1- Determination of the structure of the thermostat
The installation surface of the temperature control element of this indoor heater is a flat surface. In order to ensure the temperature sensing effect, a bimetallic surface mount thermostat can be used. This type of temperature control element can be installed by contact temperature sensing. When the indoor heater is working normally, the bimetal contact is closed. When the temperature reaches the operating temperature, the bimetal is heated to generate internal stress and act quickly, opening the contact Point, cut off the circuit, when the indoor heater cools to the set temperature, the contact automatically closes and restores the normal working state, thus playing a role in temperature control. This type of temperature control element has the advantages of stable performance, high accuracy, small size, high reliability and long life.
2- Determination of the installation position of the thermostat:
Due to the natural convection heat exchange of air, the convection indoor heater is greatly affected by the environment, and the internal temperature of each location is inconsistent, so you should choose a suitable installation location. The proper installation position can make the indoor heater exert its maximum heating effect under the premise of ensuring compliance with safety standards. In order to confirm the installation position of the temperature control element, first select 6 points on the top surface of the heating plate. Among them, position 1-the heating plate is close to the electric heating tube; position 2 is the side shield plate under the metal shield of the terminal end; position 3 is the center of the side shield on the heating plate; position 4 is the side shield away from the wiring End to end under the metal shield; position 5-position 2, 3 center; position 6-position 3, 4 center. Select the temperature control element with a parameter of lO5 ℃, install them in the above positions respectively, and work at 1.15 times the rated input power under normal working conditions according to the standard requirements. .
When the temperature control element is installed at position 1, the indoor heater cannot exert its heating effect, and the temperature control element frequently operates. The specific performance is as follows: when the electric heating tube is rapidly heated to the operating temperature of the temperature control element, the indoor heater stops heating. The temperature control element operates frequently. After the work is stable, the indoor heater cannot reach its maximum heating effect, and frequent operation will shorten the life of the thermostat and may cause interference to the home power grid. When the temperature control element is installed in positions 2 and 4, due to the influence of environmental convection, the temperature is unstable and changes frequently, causing the temperature control element to operate irregularly. When the temperature control element is installed at positions 3, 5, and 6, the curve is stable, and at position 5, the surface temperature of the indoor heater reaches the highest value of 100 ° C. Therefore the temperature control element can be installed between positions 2 and 3. Another 4 points were taken for the above experiment (room temperature is 21.6 ° C). According to the temperature rise curve: the temperature control element is located on the side protection plate of the heat dissipation plate. When the distance between the Ii point of the temperature control element and the edge of the power end of the heat dissipation plate is 200mm, the temperature rise curve of the indoor heater is the most stable and is affected by the environment. The effect is minimal, and the temperature at the center of the front is the highest, which can exert its maximum heating effect.
3-Determination of thermostat parameters
The temperature control elements of 1O5 ℃, 110 ℃, 115 ℃, and 120 ℃ were selected and installed in the above positions, and the test in Chapter 11 was carried out. The curve is shown in Figure 9. The heating curve of the indoor heater with temperature control elements of different parameters. According to the curve, when the temperature control element parameter is 115 ℃, the indoor heater can exert its maximum heating effect.