Issue:
Low evaporator refrigerant temperature for RTAA, RTWA, and RTUA chillers
Resolution:
1. Evap Water flow may be inadequately low causing laminar flow and poor heat transfer. This can be caused by restrictions in the line or evaporator barrel. Glycol can also cause laminar flow conditions to be present.
2. Undercharge of refrigerant will cause this. With a low charge the rate of heat rejection the refrigerant gives up increases rapidly driving down the temperature.
3. Sensors may be bad. These include a) saturated evaporator temperature b) compressor suction temperature.
4. EXV could be hanging up.
5. You could see a high approach due to an oil over charge.
6. You could see compressor starting loaded and drying out evaporator. This causes the temperature and pressure to drop in the evaporator. And subsequent trip. This can be caused by slide valve piston seals leaking or by load unload solenoid problems. Refer to RTAA-SVD01A-EN or equivalent literature, depending on the compressor being worked on.
7. Less than 2 minute loop (volume of water in evaporator loop) may cause this diagnostic due to the controls not being able to respond fast enough.
8. LRTC (Low Refrigerant Temperature Cutout) set incorrectly for the glycol concentration in chiller.
Rate of change control capability is 1-2 F /min. of change. Some systems are such that rate of change of load exceeds this and the chiller will load too fast, drying out the evaporator and causing low refrigerant cut out trips.
Notes:
If there is glycol in the chilled water loop, the low refrigerant temperature cutout must be set appropriately. Reference the IOM for specific values.
Changes:
Other Question/Problem/Cause Statements:
- Chiller tripping on Low Evaporator Refrigerant Temperature
- Low evaporator refrigerant temperature
- LRTC?
- Low evap?
- Low evap refrigerant temps
- Chiller tripping on low evap temp circuit A
Facts:
- Air-Cooled Chiller (Pueblo) (RTAA 130-400 Ton)
- Air-Cooled Chiller (Pueblo) (RTAA 70-125 Ton)
- Water-Cooled Chiller (Pueblo) (RTWA)
Document Identifier: DOC-79794
Document Identifier: 79794
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.