Applicable Systems
Carrier Transicold Refrigeration Unit
Symptoms
The Carrier Transicold unit displays alarm CR007, indicating expansion valve ice blockage. Moisture has frozen at the expansion valve orifice, restricting refrigerant flow and starving the evaporator.
Possible Causes
- Moisture has entered the system through a leak on the low side during vacuum or service
- The liquid line filter drier has become saturated and is no longer absorbing moisture
- System was not evacuated adequately before charging, leaving residual moisture in the system
Troubleshooting Steps
- Step 1: Check the expansion valve bulb temperature and the pressure drop across the valve
Bulb temperature and valve pressure drop indicate the valve is not restricted by ice - Step 2: Inspect the liquid line filter drier sight glass for moisture indicator color
Sight glass color is green, indicating the system is dry with no moisture present - Step 3: Measure the evaporator superheat at the evaporator outlet to confirm the valve is feeding
Superheat is 4-8C, confirming the expansion valve is feeding refrigerant correctly
How to Reset
To reset: 1) Replace the liquid line filter drier with a new one. 2) Evacuate the system to below 500 microns. 3) Recharge with the correct refrigerant amount. 4) Press RESET and verify superheat is stable.
Source: Carrier Transicold Refrigeration Unit Manual, Carrier Corporation
Category: Refrigeration