How to choose a thermostat for an electric heating boiler

There are two ways to maintain the temperature of the coolant in a house heated with electricity:

• in manual mode;

• using automation.

Nowadays, most people refuse manual control, choosing the second method. To use it, you must have a device that constantly measures the temperature and, depending on its value, turns off or turns on the heating.

For this purpose, devices are used that constantly perform the following functions:

• temperature control of the working environment;

• transmitting and receiving signals over communication channels;

• information processing and team building for the executive power unit;

• switching circuitry;

• Feedback.

The block principle of the control system is shown in the figure.

Structurally, such devices can be performed:

1. mechanical autonomous devices of direct impact;

2. electronic automatic installations.

Direct Thermostats

They work on the principle of changing the geometric dimensions of a bimetallic plate, a working fluid, gas or paraffin during heating and cooling.

Composite plates of two metals with different coefficients of linear thermal expansion are used in low-power devices on thermal relays of various designs. When heated, the bimetal bends and opens the contacts, turning off the power. After cooling the plates, the circuit returns to working condition.

The direct-acting thermostat design includes:

• housing;

• spool with valve and stem;

• bellows with a working thermal medium.

The whole device is mounted in the hot water supply pipe, senses its temperature. When heated, the working medium expands and acts on the valve, which moves, blocking the passage section of the line. When cooling the coolant, the valve returns to its place.

Direct thermostats measure the temperature of the water circulating through the heating system to regulate it. This method only indirectly maintains heat in the premises, does not take into account its true value.

Air electronic temperature sensors

Sensors that control the temperature of the air in the room help to maintain a better indoor climate. They are usually called thermostats and add the word "air".

Thus, it turns out that the thermostat simply maintains the temperature of the coolant in a certain range, and the thermostat works more precisely, stabilizing the microclimate of the room. If the air in the room is additionally heated by any sources, for example, by the sun's rays through the glass of windows or from the heat of working electrical appliances, the thermostat will not soon feel these factors, and the thermostat will quickly respond, saving energy and equipment life.

Thermostats work as a part of electronic automatic devices, have a certain range of temperature stabilization and, by their design, can transmit information to the logic and control unit:

1. by wire;

2. Using radio waves.

All of them need power. The former are powered by circuit power supplies, while the latter are powered by built-in batteries or accumulators. To save their energy, an intermittent mode is often used when the air thermostat takes measurements for a fraction of a second and passes them to the logic unit, and then turns off for several minutes. The following measurements are repeated in a similar cycle.

Management principle electric boiler (click on the picture to enlarge):

Wireless thermostats typically operate on one of two frequency ranges officially designed for household appliances:

• 868 MHz (elite class);

• 433 MHz (economy class).

The quality of the room temperature is affected by the installation location of the thermostat. For example, you must consider that:

• in the kitchen, additional appliances often produce heat, which will be taken into account by the thermostat;

• air mass rises to the ceiling during heating, and the temperature decreases near the floor;

• when the windows open, heat exchange begins with the street;

• isolation of the thermostat from the natural air circulation disrupts the operation of automation;

• Frequent use of the door can affect the mechanical contacts of the sensor located near it.

Logic blocks equipped with microprocessor control circuits in automatic mode have different functions:

• individual models allow you to set the temperature in the rooms depending on the time of day (during working hours, comfort is created, and at night - savings) and day of the week;

• the presence of the mode "frost protection temperature";

• installation of protection against loss of connection between the receiver and the transmitter when the boiler control switches to the “memory of switching cycles” mode for the last day;

• the function of accounting for the operation of heating equipment, as on separate electric meters;

• use of potential-free executive contacts;

• increased communication range between transmitter and receiver;

• protection of radio channels from interference;

• touch control;

• the presence of a timer for outputting the program for a time from one hour to several months to set your own settings. This is convenient to use when not in the premises for a long time, for example, when traveling on business trips or vacations.

The manufacture of temperature controllers and air thermostats for electric boilers is engaged in by many manufacturers of world renown. The devices provided by companies are popular:

• BOSCH;

• Ariston;

• SALUS Controls Ltd;

• Viessmann;

• Vaillant;

• Ferolli

• Baxi;

• Beretta;

• Alpha Calor.

When choosing a temperature control scheme, a temperature sensor should be selected for the specific conditions of its operation, taking into account the needs of the consumer.