Proper Refrigeration Piping Installation Practices – Installing a new air conditioning and heating system requires skill and knowledge of proper procedures in electrical wiring, controls wiring, and pipework. On commercial projects a skilled electrician handles the electrical hookups, a controls technician handles the control wiring, and a pipefitter handles the pipework including the refrigeration piping which can include chilled water and refrigeration pipework.
Proper Refrigeration Piping Installation Practices - Installation Factors and Considerations
In residential installations, two or three skilled HVAC technicians usually handle the complete installation except for running line voltage from a breaker panel to the air handler and the outdoor unit. By code that requires an electrician and an electrical permit (In many municipalities however code requirements vary). It is important that all the work be done correctly according to code and best industry practices following basic fundamentals. This is very important in many regards including correct installation, the finished job looking professional, and the reliability of the system for its operating life. This requires a skilled knowledgeable technician that can wear many different hats to get the job done right.
Proper Refrigeration Piping Installation Practices – R-22 to R-410A Retrofit Factors and Considerations
When manufacturers began selling the newer R-410A refrigerant in air conditioners and heat pumps, because of government regulations, it forced HVAC contractors and homeowners to not only replace the condenser when the condenser failed but also the indoor evaporator coil. The reason for this is because the old R-22 refrigerant coil and the newer R-410A refrigerant will not work together.
If the refrigerants mix between the two systems then it will cause the compressor to fail prematurely. One system uses a natural oil and the other system uses a synthetic oil. When the oil mixes it will create a toxic sludge that is very bad for the compressor. It is possible to reuse the old refrigerant pipe and possibly an old R-22 evaporator coil with a new R-410A condenser (if the coil/piping size matches the capacity and technical requirements) but the system needs to be flushed thoroughly. The flush needs to rid the old pipe and/or evaporator coil of all residual oil or other contaminants left in the old piping.
Recommendations for the Old Piping Replacement
Recommendations are that the old system is completely replaced simply to prevent cross contamination and failure of the new system. It is best to be safe than sorry later. It will cost more to replace everything but the cost of replacing a new compressor that failed prematurely due to cross contamination is more costly than simply replacing everything in most cases and among other costs. Replace the refrigerant pipe and the evaporator when retrofitting R-410A with an old R-22 system.
The bottom line is if you are doing a retrofit and using a different refrigerant than was in the old unit either replace the entire line set or flush the old line set if you are reusing it. Additionally, always be very vigilant about protecting the pipes from accidental debris getting into the pipe. Cover all pipe openings with tape, caps or plug the pipe opening with a rubber plug until you are ready to braze the ends.
This provides insurance by keeping all foreign matter out of the piping. Additionally, it will save you much time and money later. Take zero risk on contaminating the refrigeration piping with foreign debris or worse, moisture. Before brazing the pipe it is not a bad idea to go ahead and blow the pipe out with a nitrogen purge just to make sure nothing got in the pipe. Using installation practices like this can and will save time, effort, and money in the future.
Proper Refrigeration Piping Installation Practices - Other fundamentals for refrigerant pipe design and installation include:
Always follow manufacturers guidelines for pipe sizing and installation. If unsure call the manufacturers engineering support line to make certain you are using proper sizes and methods according to the manufacturer’s guidelines. This is especially important for longer horizontal or vertical piping runs. Make sure you do not need an oil trap in the refrigeration circuit and if you do where is the optimum place to install the trap according to the manufacturer.
Local/Other Related Refrigerant Piping Codes
Always follow the local code. Many local codes often defer to the International Mechanical Code but always double check with the local municipalities. If there is a conflict with the code and the manufacturers instructions typically the manufacturers instructions will win. However, always check with the local Authority Having Jurisdiction (AHJ) or the code inspectors to make sure it is settled before installation.
Clean System Protected from Atmosphere During Installation
Proper Refrigeration Piping Installation Practices - Ensuring that new system is clean and free of debris especially in the piping. When finished brazing the pipe joints always use caps or plugs on any piping exposed to the atmosphere. Keeping trash and moisture out of the system is very important and will save time later on when the system is permanently sealed and ready for evacuation procedures. Using nitrogen flow to prevent oxidation will also keep the piping clean and free of contaminants.
