The application of sensors in the HVAC and air handling systems

The application of sensors in the HVAC and air handling systems

The role of sensors in AHU systems

The Air handlers are sophisticated systems and composed of different parts where each of these components contributes to the final scope of the air handling unit: the control and regulation of the air in a given environment. The sensors, also known as sensing device, are part of this set of parts and they have a major role in monitoring the conditions of the environment and sending these inputs to the air handling unit system.

What an HVAC sensor is and how a sensor works

As part of an AHU, the sensors are common control components and their use is focused on monitoring one or more specific values of a fluid. If one of the main scopes of an HVAC system is to ensure the high quality of the air, the ahu sensors play an important role as they check the status of the area in order to have the HVAC performances meet the required standards.

What are the types of sensors?

The Sensors, in HVAC and air handlers systems, differ for the values they have to monitor and their accessories. Their ability to monitor and control temperature, pressure, humidity and air quality defines the type of sensing device.

The main sensors in HVAC and air handling systems are:

Pressure sensors

Temperature sensors

Humidity sensors

Indoor air quality sensors

Room Sensors

What are sensors applications and uses?

The use of a sensor is defined by the type (temperature, humidity,air quality, pressure). A temperature sensor controls the temperature values of a given environment.

What is the difference between active and passive sensors?

The type of sensors is defined by how they work to monitor a specific area as well. A sensor, indeed, is either active or passive. 

What an active sensor is in HVAC and how it works

An active sensor is a sensing device that requires ans external source of power to operate. Active sensing devices gather information related to the environment and translate this into a digital signal to be transmitted to the control. The controller will then convert the value coming from the sensing device into a temperature reading.

What is the benefit of an active sensor?

The main advantage coming from an active sensor is its ability to gather information anytime without any environmental restrictions, as long as it is supported by the required voltage.

What is a passive sensor and how does it work?

The passive sensors, or probes, in air handling systems, are devices providing resistance values to the controller whose they are wired with. The resistance value is then converted by the control.

What are examples of an active and a passive sensor?

An example of an active sensor is the DPPC212000 - Carel Temperature (-20T70 °C) and humidity (0 to 100% RH) sensor for the industrial environment. This sensor needs a power supply only to monitor the temperature in an environment.

Otherwise, the Carel range of NTC probes is the typical example of a passive sensing device where the values are transmitted by resistance.

What a pressure sensor is

In HVAC systems, the pressure sensor is the device used to monitor the pressure drop and it is applied in different zones of the Air handling system. The measurement provided by these sensing devices has to be accurate as they directly affect the overall performance of the HVAC system. The pressure measurement unit depends on the type of the sensor and the value to be measured, however, the Pascal (Pa) is the most common. The main types of pressure measurement are differential pressure, the highest and lowest levels of pressure in an AHU system. 

Pressure transducers are part of this specific category and include different types. 

The differential pressure transducers, in HVAC, are used to size the pressure in two different spots and compare the two values. In this category there are the HVAC pressure transducers, these are devices used to size the pressure of a fluid.

The high-pressure transducer, in HVAC, is used to measure the highest level of pressure in a given part of the environment.

What is an example of a pressure sensor?

The Belimo range of 22ADP pressure sensors is an example of a sensing device focused on the differential pressure value in HVAC and ventilation systems. There are different types of temperature sensing devices such as outdoor air temperature sensors, duct temperature sensors, pipe and room temperature sensors.

What is a temperature sensor?

A temperature sensor is a device, as the name suggests, focused on gathering information related to the temperature in an environment and it is extremely important to set the workload of the AHU system to deliver the specific required temperature.

How does the temperature sensor work?

As part of an HVAC system, the temperature sensor has the role of monitoring the temperature of the air or water and then sending these inputs to a heater which has to adjust the overall temperature of the environment.

Temperature sensor examples

The type of temperature sensor depends on how and where the sensor has to be applied, here are a few examples:

The immersion temperature sensor is a device used to measure the temperature in liquids. The Sontay TT-S-L is an immersion temperature sensor available in our stock.

The Space temperature sensors are focused on measuring the indoor environment, as the TT-S-A Sontay space temperature sensor.

Many sensors are now able to monitor temperature and humidity at the same time: the Carel DPPC212000 Carel Temperature and humidity sensor for the industrial environment is another example.

How do humidity sensors work?

The humidity measurement sensor is the next type here described. It is one of the most common sensors and it often controls the temperature and pressure as well. These devices control and manage the humidity in a given environment by adding steam to the air to balance the humidity level.

The types of electronic humidity sensors differ for applications and humidity value controlled.

Where are humidity sensors used?

The HVAC humidity sensor is suitable to protect building infrastructures and specific delicate environments as museums store artwork, production chains, products requiring specific humidity levels.

How many types of humidity are there?

The humidity values that sensors are capable to detect are:

Relative humidity

Absolute humidity

Specific humidity

Humidity sensor examples

The Belimo 22DTH-15M is a classic duct sensor for temperature and humidity used along with valves and actuators in AHU systems.

The Siemens QFA2000 humidity sensor is a different device, it monitors the humidity in an indoor space as, for example, a room.

What is an indoor air quality sensor?

These types of sensors have a key role in maintaining the quality of the air in an environment at the requested standard of quality. How is indoor air quality monitored? These sensing devices are focused on ensuring the environment is ventilated and the air is filtered in order to avoid the spread of potential viruses.

Room sensors

The function of a room sensor depends on the value that this device is going to detect. The main sensors monitoring rooms are:

Room Temperature sensor

Room Humidity sensor

These types are also capable of monitoring CO2. The room sensors aim to make the indoor environment more comfortable and safe by monitoring the variations in temperature and humidity.

The Siemens QPA2060 Room air quality sensor is a device monitoring the temperature and the CO2 levels in an indoor environment.

Conclusion

In this article, we have had an overview of what an sensor is, how it works and the applications in an HVAC system and AHU unit. All the types of sensors here mentioned are available here in their specific category with the related spares, the main brands in stock are Belimo, Carel, Axio and Siemens

If you want to add anything relevant related to the topic or your direct experience, feel free to leave a message, we would like to hear from you.

If you need any additional info and details do not hesitate to contact us at support@i-acs.co.uk