Range of wireless controllers TECH: what affects signal reliability

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Range of wireless controllers TECH: what affects signal reliability

Wireless heating control is now standard in new builds and renovations. There is no need to lay cables, no need to break walls, and the entire system can be installed within a few hours. Despite this, in practice we still encounter situations where the customer calls saying the controller "isn't working" – the panel reports communication failure, room temperature is not controlled properly, or the sensor simply "drops out" every two to three days. In most cases, the cause is not a faulty product, but rather a lack of understanding of how wireless signals work in real buildings. This article therefore focuses precisely on that: what specifically affects the range of wireless components in TECH systems, what are the real values, what weakens the signal, and how to avoid it even before installation.

Basics: how wireless TECH components communicate

Wireless components of TECH systems – controllers, sensors, and control panels – communicate at the frequency 868 MHz. This is a standard ISM band (Industrial, Scientific, Medical), which in Europe is reserved precisely for such devices – home automation, building management systems, and various sensor networks. Compared to Wi-Fi (2.4 GHz or 5 GHz), the 868 MHz signal has significantly better ability to penetrate building structures and has a longer range at the same transmitter power.

The devices do not communicate continuously – they do not transmit a signal every second. Most sensors send temperature updates at regular intervals (typically every 3 minutes, sometimes longer depending on the settings), and only send an immediate message when the demand changes (for example, when the knob on the controller is turned). This approach saves battery life and also reduces potential interference in the band. The consequence for practice is important: if the signal is weak, the failure may not be immediately apparent – the panel may "remember" the last value for a while, and only after several missed messages will it report a communication error.

Declared range vs. range in a real building

Manufacturer TECH typically states the range of wireless communication in the range of 30 to 100 meters, with this value applying to direct visibility without obstacles – essentially outside, in open space. In a real building, the situation is significantly different. Every building structure weakens the signal, and to varying degrees depending on the material, thickness, and moisture content.

As a reference, here is a summary of signal attenuation when passing through various types of structures that we commonly encounter:

Type of structure	Typical thickness	Approximate signal attenuation
Gypsum board partition (simple)	10–12 cm	low (2–5 dB)
Brick partition	12–25 cm	medium (5–15 dB)
Full brick load-bearing wall	30–50 cm	high (15–25 dB)
Concrete wall (plain concrete)	15–25 cm	high (15–20 dB)
Reinforced concrete wall / ceiling	20–30 cm	very high (20–35 dB)
Concrete slab with reinforcement	20–25 cm	very high (25–40 dB)
Metal cladding / aluminum foil in insulation	practically any	extreme, the signal may be completely blocked
Wooden wall or partition	10–20 cm	low to medium (3–10 dB)

From practice: in an old apartment building with a load-bearing reinforced concrete structure and two partition walls between the sensor and the panel, the real range was sometimes only 10–15 meters, despite the air distance being only 8 meters. The panel was in the basement boiler room, the sensor in the living room on the first floor – directly above, but through a reinforced concrete ceiling slab. The communication was unstable precisely due to the reinforcement in the ceiling.

Factors that most affect range and reliability

1. Type and thickness of building structures

This is by far the most important factor. As the table above shows, the difference between a gypsum board partition and a reinforced concrete ceiling can be 30 dB or more. In practice, every 10 dB of attenuation means the signal must be 10 times stronger to be acceptable – at 30 dB of attenuation, it must be a thousand times stronger. If the signal must pass through two reinforced concrete ceilings and one concrete wall, the real range may drop to less than 5 meters of air distance.

An interesting phenomenon that surprises many in practice: a wet wall attenuates the signal significantly more than a dry one. A brick wall in the basement of a building, where moisture condenses, may have an attenuation 5–10 dB higher than the same wall in a dry state. Therefore, wireless communication in old basements, cellars, or wet technical rooms may be unreliable even at short distances.

2. Number of walls and ceilings between devices

The number of structures the signal passes through is more important than the distance itself. A sensor 3 meters away but behind two brick-concrete walls may have worse communication than a sensor 15 meters away but in direct visibility. A rule I recommend to customers as a guideline: in a typical family home with brick walls, count on reliable communication being ensured if the signal passes through no more than two full walls or one ceiling. Every additional structure is a risk.

