In refrigeration and air conditioning systems, the temperature of each unit component is maintained within a specific normal range, which is an important guarantee for the stable operation of the system. Once these temperatures exceed the normal range, it may indicate that there is a fault or improper adjustment in the system, requiring immediate cause analysis and handling. Since temperature points are difficult to measure directly with a thermometer, technicians rely on their hands to make a preliminary estimate.
1. Exhaust temperature
The discharge temperature is an important indicator for measuring the operating state of a compressor. During high-temperature seasons such as summer, the discharge temperature of the compressor may be relatively high, and may even be too hot to touch. An excessively high discharge temperature is usually caused by either an excessively high suction temperature or an excessively high condensation temperature of the compressor. This situation requires great attention, as an excessively high discharge temperature not only affects the efficiency of the compressor but may also cause damage to its internal components.
If the exhaust temperature is too low, meaning that the exhaust pipe is not hot to the touch, this may indicate that the suction temperature is particularly low, and the compressor may be operating in a wet stroke state or the system refrigerant is severely insufficient. Operating in a wet stroke state can easily damage the compressor valve structure, while insufficient refrigerant can affect the heat dissipation of the motor windings and accelerate the aging of insulating materials.

II. Compressor housing temperature
The change in temperature of the compressor housing has a significant impact on the overall performance of the compressor and refrigeration system. The temperature field on the exterior of the fully enclosed compressor housing can be divided into two parts: the upper housing is affected by the suction steam and has a lower temperature, while the lower housing has a higher temperature due to the heat generated by the motor and the frictional heat carried away by the refrigeration oil.
Excessively high shell temperature is typically attributed to the high suction temperature of the refrigeration system, which impacts the cooling effect of the oil, subsequently affecting the lubrication and wear of moving parts. In severe cases, it may even lead to serious failures such as bearing seizure. Conversely, excessively low shell temperature may be due to too low a suction temperature, which, although beneficial for the cooling of refrigeration oil and motor windings, can result in a decrease in refrigeration capacity and potentially trigger dangerous situations such as liquid hammer.  

III. Condensation temperature
The condenser is one of the key components in the refrigeration system, and its temperature condition directly reflects the heat dissipation effect of the system. Under normal circumstances, the heat dissipation tubes in the front half of the condenser are very hot, with the temperature gradually decreasing; the heat sensation of the heat dissipation tubes in the rear half is significantly reduced.
If the front half of the condenser is not very hot or the rear half is close to room temperature, it may be caused by the compressor inhaling wet vapor refrigerant or insufficient refrigerant. However, if the entire condenser tube is hot, it may be caused by factors such as too much refrigerant, low ventilation, or high ambient temperature.  

IV. Temperature of condenser shell
For different types of condensers, the normal range of shell temperature varies. For example, the shell of a shell-and-tube condenser is normally hotter in the upper half and warmer in the lower half; while the fins of an air-cooled finned condenser are hotter in the upper half and warmer in the lower half.
If the temperature of the condenser shell is abnormal, it may be caused by factors such as insufficient refrigerant quantity, inadequate cooling water volume, or poor heat dissipation effect. At this time, it is necessary to promptly check and adjust the system parameters to ensure the normal operation of the system.  

V. Temperature of liquid tube and filter
Under normal circumstances, the liquid pipe is warm. If the liquid pipe is relatively hot, it may be caused by poor heat dissipation of the condenser, high condensing temperature, or excessive refrigerant flow.
As one of the key components in the refrigeration system, the temperature condition of the filter directly reflects the operating state of the system. Under normal circumstances, the temperature of the filter and the infusion tube is basically the same. However, if the filter is cool or not hot, it may be caused by the filter mesh being blocked by sludge or **. In this case, it is necessary to clean or replace the filter mesh in time to ensure the normal operation of the system.

VI. Temperature condition of the suction tube
The temperature condition of the suction pipe is one of the important bases for judging whether the refrigeration system is operating normally. Under normal circumstances, the suction pipe feels cool to the touch and is covered with dew. If the suction pipe is too cold and there is too much dew, resulting in extensive condensation on the casing; or if the suction pipe is not cool, does not condense, and the casing is very hot, it may be due to too little refrigerant flow or insufficient refrigerant quantity. In this case, it is necessary to replenish the refrigerant or adjust the system parameters in a timely manner to ensure the normal operation of the system.

VII. Temperature and evaporation temperature of the thermostatic expansion valve
The thermostatic expansion valve is one of the key regulating components in the refrigeration system. Under normal circumstances, the lower half of the expansion valve body is very cold and covered with dew, and the sound of refrigerant flowing is dull. If the valve body is relatively cold and there is a lot of dew or even frost on the surface, or if you can't hear the sound of refrigerant flowing but only the sound of gas flowing, it may be caused by a blocked filter screen or refrigerant leakage in the power box. In this case, it is necessary to clean or replace the filter screen in a timely manner, and check the condition of the refrigerant in the power box.

VIII. Temperature condition of the evaporator
The evaporator is another key component in the refrigeration system. Under normal circumstances, the outer surface of the evaporator is very cold and condensation droplets continuously drip down, resulting in a large temperature difference between the inlet and outlet air. If the evaporator surface is not too cool, there is not much condensation, or no condensation at all, and the sound of refrigerant flowing is very loud, with a small temperature difference between the inlet and outlet air, it may be due to insufficient refrigerant or a small opening degree of the expansion valve. In this case, it is necessary to replenish the refrigerant or adjust the opening degree of the expansion valve in a timely manner to ensure the normal operation of the system.  

IX. Ambient temperature requirements for outdoor units
As an essential component of the refrigeration system, the outdoor unit's operating state is directly influenced by the ambient temperature. According to national standards, the outdoor unit should ensure normal operation and achieve the cooling capacity and other indicators indicated on the product nameplate when the ambient temperature is below 35°C. When the ambient temperature ranges from 35°C to 43°C, although the air conditioning unit can operate, it cannot guarantee the cooling capacity indicated on the nameplate; and when the outdoor temperature exceeds 43°C, the air conditioning unit may operate in an overload state, causing the electronic control protection device to actuate and cut off the power supply to stop operation. Therefore, when using air conditioning, it is necessary to pay attention to changes in the outdoor ambient temperature and adjust the operating state of the air conditioning in a timely manner to avoid overload operation and activation of the electronic control protection device.