Common Sense and Selection of Refrigerant Gauges

Common Sense of Refrigerant Gauges:

Refrigerant gauges (also known as refrigerant pressure gauges or refrigerant pressure gauge sets) are core tools for the maintenance, monitoring, and commissioning of refrigeration equipment. They are mainly used to detect the pressure, temperature, and charge amount of refrigerants in the system, with their working principle centered on “pressure measurement” and “correlation with refrigerant thermodynamic properties”.

The core function of refrigerant gauges is pressure measurement, but in practical applications, equipment maintenance and monitoring personnel pay more attention to “the refrigerant temperature corresponding to the pressure” (such as judging whether the evaporation temperature and condensation temperature are normal). This correlation relies on the thermodynamic property of refrigerants — a one-to-one correspondence between pressure and temperature in the saturated state.

Refrigerants exist in a “saturated state” in refrigeration systems (gas-liquid coexistence, such as boiling in evaporators and condensation in condensers). At this time, there is a fixed corresponding relationship between their saturated pressure and saturated temperature (determined by the type of refrigerant). For example, the saturated pressure of R410A is approximately 0.8MPa at 0℃ and about 2.4MPa at 50℃.

The dial of refrigerant gauges is additionally marked with “refrigerant temperature scales” (such as temperature values for R22 and R410A). Essentially, this converts “pressure values” into temperatures in advance through the “saturated pressure-temperature conversion table” of the refrigerant, presenting them directly to users without the need for additional table lookup. Users can read the corresponding saturated temperature through the position of the pressure pointer to quickly judge the system operating conditions (such as whether the evaporator temperature is too low or the condenser has poor heat dissipation).

Low-pressure gauges are connected to the “low-pressure interface” of the system (such as the evaporator return pipe and compressor suction pipe) through blue hoses to measure suction pressure. High-pressure gauges are connected to the “high-pressure interface” (such as the condenser liquid outlet pipe and compressor discharge pipe) through red hoses to measure discharge pressure. By reading both high and low pressures simultaneously, the working status of the compressor can be judged (such as whether there are faults like excessively high high pressure or excessively low low pressure).

Distinction between High-Pressure and Low-Pressure Refrigerant Gauges: Internationally, the universal distinction is by color — red represents high-pressure gauges, and blue represents low-pressure gauges.

1 Reading of Measured Values:

The gauge shown in the figure above is a “single-loop refrigerant pressure gauge”, which is a specialized tool for detecting the pressure and temperature of a single loop in a refrigeration system.
2 Application Scenarios:

1.Suitable for measuring the system pressure with various refrigerants as the medium, and can display the relationship between pressure and refrigerant evaporation temperature;

2.Heat pump industry;

3.Air conditioning systems;

4.Refrigeration equipment;

5.Cold storage systems;

3 Selection of Refrigerant Gauges:

1.Refrigerant Compatibility:The dial is marked with compatible refrigerant types (e.g., R134A, R22, R404A, R407C). It shall not be used for media not marked on the dial.

2.Distinction Between High-Pressure and Low-Pressure Types:

●If the customer needs to measure the “evaporator return pipe” or “compressor suction pipe” (low-pressure end of the system with low temperature) → recommend the low-pressure type;

●If the customer needs to measure the “condenser liquid outlet pipe” or “compressor discharge pipe” (high-pressure end of the system with high temperature) → recommend the high-pressure type;

●If the customer is unsure about “high-pressure or low-pressure”: Guide them to describe the “temperature of the detection part” — “the part that feels cool is the low-pressure end, and the part that feels hot is the high-pressure end” — then recommend the corresponding type.