Cleaning Up Contaminated Ice Machines

February 27, 2002
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System contamination has to be of prime concern to a refrigeration contractor.

The purpose of this article is to describe the basic requirements for restoring contaminated ice machine systems to reliable service.

System contamination is generally caused by the introduction of moisture or residue from a compressor burnout into the refrigeration system.

Inspection of the refrigerant is usually the first indication that there are contaminants in the system. If obvious moisture or an acrid odor indicate burnout is present in the refrigerant, you must take steps to determine the severity of contamination, as well as to determine the cleanup procedure.

If visible moisture or an acrid odor is detected, or if contamination is suspected, the use of a Totaltest Kit from Totaline or a similar diagnostic tool is recommended. These devices read refrigerant, therefore eliminating the need for initial oil samples for testing.

If a refrigerant test kit indicates harmful levels of contamination, or if the kit is not available, inspect the compressor oil as follows:

1. Remove the refrigerant charge from the ice machine.

2. Remove the compressor from the system.

3. Check the odor and condition (appearance) of the oil.

4. Inspect open suction and discharge lines at compressor for burnout deposits.

5. If contamination signs are not evident during the above procedure, perform an acid oil test to ensure that no harmful contamination is present.

TYPES OF CONTAMINATION

The following lists describe different types of contamination and detail the appropriate clean-up procedure in each case.

Symptoms/findings:
Moisture/air contamination: one or more of the following will exist —

  • Refrigeration system is open to atmosphere for prolonged periods.
  • Refrigeration test kit and/or acid oil test shows contamination.
  • There is a leak in the water-cooled condenser.
  • Oil appears muddy, or there is visible moisture in oil.
    Required cleanup procedures:
    Mild contamination cleanup procedures. (See details further into this article.)

    Symptoms/findings:
    Mild compressor burnout —

  • Oil appears clean with acrid odor; and/or
  • Refrigeration test kit or acid oil test shows harmful acid content;
  • No burnout deposits in open compressor lines.
    Required cleanup procedures:
    Mild contamination cleanup procedures.

    Symptoms/findings:
    Severe compressor burnout —

  • Oil is discolored and acidic with acrid odor, there are burnout deposits in compressor, discharge and suction lines, and other components.
    Required cleanup procedures:
    Severe contamination cleanup procedures. (See details further into this article.)

    MILD CONTAMINATION CLEANUP PROCEDURES

    1. Replace failed components if necessary. If the compressor checks out well, change oil in the compressor.

    2. Replace the liquid-line drier.

    3. Follow normal evacuation procedures, but replace the evacuation step with the following:

    a) Pull a vacuum to 1,000 microns. Break the vacuum with dry nitrogen and sweep the system. Pressurize to a minimum of 5 psi.

    b) Pull a vacuum to 500 microns. Break the vacuum with dry nitrogen and sweep the system. Pressurize to a minimum of 5 psi.

    c) Change the vacuum pump oil. Pull the system down to 250 microns. When 250 microns have been achieved, allow the vacuum pump to run for 30 min on self-contained models, 1 hr for remotes. A standing vacuum test may be performed at this time as a preliminary means of leak checking; however, the use of an electronic leak detector is recommended after the system has been charged.

    Note: If the contamination is from moisture, the use of heat lamps or heaters is recommended during evacuation. Place heat lamps at the compressor, condenser, and at the evaporator prior to evacuation. (Ensure that heat lamps are not positioned too close to plastic components such as evaporator extrusions, water trough, etc., as they could melt, warp, etc.)

    Important: Dry nitrogen is recommended for this procedure to prevent refrigerant release into the atmosphere.

    4. Charge the system with the proper refrigerant to the charge indicated on the nameplate.

    5. Operate the ice machine.

    SEVERE CONTAMINATION CLEANUP PROCEDURES

    1. Remove the refrigerant charge.

    2. Remove the compressor.

    3. Disassemble the hot gas solenoid valve. If burnout deposits are found inside the valve, install a rebuild kit and replace the TXV. If contaminants are found, replace the harvest pressure limiter control.

    4. Check discharge and suction lines at the compressor for burnout deposits. Wipe out as necessary.

    5. Sweep through the open system with dry nitrogen. (Sweeps with refrigerant are not recommended, as that method releases refrigerants into the atmosphere.)

    Installation procedures:

    6. Install the new compressor and start components.

    7. Install an adequately sized suction-line filter-drier with acid- and moisture-removal capability and inlet/outlet access valves. Place the filter-drier as close to the compressor as practical.

    8. Replace the liquid-line filter-drier.

    9. Follow normal evacuation procedures, except replace the evacuation step with the following (remembering that dry nitrogen is recommended for this procedure to prevent refrigerant release into the atmosphere):

    a) Pull a vacuum to 1,000 microns. Break the vacuum with dry nitrogen and sweep the system. Pressurize to a minimum of 5 psi.

    b) Change the vacuum pump oil. Pull a vacuum to 500 microns. Break the vacuum with dry nitrogen and sweep the system. Pressurize to a minimum of 5 psi.

    c) Change the vacuum pump oil. Pull the system down to 250 microns. When 250 microns have been achieved, allow the vacuum pump to run for 30 min for self-contained models, 1 hr for remotes. (A standing vacuum test may be performed at this time as a preliminary means of leak checking; however, use an electronic leak detector after the system has been charged.)

    10. Charge the system with the proper refrigerant to the charge indicated on the nameplate.

    11. Operate the ice machine.

    a) Check pressure drop across the suction-line filter-drier after 1 hr running time. If pressure drop is not excessive (up to 1-psi differential), the filter-drier should be adequate for complete clean up. Proceed to step 12.

    b) If pressure drop is greater than 1 psi after 1 hr run time, change the suction-line filter-drier and liquid-line drier. Repeat until the ice machine will run 1 hr without pressure drop.

    12. Remove suction-line filter-drier after 48 to 72 hrs run time. Change the liquid-line drier and follow normal evacuation procedures.

    Important: Manitowoc Ice Inc. assumes no responsibility for the use of contaminated refrigerant. Damage resulting from the use of contaminated, recycled refrigerant is the sole responsibility of the servicing company.

    This material was prepared by Manitowoc Ice Inc. For more information, visit www.manitowocice.com (website).

    Publication date: 03/04/2002

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