Use and Care Manual
Table Of Contents
- Foreword
 - Safety Notice
 - CONTENTS
 - Safety Notice on Maintenance
 - Safety Notice on Operation
 - 1 Product Introduction
 - NOTE: 1 Ton =12000Btu/h = 3.517kW 1.2 Electrical Parameters
 - 2 Control
 - 3 Troubleshooting
- 3.1 Wiring Diagrams
 - 3.2 PCB Layout
 - 3.3 Error Code
 - 3.4 Troubleshooting
- 3.4.1 “E1” Compressor High Pressure Protection
 - 3.4.2 “E3” Compressor Low-pressure Protection, Refrigerant Shortage Protection, Refrigerant Recovery Mode
 - 3.4.3 “E4” Compressor Air Discharge High-temperature Protection
 - 3.4.4 “F2” Condenser Temperature Sensor Error
 - 3.4.5 “F3” Outdoor Ambient Temperature Sensor Error
 - 3.4.6 “F4” Discharge Temperature Sensor Error
 - 3.4.7 “F6” ODU Tube Temperature Sensor Error
 - 3.4.8“EE” ODU Memory Chip Error
 - 3.4.9 “H4” Overload
 - 3.4.10 “H5” IPM Protection
 - 3.4.11 “H6” DC Fan Error
 - 3.4.12 “H7” Driver Out-of-Step Protection
 - 3.4.13 “HC” PFC Protection
 - 3.4.14 “Lc” Startup Failure
 - 3.4.15 “P0” Driver Reset Protection
 - 3.4.16 “P5” Over-Current Protection
 - 3.4.17 “P6” Master Control and Driver Communication Error
 - 3.4.18 “P7” Driver Module Sensor Error
 - 3.4.19 “P8” Driver Module High Temperature Protection
 - 3.4.20 “PA” AC Current Protection
 - 3.4.21 “Pc” Driver Current Error
 - 3.4.22 “PL” Bus Low-Voltage Protection
 - 3.4.23 “PH” Bus High-Voltage Protection
 - 3.4.24 “PU” Charge Loop Error
 - 3.4.25 “ee” Drive Memory Chip Error
 
 - 3.5 Failures Not Caused by Errors
 
 - 4 Maintenance
 - Appendices
 - 1 Resistance/Temperature Lists of Temperature Sensors
- 1.1 Voltage List of 15 KΩ Temperature Sensors (including ODU temperature sensors)
 - 1.2 Voltage List of 20 KΩ Pipeline Temperature Sensors (including temperature sensors for defroster, IDU and ODU pipes)
 - 1.3 Voltage List of 50 KΩ Discharge Temperature Sensors (including discharge air temperature sensor)
 
 - 2 Temperature/Pressure List of Refrigerant
 - 3 Operation Tools
 
MRCOOL DC INVERTER COOLING ONLY CONDENSING UNIT 
59 
NOTE:
Confirm whether the compressor needs to be replaced. The pipe mouths of the faulted compressor must be 
sealed by adhesive tape as soon as the compressor is detached. Make sure the compressor is well preserved for 
the ease of future analysis.   
Step 6: Check the components 
If the oil is contaminated, check the components of the unit, including the gas-liquid separator.   
Check the gas-liquid separator 
When the separator is detached, check whether there are impurities inside. For disassembly steps, refer to 
section 4.5. 
NOTE: 
When pouring the liquid from the separator, make sure the discharge pipe is at the lower position.Slant at an 
angle not larger than 20° 
Use a transparent container to collect the content inside the separator. Check its color, seal it well and return 
it to the factory for inspection. 
NOTE: 
If the compressor is damaged and needs to be replaced, the gas-liquid separator should also be replaced, 
whether or not there are impurities in the separator or other abnormal conditions.   
Confirm which parts of the system should be replaced. Make sure the pipe mouths of the damaged parts or 
components are sealed by adhesive tape as soon as they are detached. Keep them in the original condition for 
future analysis. 
Step 7: Clear the pipeline 
After confirming  which  parts  of  the  system  should  be  replaced,  check  the  pipeline  of  the  system.  Blow 
through  the  main  pipeline  with  nitrogen.  After  clearing  the  pipeline,  if  the  components  are  not  replaced 
immediately, seal the pipeline with adhesive tape to prevent the system from being contaminated by water and 
impurities in the air.   
Step 8: Replace the compressor 
For the removal of compressor, please refer to the section: Removal of Major Components. 
Step 9: Check/Replace the gas-liquid separator 
NOTE:
If a compressor is damaged and needs to be replaced, its gas-liquid separator should also be replaced. This 
is to avoid the abnormal condition of the separator from affecting the safe and reliable operation of the system. 










