First, indoor unit auxiliary electric heating
We have said in the principle of refrigeration that the principle of air conditioners is "moving heat" instead of generating heat. We often say that the COP (heating energy efficiency ratio) of air conditioners is relatively high, which is based on the heat transfer of air conditioners using refrigerants. Purpose of heating.
For example, an air conditioner consumes 1,000 watts of electricity and can generate more than 3,000 watts of heat energy. Compared to electric heating, an air conditioner will save more power.
Sometimes, in order to ensure the heating effect under the low outdoor temperature or extreme weather conditions in winter, the air conditioner can add auxiliary electric heating on the indoor unit heat exchanger.
In order to save the power consumption, the indoor unit of auxiliary electric heating is added. Generally, the power of electric heating is very small, which is basically less than 20% of its heating capacity.
In the control of electric heating, special logic control is also performed. For example, the opening logic of the electric heating is set to the indoor heat exchanger temperature below 48 degrees. That is, when the indoor heat exchanger temperature exceeds 48 degrees, the electric heating is Not working, different brands have different control logic.
对于 For the Yangtze River Basin, especially in East China, because the temperature is often below 5 degrees in winter, and there is no heating supply in the Yangtze River Basin, you can consider adding auxiliary electric heating to prepare for extreme weather when choosing central air conditioning.
There are two types of electric heating elements: PTC type and electric heating tube type. PTC type is commonly used for small air conditioners, and electric heating tube heaters are used for large and medium air conditioners.
The material of PTC heating element is barium titanate ceramic. Because it is a ceramic body, it has the characteristics of corrosion resistance, long service life (up to tens of thousands of hours), and high heat exchange efficiency (up to 98%).
When the temperature of the PTC is high due to the influence of factors such as ambient temperature and voltage fluctuations, its resistance value will increase multiples until it is close to the insulation, so the PTC itself will cut off the power and bring the temperature back down. This automatic constant temperature heating feature prevents it from overheating and is quite safe.
When the electric heater fails to heat during the maintenance process, the maintenance personnel should start from the following aspects:
1. Use a multimeter to test its resistance value during maintenance. If it is infinite, it will be open circuit, if it is small, it will be short circuit. The operation of the electric heater is controlled by a computer board chip and a relay, and a heating instruction is issued.
2. As mentioned above, the electric heating work needs to detect the temperature of the indoor thermal sensor. Therefore, the failure of the temperature sensor may cause the electric heater to not work.
3. If the electric heater is working but no hot air is blown out after the command is issued, the heating wire may be faulty or the circuit board may be faulty. Check the circuit board with a multimeter to see if the relay has power output.
4. Insulation inspection method: Use a multimeter to test the insulation resistance of the electric heater terminals and its metal casing, and the value should be greater than 30 megohms.
2, heating belt at the bottom of the press
The bottom of the compressor of the central air-conditioning outdoor unit is generally equipped with a press heating belt (also called a crankcase heater).
加热 The main role of the heating belt at the bottom of the compressor is to prevent the compressor from generating liquid compression during startup and operation. In the course of refrigeration theory, the small mouse repeatedly emphasized that the compressor can only compress the gas refrigerant.
Before the air conditioner runs in different seasons, or just after the central air conditioner is installed, the unit must be powered up and warmed up (usually more than 6 hours) before the first startup (or commissioning).
After the power is delivered in advance, the compressor is heated to supply power, which can evaporate the liquid refrigerant in the compressor in advance to ensure the service life of the compressor. (Tip: When the air conditioner is not used for a long time, be sure to power off the internal and external units, because the electric heating belt will cause a certain amount of power loss.)
The control logic of the electric heating belt is mainly controlled according to the temperature sensor at the bottom of the compressor. The central air conditioner will be more complicated, which will involve the problem of overheating corresponding to the value detected by the low pressure pressure sensor.