Comparison Terneo sx vs Devi DEVIreg Smart Wi-Fi

The maximum load in terms of current power that the thermostat can withstand. In other words, the maximum electrical power that it can pass through itself without failures and damage.

The choice for this parameter directly depends on the power consumed by the boiler or heater connected through the thermostat; load limitation is of particular importance when working with electric boilers, the energy consumption of which is measured in kilowatts. When connected directly, the power of the heater should not exceed the maximum load of the thermostat, otherwise the latter will simply fail. However, when using additional protective devices (contactors), many models allow connection to a more powerful load than originally allowed.

Automatic temperature control hysteresis provided by the device.

Hysteresis can be described as the difference between the on and off temperatures of a system controlled by a thermostat. Usually, the permissible deviations of the actual temperature from the nominal one in one direction or another are half the hysteresis. So, at a set temperature of 22 °C and a hysteresis of 0.5 °C, the controller will turn on the heating as soon as the room temperature drops to 21.75 °C, and turn it off when it rises to 22.25 °C. Accordingly, the lower this indicator, the more carefully the temperature is maintained and the fewer fluctuations. On the other hand, small hysteresis values require accurate and expensive thermal sensors, increase fuel/energy consumption and wear of the entire system, and create an increased risk of false alarms (for example, from a cool draft on the thermal sensor). In addition, relatively small temperature fluctuations are practically imperceptible in terms of human comfort. Therefore, many modern thermostats have a hysteresis of 1 °C — this, usually, is quite enough for domestic use.

Also note that this parameter can be both fixed and adjustable. The first option is simpler and cheaper, and the second provides additional options for setting the thermostat to the specifics of the situation.

The presence of an air temperature sensor in the design or delivery set of the controller — such a sensor can be either built into the device or external.

Air temperature is one of the key parameters that determine the climate in the room and the comfort of staying in it. Accordingly, the air temperature sensor allows the regulator to evaluate the general conditions in the room and control the heating operation, taking into account how the microclimate corresponds to the desired one. However, note that such sensors are not always applicable. For example, in kitchens and bathrooms, they may not work correctly (when hot water, a gas stove or a water heater is turned on, etc.), so in such conditions it is better to use floor temperature sensors (see below).

The length of the supplied cable in the wired thermostat sensor (see "Type"). The longer the cable, the further the temperature sensor can be installed from the device. At the same time, the principle “the more the better” is quite relevant: excess wire usually does not create any special problems, but if the length is insufficient, you will have to lengthen the cable, or even purchase another sensor.

Note that in modern models, the cable length usually does not exceed 4 m — this is usually enough when installing a thermostat in the same room but with the removal of the device outside the room, difficulties may already arise.

The type of timer provided in the design of the thermostat. In this case, a timer means a scheduler that allows you to programme different operating modes for different periods (for example, lower the temperature at night and increase it by the time you get up). Such schedulers are divided into types depending on the time covered.

— Daily. The timer allowing to set the programme within 24 h; then the programme will be repeated every day. This variety is the simplest and, as a result, inexpensive. On the other hand, for most users, the daily routine on weekdays and weekends are noticeably different, and, most likely, the timer will have to be reprogrammed at least twice every week — before the weekend and at the end of the weekend.

— Weekly. A timer that allows you to set a work programme for certain days of the week. The simplest varieties of such schedulers work according to the “5 + 2” scheme: one programme is set for 5 working days, the other for 2 days off. However, there are more advanced options — up to the ability to programme each day of the week separately. Anyway, weekly timers are more convenient and require less reprogramming than daily timers but they are much more expensive.

The shortest duration a programmable thermostat cycle can have (see "Programmable cycles per day").

The lower this parameter (with the same number of cycles per day) — the wider the possibilities for programming the operation of the thermostat, in particular, for its specific setting (for example, you can provide a short period of preliminary "intensive heating" after working at low temperatures). On the other hand, due to a certain inertia in the operation of heating systems, it makes no sense to make an interval shorter than 10 minutes — the thermostat simply does not have time to work out the specified settings in less time. And in the most "long" models, this parameter is about 30 minutes.

— Display. The presence of its own screen in the design of the regulator. Such a screen is usually a simple LCD matrix with segment digits. However, even on such a screen, very diverse data can be displayed (including temperature with an accuracy of fractions of a degree), and this function significantly expands the capabilities of the thermostat and makes it more convenient. Note that it makes sense to install the display primarily in electronic models (see "Device type"), for such thermostats it is almost mandatory (but in mechanical ones, on the contrary, it is almost never used).

— Protection of the pump from "souring". During non-working hours — for example, between heating seasons — deposits can form on the parts of the circulation pump of the heating system, which can make it difficult to rotate the impeller, reduce the efficiency of the pump, or even disable it altogether. This phenomenon is called "souring". To avoid it, automatic regulators may provide protection against acidification: periodically (once every few weeks) the pump is turned on for a short time, which prevents the formation of deposits (and removes those that have already formed).

— Holiday function. A special regime provided for in case of a long absence of people in the house (for example, during a vacation — hence the name). In holiday mode, you can set a certain temperature to...be maintained for several days (for example, a week; the maximum duration depends on the thermostat model). At the same time, in some models, this function is combined with frost protection (see below) and allows you to set only the minimum temperature (usually 5 °C); in others, the holiday temperature can be programmed.

— Random mode. A mode that provides for the inclusion of various heating functions in a random order (but without causing critical loads on the heating system). The most popular use of this feature is to simulate that someone is at home; this can stop intruders planning a theft in the absence of the owners.

— Management via the Internet. Ability to control the controller via the Internet. The device itself is usually connected to the network via Wi-Fi, and the control features may be different. For example, in some models you need to use a proprietary application installed on a smartphone or tablet, in others it is enough to open a special page in any browser. However, anyway, this function allows you to control the heating system remotely, from anywhere in the world. This can be extremely convenient in unforeseen situations — for example, if during the absence of the owner on the street it gets warmer. In addition, additional features such as advanced timer programming may be available with Internet control.

— Frost protection. A function that prevents freezing of the coolant in heating systems. Freezing water expands, which can lead to mechanical damage and depressurization of the system. To avoid this, regulators with this function are able to "monitor" that the temperature of the coolant does not fall below 5 °C, and, if necessary, turn on the heating to maintain the temperature. This function is relevant primarily for cases when the disconnected heating system must be left unattended for a long time during the cold season.

— Protection from children (blocking). The ability to lock the control panel of the regulator so that a curious little child cannot knock down its settings. The lock, usually, is turned on and off in such a way that an adult, but not a child, can easily do it — for example, by simultaneously pressing certain keys.

— Heater operating hours counter. Built-in counter that tracks the total heating time. This feature makes it much easier to keep track of the operating mode and heat costs, eliminating the need for the user to keep records manually and allowing you to track working hours even when there is no one nearby.

— Sensor calibration t. Possibility to calibrate the temperature sensor of the thermostat. In fact, situations may arise when the readings of the temperature sensor for one reason or another differ from the actual temperature in the room — for example, the controller is installed near an electrical appliance that generates heat and knocks down the setting, and neither device can be moved. For such cases, calibration is provided — an amendment to the readings of the temperature sensor. For example, if the thermometer in the middle of the room reads 20°C and the regulator's sensor reads 22°C, you can correct the thermostat to -2°C and the temperature displayed on the regulator will correspond to the true temperature. Of course, the correction can also be taken "in the mind" without reconfiguring the device; however, most often it is easier to set the necessary parameters in advance and not get confused in the calculations.