3. Antenna placement of devices

The radio antenna is inside the body of every wireless TECH device – sensor, controller, and panel – and its position relative to surrounding structures significantly affects how well the signal is transmitted and received. Devices with built-in antennas are sensitive to:

Placement in metal – for example, inserting a sensor into a metal box, mounting it behind a metal radiator cover, or into an electrical distribution cabinet dramatically weakens or completely blocks the signal.
Placement behind large metal objects – proximity to a large steel radiator, a kitchen unit with a metal cladding, or a steel partition structure.
Mounting directly into room corners – a corner formed by two or three walls is a "shadow zone" for the signal, where waves reflect and attenuate.
Horizontal vs. vertical orientation – most antennas in these devices have a radiation pattern that assumes vertical mounting on a wall. A horizontally placed device (e.g., a sensor left on a table) may have significantly worse range.

4. Interference from other devices

The 868 MHz band is relatively "clean" in Europe compared to the overloaded 2.4 GHz band (where Wi-Fi, Bluetooth, microwave ovens, and thousands of other devices operate). Despite this, interference does occur. Typical sources of interference in residential spaces:

Other home automation systems on 868 MHz (smart home hubs, security systems)
Certain types of wireless doorbells and weather stations
Industrial equipment in the vicinity (if the house is near a factory or warehouse with automation)
Large frequency converters (VFDs) and dimmers – these generate broadband interference that can affect even 868 MHz

The good news is that the TECH protocol includes message integrity checking and retransmission. Short-term interference is usually only noticeable as a delay, not a permanent outage. Problems arise only with prolonged, strong interference.

5. Power supply and battery condition

Battery-powered sensors, such as the TECH EU-C-8r wireless room temperature sensor or the TECH EU-C-mini, vary the transmitter power depending on battery voltage. A new alkaline battery (1.5 V) provides sufficient power for transmission without problems. When the battery drops to 1.1–1.2 V, the device still functions and does not immediately display a low battery warning, but the transmitter power is lower. Result: the same route that worked flawlessly with a new battery may become unreliable when the batteries are at 20–30% capacity. In practice, this looks like a customer calling in with the complaint that "the sensor is not working" – and after replacing the batteries, the problem disappears. This is one of the most common causes of reported outages.

Recommendation: always use high-quality alkaline batteries (Duracell, Energizer, Varta or equivalent). Cheap batteries from promotions have significantly lower capacity and drop in voltage more quickly. Rechargeable NiMH batteries are not suitable – their nominal voltage is 1.2 V instead of 1.5 V, which corresponds to an "almost dead" alkaline battery and the device may operate unstably from the start.

Special situations that make wireless communication problematic

Houses with external insulation with mesh (ETICS / façade insulation system)

This is a relatively new phenomenon that is becoming increasingly common in renovations. The ETICS system (so-called contact insulation) includes a glass fiber mesh embedded in adhesive mortar. The glass fiber mesh itself does not attenuate the signal. The problem arises when a mesh with a higher metal content is used during implementation (e.g., steel reinforcing mesh in non-standard solutions) or when there is a metal vapor barrier with an aluminum foil behind the façade cladding. In such cases, it may happen that a sensor placed near a window on an external wall has worse communication towards the inside of the building than a sensor on an internal wall.

Underfloor heating with anhydrite screed

In modern timber frame buildings and new constructions, anhydrite or cement screed with underfloor heating is commonly used. When the floor is cold and dry, the attenuation is acceptable. After the system is filled and in operation – that is, when hot water flows through the screed – the dielectric constant of the screed changes and the signal attenuation through the floor slab increases. In practice, this may mean that a sensor on the ground floor and a control panel in the basement communicate well during the first testing before the heating is turned on, but after the system is started, communication deteriorates.

Metal decorative elements and furniture

This may sound trivial, but in practice, we have encountered cases where a customer disrupted an originally working system by moving furniture. A large steel bookcase, a metal cabinet, or even a massive refrigerator placed between the sensor and the panel can significantly worsen communication. The sensor should not be "hidden" behind furniture – ideal is mounting on a free wall at a height of 1.2–1.5 m above the floor, without any metal objects in the immediate vicinity (at least 30 cm from any metal surface).

