Sensors for the ventilation system with recuperation
Sensors for the ventilation system with recuperation
We often get questions from clients about what sensors to use or if sensors even make sense. In this article we will look at the sensors in more detail.
Outline of the article:
Why use sensors to control the ventilation of a family home
Selection of sensor type and location
Sensor communication with the recuperation unit
Sensor lifetime - when the sensor begins to lie
Why use sensors to control the ventilation of a family home
Based on the measured values from the sensors, we are able to accurately and continuously control the performance of the recuperation unit so that the value of the controlled quantity remains within the set limits.
Another, and probably the biggest, advantage of control using sensors is the complete automation of control of the entire system . From the initial setting, the system runs without the client's intervention in the management. The client therefore only has to look after the replacement of filters and, if necessary, the necessary service and cleaning of the entire system.
Selection of sensor type and location
In the ventilation system, the sensors usually monitor the value of the quantities that we want to keep within a certain range.
The most frequently used sensors in ventilation systems with recuperation of family houses:
CO 2 (carbon dioxide) – CO 2 concentration is given in units of ppm (Parts Per Million)
They are generally referred to as exhaled air sensors.RH (relative humidity) - relative humidity is expressed as a percentage.
Protects the household from mold.VOC (Volatile Organic Compounds)
It deals with dangerous substances escaping from furniture, from cooking, products of the metabolism of living organisms, bio-waste substances or vapors from various materials, chemicals, cleaning agents or from other technological processesRadon (carcinogenic substances, highly radioactive gas) - measured in Bq/m 3
They determine the intensity of ventilation for radon dilution or give information about the need to turn on the overpressure mode - always consult with the designerTemperatures (they help to maintain the temperature according to the user's ideas) - expressed in °C
They are mainly used for the correct setting of the recuperator by-pass in units with a counter-flow recuperator or for controlling heaters and coolers in the air handling system.Combination of sensors (VOC+RH, VOC+CO2)
It is very useful if we want to protect ourselves from several harmful substances at once.
Peripherally used sensors:
Dust (monitors airborne particles)
Cigarette smoke
Refrigerant leakage
Sensor location
For the sensor to work well, it must be properly positioned.
Sensors can be:
Spatial – suitable for households, the most commonly used type
Pipe (ducted) – a less common design, which is rather abandoned in this segment of air conditioning
Room CO 2 sensors
Monitoring the CO 2 concentration value is currently the most used solution for effective ventilation control. The concentration of carbon dioxide is a great indicator of how the air is currently being exhaled.
We therefore place these sensors in living rooms where humans are the main producer of CO 2 .
We place them in bedrooms, children's rooms, offices, children's playrooms and living rooms. We install them at a height of 1-1.5 m from the floor . They are most often found at the height of switches.
It is also important to ensure that the sensor is not placed near the fresh air inlet and the measured data of the sensor is not distorted. It is also a good idea to keep the sensor away from openings in structures where air with a lower concentration of CO2 can flow (doors, windows, etc.). Similarly, the sensor should not be blocked by furniture, there again dust and clogging of the sensor filter can be a problem. It is advisable to place the sensor not far (e.g. 1m) from the drainage outlet.
If you plan to use CO 2 sensors, it is a good idea to place the sensor in all living rooms . If the sensor is placed, for example, only in the children's room, there may be a case where the CO 2 level is low in the children's room, but the values in the bedroom exceed the acceptable limit.
Our recommended room CO2 sensors can be found here .
Room sensors RH
This type of sensor is, of course, particularly suitable for rooms with expected high humidity, namely bathrooms, toilets, wellness and laundry rooms . However, their usefulness does not end in these rooms. In some cases, it is also necessary to monitor the humidity in other rooms, where mold can otherwise develop, for example.
A suitable installation is up to a height above 1-2 m from the floor . Choose the location similarly to CO 2.
Our recommended room humidity sensors can be found here .
Room VOC sensors
What exactly is a VOC? In very layman's terms, they are smells. Their source can be a person (breath, sweat, metabolic activities) or, for example, cooking, cosmetics, cleaning products, etc.
VOC sensors can be used in kitchens, toilets, cloakrooms, etc.
We install at a height of 1-2 m from the floor, min. 1 m from room corners, min. 1 m from the door. It is advisable to place the sensor not far (e.g. 1m) from the drainage outlet.
