Application Bulletin

Transcription

1 Bristol Compressors, Inc. Number: 124 Application Bulletin HIGH TEMPERATURE RETROFIT FROM R22 TO R407C Release EN Number C18811 Release Date 10/20/95 D /9/96 E /17/97 L /21/03 REVISIONS

2 Bristol Compressors, Inc. Application Bulletin No. 124 Release E/N: C18811 Date: 10/20/95 Revision E/N: L00910 Date: 2/21/03 Subject: High Temperature Retrofit from R22 to R407C These are general guidelines only and in no way should they replace, contradict or otherwise take precedence over any local, state or federal law or regulation pertaining to the recovery, reclamation, and recycling of refrigerants. With the phase-out of HCFC s, existing air conditioning/heat pump equipment will need to be replaced with new equipment or retrofitted with new components (including the compressor) that are approved for use with the new refrigerant and their lubricants. Using the procedures described below, existing R22 systems can be retrofitted for use with R407C, allowing them to continue in service for the remainder of their useful life. Bristol Compressors does not recommend the changeover of HCFC refrigerants to HFC s in systems that are operating and have no leaks. R407C is a zeotropic blend of refrigerants of the following composition: R32 23% R125 25% R134a 52% New High Temperature R407C Compressors are identified by the number 7 in the second digit of the model number (example: H75B28QABC). These compressors are factory oil charged with Polyol ester (POE) lubricant and employ an improved lubrication system which are required for the new refrigerant. For Bristol s approved lubricant type and required oil charge amounts for use with R407C, refer to the individual compressor model specification sheet. This information can be found on Bristol s website The use of any other lubricant may void the compressor warranty. Application Bulletin Page 2 of 13

3 SYSTEM DESIGN 1.0 Refrigerant Metering Devices The performance of each system is very dependent on the proper operation of each metering device. Devices such as solenoid valves, capillary tubes, fixed orifice valves, and expansion valves can perform differently if they are not correctly adjusted or properly sized. For example, the port size of a valve may not be correct for the new refrigerant density. Each valve and metering device manufacturer should be consulted, along with the system's manufacturer, to ensure all components will work properly in the presence of the new refrigerant and lubricant. 2.0 Filter Driers The proper selection of a system's filter drier is very important. Some filter driers may not be suitable for R407C refrigerant and polyol ester lubricant. Therefore, the original equipment manufacturer should be contacted for the proper filter drier selection. It is important to replace the filter drier any time the refrigerant or lubricant in a system is changed. Specifically, Bristol Compressors requires a new suction line filter drier be installed during any compressor replacement. Maintaining good system performance, reliability and cleanliness is closely linked to proper filter drier operation. 3.0 Controls The proper operation of many types of air conditioning/heat pump equipment requires that the control systems function correctly. The control system could be pressure controls, temperature controls, timing devices, or sophisticated electronic controls. Changing to R407C refrigerant and polyol ester lubricant in a system could adversely affect these control systems. Each equipment manufacturer should be consulted to ensure each control system will operate correctly with the R407C refrigerant/polyol ester lubricant combination. Changes most likely will have to be made for continued good equipment performance. These changes could involve adjusting temperature or pressure set points to new values or replacing the control system with a newly designed unit. 4.0 Explanation of R407C vs. R22 Condenser and Evaporator Temperature/Pressure Graphs Pressure versus temperature charts and graphs are included on pages 4 through 8 as a general information guideline. More detailed specific saturated property tables can be obtained from the chemical manufacturer and should be used when conducting system retrofits. The graphs are intended to represent the pressures that R407C delivers versus R22 at the equivalent saturated evaporator and condenser temperatures. 4.1 Explanation of refrigerant glide inherent to R407C R407C has refrigerant glide. Glide is due to the different boiling and condensing temperatures of the three components that make up R407C. This means there is not a one to one relationship between pressure and temperature as with R22. The saturated vapor and saturated liquid values are approximately 10 F apart for a given pressure, whereas with R22 they are one and the same The temperature glide of this refrigerant should not cause any problems as long as you keep in mind the following points about the relationship between pressures and temperatures of the evaporator and condenser. Application Bulletin Page 3 of 13

