Characteristics and applicable occasions of roof-mounted air-conditioning units

Characteristics and applicable occasions of roof-mounted air-conditioning units

A roof-mounted air conditioner (hereinafter referred to as RTU) is a unit-integrated unit that integrates cooling, heating, air supply, air purification, and electrical control, and is mostly installed on the roof, so it is called a roof-mounted air conditioner.

In recent years, RTU has been more and more used in air-conditioning projects due to its compact structure, wide energy range, convenient adjustment, reduced installation time, and cost savings.

1. Features of the unit

     1. The unit has a compact structure, comes with a cold and heat source, and is air-cooled. In recent years, most of the units are designed in a modular manner, which is convenient to assemble and saves the cooling water system.

     2. The structure of the unit takes rainproof measures into consideration. When installed on the roof or outdoor platform, rainproof and sunshade facilities may not be provided.

     3. The unit comes with full computer control, high degree of automation, and the electrical connection of the unit is compact, only a few control lines and main power lines need to be connected on site.

     4. The refrigeration system of the unit is efficient and reliable, which can meet the requirements of various types of air conditioning. The condenser and evaporator are generally made of copper tubes with aluminum fins, which have high heat transfer efficiency.

     5.RTU does not occupy the effective area of the room. In some areas, it can save electricity compared with water-cooled units.

2. Applicable areas of rooftop air conditioners

     1. The water cooler is based on the wet bulb temperature, while the air cooler is based on the dry bulb temperature, so RTU is generally more beneficial to use in areas where the dry bulb temperature changes greatly within a day.

     2. Because RTU is air-cooled, it can be used in water-scarce areas. Most of the countries in the Middle East and Las Vegas in the United States use RTU.

     3. The water chiller is limited by the height of the building, and the water pressure should not be too high. Usually, the height is 100m, and the setting of the cooling tower will affect the appearance of the building. Therefore, at present, there are too many super high buildings above 200m in the world that use air cooling. machine.

3. Unit settings

     1. For the installation of rooftop units, the most economical installation location must be selected first, that is, the place where the load is concentrated, so as to reduce the cost of the pipe network.

     2. Consider the impact of noise on the environment. The noise of the unit should not exceed the allowable noise standard. According to some data, the noise standard within 5m from the unit. Some data show that the noise has a greater impact on the environment within 5m from the unit, and has a greater impact outside 5m. Set up the unit above 5m above the residential building. In addition to laying sound-absorbing materials on the surface of the assembly or lining, the current noise reduction measures can also place the compressor in the sound-proof enclosure. In addition, reducing the speed of the exhaust fan and installing a muffler at the air inlet and outlet are effective measures to reduce noise.

     3. The impact of unit vibration on buildings should be considered to prevent solid sound transmission from entering the working and living environment. Generally, rubber pads should be installed under the unit, and vibration-damping joints should be installed on the water inlet and outlet pipes, and the unit should be arranged on the load-bearing wall as far as possible to prevent resonance when it is installed in the middle of the roof slab.

     4. The location of the exhaust fan and the ventilation opening on the building should be taken into account when setting up the unit, because the exhaust air flow in these places will affect the air flow on the roof, so the RTU should keep a certain distance from the ventilation opening.

     5. Local wind conditions will affect the operation of the condensing fan of the unit. When the fan rotates freely with the wind, the air flow of the condenser will be blocked, and the one-way rotating fan cover can prevent the above phenomenon from happening. Also, high winds can make it difficult for lighter RTUs to stabilize, so local wind conditions should also be considered.

     6. For high-rise buildings, it is necessary to consider whether the power of the crane is limited, so the weight of the unit should be determined before installation.

4. Matters needing attention when selecting and installing the unit

     1. The airtightness of the unit and the anti-leakage of the panel are very important. Rain, snow, dust, hot and cold air will infiltrate with the air, which will reduce the capacity and life of the unit. Also consider the slope of the roof to keep the unit level.

     2. A large amount of condensed water in the unit should be removed in time, because when there is accumulated water, microorganisms and algae will grow and affect the air quality. Condensed water should not be discharged on the roof, which will reduce the life of the roof surface layer, and can generally be drained away through the sewer.

     3. The steam trap is best installed inside the unit to prevent freezing.