How Hotel Air Conditioners Work?


Almost all hotels have air conditioning. However, many hotel air conditioners are no way to be seen. Instead, we only see HVAC diffusers and grilles on the hotel ceiling. So, how do hotel air conditioners work?

Most hotel air conditioners are concealed above the ceiling. They use chilled water produced by centralized chillers for air conditioning. Concealed hotel air conditioners use ducts to distribute air through their respective supply air diffusers that can be seen on the hotel ceiling.

Since most hotel air conditioners are concealed above the ceiling, their working principle is a mystery to many people. Hence, let’s take a closer look at concealed hotel air conditioners.

How Does Air Conditioning Work in Hotel?

A hotel can be fitted with several types of air conditioning systems as well as different types of air conditioners. However, the most common type of air conditioning system used in hotels is chilled water system. Meanwhile, the most common type of air conditioner used in hotel rooms is a fan coil unit.

Budget hotels (1-star to 2-star) usually don’t have many hotel rooms. Hence, they mostly use split air conditioners. Big luxury hotels (4-star to 5-star) often have a lot of hotel rooms and thus, they always use a chilled water fan coil unit in their hotel rooms.

Hotel Rooms

The air conditioning in a hotel room starts with the hotel key card system. After you get inside your hotel room, you need to insert your hotel card into a dedicated card slot in order to provide power to the appliances in the hotel room.

Once the hotel key card system is activated, the air conditioner located above the hotel room ceiling is powered on. Usually, the air conditioner will run immediately based on the default temperature and fan speed settings.

Hotel Air Conditioning System

The hotel room air conditioner is controlled by a thermostat. Usually, the thermostat is in the form of a display controller. You can set the room temperature, fan speed and other settings using the display controller.

Now, let’s say the hotel room temperature is 28°C and the set temperature is 24°C. Upon you put in the hotel card, the air conditioner starts pulling in the air inside the hotel room and pushes the air through its cooling coil.

Right next to the hotel air conditioner, there is a valve that controls the chilled water supply into the cooling coil of the air conditioner. The other end of the valve is controlled by the thermostat (display controller).

If the set temperature is below the hotel room temperature, the valve will stay open to let chilled water flow through the cooling coil of the air conditioner thereby allowing the air conditioner to cool the hotel room.

Air Conditioner Display Controller

Once the hotel room temperature matches with the set temperature, the valve will close to stop the chilled water from flowing through the air conditioner and therefore, the cooling stops.

The valve used to control chilled water for the air conditioner is also known as the chilled water on/off valve.

Air conditioners that are concealed above the hotel room ceiling use a short piece of duct and a supply air diffuser to distribute cold air. At the same time, they have a return air grille and a mixing plenum box to circulate back the air.

Theoretically, the temperature of the return air is equivalent to the temperature of the hotel room. So, a temperature sensor that is used to control the chilled water valve can often be found on the return air section of the air conditioner.

Depending on factory settings, the air conditioner may provide cooling again when the hotel room temperature is 1°C above the set temperature. The cooling cycle repeats until the air conditioner is switched off or you pull out the hotel card.

Hotel Lobby, Hallway and Restaurants

The air conditioners in hotel lobbies, hallways and restaurants work basically the same as the air conditioners in hotel rooms except, they are not connected to the hotel key card system.

Hotel air conditioners that serve the public area are operated by the hotel maintenance personnel. Similarly, they have thermostats, temperature sensors, ducts, supply air diffusers, return air grilles and mixing plenum boxes.

Usually, these public hotel air conditioners run by schedules programmed by the hotel. Besides, they can be remotely controlled from the hotel control room.

Most of the time, the entire hotel air conditioners use the chilled water generated by large centralized chillers that are located either at the basement or at a dedicated mechanical floor. With large chillers, hotel air conditioners are more efficient.

Do Hotel Air Conditioners Pull Air from Outside?

A hotel typically has hundreds of hotel rooms and air conditioners. However, we often don’t see many louvers or grilles on the exterior wall of the hotel. Hence, do hotel air conditioners pull air from outside?

Hotel air conditioners do pull air from outside and bring in fresh air into the hotel. Most hotels have a centralized fresh air system. They connect large fresh air fans to hotel air conditioners so that fresh air can be introduced into hotel rooms and other areas of the hotel.

Hotel fresh air fans can be located on the roof or on dedicated mechanical floors. They draw in outside air and supply it to their respective hotel air conditioners via ductwork.

Usually, hotel air conditioners receive fresh air at their mixing plenum box. As the name suggests, hotel air conditioners mix the return air with the fresh air before filtering the air and supplying the air back to the hotel room.

Some hotels use pre-cool air handling units (PAU) to reduce the outside air temperature as well as clean the outside air before introducing them to individual hotel air conditioners to reduce power consumption as well as better indoor air quality.

The amount of fresh air introduced in each hotel room is controlled by an air volume control damper (VCD). Usually, the percentage of fresh air relative to the supply airflow is about 10%.

So, although we don’t get to see how hotel air conditioners pull air from outside because they are concealed, most hotel air conditioners do supply a sufficient amount of fresh air into the hotel room.

What Kind of Air Conditioners Do Hotels Use?

There are many kinds of air conditioners in the market. Hotels have certain requirements and thus, they need to use a certain type of air conditioner. So, what kind of air conditioners do hotels use?

Generally, budget hotels use wall-mounted air conditioners that work with their respective condenser. Standard hotels and luxury hotels use ceiling concealed fan coil units that work by using chilled water produced by centralized chillers.

Budget hotels usually use split air conditioners while standard hotels and luxury hotels use chilled water fan coil units. However, some standard hotels may use VRF air conditioners depending on the hotel requirements.

One of the most efficient kinds of air conditioning system is chilled water system. It has centralized chillers that produce chilled water for individual hotel air conditioners.

Hotel restaurants, ballrooms and the main lobby usually use air handling units that are many times larger than the fan coil unit in hotel rooms. These air handling units also use chilled water for air conditioning and ducts and grilles for air distribution.

Why Does a Hotel Room Typically Use Fan Coil Unit?

Hotel air conditioners are mostly a ceiling concealed or ceiling ducted type of indoor fan coil unit because ceiling ducted fan coil units are slim (flat/thin). Thus, they are suitable to be installed above the tight hotel room ceiling.

Chilled Water Fan Coil Unit

Furthermore, aesthetics are very important in hotels. Hence, most hotel air conditioners are concealed above the ceiling. Only aesthetically-appealing diffusers and grilles are exposed under the ceiling.

However, other areas of the hotel such as administrative offices, maintenance offices and control rooms may not need to have decorations. So, these areas may be fitted with conventional wall-mounted split air conditioners.

In addition, fan coil units usually don’t have any sort of built-in program and control. Hence, their controls can be customized to the hotel needs. Many fan coil units are integrated with the hotel smart control system.


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Yu Chang Zhen

I enjoy working on air conditioners and ventilation fans because Malaysia is a very hot country.

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