Issue:
EXV Checkout
Resolution:
Improper expansion valve operation can cause a number of problems, including Low Evaporator Refrigerant Temperature, and Liquid Level Sensor diagnostics. To validate the expansion valve is working correct, do the following:
1. Connect KestrelView to the microprocessor.
2. If possible, allow the circuit to run in order to build pressure differential in the system.
3. Ideally, it is best to perform a service pumpdown prior to performing the test. Please beware of the considerations when performing a pumpdown, and do not allow the suction pressure to fall below 20 psig. See the IOM for more details. Using a gauge, be prepared to shut the chiller off the pressure drops below 20 psig.
Note: The remainder of this test can only be done while the entire chiller is off. It is strongly recommended that the chilled water pump remain on.
4. Push the "Stop" button on the front panel.
5. Walk to the EXV of the circuit you are working on. Shortly after the compressor has stopped, the EXV should close completely.
6. Look at the sightglass and verify that refrigerant is not flowing into the evaporator. If it is, the EXV is stuck open and may need to be replaced.
7. If flow stops, go to the laptop and access the "Circuit" tab for the expansion valve you are interested in checking.
8. Record the Liquid Level in the evaporator. If the chiller has been pumped down, or if the condenser is much colder than the evaporator, the Liquid Level should read approximately -1.1"
9. Now access the "Compressor Service" tab and manually open EXV to 100%.
10. Once again, watch sightglass and verify that a stream of liquid moves between the condenser and evaporator. The amount of liquid and the speed at which it moves will be driven by the amount initially in the condenser and the differential pressure between the condenser and the evaporator.
11. After verifying that the refrigerant is moving, access the "Circuit" tab and monitor the Liquid Level. If the evaporator is cooler than the condenser, the liquid will migrate very quickly to the evaporator and raise the Liquid Level. As you watch the laptop, the level should move from -1.1" to +1.1".
12. If the liquid does not move at all, it may be that the EXV is stuck closed, or that the circuit is very low on charge. You may need to check the What should the subcooling be for the RTAC Chiller? on the circuit to ensure that you are not undercharged. If necessary, leak check the unit add refrigerant.
13. Return the chiller to service.
Notes:
** Reference RLC-SVD05A-EN for additional troubleshooting
Changes:
Other Question/Problem/Cause Statements:
- EXV Checkout
Facts:
- RTAC
Document Identifier: DOC-74876
Document Identifier: 74876
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.