. In such cases the room has to be kept hot by using the room heaters or heat pump. The heaters are the ordinary electric heaters, while the heat pump is an air-conditioner with it operation reversed.

    The HVAC designer should have thorough knowledge of the various principles of thermodynamics, the properties of air, fluid mechanics, heat transfer, comfort conditions, various types of air-conditioning systems and their working etc.