How to choose sensors for a ventilation system with heat recovery
We often get questions from clients about what sensors to use or whether sensors even make sense. In this article, we will take a closer look at the sensors themselves and the most frequently asked questions related to them, which are:
Why use sensors to control ventilation in a family home?
Based on the measured values from the sensors, we are able to accurately and continuously control the power of the recuperation unit so that the value of the controlled variable remains within the set limits.
Another and probably the biggest advantage of sensor control is the complete automation of the entire system . From the initial setup, the system runs without client intervention. The client only has to watch out for filter replacements, or necessary service and cleaning of the entire system.
Sensor selection
In a ventilation system, sensors usually monitor the value of variables that we want to keep within a certain range.
The most commonly used sensors in ventilation systems with heat recovery in single-family homes:
- CO 2 (carbon dioxide) – CO 2 concentration is given in ppm (Parts Per Million) units
They are generally referred to as exhaled air sensors . RH (relative humidity) - relative humidity is expressed in percentage.
Protects the home from mold.VOC (volatile organic compounds)
It addresses hazardous substances leaking from furniture, cooking, metabolic products of living organisms, bio-waste or fumes from various materials, chemicals, cleaning agents or other technological processes.Radon (carcinogenic substance, highly radioactive gas) - measured in Bq/m 3
They determine the intensity of ventilation for radon dilution or provide information on the need to turn on the overpressure mode - always consult with the designer.Temperatures (help maintain the temperature according to the user's preferences) – expressed in °C
They are mainly used for correct adjustment of the recuperator bypass in units with a counter-flow recuperator or for controlling heaters and coolers in the air conditioning system.Sensor combination (VOC+RH, VOC+CO2)
It is very useful if we want to protect ourselves from multiple harmful substances at once .
Peripherally used sensors:
Dust (monitors airborne particles)
Cigarette smoke
Refrigerant leakage
Sensor location
For the sensor to work well, we need to place it appropriately.
Sensors can be:
Spatial – suitable for households, the most commonly used type
Duct (duct) – a less common design, which is being phased out in this segment of air conditioning.
CO 2 room sensors
Monitoring the CO2 concentration value is currently the most widely used solution for effective ventilation control. The carbon dioxide concentration has a great informative value about how the air is currently exhaled.
We therefore place these sensors in living rooms , where humans are the main producer of CO2 .
We place them in bedrooms, children's rooms, offices, children's playrooms and living rooms. We install them at a height of 1-1.5m 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 sensor data is not distorted. It is also a good idea to keep the sensor away from openings in structures where air with a lower CO2 concentration can flow (doors, windows, etc.). Likewise, the sensor should not be blocked by furniture, as dust and filter clogging can be a problem there . It is advisable to place the sensor close to (e.g. 1m) the exhaust outlet.
If you plan to use CO2 sensors , it is a good idea to place a sensor in all living rooms . If the sensor is placed in, for example, only the children's room, it may happen that the CO2 level in the children's room is low , but in the bedroom the values exceed the acceptable limit.
OUR TIP:
Our recommended room CO2 sensors
{ADS-CO2-24;NL-ECO-CO2;CL-CO2}
Room RH sensors
This type of sensor is particularly suitable for rooms where high humidity is expected, namely bathrooms, toilets, wellness rooms and laundries . However, their usefulness does not end there. In some cases, it is necessary to monitor humidity in other rooms as well, where, for example, mold may otherwise develop.
Suitable installation is at a height of 1-2 m above the floor . Choose a location similar to CO 2.
OUR TIP:
Our recommended room humidity sensors
{ADS-RH-24;NL-ECO-RH-BA;Z-CRJ-P-001}
VOC room sensors
What are VOCs? In layman's terms, they are odors. Their source can be humans (breath, sweat, metabolic activities) or, for example, cooking, cosmetics, cleaning products, etc.
VOC sensors can be used in kitchens, toilets, changing rooms or home gyms.
We install at a height of 1-2m from the floor, min. 1m from the corners of the rooms, min. 1m from the door. It is advisable to place the sensor not far away (e.g. 1m) from the exhaust outlet.
OUR TIP:
Our recommended VOC room sensors
{ADS-VOC-230;ADS-VOC-24}
Room temperature sensors
Room temperature sensors are often needed for the operation of a heat recovery unit with cooling or heating. These units often have a temperature sensor in the controller , but this is not necessary if the client prefers manual control.
We place the sensors in rooms with the greatest exposure to cold or heat - typically a room with a fireplace or attic rooms.
OUR TIP:
{NL-ECO-T;NL-ECO-TD}
There are a number of sensors beyond those we have presented to you so far. We have selected types relevant to ventilation systems in single-family homes.
Sensor communication with the heat recovery unit
Common sensors offer 3 types of outputs that can be used to communicate with other system elements.
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 heat recovery, e.g. starting increased exhaust from the fireplace when a certain temperature in the room is exceeded or immediately increasing the power of the heat recovery unit.
0-10V output
Suitable for smooth control of the power of a heat recovery unit or fan. This is the most common variant of sensor-unit communication.
This type of communication is completely sufficient for complete control of the ventilation unit's performance and, when implemented correctly, is the most economical and convenient way to control ventilation.
Modbus output
The answer to the increasing frequency of superior systems (smart home) in new family houses. Some modern heat recovery units are also 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 quantity via Modbus communication. It is not like the previous solution, where only 0-10V goes to the unit and it is necessary to recalculate according to the sensor characteristics. This option is therefore probably the most intuitive.
How do I power the sensors?
Now we know what quantities the sensors can measure, where to install them, and how they communicate with our unit/fan. So let's 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 option is the most common and the sensors are also slightly cheaper than the other options. In most cases, the sensors are connected to the heat recovery 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 on the type of unit.
Battery sensors
Battery sensors are mainly used in renovations or when sensors are added later. There is no need to deal with any wiring, just install the sensors in the desired locations and attach a receiver to the unit, which connects to the unit.
Nowadays, batteries have a long lifespan, so they are usually replaced once a year. This solution can therefore, of course at a higher purchase price, fully replace the wired version of the sensors.
Sensor life - when does the sensor start 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 self-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 - 400 ppm. For the self-calibration to function properly, it is necessary to properly ventilate the indoor space to values close to the outdoor air once every 10 days.
Of course, the lifespan of sensors is not unlimited , just like anything else. However, the sensors offered to our clients in the e-shop and for our ventilation installations with recuperation can boast a minimum lifespan of 10 years.
After reaching the tenth year, the sensor may start to measure inaccurate values. Therefore, we recommend checking the reliability of the sensor and possibly replacing it with a new one.