4 a) When specifying the evaporating and condensing temperatures use the mean (or average of dew and bubble point) temperatures. b) When setting evaporator superheat, calculate it from the saturated vapor (or dew point) temperature. c) When setting subcooling, calculate it from the saturated liquid (or bubble point) temperature Specific examples: (Some interpolation between values may be required) Set conditions to run a 45 F evaporator, 130 F condenser with 20 F superheat and 15 liquid subcooling. a) Find the 45 F mean temperature from Table 1. The pressure corresponding to this mean temperature is your suction pressure = 94.4 psia. b) Calculate the return gas temperature using the dew point temperature at this pressure. Example: F + 20 F superheat = F return gas temperature. c) Find 130 F mean temperature from Table 1. The pressure corresponding to this mean temperature is your discharge pressure = psia. d) Calculate the liquid temperature using the bubble point temperature at this pressure. Example: 126 F - 15 F subcool = 111 F liquid temperature Determine the amount of superheat on a system that measures a suction pressure of 68 psig at the bulb, and the temperature at the bulb reads 52 F. a) Convert 68 psig to psia = (atmospheric pressure) = 82.7 psia. Look up the dew point temperature from Table 1 at 82.7 psia. This value is 43.3 F. Your superheat is 52 F F = 8.7 F. Application Bulletin Page 4 of 13

5 R407C PRESSURE/TEMPERATURE TABLE Saturated Liquid and Saturated Vapor Properties PRESSURE DEW POINT MEAN TEMP BUBBLE POINT PSIA PSIG F F F TABLE 1 Application Bulletin Page 5 of 13

6 R407C PRESSURE/TEMPERATURE TABLE (Page 2) PRESSURE DEW POINT MEAN TEMP BUBBLE POINT PSIA PSIG F F F TABLE 1 Application Bulletin Page 6 of 13

7 R407C PRESSURE/TEMPERATURE TABLE (Page 3) PRESSURE DEW POINT MEAN TEMP BUBBLE POINT PSIA PSIG F F F TABLE 1 Application Bulletin Page 7 of 13

8 Saturated Properties of R407C and R22 Pressure vs. Temperature Graph Condenser Pressure vs. Temperature Pressure (Psia) R22 R407C SAT VAPOR R407C SAT LIQUID Condenser Temperature ( F) FIGURE # 1 Application Bulletin Page 8 of 13

9 Saturated properties of R407C and R22 Pressure vs. Temperature Graph Evaporator Pressure vs. Temperature R22 R407C SAT VAPOR R407C SAT LIQUID 80 Pressure (Psia) Evaporator Temperature ( F) FIGURE # 2 Application Bulletin Page 9 of 13

10 5.0 Maximum Continuous Current (MCC) Data Extensive testing has been done at maximum continuous current (MCC) test conditions with R407C and R22 refrigerant on many different displacement compressors. The MCC values of the compressors did not change from the published R22 values when R407C refrigerant was utilized. 6.0 Retrofit Procedure Summarized below are the recommended procedures for retrofitting an R22 system to R407C: 6.1 Compatibility. Consult the original equipment manufacturer of the system components for their recommendation on the following: - Plastics compatibility - Elastomers compatibility - Lubricant (viscosity, manufacturer, additives) - Solid core driers: Check with drier manufacturer for recommendation 6.2 If compressor has failed: a. Determine reason for system/compressor failure and correct b. Recover refrigerant (see step 6.4) c. Remove compressor (see step 6.5) d. Measure lubricant remaining in compressor - should be greater than 95% of original charge to minimize removal efforts in step (e) e. Assure removal of residual levels of original lubricant (must be less than 5%) - Purge system heat transfer components using high pressure inert gas (e.g., nitrogen) - Disconnect and purge line sets, or any other component that could trap lubricant (e.g., oil separator, valves, etc.) - Large system/long line sets may require up to three (3) oil changes after replacing compressor f. Go to If compressor has not failed: a. Run at reference condition and record on data sheet (see Appendix 2) which will be used to confirm R407C charge requirement b. Run system at a high flow condition (highest suction pressure) for minutes for optimum lubricant pick-up/return to compressor e. Go back to step 6.2, item (b) through (f) 6.4 Remove R22 charge. Remove refrigerant and collect in a recovery cylinder using a recovery device capable of pulling in. Hg vacuum. If the correct R22 charge size for the system is not known, weigh the amount of refrigerant removed. The initial quantity of R407C charged in the system will be determined from this weight. 6.5 Remove compressor. The compressor must be removed from system since it will not be compatible with HFC s/poe lubricant. 6.6 Replace filter drier. Replace filter drier with one approved for use with R407C refrigerant/polyol ester lubricant. 6.7 Install compressor. Using normal service practices, install compressor approved for R407C refrigerant/polyol ester lubricant. Application Bulletin Page 10 of 13

