Equipment Retrofit Procedures

Most retrofits are NOT DROP-IN procedures; there are important issues to consider. When considering a retrofit to a non-CFC refrigerant, it is suggested that contact be made with the chiller manufacturer for recommendations on the conversion and expected changes in performance. The manufacturer may offer to quote a price for performing the conversion, which can be compared to other options for performing the retrofit.

In some cases, when changing from a CFC to an alternative refrigerant, the lubricant must be changed to avoid operational problems. Typical applications are shown here.

CFC-11 to HCFC-123

Due to compatibility issues associated with the use of R-123 in centrifugal chillers it is recommended the retrofit be evaluated on an individual basis by a qualified representative of the chiller manufacturer or certified service personnel. Modifications required may include impeller and/or gear changes, seal and gasket replacement, and possibly motor modifications on semi-hermetic units. All manufacturer's guidelines and procedures should be followed carefully in order to achieve optimal results.

CFC-12 to HFC-134a

These are typical steps taken in retrofitting a chiller from an existing CFC refrigerant to this environmentally acceptable alternative refrigerant.

1. Gather baseline data from the present system to be used to optimize the system when using the alternative refrigerant. Note the current CFC charge in pounds, lubricant type and charge (in pints, quarts, gallons, etc.), existing operating temperatures and pressures, and overall system performance. Leak test the system and repair is needed.

2. Removal of existing mineral oil from the system, with residual content reduced to less than 5%. This is typically done by draining the mineral oil from all accessible points in the system and replacing with an equivalent charge of polyester lubricant. The system is then operated with the R-12 sufficiently to insure miscibility of the two lubricants. Test for residual mineral oil content and repeat procedure until the residual content is reduced to less than 5%. Typically this takes three cycles operating at 24 hour intervals.

3. Recover the existing R-12 charge and lubricant charge using standard industry recovery equipment and guidelines. A number of refrigerant recovery services are available commercially.

4. Replace filter driers with new cores. Examine sight glass for compatibility to necessary new (150 ppm) moisture-level indication levels. As new refrigerants can retain more moisture, do not omit this step.

5. Evacuate the system using a deep vacuum (at least 500 microns) to insure all remaining moisture has been removed.

6. Charge system with the proper polyester lubricant and HFC-134a refrigerant. Typically the R-134a charge will be about 90% of the original charge. Refer to pressure-temperature charts for final adjustment. Visual indication through the sight glass is not recommended as the nature of the refrigerant and lubricant is to appear cloudy in the liquid portion of the system.

7. Place proper markings and identification on the system to indicate the retrofit to R-134a and polyester lubricant. Indicate the pounds of the new R-134a charge in a visible location.

8. Start the system and make final expansion valve adjustments to achieve the proper superheat settings. Typical normal R-134a operating pressures are 2-5% lower on the evaporator side and 2-5% higher on the condenser side.