Proper pipe support is essential in the design and installation of the piping. Lose piping will vibrate and move. This will eventually eat a hole in the piping leading to catastrophic system failure in a regrigeration system. Ensure equipment has spring isolators or rubber vibration isolators to reduce vibration in the line set and equipment.
Do not install the piping where it will be subject to accidental tripping or piercing. Anything that can potentially damage the piping needs to be addressed in the installation and design. Protecting the refrigerant pipe from any future damage is essential and can also make the job look professional when complete. That will make the customer happy also.
Technical Details for Longer Runs
Proper Refrigeration Piping Installation Practices - If running the refrigerant pipe for an extended distance keep refrigerant pipe within the manufacturers recommended limits. Always keep in mind the risers and possible pressure drop in the refrigerant piping based on total equivalent length (TEL). Oil traps should be used as recommended by the manufacturer. Keeping liquid refrigerant from reaching the compressor is essential to protecting the compressor especially reciprocating compressors. Proper refrigerant pipe is essential and recommended by the manufacture. Refrigerant pipe sizing charts are available in the installation instructions. All these things must be factored into the design and proper installation of refrigerant pipe work.
Refrigerant Piping Valves
Does the system call for hot gas bypass or a pump down cycle? If so has the valves been properly sized? What will be the control voltage be for the solenoid and if the voltage is high voltage have you arranged for an electrician to run the wire for this circuit?
Home Runs When Possible - Avoiding Unnecessary Solder Joints
Avoid solder joints when necessary using home run piping from the condenser to the evaporator when possible. After brazing is complete proper refrigerant pipe evacuation and pressure testing is necessary. This is done to purge all non-condensing gasses/moisture from the refrigerant piping. Dry nitrogen should be used for the pressure testing and purging and then a proper vacuum of the system should be done. Pressure testing includes a test that the system will hold a charge of nitrogen (300 to 400 p.s.i.g but follow manufacturers instructions for maximum pressure testing limitations - remember the evaporator coil pressure limitations also) for at least 15 minutes and the same with the vacuum pressure testing.
A micron gauge should be used and a 500-micron vacuum should be held for at least 15 minutes with the refrigerant piping system in a vacuum. Proper pressure testing ensures no leaks in the refrigerant piping or the evaporator coil. It tests any and all connections between the condenser and the evaporator coil. When the refrigerant piping is pressurized with dry nitrogen it is good practice to inspect all the solder joints. Additionally, any other connections. Check connections such as metering devices, filter-driers, solenoid valves, and flare connections with soap bubbles to ensure integrity of the refrigerant piping. For best practice in evacuating the piping system follow the instructions for a triple evacuation. It may take a little more time and a little nitrogen but will save in headaches later.
Refrigerant Charging Methods
Proper charging methods need to be used when charging the system. Most condensers come pre-charged with enough refrigerant with enough refrigerant for the condenser and a refrigerant line set of 25 feet. Other condensers come pre-charged with dry nitrogen and have weigh charge instructions with the new unit. The weigh in instructions should be followed and additionally proper superheat and sub-cooling charging methods should be done to make sure the final charge is correct.
Additionally some manufacturers also include a pressure temperature chart for various outdoor ambient temperatures and indoor load temperatures. It doesn’t hurt to use all the tools available to ensure the system is properly charged. Many HVAC companies use senior HVAC technicians to perform start up of any new installations. The final sign off on the finished installation is this senior HVAC technician. He goes over the final installation with a fine-toothed comb to make sure everything is correctly installed and operating as designed.
Piping Materials and Material Quality
Proper Refrigeration Piping Installation Practices - Finally, make sure to use all the proper and rated materials for the installation. Silver solder for brazing and only piping for refrigeration should be used. When in doubt about any technical details, installation methods, or quality and rating of materials always call the technical representative for the manufacturer.
Proper Refrigeration Piping Installation Practices - Conclusion for Proper Installation and Design Practices
By following all the fundamentals and doing quality work the new installation will have reliability. And keep working reliably for years to come. Proper installation also ensures you will get the efficiency the unit is rated for by the manufacturer. Another reason why it is recommended to hire qualified HVAC contractors when purchasing and installing new equipment.
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Proper Refrigeration Piping Installation Practices
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