11 CAUTION: Do not leave compressor or system open to atmosphere for longer than 15 minutes maximum. Polyol ester lubricants are at least 100 times more hygroscopic (ability to absorb moisture) than mineral oils. It is almost impossible to remove the moisture absorbed by the lubricant even with heat and vacuum. 6.8 Leak check system. Use normal service practices. If a leak detector is used, consult the leak detector manufacturer for unit s sensitivity to R407C. 6.9 Evacuate. Use normal service practices to remove air and other non-condensables in the system, evacuate to at least 200 microns Charge system with R407C. To ensure that the proper refrigerant composition is charged in the system, it is important that liquid only be removed from the charging cylinder. Once removed from the cylinder, R407C can be charged to the system as vapor as long as all of the refrigerant removed from the cylinder is transferred to the system. Due to the liquid density difference of R407C versus R22, the refrigeration system will requires less weight of R407C than R22. The optimum charge will vary depending on the operating conditions, size of the evaporator and condenser, size of receiver (if present), and length of pipe or tubing runs in the system. For most systems, the optimum charge will be 85-90% by weight of the original R22 charge. It is recommended that the system be initially charged with about 85% by weight of the original R22 charge (refer to section 6.4). Add the initial charge to the liquid line of the system with the compressor not running. When the system and cylinder pressures are equal, start the compressor and meter the remainder of the refrigerant into the suction line of the system. Since some compressors may be damaged if liquid refrigerant enters the suction side of the compressor, it is important to charge the refrigerant slowly into the suction line to allow it to vaporize before it enters the compressor. A throttling valve can be used to ensure that the liquid is converted to vapor prior to entering the system Charge adjustment. Allow the system to run until conditions stabilize. Add additional R407C in small amounts until the system conditions reach the desired levels (refer to data recorded in step 6.3). Be sure to charge by evaporator/condenser temperatures since the pressures will be higher at the temperatures equal to R22. Total charge should not exceed original R22 charge levels Label components and system. After completion of retrofit, label the system and the converted components to identify the type of refrigerant and lubricant, so proper service will be performed in the future. Attached is a Retrofit Checklist (Appendix 1) for R407C to assist you in the retrofit process and a System Data Sheet (Appendix 2) to record the system operating conditions for your records. Application Bulletin Page 11 of 13

12 Appendix 1 Checklist for R407C Retrofit 1. Consult the original equipment manufacturer of the system components for their recommendation concerning compatibility and their retrofit procedures in order to sustain warranty 2. If compressor is operable, run high flow condition (highest suction pressure for minutes to maximize oil return to compressor). 3. Remove R22 charge from system (need in. Hg vacuum to remove charge). Use recovery cylinder --Do not vent to atmosphere-- 4. Replace filter drier with new filter drier approved for use with R407C. - Loose fill driers: Use XH7 or XH9 desiccant or equivalent. - Solid core driers: Check with drier manufacturer for recommendation. 5. Replace compressor with one approved for usage with R407C. - Measure and record oil remaining in old compressor - Residual lubricant should be less than 5% by weight of the total lubricant used in system 6. Leak check system. 7. Evacuate with vacuum pump using normal service practices (200 microns minimum). 8. Charge system with R407C. - Initially charge 85% by weight of original equipment manufacturer specified R22 charge. - Amount of refrigerant charged: 9. Start up equipment and adjust charge until desired operating conditions are achieved. - If low on charge, add in increments of 2-3% of original R22 charge. - Amount of refrigerant charged: 10. Total Refrigerant Charged (add 8 and 9) - Should not exceed original R22 charge level 11. Label components and system for type of refrigerant (R407C) and lubricant (polyol ester oil). 12. Conversion is complete!! Application Bulletin Page 12 of 13

13 SYSTEM DATA SHEET Appendix 2 Type of System/Location: Equipment Mfg.: Model No.: Serial No.: Drier Mfg.: Model No.: Condenser Cooling Medium (Air/Water): Expansion Device (check one): Capillary Tube: Expansion Valve: If Expansion Valve: Manufacturer: Model No.: Control/Set Point: Location of Sensor: Other System Controls (e.g.: head press control); Describe: Compressor Mfg.: Model No.: Serial No.: Original Lubricant: Type/Mfg.: Charge Size: New Lubricant: Type/Mfg.: 1st Charge Size: 2nd Charge Size: Additional Charge Size: Drier type (check one): Loose Fill: Solid Core: (circle units used where applicable) Date/Time Refrigerant Charge Size Lb. Ambient Temperature ( F/ C) Relative Humidity Compressor: Suction Temperature ( F/ C) Suction Pressure psig DischargeTemperature ( F/ C) Discharge Pressure psig Indoor Temperature ( F/ C) Evaporator: Refrigerant Inlet Temperature ( F/ C) Refrigerant Outlet Temperature ( F/ C) Coil Air/H O In Temperature ( F/ C) 2 Coil Air/H O Out Temperature ( F/ C) 2 Refrigerant Superht. Ctl. Pt. ( F/ C) Condenser: Refrigerant Inlet Temperature ( F/ C) Refrigerant Outlet Temperature ( F/ C) Coil Air/H O In Temperature ( F/ C) 2 Coil Air/H O Out Temperature ( F/ C) 2 Exp. Device Inlet Temperature ( F/ C) Motor Amps Run/Cycle Time Comments: R22 Data R407 Data Application Bulletin Page 13 of 13