Using R-1 and AC-1 Pressure Transducers in Air Conditioning and the HVAC Industry

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If the quality of your products depends on cooling or freezing, WIKA offers the R-1 pressure transducer and AC-1 pressure transducer as the latest generation of thin-film and thick-film ceramic pressure transducers.

With rapid increases in energy costs, energy-efficient refrigeration and HVAC systems are essential. If operating your plant’s refrigeration systems involves a significant electricity expense, WIKA pressure transducers for refrigeration and air conditioning can significantly reduce energy consumption when used in conjunction with a PLC-based control system. Permanently installed pressure transducers make it simple to monitor the performance of your system and identify any problems that may occur.

The photos illustrate the WIKA R-1 pressure transducer in HVAC industry (upper right) and refrigeration (lower right) applications.

Description of a Typical Refrigeration Cycle

  • Step 1: Beginning at the compressor, the refrigerant is compressed and leaves the compressor as a high-temperature, high-pressure gas.
  • Step 2: The hot refrigerant enters the condenser, which is usually fan-forced air-cooled, then the refrigerant leaves the condenser as a warm liquid and continues on to the thermal expansion valve.
  • Step 3: The expansion valve meters the proper amount of refrigerant into the evaporator.
  • Step 4: There is a sudden pressure drop after the expansion valve converts the high-pressure warm liquid refrigerant into a low-pressure cold gas. The cold gas absorbs ambient heat from fan-forced air passing through the evaporator. This ambient heat converts the refrigerant into a cool, dry gas. From here the refrigerant reenters the compressor to be pressurized again, and the cycle repeats.

The diagram below shows a typical refrigeration cycle. Image Modified from Natural Resources Canada.

High-pressure transducers and low-pressure transducers are installed in the compressor to control and optimize the cycle.

Low refrigerant charge in a refrigeration system is detected by monitoring pressure and temperature. This monitoring is best accomplished with a pressure transducer located at or near the compressor outlet. Output signals from the pressure transducer are sent to a PLC. When a high discharge temperature with a low discharge pressure is detected, the PLC provides a low-charge signal. The PLC can also receive input about additional operating characteristics of the refrigeration system to provide a more accurate low-charge signal. The PLC is connected to a warning indicator and/or compressor so that the low-charge signal activates the indicator and/or deactivates the compressor.

Refrigeration systems often suffer from hidden equipment faults and inefficient controls. Undetected problems in a refrigeration system can result in high energy costs and shorten the life of the equipment. By installing the proper monitoring equipment and adopting an efficient control strategy, you can save money and get the maximum lifetime out of your equipment.

Refrigeration Potential Problems

  • Suction line filters keep the refrigerant clean and protect the compressor from taking in debris. If one or more of the filters becomes clogged, the restricted flow will create a pressure drop in the system. This drop will reduce efficiency and lead to unnecessary costs.
  • Hidden refrigerant leaks can eventually lead to a low refrigerant charge. Repairing leaks can bring about a significant increase in performance and efficiency. A low charge can cause efficiency losses and add to annual operating costs.
  • In many refrigeration systems, the head pressure remains fixed to guarantee reliability over a range of temperatures. This also assures enough refrigerant flow, freeze protection for the condenser, and an adequate pressure difference across expansion valves.

The excellent long-term leak resistance of the R-1 pressure transducer is achieved through a hermetically sealed weld of the thin-film pressure sensor to the process connection. On the process side, the monolithic design of the pressure sensor makes any additional seals unnecessary, which means less possibility of leakage. Elimination of the soft sealing material also removes the need for additional material compatibility testing. The R-1 pressure transducer has proven condensation resistance, one of the most important requirements for refrigeration and HVAC applications.

The economical AC-1 pressure transducer features a ceramic thick-film pressure sensor and provides a non-linearity of less than 1.0% B.F.S.L. with no measurable hysteresis error.

Both the R-1 and AC-1 pressure transducers were tested using strict protocols including the “Trane test” designed specifically for the refrigeration and HVAC industry. They both meet or exceed all test requirements, including resistance to high-pressure steam jets, condensation, dust tightness, and icing.

All WIKA pressure transducers are produced on a modern, highly flexible production line, which meets the highest quality standards. Our refrigeration and HVAC industry products offer absolute reliability at a low cost, without compromising quality, safety, or affordability.

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