Types of HVAC systems. What to select?

All the air conditioners can be divided for domestic and industrial. They differ not in design but in the application.  House air conditioners are usually have power of 7 kW, used for cooling small rooms of 15 – 80 sqm. Industrial ones used for cooling large areas, such as entire cooling buildings district . There is also a large class of air conditioners, occupying an intermediate position between the domestic and industrial systems – it is semi-industrial conditioners. With power from 7 to 25 kW, they can be used in a domestic environment such as cottages, multi-room apartments, as well as in offices, shops, factories, etc.

Here we will describe the main types of domestic and semi-industrial air conditioners. There are only two large classes of air conditioners which we can highlight concerning design of device: mono-block – consisting of one block (window, portable, etc.) and a split system – consisting of two or more blocks (wall, ducted, cassette, and the VRF system etc.).

Window air conditioning


Nowadays, almost all manufacturers offer window models of AC from 1.5 to 6 kW. The simplest of them can only cool the air, the more expensive have heating and remote control mode. The main disadvantages of window air conditioners are increased noise and the need for installation in the window opening. But there are also some advantages like low price (from 280 – $ 300) and easy to install, requiring no special tools.

  • Lowest price, simple installation.
  • Loud noises, installed in the window opening.

Portable air conditioning

mobile split system

Portable conditioner outwardly looks like a small bedside table on wheels. Such conditioners do not require special installation, you only need take out a flexible hose (duct) with a diameter of about 15 cm and a length of 1 – 2 m to the street through the window or hole in the wall. Hot air is removed via this tube. Disadvantages of mobile AC it is a lot of noise during work (compressor is actually located inside the premise) and also high price compared to the cost of a split system. Another, rather rare kind of portable units is a mobile split system – in these conditioners interblock communications are connected to the internal and external unit via plug connections (latches).

  • It does not require installation.
  • Loud noises, the high price.

Air conditioners split and multi-split systems

Wall conditioners

wall air conditioner

wall air conditioner

This air conditioner consists of the indoor and outdoor units, which are interconnected by electric cable and copper pipes, which circulates freon. With this design the most noisy and cumbersome part of the air conditioner comprising a compressor, taken out to the outside. The indoor unit can be placed in any convenient location of apartment or office.

All modern split-systems are equipped with remote control (RC) with LCD display. With it, you can set the room temperature to within 1-2 degrees also set the timer for automatically turn on and off the air conditioner at a preset time and adjust the direction of air flow and more. Inner blocks have filters of fine and coarse purification to filter the air of dust, smoke, pollen, etc.

  • Low noise level, ability choose the place of installation, a large selection of indoor units, the remote controller.
  • It requires proper installation and maintenance.

The most common and most affordable (from 550 – $ 600) – wall-mounted AC or split-system wall type. Sometimes it called a domestic split-system, as in the apartments they are most often used. Wall-mounted device can be installed in any small premise such as office, apartment or store. Their power (2 – 7 kW) can cool from 15 to 70 sq.m. Inner wall conditioning unit is usually installed in the upper part of the wall close to the window, and the outer one – under the window. This arrangement allows to reduce the distance between the blocks and the length of inter-block communications which usually does not exceed 5 – 7 meters.

  • The lowest price among the split-systems, a wide range.
  • Limited power (7 kW). Restrictions on the installation site.

Multi-split system is a kind of split systems. The difference is that a single outdoor unit connects to several internal, usually from 2 to 4 – 5 pieces. In this case the indoor units may be not only of different power (typically 2 to 5 KW), but also of different types. This design saves space on the outer wall of the building and does not spoil the appearance of the outdoor units. At the same time, contrary to popular belief, the replacement of several split systems on a single multi-split system does not lead to a gain in price, because the cost of the equipment is approximately the same but labor and installation costs – 1.5 – 2 times higher due to longer communications. In addition, in case of failure of outdoor unit of multi-split system  does not work all the indoor units. From this point of view, the reliability of several split systems is higher. Therefore, multi-split systems are usually used only when it is impossible to place several outer blocks on the outer wall of the house.

Another advantage of the split and multi-split systems is the large selection of different types of indoor units. Among them are the following modifications: wall air-conditioning, air-conditioning channel, cassette air conditioner, air conditioning, under-ceiling conditioner and columned conditioner.

