Tests and Measurements Performed Using Pressure Gauge

Tests And Measurements Performed Using Pressure Gauge







Indicators on pressure gauge
1. Temperature scale for refrigerant R134a CF3CH2F or CH2FCF3.
2. Pressure scale

Pressure gauge may have one or more temperature scales next to pressure scale. R134a scale values are allocated respectively in the vapor pressure table. Since various refrigerants create different vapor pressures at the same temperature, each temperature scale is identified for the respective refrigerant.

Pressure gauge makes the following tests and measurements possible

a. Pressure and temperature measurement at refrigerant circuit
- High pressure gauge measures pressure and temperature, which expand uniformly from outlet of A/C compressor via the condenser up to constriction (restrictor, or expansion valve) with A/C system switched on.
- Low pressure gauge measures pressure and temperature, which expand uniformly from constriction (restrictor, or expansion valve) via evaporator up to input of A/C compressor with A/C system switched on.

NOTE: The relationship between pressure and temperature indicated on the gauges only exists in a refrigerant circuit containing liquid or vapor, but not gas. In gaseous state, the temperature is approx. 10 degrees C to 30 degrees C higher than indicated on the gauge.

b. Verification of refrigerant in a closed vessel
Refrigerant R134a is present in a closed vessel or in a refrigerant circuit when temperature indicator on gauge matches the refrigerant temperature (standing fluid adopts the ambient temperature).

A closed vessel or a refrigerant circuit which has been switched off is empty when temperature indication on gauge is below the temperature of the refrigerant.

NOTE: The relationship between pressure and temperature indicated on the gauges no longer applies if no liquid is present and the pressure is built up solely by gas.