Multi-story houses and garden sheds

If the system controls multiple zones on different floors, the signal must overcome ceilings. In timber frame buildings, this is usually not a problem. In classic masonry houses with concrete ceiling slabs, the range between floors is limited. In such cases, the TECH EU-M-8n wireless control panel can be placed centrally (e.g., in a hallway on the ground floor), from where it has the best direct visibility to a larger number of sensors, rather than being tucked away in a boiler room in the basement.

How to test the range before final installation

Before you permanently embed the sensors into the wall or mount them at the planned location, it is intelligent to perform a quick communication test. The procedure is simple:

Place the control panel (e.g., TECH EU-M-8n) at the planned location and connect it to the power supply.
Pair the sensor with the panel (the procedure is described in the article Pairing a wireless sensor with the TECH control panel in this knowledge center).
Leave the sensor at the planned installation location and observe whether the panel repeatedly and stably receives the signal for 10–15 minutes.
If the panel shows an indicator of a weak signal or reports an outage, try moving the sensor by 20–30 cm in different directions – sometimes a small change in position can significantly improve the signal due to wave reflection effects.
If the signal is still unstable after adjusting the position, consider an alternative sensor placement or switch to a wired variant (see below).

When it is better to choose a wired sensor

A wireless solution is convenient, but not always the best. There are situations where a wired connection is clearly the better choice in terms of reliability. Specifically:

Heavy reinforced concrete construction with multiple ceilings and walls between the sensor and the panel
Basement or semi-buried technical room with thick concrete walls (typically where the boiler and panel are located)
Industrial and semi-industrial buildings with metal structures, frequency converters, or dense electrical installations
Situations where battery replacement is not accessible (e.g., a sensor embedded in a wall behind furniture)
A customer who does not want to deal with maintenance – a wired sensor functions without any maintenance for years

For these cases, a wired room temperature sensor TECH EU-C-7p is available, which is connected directly by cable to the control panel and range and interference are simply not an issue. More about when a wireless and when a wired solution is worth it can be found in the article Wireless vs. wired temperature sensor: when is which type worth it.

Practical recommendations for reliable wireless installation

Based on experience from real customer projects, I summarize the most important rules for reliable installation of the TECH wireless system:

Minimize the number of transitions through heavy structures. If you can place the panel and the sensor at the same level (same floor) without a reinforced concrete wall between them, do so. It is better than dealing with the problem later.
Place the panel in the center of the range, not in an extreme position. A basement with a boiler is technically a logical location, but from the perspective of radio range, it is the worst possible choice. A panel in the hallway on the ground floor will serve sensors on all floors much better.
Always mount the sensor on a free wall, at least 30 cm from metal objects, 50 cm from larger metal surfaces. Never behind a refrigerator, behind a metal radiator cover, or inside metal.
Pay attention to the correct mounting height. A height of 1.2–1.5 m above the floor is recommended not only for accurate temperature sensing but also for radio range – near the floor and near the ceiling, the signal is usually worse.
Use only alkaline batteries of recommended brands and replace the batteries preventively every year (most sensors last 2–3 years, but performance may decrease after one year). Never use NiMH batteries.
Test before final installation – do not mount the sensor permanently until you have verified the communication stability for at least 10–15 minutes.
Document the placement – if a problem arises in a few years, it is important to know exactly where the sensor is mounted and what the typical signal strength was at installation.

Impact of the environment on long-term reliability: seasonal changes

An interesting and rarely discussed phenomenon: the range of wireless communication can change throughout the year. There are several reasons for this:

Humidity in building structures – in winter, when the house is heated and the windows are closed, the walls are drier. In spring, when warm and cold days alternate and condensation can occur, the walls are more humid and signal attenuation is higher. Therefore, it can happen that a system that worked without problems all winter starts to "drop out" in spring.

Changes in furniture and people placement in the space – the human body is largely composed of water and also attenuates the signal. In an empty room, the signal may be better than in the same room full of people (for example, a holiday when the family gathers). This is a small effect, but it can be decisive when the signal is at the edge of the range.

Changes in the surrounding electromagnetic environment – neighbors install new devices, a new wireless system appears nearby. These changes cannot be predicted, but if the system was reliable until now and suddenly starts to have outages without any physical changes, interference from an external source is one of the suspects.