Ducted air conditioners


Ducted or central air conditioner is installed behind suspended or boarding ceiling which completely hides the inner block. The distribution of the cooled air is carried out through the system of thermally insulated ducts, which are also placed in the ceiling space. With this design, ducted air conditioner can cool several rooms. The typical power of these device is 12 – 25 kW, which is enough to cool a small office or a 4 – 5 room apartment. The fundamental difference of ducted conditioners from the rest systems – the possibility of fresh air feeding in the volumes necessary for thorough ventilation of conditioned space.

Thereby, the use of one channel air-conditioner allows to solve the problem of ventilation and air-conditioning of the whole office, apartment or cottage. It is only necessary to take care of the correct calculation of ventilation, air conditioning selection on the cooling power and static pressure. Also, to envisage installation of electrical or water heater for heating the outside air in the winter.

  • Hidden installation, the possibility of fresh air. It can serve multiple premises.
  • Required suspended ceiling and duct system.

Cassette air conditioners

cassette air conditioner

cassette air conditioner

To install cassette device is required suspended ceiling. Cassette system distributes the cooled air through the lower part of the block. Accordingly, the lower part of the air conditioner has size of a standard ceiling tiles – 600 x 600 mm, and at high power twice bigger  to 1200 x 600 mm and closed with a decorative grate with distributive shutters. The main advantage of this system is invisibility because only decorative lattice is visible. Another advantage is distribution of air flow in four directions, allowing you to use only one cassette conditioner to cool a large premise.

  • Hidden installation, the possibility of cooling large spaces.
  • Required suspended ceiling

Under ceiling air conditioner


If there is no suspended ceiling in room, there is always an alternative which can be wall under-ceiling (or just ceiling) conditioner. These devices have a difference in little depth 18 – 25 cm. They are installed on a bottom wall or on the ceiling. Thus the air flow in the first instance is directed upwards, in the second horizontally along the ceiling. This design allows you to evenly distribute the cooled air throughout the room, and avoid direct flow on people. There are models of ceiling air-conditioners distributing the cooled air in four directions, and the flow power is regulated separately in each area. Such conditioners can be successfully used for cooling rooms of complex shape, without a false ceiling.

  • Possibility of installing on the ceiling and bottom wall. Suspended ceiling is not required.
  • Not intended for flush mounting.

Column air conditioner


Column (floor or wardrobe) air-conditioning is used where a large cooling capacity is required and there are no strict requirements for design of the room. These conditioners on dimensions look like refrigerators, have big weight and installed on the floor. Column devices require comparatively large area for their placement because they produce strong flow of cooled air and do not allow to be in the vicinity of the air conditioner.

  • High power. False ceiling is not required.
  • Requires a large area for placement, spoil design.

Precision air conditioners


Precision air conditioners are kind of column air conditioning and have a rather narrow range of applications such as computer rooms, telephone exchanges and stations of cellular communication systems, high-precision production. With a very good reliability, these units can maintain high accuracy of  temperature (± 1°C) and humidity (± 2%). Another feature of precision air conditioners is ability to work in a wide temperature range of outside air (lower limit  up to – 35°C).

  • High accuracy of temperature and humidity. Wide temperature range.
  • Designed for industrial applications

Multi Zone conditioning systems (VRF and VRV system)


This class of air conditioners appeared relatively recent, first VRV system was introduced in 1982. In fact, this multi-split system with fundamentally new features – up to 30 indoor units to one external, centralised management using a personal computer, distance between outdoor and indoor units can reach 100 meters, and the height difference 50 meters. Using VRV and VRF systems helped to solve the problem of the placement of outdoor units, so now they can be installed in any convenient location (on the roof, in the basement, outside the building), so that they do not spoil the look of the house.

  • The unique characteristics of the length of the route, the number of indoor units and control system.
  • High price.

Which type of HVAC systems to choose?

In fact, in 90% of cases, you just need to make a choice between window mono block and wall split-system. Other types of air conditioners used only if “window device” or “wall device” does not allow to solve the problem. In a domestic environment it is extremely rare.

In this class, these units the most affordable. The lowest price have window air conditioners, so if you have limited budget the other choice is not exist. Split systems more expensive than “window air”, but have a number of advantages: equipped with a fully functional remote control, allow you to select where to install the indoor unit, low noise, easy to fit into the interior. Therefore, if you have enough money, it is better to choose a split-system wall type. Selecting split systems with other types of indoor units may be required only if you want to condition large areas – trading rooms, cottages, luxury apartments, complexes of offices, and in this case it is best to look for professional help.

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