Designers have various options to choose from when designing building air conditioning systems, and choosing one of these systems is not an easy task. The opinions of the project owners for the selection and installation of equipment, as well as the operating costs of the system should be taken into account during the design. The designer must consider performance, capacity, reliability, as well as space limitations when designing the system. The following outlines describe the different types of equipment and their applications, limitations and barriers to their use.
uses of building
The designer must consider the use of the building when choosing the equipment that will be used in the design. In office buildings that are used on a daily basis, the equipment is generally of the type of fan terminals. In spaces that are in contact with the outside air, fan terminals are usually used with auxiliary heaters (supplementary heating). It is very easy to use this system for individual spaces and it also allows the central system to be turned off during non-office hours. In non-office hours when personnel are not present, the fan terminals keep the room temperature at an acceptable level without the help of the central air conditioning system.
The size of the building
In large buildings, central ventilation systems deliver a large volume of air to different areas with different thermal needs. Indoor spaces may not need heating at all. Therefore, these spaces can be equipped either with single-channel units or with fan terminals without thermal elements. If the building is located in the tropics, the exterior areas may require electric element heating or hot water. In buildings where the owner has a great desire to reduce costs, variable volume terminals with series fans are usually used so that the static pressure in the channel is less than 0.5 inches of water (125 pascal). In the interior spaces of these types of buildings, it may be necessary to use fan terminals. Usually, parallel fan terminals are used in the parts that are connected to the outside, and single-channel units are used in the internal parts of the building.
Audio restrictions
Choosing the right equipment and their installation location in news studios, theaters and libraries is very important. If variable air volume terminals with fans are used in such spaces, it is very necessary to test the sound of the equipment.
Environmental factors
Environmental factors include indoor and outdoor air conditions as well as rules and regulations governing buildings. If a high ventilation rate is required in the interior spaces, it is necessary to use reheating. For example, reheating is used in the laboratory where the required ventilation rate is high due to the activity of hoods. In spaces where the internal load changes significantly during the day, such as outdoor spaces in high-rise buildings, where seasonal conditions, the heat load of the sun, and the change in the number of people during the day affect the heat load, the use of fan terminals It is ideal. Single-channel units are suitable in areas where the heat load is almost stable.
Pollution considerations
Buildings such as hospitals and laboratories that have special designs, operating rooms, bone marrow transplant rooms, spaces related to AIDS patients and also clean rooms need a positive pressure environment. In addition to pressure criteria, reheating coils and uncoated fiberglass are not used in these spaces to prevent the growth of microbes in hospital environments. Hospital spaces and clean rooms usually require a constant ventilation rate, so in these types of applications, the use of two-channel variable air volume terminals is considered a suitable choice. The rooms of patients suffering from highly contagious diseases such as tuberculosis must have negative pressure so that contamination does not leak out. Laboratories in which there are highly toxic and dangerous materials should also be negative pressure. For this type of buildings, single-channel or two-channel terminals are usually used.
Access and maintenance
In some buildings, such as clean rooms, terminals with high reliability are needed due to the difficulty and high costs related to the service and maintenance of equipment. For example, after any changes in the ceiling of the clean room, the space must be disinfected before reuse, and this causes costs such as the cost of lost production time as well as the cost of disinfection. In such a situation, either the equipment must be installed outside of the clean room and have high reliability, or it needs low maintenance.
Cost invoices
Before the final selection of the system, costs such as the cost of installation, commissioning and maintenance should be considered. Sometimes one of these costs is more important than the others. For example, if the owner of the project decides to sell the building before the start of the construction operation, the construction cost will be a priority for him, and the start-up, maintenance and maintenance costs will not be very important. If the tenants pay for their facilities, the start-up costs will not matter to the developer. For example, electric heating coils usually have lower installation costs and higher start-up costs than hot water coils. In order to evaluate the plan in terms of cost, it should be considered before the final decision in choosing the energy rate system in the building construction area.
