What should the low pressure gauge on an air conditioner read?
The working pressure (or vapor pressure) of the refrigerant in your compressor motor system is determined by both its temperature and ambient room temperature. Service manuals typically provide charging charts that identify the targeted suction vacuum (negative) pressure and output or discharge pressure for a particular compressor model and type of refrigerant.
The normal pressure of an air conditioner varies with the temperature of the surrounding environment. This is because the refrigerant cylinders are like pressure cookers without safety valves. When the external temperature increases, the internal pressure also increases.
For this reason, it is important to use a charging chart when servicing an AC. The chart will tell you the targeted suction vacuum (negative) and output pressure of the compressor motor. It will also tell you the evaporator saturation temperature. This will help you avoid overcharging or undercharging the system. These charts are available in service manuals. However, there are some “rules of thumb” that will get you in the ballpark if no charging chart is available.
R22 is an old refrigerant that is being phased out because of its ozone depletion and global warming potential. You will still find it in older air conditioners and refrigerators.
The pressure-temperature relationship for R22 is a little different from other refrigerants. This is because it has both liquid and gas phases in its cylinder.
This means that when you read the psig on a pressure test gauge, you will be getting a reading of both the liquid and gas pressure. You will need to refer to a charging chart for the specific compressor to get the correct pressure reading. These charts will provide you with the proper information based on actual ambient temperature and system design.
Using a digital manometer, you can measure the pressure of liquids, gases and air. The instrument measures pressure by using an electronic sensor that detects the movement of the diaphragm.
The r22 pressure-temperature chart shows you what the pressure of the refrigerant gas is at various temperatures. You can use this information to make sure you have the right amount of refrigerant in your system.
This information is also important when charging your air conditioning or heat pump system. You can find a r22 charging chart in your service manual to determine how much pressure you should charge the system with. This will help ensure that the compressor motor is operating at a safe temperature.
The pressure of R22 varies with temperature because it follows the same pressure-temperature relationship as water. As the temperature of the cylinder increases, so does its internal pressure. When this happens, it causes the evaporation temperature to rise.
It is important to keep this in mind when storing refrigerant cylinders. You should avoid storing them in direct sunlight or close to heat sources, because it can cause over-pressurisation.
During normal operation, R-22 pressures settle at 85 degrees F. This is called for on the service chart for a particular compressor model and type of refrigerant. This number will vary by indoor wet bulb temperature and outdoor ambient temperature.
R22 is being phased out because of its ozone depleting and global warming potential. This refrigerant has liquid in the bottom of its cylinder with vapour above it and just like water, the pressure within a cylinder increases or decreases as its temperature changes.
Service charts (provided in air conditioning and refrigeration manuals) will give the targeted suction vacuum (negative) pressure and output pressure for a given compressor motor. These charts also allow you to determine whether your system is correctly charged. However, these are only “rules of thumb” and get you in the ballpark if no charging chart is available. A proper air conditioner charging chart is based on actual incoming outdoor and indoor temperatures.
As the temperature rises, the pressure of R22 in the cylinder increases as well. Its pressure-temperature relationship is similar to water, except R22 has no safety valve to prevent the buildup of excessive pressure.
The pressure of the low-side suction line depends on the indoor wet bulb and outdoor ambient temperatures. A rule of thumb is that the suction saturation temperature should be 35-40 degrees Fahrenheit below the building’s return air temperature.
The optimum high-side compressor discharge pressure depends on the system design and compressor motor size. Refer to the charging chart for your unit to determine the target pressure. The chart shows what the pressure should be at various temperatures.