Regulator TECH EU-R-8b and EU-M-8n: specific recommendations for these models

Wireless room thermostat TECH EU-R-8b is a combined thermostat with an integrated temperature sensor and transmitter in one housing. Since it is an active battery-powered device, the same rules apply to it as to sensors – correct mounting height, sufficient distance from metal objects. Important: the thermostat also has a display, so customers usually have it in a visible place – which is good, as it usually means mounting on a free wall in the main part of the room, not hidden behind furniture.

Control panel TECH EU-M-8n is a mains-powered device – it is therefore not dependent on batteries and transmits and receives signals with stable performance. When installing it, make sure it is not placed in a metal cabinet of an electrical panel (the signal would be almost completely blocked). If the panel must be in a technical room, ensure that it is not surrounded by thick concrete walls on all sides.

For multi-zone systems, where one panel controls multiple zones with different sensors, it is important that all sensors have a reliable path to the panel. If a sensor has a problematic range, it is not a solution to simply increase the signal strength – it is necessary to either change the location or switch to a wired variant for that zone. More about compatibility and zone control can be found in the article Compatibility of TECH thermostats with boilers and zone control.

Most frequently asked questions (FAQ)

How far can a TECH sensor be from the panel in a typical family home?

In a typical masonry family home with brick walls and concrete ceilings, the realistic reliable range is 15–30 meters, provided the signal does not pass through more than two full walls or one ceiling. The declared 100 meters applies only to direct line of sight outdoors. In practice, it is therefore advisable to plan the panel placement centrally (ground floor corridor), not in the basement.

Why did the sensor work well in summer but drops out in winter?

Paradoxically, the cause may be a change in the humidity of building structures or the battery. Walls are more saturated with moisture in cold and humid weather, which increases signal attenuation. At the same time, batteries lose capacity at low temperatures – if the batteries in the sensor are old, winter takes away their remaining capacity. Start by replacing the batteries with new alkaline ones.

Can I use rechargeable batteries to improve the range?

No, rechargeable NiMH batteries are not suitable for TECH wireless sensors. Their nominal voltage is 1.2 V instead of 1.5 V of an alkaline battery. The device may work, but the transmitter power will be lower from the start, which will result in a shorter range and unstable communication. Always use high-quality alkaline batteries.

The sensor and panel are only 5 meters apart, but communication is unstable – why?

Distance is not the only factor. If there is a reinforced concrete ceiling or a thick concrete wall between the sensor and the panel, 5 meters of air distance may have an attenuation of 30 dB or more. Try to change the position of the sensor or panel so that the signal passes through a lighter structure (for example, move the panel to an adjacent room on the same floor). If this is not possible, consider the wired sensor TECH EU-C-7p.

Can a Wi-Fi router in the household interfere with TECH thermostats?

A standard Wi-Fi router operates at 2.4 GHz or 5 GHz, which is a completely different band than 868 MHz. Direct interference is very unlikely. Problems can be caused by home automation devices that also operate at 868 MHz – for example, some security systems, smart doorbells, or other control systems. If you have multiple wireless systems at home and problems appear after installing a new device, check the frequency on which it operates.

Is it possible to "extend" the range using a repeater?

TECH systems are primarily designed for direct communication between the sensor and the panel without intermediate links. In the current product portfolio of TECH, there is no universal repeater for standard sensors. If the range is insufficient, the correct solution is to change the panel location to a more central position or switch to a wired sensor for problematic zones. For complex layouts of larger buildings, it is advisable to consult a solution before installation.

Conclusion: range is a matter of project preparation, not the product

Wireless thermostats and sensors TECH are high-quality devices with sufficient performance for most households. Signal problems that appear in practice are in the vast majority of cases the result of incorrect placement or underestimated preparation, not a product defect. If you check the type of structure before installation, plan the panel placement centrally, test communication before permanently mounting the sensors, and use high-quality batteries, the wireless system will reliably serve you without worries.

In cases where it is technically more advantageous – heavy structures, multiple ceilings, industrial environments – do not hesitate to reach for a wired solution. A combination of wired and wireless sensors in one TECH system is fully possible and very practical in practice. More information on choosing the right solution can be found in the articles How to choose a TECH room thermostat: wired vs. wireless and Installation of a TECH room thermostat: step-by-step installation guide. If you are experiencing a specific problem with communication outages, the article Communication failure between sensor and TECH panel: causes and solutions will also help you.

Do you have a question about this topic?

Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.