Hot water in a house or apartment has long been a mandatory attribute of a comfortable stay. The issue is simply being solved in the dwellings of the city fund, where a centralized system of hot water supply and heating is available. In old city apartments and private houses with cold water, residents have to solve this problem on their own.
One of the ways to create a hot water system is to install water heating devices of various types and designs. It should be noted that these are units operating under pressure, and therefore are devices of increased danger. The reason for the occurrence of pressure in such devices is an increase in the degree of heating of water, therefore, special attention is paid to its adjustment.
Boiler room in a private house
How can I measure the temperature of the hot water system?
Let us pay attention to such a property of materials as thermal expansion upon heating. For different materials, the coefficient of linear thermal expansion is different (CTE). This is used in the design of instruments for estimating the amount of heating of various objects.
How the bimetallic strip works
This product is a mechanical connection of two metal plates with different CTE. Bimetallic steam is collected in various ways:
- soldering;
- pressure welding;
- articulation with stops.
Typical materials in the sensor can be: steel + brass; steel + copper and others. When heated, the steel part heats up more slowly than brass or copper, the investigator deforms its degree of “lag” and the product is curved. Its value can be easily measured and used to estimate the temperature of the conductor corresponding to this indicator for water.
Bimetal Sensor Device
The graduation of the scale of devices working with bimetallic strips is not performed, since the deviation depends on many factors, including the thermal regime in the room where such a device is installed. For practical use, the degree of heating of the outlet jet can be measured. liquid contact thermometer and put the mark in the right place. But in practice, this is not necessary, since this indicator is set by the manufacturer, and the temperature of the sensor is indicated in the technical documentation for the device.
If there is a need to adjust the degree of heating of water in the tank, a stop screw is used for this, with which you can change the gap between the contacts by varying the on / off temperature of the contact with the bimetal strip.
Strain gauge sensor
How to use a strain gauge
A device of this type is found in many designs for measuring various parameters. The principle of its action is to change the electrical resistance of the conductor in a stressed state. One of the materials for the manufacture of such a sensor is lead sulfide. When a strip of such material is tensioned, its electrical resistance changes. This occurs as a result of thermal expansion of the boiler body or boiler.Thus, a parameter appears that can be used to evaluate the quantitative characteristics of changes occurring as a result of heating. Using electronics, measure the magnitude of the changes, the result is displayed on the display in digital form in relation to this parameter.
How are thermocouples used?
The action of these sensitive elements is based on the use of two dissimilar conductors, that is, two strips or wires having a different composition. It was established that a potential difference occurs at the place of their connection, which is a sign of the appearance of an electric current. As the conductors heat up, the current strength at the junction increases, which makes it possible to use this indicator not only to measure temperature, but also to adjust it in a working heating or heating unit.
A feature of devices for controlling heating using a thermocouple is that they do not need an external effect to start operation - the necessary characteristics are excited by the internal capabilities of the device. Its design is very simple, there are no mechanical influences, which determines the long term of operation. The product is almost never repaired or serviced - if necessary, it is simply replaced. Almost all manufactured devices of this kind have the same connectors, so you can use any of their types with suitable technical specifications.
There are many designs of devices for temperature control in heating devices, but the basic principle is to use the variability of the physical state when the controlled parameter changes.
Thermocouple
How to change the temperature on a water heater
In the state of sale, the adjustment of the heating range is carried out, in most cases, within 20-60 degrees by adjusting the control equipment. But if it becomes necessary to obtain water of a higher temperature, the design of the devices provides for the possibility of setting the upper limit to 80 degrees. This is done as follows:
- In electromechanical devices using a bimetallic strip, a stop screw is used to adjust the amount of heating, limiting the amplitude of its movement. Since the temperature value in such devices is not visualized, monitoring should be done by contact thermometer, fixing the moment of shutdown with the stop screw.
Electromechanical heating sensor
- When using tensometric control equipment, the temperature is recorded already by an indirect sign - the resistance value of the sensor strip. This makes it possible to visualize the temperature readings by calibrating the ohmmeter scale in degrees. Naturally, in a production environment, this operation is standardized and all devices are marked equally. The scale of the standard device is equipped with a special additional arrow, set to the maximum temperature and, when it is reached, the energy supply is cut off, whether it is gas or electricity.
- The most advanced temperature control devices made on thermocouples. The upper and lower temperature limits are set according to fluctuations in the power of the signal generated at the junction of strips of various materials. When the controller is activated, the heating elements in the boiler or boiler are turned on or off. All information is read from the display; controlling the heating process with such a system is very simple and convenient.
Thermocouple with heat control
What is a water temperature sensor
The device that controls the mode of operation of the heating elements, and is such a device. It consists of a sensitive device that responds to changes in the control parameter and a command device consisting of a relay and an automaton. The device is intended, in this case, to turn off and back on the heaters.
