Friday, August 1, 2014 by
Lubricant-refrigerant mixture breakdown causes sludge formation and other corrosive materials that will hinder the normal operation of compressor valves and control devices in refrigerant and HVAC systems. Scale, solder particles, dirt, and all types of foreign substances must be removed to protect the compressor, solenoid valves, expansion valves, capillary tubes, and other close tolerance parts.
Follow this 11 step procedure to ensure you have cleaned up your system before proceeding.
- Diagnosis — Make certain that a motor burnout has actually occurred by running the proper electrical tests. Determine the severity of the burnout by analyzing the acid content of the lubricant from the burned out compressor. This can be done on the job with a TA-1 One Time Acid Test Kit. Note the color of the lubricant, the smell of the refrigerant, and if carbon deposits are present in the suction line.
- Plan the procedure — Consider the following factors: If the lubricant is not acidic and none of the other indications of severe burn out are present, then the system can be classified as a “mild burnout” and cleaned up accordingly. Under these circumstances, it is easier to save the refrigerant. If a lubricant sample is desired for checking the progress of the clean-up, then a trap should be installed in the suction line (see Form 40-141). A semi-hermetic compressor can be examined and cleaned by having the head removed. A heat pump system will frequently require replacing the 4-way valve, or other special precautions. Systems with a critical charge must have the charge adjusted due to the added volume in the oversized filter-drier that is normally installed in the liquid line.
- Mild Burnout — If the analysis of the lubricant shows no acidity, then the system can be classified as a mild burnout, and cleaned up simply by installing an oversized Catch-All Filter-Drier in the liquid line. If the lubricant is not analyzed, and the other factors indicate some doubt, then the burnout should be considered severe and cleaned up as described below. CAUTION—Acid burns can result from touching the sludge in the burned out compressor. Rubber gloves should be worn when handling contaminated parts.
- Severe Burnouts —These systems should be cleaned using the suction line filter-drier method. The refrigerant in the system can be saved,and must be removed using refrigerant recovery/recycling equipment. The exact method chosen depends upon the availability of shutoff valves, the amount of charge, and the other equipment available. See the section on “Saving the Refrigerant.”
- Remove the burned out compressor and install the new compressor.
- Install a Catch-All Suction Line Filter-Drier or RSF shell (selected from Bulletin 40-10 pages 34 and 35) ahead of the new compressor. The access valve on the drier permits the pressure drop to be checked by installing gauges on the access valve and at the gauge port on the suction service valve. For systems without service valves, install a line tap valve downstream of the Catch-All Filter-Drier for the second connection.
- Remove the liquid line drier and install an oversized Catch-All (one size larger than the normal selection size). Check the expansion valve and other controls to see if cleaning or replacement is required. Install a See•All Moisture and Liquid Indicator.
- Evacuate the system according to the manufacturer’s recommendations. Normally this will include the use of a high vacuum pump and a low vacuum micron gauge for measuring the vacuum obtained.
- Recharge the system through the access valve on the suction line filter-drier. Then start the system according to the manufacturer’s instructions
- The use of a Catch-All Filter-Drier installed permanently in the suction line permits the clean-up of a small system to be completed with one service call. The pressure drop across the suction line filter-drier should be measured during the first hour’s operation. If the pressure drop becomes excessive, then the suction line filter-drier should be replaced. If the equipment manufacturer’s recommendations are not available, the following maximum pressure drop levels are suggested. See table below.
- In 24 hours take a lubricant sample. Observe the color and test for acidity. If the lubricant is dirty or acidic, replace the suction line and liquid line filter-driers. In two weeks re-check the color and acidity of the lubricant to see if another change of filter-driers is necessary. It may also be desirable to change the lubricant in the compressor. Before the job is complete, it is essential that the lubricant be clean and acid-free.
Saving the refrigerant
The refrigerant is not damaged by the burnout, and can be reused, provided the contaminants are removed. When a mild burnout has occurred on a system with service valves, the refrigerant can be saved by closing the valves and trapping the refrigerant in the system, while changing the compressor. The system can then be pumped down with the new compressor to save the refrigerant while installing an oversized Catch-All Filter-Drier in the liquid line.
If a severe burnout has occurred, the above procedure might damage the new compressor. Therefore, it is preferred that the refrigerant be removed from the system for reclamation. If no service valves are available then the refrigerant must be removed from the system. Recovery, recycling or reclamation of the refrigerant must be performed in accordance with EPA regulations. Sporlan recommends the use of our HH style cores for cleaning up all systems after a hermetic motor burnout. These cores contain a desiccant mix that is suitable for removing all types of system contaminants.
Form 40-109 is available for selection recommendations on suction line filter-driers after hermetic burnout and for new installations.
Information on cleaning up centrifugal systems is given in Bulletin 240-10-3.
Information on clean-up after a hermetic motor burnout is also given in Section 91 of the SAM Manual published by the Refrigeration Service Engineers Society.
Article contributed by Glen Steinkoenig, Product Manager, Contaminant Control Products, Sporlan Division of Parker Hannifin
Other articles on this topic include:
Using P-T Analysis as a Service Tool for Refrigeration Systems