Our recommended VOC room sensors can be found here .
Room temperature sensors
Room temperature sensors are often needed precisely for the operation of a recuperation unit with cooling or heating. Often these units have a temperature sensor in the controller , but not always the client wants a controller.
We place the sensors in rooms with the greatest exposure to cold or heat – typically a room with a fireplace, attic rooms, etc.
Our recommended temperature sensors:
spatial: NL-ECO-T
channel: NL-ECO-TD
Of course, there are many more sensors, but here we have discussed only the types that are relevant for the ventilation systems of family houses.
Sensor communication with the recuperation unit
Common sensors offer 3 types of outputs, which can be used to communicate with other elements of the system.
Relay output
This type of output sends a signal to the unit when the set value of the measured quantity is exceeded.
It is a simpler type of communication that is more suitable for starting exhaust fans. However, it also has its uses for ventilation systems with recuperation, e.g. starting an increased draft from the fireplace when a certain temperature in the room is exceeded or an immediate increase in the performance of the recuperation unit.
Output 0-10V
Suitable for smooth power control of the recovery unit or fan. This is the most common variant of sensor-unit communication.
This type of communication is absolutely sufficient for the complete control of the performance of the ventilation unit and, when done correctly, it is the most economical and convenient way of controlling the ventilation.
Modbus output
The answer to the ever-increasing frequency of superior systems (smart home) in new family homes. Some modern recovery units are already starting to switch to Modbus communication for sensors or even for Boost buttons. These sensors will probably start to appear more and more.
It sends the measured value of the measured variable using Modbus communication. So it is not like the previous solution, where only 0-10V goes into the unit and it is necessary to recalculate according to the characteristics of the sensor. This option is probably the most intuitive.
How should I power the sensors?
So now we know what values the sensors can measure, where to install them and how they communicate with our unit/fan. So we move on to how we can power the sensor.
Sensors are usually powered by 12/24 V AC/DC, 230 V AC or batteries.
Cable-powered sensors (12/24 V and 230 V)
This variant is the most common, and compared to the next variant, the sensors are also somewhat cheaper. In most cases, the sensors are connected to the recuperation unit for communication, and in some cases the sensors can be powered directly from the unit. However, we can only power a smaller number of sensors and it depends, of course, on the type of unit.
Battery sensors
Battery sensors are mainly used for renovations or when sensors are added additionally. It is not necessary to deal with any cabling and it is enough to place the sensors in the desired places and to place a receiver on the unit, which will be connected to the unit.
The lifespan of batteries is long these days, so they usually need to be replaced once a year. This solution can, of course, at a higher purchase price, fully replace the cable version of the sensors.
Sensor lifetime - when the sensor begins to lie
Sensor maintenance
Temperature, Rh and VOC sensors are essentially maintenance-free. No calibration or maintenance is required during their operation.
At first glance, CO2 sensors are more demanding to operate, but thanks to the auto-calibration function that the sensors we offer are equipped with, reliability is significantly improved compared to cheaper substitutes.
The auto-calibration function works in such a way that the sensor corrects its accuracy over a long period of time according to the outdoor air, in which the CO 2 concentration is relatively constant at 400 ppm. For the auto-calibration to function properly, it is necessary to properly ventilate the interior space to values close to outdoor air once every 10 days.
Of course, the lifetime of sensors is not unlimited, just like anything else. However, the sensors offered for our clients on the e-shop and for our ventilation installations with recuperation can boast a minimum service life of 10 years.
Upon reaching 10 years, the sensor may begin to measure inaccurate values. Therefore, we recommend checking the reliability of the sensor and possibly replacing it with a new one.
Principle of NDIR measurement
The offered CO2 sensors use the most modern NDIR technology, thanks to this method of measurement they show excellent repeatability, long-term stability and reliability.
NDIR sensors are based on the principle of absorption of infrared radiation of a specific wavelength by CO 2 molecules in accordance with the Beer-Lambert law*. In the measuring chamber there is a source of infrared radiation and a detector. And the more CO 2 molecules there are in the air in the measuring chamber, the less infrared radiation will fall from the source to the detector. The signal from the infrared detector is then amplified and recalculated to the concentration of CO 2 in ppm.