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What Are the Temperature Sensors of Air Conditioning and How Do They Work?

What Are the Temperature Sensors of Air Conditioning and How Do They Work?

Ⅰ. Overview of air conditioning temperature sensors


The temperature control of the air conditioner mainly uses the temperature sensors to detect the temperature change of the room for cooling and heating, and controls the power-on and power-off of the compressor to control the cooling or heating temperature of the air conditioner. The temperature control of the air conditioner mainly means that the temperature sensor detects the ambient temperature under the unified command of the CPU and compares it with the manually set temperature. When the corresponding temperature is reached, the CPU controls the power-on or power-off of the compressor. The temperature control range of the air conditioner is generally between 16°C and 30°C. When cooling, the minimum set temperature will not be lower than 16℃. When heating, the maximum set temperature will not be higher than 30℃.


Ⅱ. Air conditioner temperature sensors form


The air conditioner temperature sensor is a negative temperature coefficient thermistor. It is referred to as NTC, which is also known as temperature probe. The resistance value decreases with the increase of temperature and increases with the decrease of temperature. The resistance value of the sensor is different and the resistance value at 25℃ is the nominal value. Sensors commonly used in air conditioners include indoor ambient temperature NTC, outdoor pipe temperature NTC, etc. Higher-end air conditioners also apply compressor discharge detection NTC and compressor suction detection NTC.


Ⅲ. The role of common temperature sensors


1. Indoor ambient temperature detection NTC (negative temperature coefficient thermistor)


According to the set working state, the CPU detects the temperature of the indoor environment through the indoor ambient temperature (referred to as the inner ring temperature) NTC and controls the compressor to be powered on or powered off to stop.


2. Outdoor pipe temperature detection NTC


The main function of the outdoor pipe temperature sensor is to detect the heating and defrosting temperature. Generally, after the air conditioner is heated for 50 minutes, the outdoor unit enters the first defrosting and the subsequent defrosting is controlled by the outdoor tube temperature sensor. When the tube temperature drops to -9°C, defrosting begins. When the tube temperature rises to 11~13℃, defrosting stops.


3. Compressor exhaust gas detection NTC


Avoid overheating of the compressor, detect lack of fluorine, reduce the frequency of the inverter compressor, control the flow of refrigerant, etc. There are two main reasons for the high discharge temperature of the compressor. One is that the compressor is in an overcurrent working state, mostly due to poor heat dissipation and high pressure. The second is the lack of refrigerant or no refrigerant in the refrigeration system, so that the electric heat and friction heat of the compressor itself cannot be well discharged with the refrigerant.


4. Compressor suction detection NTC


The compressor suction temperature sensor plays the role of cooling effect detection. If there is too much refrigerant, the suction temperature is low. If there is too little refrigerant or the refrigeration system is blocked, the suction temperature is high. If there is no refrigerant, the suction temperature is close to the ambient temperature. The CPU determines whether the working state of the air conditioner is normal by detecting the suction temperature of the compressor.

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